ARMY TM 5-600AIR FORCE AFJPAM 32-1088

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D E P A R T M E N T S O F T H E A R M Y A N D T H E A I R F O R C ED E C E M B E R 1 9 9 4

TM 5-600/AFJPAM 32-1088

REPRODUCTION AUTHORIZATION/RESTRICTIONS

This manual has been prepared by or for the Government and ispublic property and not subject to copyright.

Reprints or republications of this manual should include a creditsubstantially as follows: “Joint Departments of the Army and AirForce, TM 5-600/AFJPAM 32-1088, Bridge Inspection, Maintenance,and Repair.”

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ATM 5-600/AFJPAM 32-1088

TECHNICAL MANUAL HEADQUARTERSNo. 5-600 DEPARTMENTS OF THE ARMYAIR FORCE JOINT PAMPHLET AND THE AIR FORCENO. 32-108 WASHINGTON, DC, 6 December 1994

BRIDGE INSPECTION, MAINTENANCE, AND REPAIRParagraph Page

CHAPTER 1. INTRODUCTIONSection I. GENERAL INFORMATION

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1-1Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 1-1References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3 1-1

II. MAINTENANCE PLANNINGProgramming and economic considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 1-1Elements of the maintenance program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5 1-1

III. FREQUENCY OF INSPECTIONMilitary requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6 1-2Factors of frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7 1-2

IV. QUALIFICATIONS OF INSPECTION PERSONNELArmy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8 1-2Air Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9 1-2

2. BRIDGE STRUCTURESDefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 2-1Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 2-1Typical bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 2-1Box culverts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4 2-1Military bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5 2-1

3. BRIDGE ELEMENTSI. SUBSTRUCTURE ELEMENTS

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 3-1Abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 3-1Piers and bents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3 3-1

II. SUPERSTRUCTURESGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 3-1Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 3-2Floor systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 3-2Main supporting members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7 3-2Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8 3-8

III. MISCELLANEOUS ELEMENTSBearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9 3-12Pin and hanger supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10 3-12Expansion joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11 3-12Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12 3-12Railings, sidewalks, and curbs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13 3-14Deck drains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14 3-14Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15 3-14Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16 3-15Dolphins and fenders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17 3-15Welds, bolts, and rivets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18 3-16

4. MECHANICS OF BRIDGESGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 4-1Bridge forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 4-1Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3 4-1

5. BRIDGE CONSTRUCTION MATERIALSI. CONCRETE

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1 5-1Physical and mechanical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2 5-1Indication and classification of deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3 5-1Causes of deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4 5-4Assessment of concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5 5-8

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED

TM 5-600/AFJPAM 32-1088

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Paragraph PageSection II. STRUCTURAL STEEL

Physical and mechanical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6 5-11Indicators and classification of deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7 5-11Causes of deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8 5-12Assessment of deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9 5-13

III. TIMBERPhysical and mechanical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10 5-13Deterioration: indicators and causes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11 5-14Assessment of deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12 5-16

IV. WROUGHT AND CAST IRONGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-13 5-17Physical and mechanical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14 5-17Deterioration: indicators and causes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15 5-18

V. STONE MASONRYGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-16 5-18Physical and mechanical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-17 5-18Indicators of deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18 5-18Causes of deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-19 5-18

VI. ALUMINUMGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-20 5-18Deterioration: indicators and causes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-21 5-18

VII. FOUNDATION SOILSGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22 5-19Types of movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-23 5-19Effects on structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-24 5-19Indicators of movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25 5-20Causes of foundation movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26 5-22

VIII. WATERWAYSGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-27 5-25Types of movement and effects on waterways . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28 5-25

CHAPTER 6. BRIDGE REDUNDANCY AND FRACTURE CRITICAL MEMBERS (FCMs)I. GENERAL

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1 6-1Fracture critical members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2 6-1Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3 6-1Criticality of FCMs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4 6-1

II. EXAMPLESTwo-girder system (or single-box girder) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5 6-3Two-truss system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6 6-4Cross girders and pier caps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7 6-5Supports and suspended spans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8 6-5

7. INSPECTION CONSIDERATIONSI. TOOLS AND EQUIPMENT

Basic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1 7-1Concrete inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2 7-1Steel inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3 7-1Timber inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4 7-1Cast iron, wrought iron, and aluminum inspection . . . . . . . . . . . . . . . . . . . . . . . . . 7-5 7-1Special equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6 7-2

II. SAFETYGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7 7-2Bridge site organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8 7-2Personal protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9 7-2Special safety equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10 7-2Climbing of high steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11 7-2Confined spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-12 7-3

III. DOCUMENTATION OF THE BRIDGE INSPECTIONGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-13 7-4Planning and documenting the inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14 7-4Structure evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-15 7-4

IV. INSPECTION PROCEDUREGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16 7-5Inspection sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17 7-5

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Paragraph PageCHAPTER 8. BRIDGE COMPONENT INSPECTIONSection I. SUBSTRUCTURES

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1 8-1Abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2 8-1Retaining walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3 8-1Piers and bents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4 8-1Pile bents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5 8-4Dolphins and fenders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6 8-4

II. SUPERSTRUCTURESConcrete beams and girders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7 8-5Steel beams and girders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8 8-6Pin and hanger connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9 8-8Floor systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-10 8-12Diaphragms and cross frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11 8-13Trusses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-12 8-13Lateral bracing portals and sway frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-13 8-16Tied arches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14 8-16Metal bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15 8-17Elastomeric bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-16 8-18Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-17 8-18Expansion joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-18 8-20Railings, sidewalks, and curbs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-19 8-21Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-20 8-22Bridge drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-21 8-22

III. MISCELLANEOUS INSPECTION ITEMSWaterways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-22 8-23Paint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-23 8-24Signing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-24 8-24Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-25 8-26Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26 8-27

IV. INSPECTION OF RAILROAD BRIDGESGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27 8-28Railroad deck types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-28 8-28Track inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29 8-28Deck inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-30 8-28Superstructure inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-31 8-30Substructure inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-32 8-31Recommended practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-33 8-31

V. BOX CULVERTSTypes of distress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-34 8-31Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-35 8-32

9. FINAL DOCUMENTATIONAnnual (Army) and biannual (Air Force) inspection documentation . . . . . . . . . . . 9-1 9-1Triennial (Army) and every third biannual (Air Force) bridge inspection documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2 9-1

10. GENERAL PREVENTIVE MAINTENANCE, REPAIR, AND UPGRADEI. INTRODUCTION

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 10-1Preventive maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2 10-1Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3 10-1Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4 10-1Bridge upgrade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5 10-2

II. COMMON MAINTENANCE TASKSGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-6 10-2Cleaning deck drains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7 10-2Ice and snow removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8 10-2Bank restoration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-9 10-2Traffic control items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-10 10-2Bearings and rollers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-11 10-3Debris and removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-12 10-3Bridge joint systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-13 10-3Scour protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-14 10-4

III. COMMON REPAIR TASKSGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-15 104

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Paragraph PageAbutment stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-16 10-5Drift and floating ice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-17 10-5Scour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-18 10-6Settlement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-19 10-7Waterway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-20 10-9

Section IV. COMMON METHODS TO UPGRADE EXISTING BRIDGESGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-21 10-9Shortened span lengths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-22 10-9Add stringers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-23 10-10Strengthen piers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-24 10-10Reduce deadload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-25 10-10Posttensioned bridge components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-26 10-10Strengthen individual members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-27 10-10

CHAPTER 11. STEEL BRIDGE MAINTENANCE, REPAIR, AND UPGRADEI. PREVENTIVE MAINTENANCE FOR CORROSION

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1 11-1Structural steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2 11-1

II. REPAIR AND STRENGTHENGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-3 11-1Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-4 11-3Repair of structural members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-5 11-4

III. MEMBER REPLACEMENTTension members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-6 11-10Compression members/columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-7 11-10Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-8 11-10

IV. UPGRADE STEEL BRIDGESCreation of a composite action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-9 11-11Posttensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-10 11-11Truss systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-11 11-12

12. TIMBER BRIDGE MAINTENANCE, REPAIR, AND UPGRADE I. PREVENTIVE MAINTENANCE

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1 12-1Fire protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-2 12-3

II. REPAIR AND STRENGTHEN TIMBER MEMBERSGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-3 12-3Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-4 12-3Repair of graded lumber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-5 12-4Repair of piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-6 12-5Repair of posts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-7 12-7Repair of sway bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-8 12-7

III. MEMBER REPLACEMENTReplacement of tension timber components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-9 12-8Replacement of compression timber components . . . . . . . . . . . . . . . . . . . . . . . . . . 12-10 12-8Replacement of flexural timber components (stringers) . . . . . . . . . . . . . . . . . . . . . 12-11 12-9Replacement of timber decking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-12 12-10

IV. TIMBER BRIDGE UPGRADEStrengthen intermediate supports (piers) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-13 12-11Shorten span length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-14 12-11Posttensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-15 12-12Add stringers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-16 12-12Strengthen individual members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-17 12-13

13. CONCRETE BRIDGE MAINTENANCE, REPAIR, AND UPGRADEI. PREVENTIVE MAINTENANCE

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1 13-1Surface coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-2 13-1Joint maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-3 13-1Cathodic protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-4 13-2

II. REPAIR AND STRENGTHENGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-5 13-2Crack repairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-6 13-3Spall repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-7 13-6Joint repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-8 13-7Abutments and wingwalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-9 13-9Bridge seats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-10 13-9

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Paragraph PageColumns and piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-11 13-10Stringers and beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-12 13-11Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-13 13-11Replacement of concrete members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-14 13-15

Section III. UPGRADE CONCRETE BRIDGESGeneral upgrade methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-15 13-15Strengthen individual members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-16 13-16Prestressed concrete members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-17 13-18

APPENDIX A. REFERENCES AND BIBLIOGRAPHY A-1

B. SUGGESTED ITEMS FOR ARMY ANNUAL AND AIR FORCE BIANNUAL BRIDGEINSPECTIONS B-1

C. SUGGESTED ITEMS FOR ARMY TRIENNIAL AND EVERY THIRD AIR FORCE BIANNUALBRIDGE INSPECTIONS C-1

List of Figures

Figure 2-1. Structural framing system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32-2. Truss bridges: steel or timber construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-42-3. Steel bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-52-4. Reinforced concrete bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-62-5. Timber bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-72-6. Bailey bridge using bailey panel piers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-72-7. Double-double bailey bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-82-8. T6 aluminum fixed bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-92-9. Class 50 M-4 trestle bridge, aluminum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

2-10. Timber trestle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-113-1. Bridge nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23-2. Typical abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-33-3. Typical piers and bents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-43-4. Typical superstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-53-5. Typical floor systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-73-6. Rolled steel beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83-7. Plate girders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-93-8. Truss components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-93-9. Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

3-10. Metal bearing types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-133-11. Metal bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-133-12. Elastomeric bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-143-13. Bearing support for a suspended span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-143-14. Pin and hanger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-153-15. Free pin and hanger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-163-16. Fixed pin and hanger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-173-17. Expansion joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-173-18. Timber pile cluster dolphins and timber fenders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-183-19. Timber bent fenders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-183-20. Basic weld types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18

4-1. Dead load on simple span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24-2. Live load on simple span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24-3. Earth pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24-4. Bouyancy on pier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24-5. Lateral wind load (end view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24-6. Longitudinal force due to friction and live load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24-7. Forces due to temperature rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24-8. Earthquake forces (may be in any direction) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24-9. Ice pressure and stream flow against pier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4-10. Forces on a member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24-11. Axial forces and stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34-12. Truss vertical in tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34-13. Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34-14. Shear forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34-15. Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34-16. Bending stress in a beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44-17. Simple beam bending moment and shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

5-1. Pattern or map cracking on a pier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

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Page Figure 5-2. D-Cracking on a deck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5-3. Nomenclature for individual cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25-4. Light scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-35-5. Medium scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-35-6. Heavy scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-45-7. Small spall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-45-8. Large spall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-55-9. Popouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

5-10. Spall due to reinforcement corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-55-11. Joint spall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-65-12. Rust stained crack in steel girder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-125-13. Buckled flange due to collision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-125-14. Advanced wood decay in crosstie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-145-15. Advanced wood decay in bent cap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-155-16. Slight and advanced wear on a timber deck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-165-17. Buckled timber pile due to overload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-165-18. Longitudinal cracks in timber beam due to overload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-175-19. Differential settlement under an abutment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-205-20. Differential settlement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-205-21. Differential pier movement causing superstructure movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-215-22. Movement due to scour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-215-23. Abutment failure from scour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-225-24. Causes of foundation movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-235-25. Embankment erosion due to improper drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-245-26. Typical flow characteristics through a bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-255-27. General scour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-265-28. Localized scour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-265-29. Sediment deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-265-30. Pier scour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-265-31. Loose riprap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-265-32. Lined banks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-265-33. Channel constrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-275-34. Flooding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-275-35. Protruding abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-275-36. Debris problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-275-37. Bridge in a river bend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-275-38. Concrete slope protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-285-39. Riprap slope protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-295-40. Channel change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-295-41. Material removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-295-42. Obstruction removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-30

6-1. Nonload path redundant bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26-2. Load path redundant bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26-3. Examples of details in table 6-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-36-4. Portions of a girder in tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-66-5. Steel cross girder on concrete piers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-68-1. Abutment checklist items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-28-2. Concrete pier and bent checklist items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-28-3. Pier cap disintegration due to roadway drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-28-4. Steel rocker bent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-38-5. Timber bent checklist items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-48-6. Deteriorated timber dolphins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-58-7. Concrete beam checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-58-8. Shiplapped cantilever joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-68-9. Steel girder checklist items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7

8-10. Floorbeam connection plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-88-11. Cracks in ends of cover plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-98-12. Intermittent welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-98-13. Insert plates in haunched girders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-98-14. Attachments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-98-15. Intersecting welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-118-16. Flange and web attachments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-118-17. Copes and reentrant corners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-128-18. Boxbeam to column connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-128-19. Cracks near shear studs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-12

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Page Figure 8-20. Steel floorbeam checklist items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-13

8-21. Clip angle stringer connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-138-22. Diaphragm checklist items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-138-23. Lower chord of a riveted truss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-148-24. Broken eyebar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-158-25. Worn counters due to rubbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-168-26. Metal bearing checklist items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-178-27. Elastomeric pad checklist items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-188-28. Efflorescence on the underside of a concrete deck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-198-29. Rusted stay-in-place forms underneath a concrete deck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-198-30. Expansion joint checklist items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-208-31. Unprotected parapet end of a bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-218-32. Debris accumulation on bridge deck indicating drainage problems . . . . . . . . . . . . . . . . . . . . . . . . . 8-238-33. Typical military load-class signs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-248-34. Typical telltale indicating overhead clearance of bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-258-35. Appropriate markings for clearance on civilian bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-268-36. Examples of good and defective cross-ties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-298-37. Required tie support at track joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3010-1. Examples of closed joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-410-2. Abutment held in place with a deadman . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-510-3. Typical use of dolphins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-610-4. Forming a footing with a tremie encasement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-710-5. Alternate methods for confining grout under footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-710-6. Use of crushed or structural fill to repair scour damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-810-7. Repair of scour around concrete abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-810-8. Bank repair using riprap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-810-9. Concrete bank protector extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8

10-10. Settlement repair of a concrete wall pier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-910-11. Expedient methods of span length reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-10

11-1. Anodes placed on steel H piles for corrosion protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-211-2. Local buckling under compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-311-3. Repairing tie rods with splices or turnbuckles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-411-4. Strengthening pin connections using a supplementary eye . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-511-5. Use of cover plates on rolled steel sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-711-6. Iowa DOT method of adding angles to steel 1-beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-711-7. Integral pile jacket for steel piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-811-8. Details of double-nutted bolt shear connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1011-9. Method for relieving stress in tension members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-10

11-10. Replacement of a steel beam in a composite section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1111-11. Precast deck with holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1111-12. Design of posttensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1211-13. Adding supplementary members to a truss frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1311-14. Arch superposition scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1311-15. Reinforcing a pony truss with Bailey trusses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-13

12-1. Protective covers for timber members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-212-2. Flexible PVC barrier installed on a timber pile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-212-3. Common deck connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-412-4. Repair of cracked or split stringers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-512-5. Timber cap scabs provide additional bearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-512-6. Stringer splice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-612-7. Timber pile repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-712-8. Concrete jacket supporting a timber pile splice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-712-9. Shimming timber piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-8

12-10. Fender pile repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-812-11. Jacking methods for timber cap replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-912-12. Pile replacement methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-912-13. Below-deck timber stringer replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1012-14. Splicing in a wheel curb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1112-15. Diagrams of an intermediate helper bent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1212-16. Timber beam strengthened using king post posttensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1212-17. Steel cover plates used to reinforce a timber beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-13

13-1. Cathodic protection for reinforced concrete piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-213-2. Reinforcing bars inserted 90 degrees to the crack plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-313-3. Crack repair by drilling and plugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-413-4. Epoxy injection used to seal cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-4

TM 5-600/AFJPAM 32-1088

viii

Page Figure 13-5. Flexible seals used in concrete crack repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-5

13-6. Conventional procedure for sealing dormant cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-513-7. Reinforcement of a crack using stitching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-613-8. Expansion joint repair with elastomeric seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-713-9. Placing an elastomeric seal in an asphalt overlay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-8

13-10. Expansion dam repairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-913-11. Repair of abutment and wingwall faces using a jacket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-913-12. Repair of broken or deteriorated wingwalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1013-13. Typical repair of concrete bridge seats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1113-14. Concrete cap extension to increase bearing surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1213-15. Typical beam saddle design using standard steel W-sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1213-16. Standard concrete pile jacket with steel reinforcing cage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1313-17. External prestressing strands used to close a crack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1313-18. Closing a crack in a deck using prestressing steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1513-19. Jacketing of concrete columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1613-20. External shear reinforcement for concrete beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1613-21. Reinforcing boxbeams for shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1713-22. Web reinforcement of boxbeams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1713-23. Steel channel used to reinforce beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1713-24. Concrete beams reinforced with concrete sleeves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-18

List of TablesTable 5-1. Relation of symptoms to causes of distress and deterioration of concrete . . . . . . . . . . . . . . . . . . . . . 5-6

5-2. Test methods for concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-96-1. Classification of types of details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-48-1. Expansion joint data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-208-2. Minimum overhead clearances for bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-258-3. Minimum lane widths for bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-268-4. Operating restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-30

10-1. Chemical application rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-310-2. Lightweight decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1110-3. Bridge posttensioning configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1211-1. Built-up members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-913-1. Elastomeric seal size guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-713-2. Bridge deck restoration procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-14

TM 5-600/AFJPAM 32-l088

CHAPTER 1

INTRODUCTION

Section I. GENERAL INFORMATION

1-1. Purpose

This manual is a guide for the inspection, mainte-nance, and repair of bridges for military installa-tions. It is a source of reference for planning,estimating, and technical accomplishment of main-tenance and repair work and may serve as atraining manual for facilities maintenance person-nel in the Army and Air Force engaged in mainte-nance inspection and repair of bridges.

repair of bridges to retain them in continuousreadiness for support of military operations. It alsodescribes the methods used in accomplishing thismaintenance and repair work. The text includesgeneral principles of maintenance and repair foruse by all activities designated to maintainbridges at Army and Air Force installations in acondition suitable for their intended use.

1-3. References1-2. Scope Appendix A contains a list of references used inIt provides guidance for typical maintenance and this manual.

Section II. MAINTENANCE PLANNING

1-4. Programming and economic consider-ations

In maintenance planning and execution, full con-sideration must be given to future expected use ofeach bridge, the life expectancy of the bridge, andthe life-cycle cost of periodic repairs versus re-placement of a bridge or its major components.The level of maintenance and programming ofmajor repairs should be planned in consonancewith future requirement for the bridge and/orplanned replacement. The maintenance programshould be designed to include prevention of deteri-oration and damage, prompt detection of deficien-cies, and early accomplishment of maintenanceand repairs to prevent interruptions of operationsor limitation/restriction of bridge use.

1-5. Elements of the maintenance program

a. Inspection. Continuous, rigorous inspectionsare necessary for an effective maintenance pro-gram. It is recommended that inspections be madeannually of all basic structures and more fre-quently for fenders and utilities. Additional in-spections may be necessary under certain circum-stances, such as a tsunami, high tides, earth-quakes, accidents, typhoons, and heavy freezes.Inspections may be made from the structures, froma boat or float, or below the waterline by divers.Underwater television is often employed in visualinspections. Types of inspections typical to bridgesare:

(1) Operator inspection consists of examina-tion, lubrication, and minor adjustment performedby operators on a continuous basis.

(2) Preventative maintenance inspection is thescheduled examination and minor repair of facil-ities and systems that would otherwise not besubject to inspection. Pier fender systems, fireprotection systems, and under pier utilities areexamples.

(3) Control inspection is the major scheduledexamination of all components and systems on aperiodic basis to determine and document thecondition of the bridge and to generate major workrequired.

b. Maintenance. Maintenance is the recurrentday-to-day, periodic, or scheduled work that isrequired to preserve or restore a bridge to such acondition that it can be effectively utilized for itsdesigned purpose. It includes work undertaken toprevent damage to or deterioration of a bridge thatotherwise would be costly to restore. Several levelsof bridge maintenance are practiced, depending onthe complexity and frequency of the tasks in-volved. These tasks range from the clearing ofdrainpipes to the replacement of bearings. Minormaintenance consists of cleaning the drainagesystem, patch painting, removing debris, tighten-ing loose bolts, and cleaning the joints.

(1) Routine maintenance includes adjustingbearings, complete repainting, repairing potholes,filling cracks, and sealing concrete.

1-1

TM 5-600/AFJPAM 32-l088

(2) Major maintenance approaches rehabilita- replacement of joints; fatigue crack repair; water-tion in that it might include the replacement of way adjustment; and other specialized activitiesbearings; readjustment of forces, such as in cables; not performed very often.

Section Ill. FREQUENCY OF INSPECTION

1-6. Military requirements 1-7. Factors of frequency

a. Army. AR 420-72 requires that all bridges onall Army installations be thoroughly inspectedevery year and an analysis of load trying capaci-ties be made every 3 years.

b. Air Force. Bridges on Air Force bases shouldbe inspected at regular intervals not to exceed 2years. Additionally, bridges should be inspected assoon as possible after severe storms (i.e., floods,hurricanes, etc.) to evaluate possible damage andreduced load-capacity of the structure. A structuralanalysis of its load-carrying capacity should beperformed on at least every third inspection con-ducted.

a. The depth and frequency to which bridges areinspected will depend on the following factors: age,traffic characteristics, state of maintenance,known deficiencies, and climate conditions.

b. More frequent inspections shall be made ifsignificant change has occurred as a result offloods, excessive loadings, earthquake, or accumu-lated deterioration. Where changes from thoseconditions existing in the original analysis andinspection or revalidation are apparent, a rea-nalysis of themade.

load-carrying capacity shall be

Section IV. QUALIFICATIONS OF INSPECTION PERSONNEL

1-8. Army

a. Annual bridge inspection. Installation main-tenance personnel should have a knowledge ofbridge structure inspection and construction andbe able to identify the regular maintenance re-quirement and structural deficiency.

b. Triennial bridge inspection. Bridge inspec-tor should have the following minimum qualifica-tions:

(5) Inspector should be able to recognize anystructural deficiency, assess its seriousness, andtake appropriate action necessary to keep thebridge in a safe condition.

(6) Inspector should also recognize areas of thebridge where a problem is incipient so that preven-tative maintenance can be properly programmed.

(7) The qualifications of each person directlyor indirectly involved with the inspection shouldbe submitted with bid documents.

(1) Inspector should be a registered profes-sional engineer (or under the direct supervision ofa registered professional engineer).

(2) Inspector should have a minimum of 2years experience in bridge inspection assignmentin a responsible capacity.

1-9. Air Force

(3) Inspector should be thoroughly familiarwith design and construction features of the bridgeto properly interpret what is observed and re-ported.

(4) Inspector should be capable of determiningthe safe load carrying capacity of the structure.

The Air Force inspector should be a trained bridgeinspector from Maintenance Engineering. Themain responsibilities are to perform the requiredinspections, document conditions of the structure,and initiate maintenance actions. If the inspectionreveals a situation that requires a greater in-depthevaluation, the inspector (through the divisionchief) should request a design engineer to evaluatethe bridge condition and determine correctivemaintenance/repair actions.

l - 2

TM 5-600/AFJPAM 32-1088

CHAPTER 2

BRIDGE STRUCTURES

2-1. Definition

For the purpose of this manual, a bridge is definedas a structure, including supports, erected over adepression or an obstruction, such as water, high-way, or railway, having a track or passageway forcarrying traffic or other moving loads, and havingan opening measured along the center of theroadway of more than 20 feet between undercop-ings of abutments, or spring lines or arches, orextreme ends of openings for multiple boxes; itmay also include multiple pipes, where the cleardistance between opening is less than one-half ofthe smaller contiguous opening.

2-2. Classification

The inspector must be aware of bridge types toproperly describe a bridge for the inspection re-port. The main emphasis of the description shouldbe on the main span. Bridges are classified accord-ing to their function, structural type, and struc-tural material:

a. Function. The “function” of a bridge refers tothe currently approved classification of the road-way. Some typical roadway classifications are:interstate, freeway, principal arterial, minor arte-rial, collector, major, minor, military, etc.

b. Structural type. The “type” of bridge definesboth the structural framing system and the type ofsuperstructure:

(1) Structural framing system. There are basi-cally four types of structural framing systems:simple spans, continuous spans, cantilever andsuspended spans, and rigid frames. They are de-scribed as follows:

(a) Simple span. These spans consist of asuperstructure span having a single unrestrainedbearing at each end. The supports must be suchthat they allow rotation as the span flexes underload. Ordinarily, at least one support is attachedin a way that keeps the span from moving longitu-dinally. Figure 2-1 (part a) demonstrates a simplespan.

(b) Continuous span. Spans are consideredcontinuous when one continuous piece crossesthree or more supports. Figure 2-1 (part b) showsa two-span continuous structure. Note that thesupports at the ends of the continuous units aresimilar to those at the ends of a simple span.However, because the member is continuous overthe center support, the magnitude of the memberrotation is restricted in the area adjacent to the

pier. A bridge may be continuous over manysupports with similar rotational characteristicsover each interior support.

(c) Cantilever and suspended spans. Some-times it is advantageous from a structural stand-point to continue a span over the pier and termi-nate it near the pier with a short cantilever. Thiscantilever is ordinarily used to support or“suspend” the end of an adjacent span. Thisarrangement is shown in figure 2-1 (part c). Theother end of the suspended span may in somecases be supported by another cantilever or it mayrest on an ordinary simple support.

(d) Rigid frames. These are frequently usedas transverse supports in steel construction andoccasionally used as longitudinal spans. The term“rigid” is derived from the manner of constructionor fabrication which does not allow relative rota-tion between the members at a joint. A rigid framemay be rigidly attached at the base (fixed), or itmay be simply supported.

(2) Superstructure type. The various types ofsuperstructures are: slab, truss, girder, arch, sus-pension (not covered in this manual), beam-girder,stringer, and composite.

c. Structural material. The basic types of struc-tural materials are steel, concrete, timber, stone,masonry, wrought iron, cast iron, and aluminum.

2-3. Typical bridges

Based upon the above classification criteria, manytypical bridges can be defined and are summarizedin figures 2-2 through 2-5.

2-4. Box culverts

Box culverts range in size from small, single-cellunits to multicell units as large as 20 by 20 feet.While natural rock, when present, may be used asa floor, the box culvert is usually a closed, rectan-gular frame. Usually, transverse joints are pro-vided every 20 to 30 feet. Occasionally, old cul-verts consist of simply a slab on a wall. These arenot true box culverts. Some of these slabs aremade of stone, while some walls are made ofrubber masonry, rather than concrete.

2-5. Military bridges

A large variety of special-purpose military bridgesexist. These bridges, for the most part, are de-signed for expedient deployment under combatsituations. They are not intended for continued

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TM 5-600/AFJPAM 32-1088

day-to-day usage under civilian and military traf- the inspection, maintenance, and repair of thesetic. However, due to economic constraints, some of bridges must also be addressed. Several types ofthese bridges are serving as “permanent” struc- military bridges are shown in figures 2-6 throughtures on some military installations. Therefore, 2-10.

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c. Cantilever-suspended spans.Figure 2-1. Structural framing system.

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THROUGH HOWE TRUSS THROUGH PRATT TRUSS

THROUGH WARREN TRUSS QUADRANGULAR THROUGH WARREN TRUSS

THROUGH WHIPPLE TRUSS CAMEL BACK TRUSS

THROUGH BALTIMORE TRUSS K-TRUSS

THROUGH TRUSS PONY TRUSS DECK TRUSS

CANTILEVER

Figure 2-2. Truss bridges: steel or timber construction.

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STEEL VIADUCT

THROUGH-ARCH TRUSS

RIGID FRAME-STEEL

RIGID FRAME(STEEL GIRDER ELEMENT)

THROUGH GIRDER DECK GIRDER 1 BEAMFigure 2-3. Steel bridges.

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CONTINUOUS GIRDER

SPANDREL-FILLED ARCHOPEN SPANDREL ARCH

RIGID FRAME-CONCRETE

SLAB SECTION T-BEAM SECTION

RIGID FRAME-CONCRETE CONCRETE T-BEAM

ROADWAY SECTIONBOX GIRDER

Figure 2-4. Reinforced concrete bridges.

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TIMBER TRESTLE

PILE BENT FRAME BENT

Figure 2-5. Timber bridges.

Figure 2-6. Bailey bridge using bailey panel piers.

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Figure 2-7. Double-double bailey bridge.

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Figure 2-8. T6 aluminum fixed bridge.

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Figure 2-9. Class 50 M-4 trestle bridge, aluminum.

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Figure 2-10. Timber trestle.

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CHAPTER 3

BRIDGE ELEMENTS

Section I. SUBSTRUCTURE ELEMENTS

3-1. General

Typical bridge nomenclature is summarized infigure 3-1. A bridge basically consists of two mainparts: the substructure and the superstructure.The substructure includes those parts which trans-fer the loads from the bridge span down to thesupporting ground. For a single-span structure thesubstructure consists of two abutments, while formultispan structures there are also one or morepiers. Sometimes steel bents or towers are usedinstead of piers. The loads are applied to thesubstructure through the bearing plates and trans-mitted through the abutment walls or pier col-umns to the footings. If the soil is of adequatestrength, the footings will distribute the loads overa sufficiently large area. If not, the footings them-selves must be supported on pile foundations ex-tended down to a firm underlying stratum.

3-2. Abutments

Abutments are substructures supporting the end ofa single-span or the extreme end of a multispansuperstructure and usually retaining or supportingthe approach embankment. Typical abutments areshown in figure 3-2. Abutments usually consist ofa footing, a stern or breast wall, a bridge seat, abackwall, and wing walls. The backwall preventsthe approach embankment soil from spilling ontothe bridge seat, where bearings for the superstruc-ture are situated. The wing walls are retainerswhich keep the embankment soil around the abut-ment from spilling into the waterway or roadwaythat is spanned by the bridge. When U-shapedwing walls are used, parapets and railings are

often placed on top of them. Abutments may beconstructed of plain concrete, reinforced concrete,stone masonry, or a combination of concrete andstone masonry. Plain concrete and stone masonryabutments are usually gravity structures, whilereinforced concrete abutments are mostly cantile-ver or counterfort types.

3-3. Piers and bents

Typical piers and bents are shown in figure 3-3.Piers transmit the load of the superstructure tothe foundation material and provide intermediatesupports between the abutments. Footings, col-umns or stems, and caps are the main elements ofpiers. The footings are slabs which transmit theload to the soil, rock, or to some other foundationunit such as piles, caissons, or drilled shafts. Thecolumns or stems transmit vertical load and mo-ment to the footings. The cap receives and distrib-utes the superstructure loads. River bridges, rail-way bridges, and some highway underpasses arelikely to use the solid wall pier. Highway gradeseparations of normal width often use multileggedpiers, often with a cap binding the whole unit intoa rigid frame. “Bents” are basically piers withoutfootings, which consist of a row of two or moreposts or piles, tied together at the top with a cap.Piers and bents may be made of timber, steel,concrete, stones, or combination of materials. Pilesare used to transmit the bridge loads to thefoundation material when the foundations are tobe on soft soils, in deep water, or in swift streams.Typical pile types are: steel H Piles, timber,

concrete piles (both CIP and precast/prestressed),and concrete filled pipe or shell piles.

Section II. SUPERSTRUCTURES

3-4. General

The superstructure includes all those parts whichare supported by the substructure, with the mainpart being the bridge spans. Vehicular forces aretransmitted from the bridge deck, through the sup-porting beams or girders of the span, and into thesubstructure. The reinforced concrete slab bridgehas the simplest type of superstructure since theslab carries the load of the vehicle directly to the

abutment or piers. On beam or girder bridges, theslab is supported on longitudinal steel, concrete, ortimber members which, in turn, carry the load tothe abutment or piers. Some superstructures con-sist of the deck, a floor system, and two or moremain supporting members. Figure 3-4 shows sev-era1 different types of superstructures and theirassociated elements. The components of super-structures are summarized in the following para-graphs.

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ABUT1 BENT2 BENT3 PEIR4

ABBREVIATIONS

CDF CREOSOTED DOUGLAS FIR (PRESSURE TREATED)

WS WEARING SURFACE

WL WATER LEVEL

HWM HIGH WATER MARK

PlER5 PIER6 BENT7 BENT8 ABUT9

RC REINFORCED CONCRETE VC VERTICAL CLEARANCE

RW REDWOOD b b DISTANCE BACK TO BACK

UF UNTREATED FIRb b DISTANCE BACK TO BACK

BTF BRUSHED TREATED FIR (WOOD PRESERVATIVE)

Figure 3-1. Bridge nomenclature.

3-5. Decks 3-7. Main supporting members

The deck is that portion of a bridge which providesdirect support for vehicular and pedestrian traffic.The deck may be a reinforced concrete slab, timberflooring, or a steel plate or grating on the topsurface of abutting concrete members or units.While normally distributing load to a system ofbeams and stringers, a deck may also be the mainsupporting element of a bridge, as with a rein-forced concrete slab structure or a laminatedbridge. The “wearing course” of a deck providesthe riding surface for the traffic and is placed ontop of the structural portion of the deck. There arealso wearing courses poured integral with thestructural slab, and then the deck is referred to asa monolithic deck.

The main supporting members transmit all loadsfrom the floor system to the supports at points onthe piers and abutments. The strength and safetyof the bridge structure depends primarily on themain supporting members. These members may betimber, steel, or concrete beams; steel plate gird-ers; timber or steel trusses or concrete rigidframes; arches of various material; or steel cables.The most general types of these members arediscussed as follows:

a. Rolled beams. The rolled beam is used forshort spans. It comes from the rolling mill as anintegral unit composed of two flanges and a web.The flanges resist the bending moment and theweb resists shear. The more common types ofrolled beam shapes are shown in figure 3-6.

3-6. Floor systems

The floor system may consist of closely spacedtransverse floor beams between girders (refer tothe deck girder bridge in figure 3-4, sheet 2, partc) or several longitudinal stringers carried by trans-verse floor beams (refer to the through girder offigure 3-4, sheet 2, part c). In floors of this type,the stringers are usually wide flange beams whilethe floor beams may be plate girders, wide flangebeams, or trusses. Where floor beams only areused, they may be rolled beams or plate girders.Several floor systems are shown in figure 3-5.

b. Plate (built-up) girders. This type of structuralmember is used for intermediate span lengths notrequiring a truss and yet requiring a memberlarger than a rolled beam. The basic elements of aplate girder are a web to which flanges are rivetedor welded at the top and bottom edges. The mostcommon forms of cross section are shown in figure3-7. The component parts of a plate girder are asfollows (figure 3-7):

(1) Flange angles. These are used for rivetedplate girders and carry tensile or compressiveforces induced by bending.

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Figure 3-2. Typical abutments

(2) Cover plates. These are welded or rivetedto the top and/or bottom flanges of the girder toincrease the load carrying capacity.

(3) Bearing stiffeners. These are plates or an-gles placed vertically at the locations of the sup-port and attached to the web. Their primaryfunction is to transmit the shearing stresses in theweb plate to the bearing device and, by so doing,prevent web crippling and buckling.

(4) Intermediate stiffeners. These are used at

points of concentrated loads or for deep girder toprevent web crippling and buckling.

c. Concrete beams. These beams are usuallyreinforced wherein the tensile stresses, whetherresulting from bending, shear, or combinationsthereof produced by live and dead loadings, are bydesign carried by the metal reinforcement. Theconcrete takes compression (and some shear) only.It is commonly rectangular or tee-shaped with itsdepth dimension greater than its stem width.

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Figure 3-3. Typical piers and bents.

d. Trusses. The truss is one form of structuralsystem which, because of its characteristics, pro-vides high load-carrying capacities and can beused to span greater lengths than rolled beamsand girders. The truss functions basically in thesame manner as a rolled beam or girder inresisting loads, with the top and bottom chordsacting as the flange and the beam and the diago-nal members acting as the web. While mosttrusses are of steel, timber trusses also exist.Truss members may be connected with rivets,bolts, or pins. Although the configuration oftrusses varies widely, the essential components

are common to all. Truss members may be built-up sections, rolled sections, tubing, pipe, eye-bars, or solid rods. An earlier commonly usedconstruction practice was to connect channels bylacing bars and stay plates at the ends. Interiorverticals and diagonals on old bridges may consistof relatively slender solid rods when the memberis subject only to tension. When two opposingtension diagonals are provided in the panel of atruss, they are termed “counters.” The basic partsof a truss are summarized in figures 3-1, 3-4(sheet 1, part b) and 3-8. They are discussed asfollows:

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A. MASONRY ARCH BRIDGE.

B. TRUSS

Figure 3-4. Typical superstructures. (Sheet 1 of 2)

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c. GIRDER BRIDGE

d. STEEL STRINGER BRIDGEFigure 3-4. Typical superstructures. (Sheet 2 of 2)

(1) Chord. In a truss, the upper and the lowerlongitudinal members extending the full spanlength are called chords. The upper portion isdesignated as the upper or top chord and corre-spondingly lower portion is designated as thelower or bottom chord. For simple span, the topchord will always be in compression, and thebottom chord will always be in tension and shouldbe considered a main structural member. Failureof either chord will render the truss unsafe.

(2) Diagonals. The diagonal web membersspan between successive top and bottom chords

3-6

and will resist tension or compression, depend-ing on the truss configuration. Most diagonals arealso main structural members and their failurewould be extremely critical and render the trussunsafe.

(3) Verticals. Vertical web members spanbetween top and bottom chords, which will re-sist tension or compression stresses dependingupon the truss configuration. Most verticals area main structural member, and their failurewould usually be critical and render the trussunsafe.

TM 50-600/AFJPAM 32-1088

Figure 3-5. Typical floor systems. (Sheet 1 of 3)

Figure 3-5. Typical floor systems. (Sheet 2 of 3)

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Figure 3-5. Typical floor systems. (Sheet 3 of 3)

a. CROSS SECTIONS

b. TYPICAL LONGITUDINAL SECTION

Figure 3-6. Rolled steel beams.

(4) Panel point. The panel point is the point ofintersection of primary web and chord members ofa truss. Note: Items 5 through 11 can be consid-ered secondary structural members and althoughtheir failure should receive immediate attention,an individual member failure will not render thestructure unsafe.

(5) Portal bracing. The portal bracing is foundoverhead at the end of a through truss andprovides lateral stability and shear transfer be-tween trusses.

(6) Sway bracing. This bracing spans betweenthe trusses at interior panel points and provideslateral stability and shear transfer betweentrusses.

(7) Top lateral bracing. The top lateral braceslie in the plane of the top chord and providelateral stability between the two trusses and resis-tance to wing stress.

(8) Bottom lateral bracing. These braces lie in

3-8

the plane of the bottom chord and provide lateralstability and resistance to wind stresses.

(9) Floor beam. The floor beam spans betweentrusses at the panel points and carries loads fromthe floor stringer and deck system to the trusses.

(10) Stringers. These span between floorbeams and provide the primary support for thedeck system. The deck loading is transmitted tothe stringers and through the stringers to the floorbeams and to the truss.

(11) Gusset plates. These plates connect thestructural members of a truss. On older trusses,pins are used instead of gussets.

3-8. Bracing

The individual members of beam and girder struc-tures are tied together with diaphragms and crossframes; trusses are tied together with portals,cross frames, and sway bracing. Diaphragms andcross frames stabilize the beams or trusses anddistribute loads between them (figure 3-9). Adiaphragm is usually a solid web member, eitherof a rolled shape or built up, while a cross frame isa truss, panel, or frame. Since portals and swaybraces help maintain the cross section of thebridge, they are positioned as deep as clearancerequirements permit. Portals usually are in theplane of the end posts and carry lateral forces fromthe top chord bracing to the supports (figure 3-8,sheet 1). Lateral bracing placed at the upper orlower chords (or flanges), or at both levels, trans-mits lateral forces (such as wind) to the supports(figures 3-8 (sheet 3), 3-8 (sheet 4), and 3-9).

TM 5-600/AFJPAM 32-1088

a. CROSS SECTIONS

b. TYPICAL LONGITUDINAL SECTION

Figure 3-7. Plate girders.

Figure 3-8. Truss components. (Sheet 1 of 5)

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Figure 3-8. Truss components. (Sheet 2 of 5)

Figure 3-8. Truss components. (Sheet 3 of 5)

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Figure 3-8. Truss components. Sheet 4 of 5)

Figure 3-8. Truss components. (Sheet 5 of 5)

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Figure 3-9. Bracing. (Sheet 1 of 2) Figure 3-9. Bracing. (Sheet 2 of 2)

Section III. MISCELLANEOUS ELEMENTS

3-9. Bearings

Bearings transmit and distribute the superstruc-ture loads to the substructure, and they permit thesuperstructure to undergo necessary movementswithout developing harmful overstresses. They arevitally important to the functioning of the struc-ture. If they are not kept in good working order,very high stresses may be induced in the structurethat could shorten the usable life of the structure.Bearings are of two general types, fixed andexpansion. Fixed bearings resist lateral and longi-tudinal movement of the superstructure but per-mit rotation. Expansion bearings allow longitudi-nal movement to account for expansion andcontraction of the superstructure. Depending onstructural requirements, the bearings may or maynot be designed to resist vertical uplift. Bearingsare metal or elastomeric. Typical metal bearingsare shown in figures 3-10 and 3-11. Elastomericbearing pads (figure 3-12) have become a popularchoice for use as expansion bearings. They aremade of a rubber-like material or elastomermolded in rectangular pads, or in strips. Note thatbearings can also be used to support suspendedspans as shown in figure 3-13.

3-10. Pin and hanger supports

These are devices used to attach a suspendedsection to a cantilevered section (figure 3-14).These connections may be free or fixed at one endas shown in figures 3-15 and 3-16.

3-11. Expansion joints

Since all materials expand and contract with

3-12

changes in temperature, provisions must be madein the bridge superstructure to permit movementto take place without damage to the bridge. Onvery short superstructures, there is usually suf-ficient yielding in the foundation to allow thesmall amount of movement to occur without dif-ficulty. On longer structures, however, specific-ally designed expansion joints are provided inthe deck. Where only moderate amounts of move-ments are expected, the joint may be only anopening between abutting parts. When a water-tight seal is desired, a premolded filler topped witha poured-in-place sealer or a preformed com-pression seal is inserted (figure 3-17, sheet 1).Where traffic is heavy, the unprotected edge of thejoint is usually armored with steel angels set inthe concrete. When larger movements must beaccommodated, a sliding plate or finger plateexpansion joint may be used (figure 3-17, sheet 2).A trough is often provided beneath a finger plateexpansion joint to catch water from the roadway.

3-12. Approaches

The approach provides a smooth transition be-tween the roadway pavement and the bridge deck.This is important because it reduces impact forcesacting on the bridge. Rough approaches are usu-ally the result of a volume change either fromsettlement in the backfill material or from ageneral consolidation of subsoil and approach fills,while the bridge, supported on piles, does notsettle at all. To avoid problems from differentialsettlement, approach slabs are often used whichspan the 15 to 25 feet of fill immediately behindthe abutments.

TM 5-600/AFJPAM 32-1081

A. FIXED BEARING. B. SIMPLE EXPANSION BEARING

C. EXPANSION BEARING. D. ROLLER EXPANSION BEARING

Figure 3-10. Metal bearing types.

Figure 3-11. Metal bearings. (Sheet 1 of 4)

Figure 3-11. Metal bearings. (Sheet 2 of 4)

Figure 3-11. Metal bearings. (Sheet 3 of 4)

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Figure 3-11. Metal bearings. (Sheet 4 of 4)

Figure 3-12. Elastomeric bearings.

3-13. Railings, sidewalks, and curbs

a. Railings. Railings should be sufficientlystrong to prevent an out-of-control vehicle fromgoing off the bridge. However, many existingbridges have vehicle guard rails that are littlebetter than pedestrian handrails. Such guard railsare inadequate for safety, are easily damaged byvehicles, and are susceptible to deterioration. On

3-14

Figure 3-13. Bearing support for a suspended span.

the other hand, an unyielding guard rail poses ahazard to vehicular traffic particularly if struckhead on. Unprotected parapets pose a similardanger.

b. Sidewalks. Sidewalks are provided to protectpedestrians crossing the bridge.

c. Curbs. A curb is a stone, concrete, or woodenbarrier paralleling the side unit of the roadway toguide the movement of vehicle wheels and safe-guard bridge trusses, railings, or other construc-tions existing outside of the roadway unit and alsopedestrian traffic upon sidewalks from collisionwith vehicles and their loads.

3-14. Deck drains

Bridge drainage is very important since trapped orponded water, especially in colder climates, cancause a great deal of damage to a bridge and is asafety hazard. Therefore, an effective system ofdrainage that carries the water away as quickly aspossible is essential to the proper maintenance ofthe bridge.

3-15. Utilities

It is common for commercial and industrial utili-ties to use highway rights-of-way and/or adjacentareas to provide goods and services to the public.This means that some utility operations will befound on a number of bridge structures. Theseoperations may be one or more of the following:gas, electricity, water, telephone, sewage, and liq-uid fuels. Utility companies perform most of their

TM 5-600/AFJPAM 32-1088

Figure 3-14. Pin and hanger connection.

facilities installation and most of the requiredmaintenance. While the large commercial enter-prises, e.g., gas, light, and telephone companies,will usually perform the scheduled maintenance oftheir facilities, some of the smaller publicly ownedutilities, e.g., water companies, are less likely toperform adequate maintenance since they may notbe as well staffed. Most utility lines or pipes aresuspended from bridges between the beams or be-hind the fascia. On older bridges, water pipes andsewer pipes may be installed along the sides of thebridge or may be suspended under the bridge.

3-16. Lighting

Lighting on bridges will consist of “whiteway”lighting, sign lights, traffic control lights, naviga-tion lights, and aerial obstruction lights. The lasttwo types of lights are special categories which areencountered only on bridges over navigable water-ways or on bridges having high towers. There will,of course, be many bridges with no lighting at all.

3-17. Dolphins and fenders

Dolphins and fenders around bridges protect thestructure against collision by maneuvering vessels.The fender system absorbs the energy of physicalcontact with the vessel. The various types ofdolphins and fenders are as follows:

a. Dolphins.(1) Timber pile clusters. This type of dolphin is

widely used and consists of a cluster of timberpiles driven into the harbor bottom with the topspulled together and wrapped tightly with wirerope (figure 3-18).

(2) Steel tubes. Steel tube dolphins are com-posed of one or more steel tubes driven into theharbor bottom and connected at the top withbracing and fendering systems.

(3) Caissons. These are sand-filled, sheet-pilecylinders of large diameter. The top is covered bya concrete slab, and fendering is attached to theoutside of the sheets.

b. Fenders.(1) Timber bents. A series of timber piles with

timber walers and braces attached to the tops arestill used (figure 3-19). Steel piles are sometimesused in lieu of timber.

(2) Cofferdams. On large bridges with widefootings, the cofferdam sheets left in place andbraced by a concrete wall act as pier protection. Agrid or grillage of timber or other resilient mate-rial on the outside of the sheets forms a collisionmat.

(3) Steel pile fenders. Steel piles driven inpairs to form a frame, with a concrete slab tyingthe piles together, make a good fender. Timbergrillages are attached to the outside to absorbcollision impact.

(4) Steel or concrete frames. Steel or concreteframes are sometimes cantilevered from the pierand faced with a timber or rubber cushioning toreduce collision impact.

(5) Timber grids. Timber grids, consisting ofposts and walers, are attached directly to the pier(figure 3-18).

(6) Floating fenders. Floating frameworkswhich partly or completely surround the pier aresometimes used as fenders. The main frames are

3-15

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DETAILS

EXPLODED VIEW

Figure 3-15. Free pin and hanger connection.

usually made of steel or concrete with timbercushioning on the outside face.

(7) Butyl rubber fenders. Butyl rubber may beused as a fendering system.

3-18. Welds, bolts, and rivets

a. Welds. Welding is a method of joining twometals together by melting metal at the joints andfusing it with an additional metal from a weldingrod. When cool, weld metal and base metal form a

continuous and almost homogeneous joint. The twobasic types of welds are shown in figure 3-20.

b. Bolts. The A325 high-strength bolt has be-come the primary field fastener of structural steel.Specifications usually call for a heavy hexagonstructural bolt, a heavy semifinished hexagon nut,and one or two washers. Bevel washers may berequired.

c. Rivets. Rivets are sometimes used instead ofbolts, especially in older structures.

3-16

Figure 3-16. Fixed pin and hanger connection.

Figure 3-17. Expansion joints. (Sheet 1 of 2)

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Figure 3-19. Timber bent fenders.

Figure 3-20. Basic weld types.

Figure 3-17. Expansion joints. (Sheet 2 of 2)

Figure 3-18. Timber pile cluster dolphins and timber fenders.

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TM 5-600/AFJPAM 32-1088

CHAPTER 4

MECHANICS OF BRIDGES

4-1. General

This chapter provides the inspector with the basicsof bridge structures. A more thorough understand-ing of the behavior of bridges, and the forcesimposed on them, will help the inspector to betterunderstand the importance of his job and itsassociated critical aspects.

4-2. Bridge forces

The solid bodies to be considered are the substruc-ture and the superstructure of the bridges, whilethe forces exerted on them (represented by arrowsin the following diagrams) include various combi-nations of loads. The principal force is that ofgravity acting on the weight of the structure itself(figure 4-1), on the vehicles (figure 4-2), or onother live loads being carried by the structure.Other forces to be considered are those created byearth pressures (figure 4-3); buoyancy or uplift onthat portion of a structure which is submergedbelow water level (figure 4-4); wind loads on thestructure, vehicles, or live loads (figure 4-5); longi-tudinal forces due to changes in speed of the liveload or due to friction at the expansion bearings(figure 4-6); temperature change (figure 4-7),earthquake (figure 4-8) stream flow and ice pres-sure (figure 4-9); and, in the case of masonrystructures, shrinkage and elastic rib shortening.

4-3. Stress

The load per unit of area is called unit stress. Unitstress is a very widely used standard for measure-ment of safe load. Generally, a limiting unit stressis established for a given material. This allowableunit stress multiplied by the cross-sectional areagives the safe load for the member. Since thismanual can give only a very elementary introduc-tion to the mechanics of structures, it will belimited to a consideration of the forces due to deadand live loads acting on simple tension or compres-sion members of simple-span structures. For anunderstanding of other forces and other types ofstructures, it is suggested that the bridge inspectorrefer to standard structural analysis textbooks.Loads or forces acting upon members may beclassified as axial, transverse, rotational, and tor-sional. Figures 4-10 and 4-11 illustrate the actionof these forces. Both axial and transverse forcesare gravity forces and are expressed in pounds,kips (1,000 pounds), tons, or kilograms. When theaxial or longitudinal loads exert a pull on the

member, the force is said to be tensile; when theaxial load pushes or squeezes a member, the forceis compressive. In the pure case, axial forces loadthe cross-sectional area uniformly as shown infigure 4-11. The formula for axial stress is:

f = P / Awhere

(eq 4-1)

f = stressP = loadA = cross-sectional areaa. Tension. A simple tension member could be

one of the subvertical members of a through truss(figure 4-12). Both dead and live loads causedownward vertical forces which pass from theroadway slab through the stringers and floorbeams, each adding its own dead weight force tothat already being exerted on it. These combinedforces are applied to the subvertical member inquestion through the floor beam connection to thetruss. The tensile force acts on the entire crosssection (less rivet or other holes) of the memberand produces a certain intensity of stress. If thatintensity, or unit stress, is within allowable limits,the member can withstand the applied loads andthe member can be considered “safe.” If, however,corrosion has reduced the effective area of themember, the intensity of the stress is increasedand may exceed the allowable limit. Corrosionmay also cause a notch effect which concentratesthe stress and further weakens the member.

b. Compression. A simple compression membercould be a vertical steel column of a viaduct(figure 4-13). Here the dead and live loads causedownward forces which produce a certain intensityof compressive stress on the entire cross section ofthe member. In compression members the unitstress not only has to be within allowable limits,as is the case with tension members, but theallowable stress becomes smaller as the slender-ness ratio becomes greater. That is, for any givencross section, the longer the column the lower theallowable stress in compression. This is becauselong compression members will buckle rather thancrush.

c. Shear. Transverse forces exert a shearingforce or tendency to slide the part of a member toone side of a cross section transversely withrespect to the part of the member on the other sideof the section. This scissor-like action is illustratedin figure 4-14. Oddly enough, the real shear stressproduced by a transverse load is manifested in a

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Figure 4-1. Dead load on simple span.

Figure 4-2. Live load on simple span.

RETAINING WALL

Figure 4-3.

BOX CULVERT

Earth pressure.

Figure 4-4. Buoyancy on pier.

Figure 4-6. Longitudinal force due to friction and live load.

Figure 4-7. Forces due to temperature rise.

Figure 4-8. Earthquake forces (may be in any direction).

Figure 4-9. Ice pressure and stream flow against pier.

Figure 4-10. Forces on a member.

Figure 4-5. Lateral wind load (end view).

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Figure 4-11. Axial forces and stress.

Figure 4-12. Truss vertical in tension.

Figure 4-13. Compression.

Figure 4-14. Shear forces.

Figure 4-15. Shear. (Sheet 1 of 2)

Figure 4-15. Shear. (Sheet 2 of 2)

horizontal shear stress (figure 4-15, sheet 1).However, it is accompanied by a vertical shearstress of equal magnitude as shown in figure 4-15(sheet 2), which is an enlargement of the littleelement of figure 4-15 (sheet 1). It can easily beseen that the four shear stresses will combine toform a tensile stress. While this is the most likelysource of shear problems, most design criteriaconsider vertical shear as the criterion of shearstrength. The formula for vertical shear stress is:

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f v = V / A w

wherefv = unit shear stress

(eq 4-2)

V = vertical shear due to external loadsAw = area of webd. Rotational force. A rotational force or mo-

ment exerts a turning or bending effect on amember in the plane of the member and may beconsidered as a force acting at the end of a rigidstick. The units of a moment are the product of aforce and a distance (or arm). These may bepound-inches, pound-feet, kip-inches, kip-feet, etc.When an external moment is applied to a beam ormember, an internal resisting moment is devel-oped. This internal moment is formed by longitudi-nal compressive and tensile fiber stresses through-out the beam, acting about the neutral axis. Thisaction is illustrated in figure 4-16. Note that thestresses are greatest at the upper and lower beamsurfaces and decline linearly to zero at the neutralaxis. The maximum flexural (or bending, or fiber)stress are calculated by the following formula:

fb = MC / Iwhere

fb = bending stressM = moment

(eq 4-3)

c = distance from neutral axis to extreme fiber(or surface) of beam

I = moment of inertiaFor stresses at points between the neutral axisand the extreme fiber, use the distance from theneutral axis to the point in question rather than“c.” While bending occurs in many structures, it ismost common in beam and girder spans. The mostcommon use of a beam is in a simple span. Asimple span could be a timber, concrete, or steelbeam supported on abutments at each end. Thedead and live loads cause downward forces which,with the reactions form external moments, re-sult in the bending of the beam between its

supports. The bending produces compressivestresses in the upper, or concave, portion of thebeam and tensile stresses in the lower or convexportion of the beam (figure 4-17). A momentproducing this type of bending is considered posi-tive. Positive moment is typical of vertical loadsacting on simple beams.

e. Negative movement. A continuous (over inter-mediate supports) beam is shown in figure 2-1(part b). It is apparent that the same type ofloading will produce a positive moment acting onthe middle of the span. However, over the support,the upper part of the beam will elongate while thelower part will shorten. This is called negativemoment and is present in continuous structures. Anegative moment can also be produced in a simplebeam (figure 2-1, part a> by an uplift force.

f. Vertical loads. In addition to these horizontalfiber stresses, the vertical loads on the structureare carried to the reactions at the span ends bymeans of shearing stress in the web of the beam.The beam must, of course, be sized so that all thestresses which it is to withstand will be withinallowable limits. It is also important that thebeam be rigid enough to keep its deflection withinproper limits even when the stresses do not ap-proach limiting values.

Figure 4-16. Bending stress in a beam.

Figure 4-17. Simple beam bending moment and shear.

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CHAPTER 5

BRIDGE CONSTRUCTION MATERIALS

Section I. CONCRETE

5-1. General

Concrete is essentially a compressive material.While it has adequate strength for most structuraluses, it is best suited for relatively massive mem-bers that transmit compressive loads directly tothe founding material. Although concrete has lowtensile strength, reinforcing it with steel barsproduces a material that is suitable for the con-struction of flexural members, such as deck slabs,bridge girders, etc. Prestressed concrete is pro-duced by a technique which applies compression toconcrete by means of highly stressed strands andbars of high strength steel wire. This compressivestress is sufficient to offset the tensile stresscaused by the applied loads. Prestressing hasgreatly increased the maximum span length ofconcrete bridges.

5-2. Physical and mechanical properties

a. Strength. Compressive strength is high, butshear and tensile strengths are much lower, beingabout 12 percent and 10 percent, respectively, ofthe compressive strength.

b. Porosity. Concrete is inherently porous andpermeable since the cement paste never com-pletely fills the spaces between the aggregateparticles. This permits absorption of water bycapillary action and the passage of water underpressure.

c. Extensibility. Concrete is considered extensi-ble, i.e., undergoes large extensions without crack-ing. However, this presupposes a high-quality con-crete and freedom from restraint.

d. Fire resistance. High-quality concrete ishighly resistant to the effects of fire. However,intense heat will damage concrete.

e. Elasticity. Concrete under ordinary loads iselastic, i.e., stress is proportional to strain. Undersustained loads, the elasticity of concrete is signifi-cantly lowered due to creep. This makes concreteless likely to crack.

f. Durability. The durability of concrete is af-fected by climate and exposure. In general, as thewater-cement ratio is increased, the durability willdecrease correspondingly. Properly proportioned,mixed, and placed, concrete is very durable.

g. Anisotropy. Concrete itself is generally isotro-pic, but once reinforced with steel bars or pre-

stressed with steel wires, it becomes anisotropic,i.e., its strength varies depending on the directionin which it is loaded.

5-3. lndication and classification of deteriora-tion

While performing an inspection of concrete struc-tures, it is important that the conditions observedbe described in very clear and concise terms thatcan later be understood by others. The commonterms used to describe concrete deterioration arediscussed:

a. Cracking. Cracks in concrete may be de-scribed in a variety of ways. Some of the morecommon ways are in terms of surface appearance,depth of cracking, width of cracking, current stateof activity, and structural nature of the crack:

(1) Surface appearance. The surface appear-ance of cracks can give the first indication of thecause of cracking. Two categories exist:

(a) Pattern or map cracks. These are rathershort cracks, usually uniformly distributed andinterconnected, that run in all directions (figure5-1). These cracks are the result of restraint ofcontraction of the surface layer or possibly anincrease of volume in the interior of the concrete.Another type of pattern crack is “D-cracking.”These cracks usually start in the lower part of aconcrete slab adjacent to joints, where moistureaccumulates and progresses away from the cornersof the slab (figure 5-2). Vertical cracks nearvertical expansion joints in abutments and wallscan also be classified as D-cracks.

(b) Individual cracks. These cracks run indefinite directions and may be multiple cracks inparallel at definite intervals. Individual cracksindicate tension in the direction perpendicular tothe cracking. Several terms may be used to de-scribe the direction that an individual or isolatedcrack runs: diagonal, longitudinal, transverse, ver-tical, and horizontal. The directions of these cracksare demonstrated in figure 5-3.

(2) Depth of cracking. This category is self-explanatory. The four categories generally used todescribe crack depth are surface, shallow, deep,and through.

(3) Width of cracking. Three width ranges areused: fine (generally less than 1/32 inch); medium

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Figure 5-1. Pattern or map cracking on a pier.

Figure 5-2. D-cracking on a deck.

ELEVATION VIEW OF A PIER

Figure 5-3. Nomenclature for individual cracks.

(between 1/32 and 1/16 inch); and wide (over 1/16inch).

(4) Current state of activity. The activity of thecrack refers to the presence of the factor causingthe cracking. The activity must be taken intoaccount when selecting a repair method. Twocategories exist:

(a) Active cracks. These are cracks for whichthe mechanism causing the cracking is still atwork. If the crack is currently moving, regardlessof why the crack formed initially or whether theforces that caused it to form are or are not still atwork, it must be considered active. Also, any crack

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for which an exact cause cannot be determinedshould be considered active.

(b) Dormant cracks. These are cracks whichare not currently moving or for which the move-ment is of such magnitude that a repair materialwill not be affected by the movement.

(5) Structural nature of the crack. Cracks mayalso be categorized as structural (caused by exces-sive live or dead loads) and nonstructural (causedby other means). Structural cracks will usually besubstantial in width, and the opening may tend toincrease as a result of continuous loading andcreep of the concrete. In general, it can be difficultto determine readily during a visual examinationwhether a crack is structural or nonstructural.Such a determination will frequently require astructural engineer.

(6) Combination of descriptions. To describecracking accurately, it will usually be necessary touse several terms from the various categorieslisted. For example: (1) shallow, fine, dormant,pattern cracking, or (2) shallow, wide, dormant,isolated short cracks.

b. Disintegration. Disintegration of concretemay be defined as the deterioration of the concreteinto small fragments or particles due to any cause.It differs from spalling in that larger pieces ofintact concrete are lost when spalling occurs.Disintegration may be caused by a variety ofcauses including aggressive water attack, freezingand thawing, chemical attack, and poor construc-tion practices. Two of the most commonly usedterms used to describe disintegration are scalingand dusting:

(1) Scaling. This is the gradual and continu-ing loss of surface mortar and aggregate over anarea. The inspector should describe the characterof the scaling, the approximate area involved, andthe location of the scaling on the bridge. Scalingshould be classified as follows:

(a) Light scale. Loss of surface mortar up to¼ inch deep, with surface exposure of coarseaggregates (figure 5-4), is considered light scale.

(b) Medium scale. Loss of surface mortarfrom ¼ to ½ inch deep, with some added mortarloss between the coarse aggregates (figure 5-5), isconsidered medium scale.

(c) Heavy scale. Loss of surface mortar sur-rounding aggregate particles of ½ to 1 inch deep isconsidered heavy scale. Aggregates are clearlyexposed and stand out from the concrete (figure5-6).

(d) Severe scale. Loss of coarse aggregateparticles as well as surface mortar and the mortarsurrounding the aggregates is considered severescale. Depth of the loss exceeds 1 inch.

Figure 5-4. Light scale.

Figure 5-5. Medium scale.

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Figure 5-6. Heavy scale.

(2) Dusting. Dusting is the development of apowdered material at the surface of hardenedconcrete. Dusting will usually be noted on horizon-tal concrete surfaces that receive a great deal oftraffic. Typically, dusting is a result of poor con-struction practice. For example, sprinkling wateron a concrete surface during finishing will fre-quently result in dusting.

c. Spalling. Spalling is defined as the develop-ment of fragments, usually in the shape of flakes,detached from a larger mass. As previously noted,spalling differs from disintegration in that thematerial being lost from the mass is concrete andnot individual aggregate particles that are lost asthe binding matrix disintegrates. The distinctionbetween these two symptoms is important whenattempting to relate symptoms to causes of con-crete problems. Spalls can be categorized as fol-lows:

(1) Small spall. These are not greater than ¾inch in depth nor greater than 6 inches in anydimension (figure 5-7).

(2) Large spall. These are deeper than ¾ inchand greater than 6 inches in any dimension (figure5-8).

(3) Special case of spalling. Two special casesof spalling must be noted:

(a) Popouts. These appear as shallow, typi-cally conical depressions in a concrete surface(figure 5-9). They may be the result of freezing ofconcrete that contains some unsatisfactory aggre-gate particles. They are easily recognizable by theshape of the pit remaining in the surface and by a

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Figure 5-7. Small spall.

portion of the offending aggregate particle usuallybeing visible in the hole.

(b) Spalling caused by the corrosion of rein-forcement. One of the most frequent causes ofspalling is the corrosion of reinforcing steel. Dur-ing a visual examination, spalling caused by corro-sion of reinforcement is usually an easy symptomto recognize since the corroded metal will bevisible along with rust staining, and the diagnosiswill be straightforward (figure 5-10).

(c) Joint spall. This is an elongated depres-sion along an expansion, contraction, or construc-tion joint (figure 5-11).

5-4. Causes of deteriorationOnce the inspection of a concrete structure hasbeen completed, the cause or causes for any deteri-oration must be established. Since many of thesymptoms may be caused by more than one mecha-nism acting upon the concrete, it is necessary tohave an understanding of the basic underlyingcauses of damage and deterioration. Table 5-1summarizes the various causes of deterioration inconcrete and their associated indicators. Thesecauses are discussed:

a. Accidental loadings. These loadings are gen-erally short-duration, one-time events such as ve-hicular impact or an earthquake. These loading:

TM 5-600/AFJPAM 32-1088

Figure 5-8. Large spall.

Figure 5-9. Popouts.

can generate stresses higher than the strength ofthe concrete resulting in localized or general fail-ure. This type of damage is indicated by spallingor cracking of the concrete. Laboratory analysis isgenerally not necessary.

b. Chemical reactions. This category includesseveral specific causes of deterioration that exhibita wide variety of symptoms as described:

(1) Acid attack. Portland cement is generallynot very resistant to attack by acids, althoughweak acids can be tolerated. The products ofcombustion of many fuels contain sulfurous gaseswhich combine with moisture to form sulfuric acid.

Figure 5-10. Spa11 due to reinforcement corrosion.

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Figure 5-11. Joint spall.

Table 5-1. Relation of symptoms to causes of distress and deterioration of concrete

Other possible sources for acid formation are sew- cracking, and spalling may be seen. If the natureage, some peat soils, and some mountain water of the solution in which the deteriorated concretestreams. Visual examination will show disintegra- is located is unknown, laboratory analysis can betion of the concrete leading to the loss of cement used to identify the specific acid involved.paste and aggregate from the matrix. If reinforc-ing steel is reached by the acid, rust staining,

(2) Alkali-carbonate rock reaction. Certain ag-gregates of carbonate rock have been reactive in

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concrete. The results of these reactions have beenboth beneficial and destructive. Visual examina-tion of those reactions that are serious enough todisrupt the concrete in a structure will generallyshow map or pattern cracking and a generalappearance which indicates swelling of the con-crete. This reaction is distinguished from that ofthe alkali-silica reaction by the lack of silica gelexudations at cracks. Petrographic examinationmay be used to confirm the presence of alkali-carbonate rock reaction.

(3) Alkali-silica reaction. Some aggregates con-taining silica that is soluble in highly alkalinesolutions may react to form expansive productswhich will disrupt the concrete. This reaction isindicated by map or pattern cracking and a gen-eral appearance of swelling of the concrete. Petro-graphic examination may be used to confirm thepresence of this reaction.

(4) Miscellaneous chemical attack. Concretewill resist chemical attack to varying degreesdepending upon the exact nature of the chemical.Concrete which has been subjected to chemicalattack will usually show surface disintegrationand spalling and the opening of joints and cracks.There may also be swelling and general disrup-tion of the concrete mass. Aggregate particles maybe seen protruding from the remaining concretemass.

(5) Sulfate attack. Naturally occurring sulfatesof sodium, potassium, calcium, or magnesium aresometimes found in soil or in solution in groundwater adjacent to concrete structures. The reac-tions involving these sulfates result in an increasein volume of the concrete. Visual inspection willshow map and pattern cracking as well as ageneral disintegration of the concrete. Laboratoryanalysis can verify the occurrence of the reactionsdescribed.

c. Construction errors. Failure to follow specifiedprocedures and good practice or outright careless-ness may lead to a number of conditions that maybe grouped together as construction errors. Typi-cally, most of these errors do not lead directly tofailure or deterioration of concrete. Instead, theyenhance the adverse impacts of other mechanismsidentified in this chapter. The following are someof the most common construction errors:

(1) Addition of water to concrete. The additionof water while in the delivery truck will often leadto concrete with reduced strength and durability.The addition of water while finishing a slab willcause crazing and dusting of the concrete inservice.

(2) Improper consolidation. Improper consoli-

dation of concrete may result in a variety ofdefects, the most common being bugholes, honey-combing, and cold joints. These defects make itmuch easier for any damage-causing mechanism toinitiate deterioration of the concrete.

(3) Improper curing. Unless concrete is givenadequate time to cure at a proper humidity andtemperature, it will not develop the characteristicsthat are expected and that are necessary to pro-vide durability. Symptoms of improperly curedconcrete can include various types of cracking andsurface disintegration. In extreme cases wherepoor curing leads to failure to achieve antici-pated concrete strengths, structural cracking mayoccur.

(4) Improper location of reinforcing steel. Thissection refers to reinforcing steel that is eitherimproperly located or is not adequately secured inthe proper location. Either of these faults may leadto two general types of problems. First, the steelmay not function structurally as intended result-ing in structural cracking or failure. The secondtype of problem stemming from improperly locatedor tied steel is one of durability. The tendencyseems to be for the steel to end up close to thesurface of the concrete. As the concrete cover overthe steel is reduced, it is much easier for corrosionto begin.

d. Corrosion of embedded metals. Under mostcircumstances, Portland-cement concrete providesgood protection to the embedded reinforcing steel.This protection is generally attributed to the highalkalinity of the concrete adjacent to the steel andto the relatively high electrical resistivity of theconcrete. However, this corrosion resistance willgenerally be reduced over a long period of time bycarbonation, and the steel will begin to corrode.Deicing salts are the most common cause of thecorrosion. Corrosion of the steel will cause twothings to occur. First, the cross-sectional capacityof the reinforcement is reduced which in turnreduces the load-carrying capacity of the steel.Second, the products of the corrosion expand sincethey occupy about eight times the volume of theoriginal material. This leads to cracking and ulti-mately spalling of the concrete. For mild steelreinforcing, the damage to the concrete will be-come evident long before the capacity of the steelis reduced enough to affect its load-carrying capac-ity. However, for prestressing steel slight reduc-tions in section can lead to catastrophic failure.Visual examination will typically reveal ruststaining of the concrete. This staining will befollowed by cracking. Cracks produced by corrosionusually run in straight, parallel lines at uniform

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intervals corresponding to the spacing of the rein-forcement. As deterioration continues, spalling ofthe concrete over the reinforcing steel will occurwith the reinforcing bars becoming visible. Alaboratory analysis may be beneficial to determinethe chloride contents in the concrete throughoutits depth. This procedure may be used to deter-mine the amount of concrete to be removed duringa rehabilitation project.

e. Design errors. Design errors generally resultfrom inadequate structural design or from lack ofattention to relatively minor design details:

(1) Inadequate structural design. This willcause cracking and/or spalling in areas which aresubject to the highest stresses. To identify this asa source of damage, the locations of the damageshould be compared to the types of stresses thatshould be present in the concrete. A detailedstructural analysis may be required, and thus aqualified structural engineer should be consulted ifthis problem is apparent.

(2) Poor design details. Poor detailing mayresult in localized concentrations of high stressesin otherwise satisfactory concrete. The followingare some of the more design detail problems:

(a) Abrupt changes in section. This maycause stress concentrations that may result incracking. Typical examples would include the useof relatively thin bridge decks rigidly tied intomassive abutments or patches and replacementconcrete that are not uniform in plan dimensions.

(b) Reentrant corners and openings. Theselocations are subject to stress concentrations, andwhen insufficiently reinforced, cracking may occur.

(c) Inadequate drainage. This will causeponding of water, which may result in excessiveloading or, more likely, leakage or saturation ofconcrete. Concrete subject to freeze-thaw cycles isespecially vulnerable to this type of damage.

(d) Insufficient travel in expansion joints.Inadequately designed expansion joints may resultin spalling of concrete adjacent to the joints.

(e) Rigid joints between precast units. De-signs utilizing precast elements must provide formovement between adjacent precast elements orbetween the precast elements and the supportingframe. Failure to provide for this movement canresult in cracking or spalling.

f. Wear and abrasion. Traffic abrasion and im-pact cause wearing of bridge decks; while curbs,parapets, and piers are damaged by the scrapingaction of such vehicles as snow plows and sweep-ers. Deck wear also appears as cracking andravelling at joint edges.

g. Freezing and thawing. The cyclic freezing andthawing of critically saturated concrete will causeits deterioration. Deicing chemicals may also accel-erate the damage and lead to pitting and scaling.This damage ranges from surface scaling to exten-sive disintegration. Laboratory examination of con-crete cores with this damage will often show aseries of cracks parallel to the surface of thestructure.

h. Foundation movement. These movements willcause serious cracking in structures. Further dis-cussion of this problem is provided in section VIIof this chapter.

i. Shrinkage. Shrinkage is caused by the loss ofmoisture from concrete. It may be divided into twocategories: that which occurs before setting (plasticshrinkage) and that which occurs after setting(drying shrinkage). Cracking due to plastic shrink-age will be seen within a few hours of concreteplacement. The cracks are generally wide andshallow and isolated rather than patterned. Cracksdue to drying shrinkage are characterized by theirfineness and absence of any indication of move-ment. They are usually shallow, a few inches indepth, and in an orthogonal or blocky pattern.

j. Temperature changes. Changes in tempera-ture cause a corresponding change in volume ofthe concrete, and when sufficiently restrainedagainst expansion or contraction cracking willoccur. Temperature changes will generally resultfrom the heat of hydration of cement in largeconcrete placements, variations in climatic condi-tions, or fire damage.

5-5. Assessment of concrete

Assessment of existing reinforced concrete inbridges is basically associated with fully identify-ing the cause and extent of observed or suspecteddeterioration. The method of description of dam-aged concrete and the possible causes for deteriora-tion were discussed in paragraph 5-5. This sectionwill provide guidance concerning the available testmethods for determining the causes of the deterio-ration and quantifying its extent. The range ofavailable test methods is large and includes in situnondestructive tests upon the actual structure aswell as physical, chemical, and petrographic testsupon samples removed from the structure, andload testing. Table 5-2 summarizes basic charac-teristics of the most widely established test meth-ods classified according to the features which maybe assessed most reliably in each case. An over-view of some of the more common tests follows.

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Table 5-2. Test methods for concrete

Property UnderInvestigation Test

Corrosion ofembedded steel

Half-cell potentialResistivityCover depthCarbonation depthChloride penetration

Concrete quality,durability anddeterioration

Rebound hammerUltrasonic pulse velocityRadiographyRadiometryPermeabilityAbsorptionPetrographicSulphate contentExpansionAir contentCement type and content

Concrete strength CoresPulloutPulloffBreakoffInternal fracturePenetration resistance

Integrity andstructuralperformance

TappingPulse-echoDynamic responseThermographyStrain or crack measurement

ASTMDesignation

C876

C805C597

C856

C457C85, C1084

C42, C823C900

C803

C215

Equipment Type

ElectricalElectricalElectromagneticChemical and microscopicChemical and microscopic

MechanicalElectronicRadioactiveRadioactiveHydraulicHydraulicMicroscopicChemicalMechanicalMicroscopicChemical and microscopic

MechanicalMechanicalMechanicalMechanicalMechanicalMechanical

MechanicalMechanical/electronicMechanical/electronicInfraredOptical/mech./elec.

Additional references should be consulted prior toactual usage of these tests.

a. Core drilling. Core drilling to recover con-crete for laboratory analysis or testing is the bestmethod of obtaining information on the conditionof concrete within a structure. However, since coredrilling is expensive and destructive, it should beconsidered only when sampling and testing ofinterior concrete is deemed necessary. The coresamples should be sufficient in number and size topermit appropriate laboratory examination andtesting. For compressive strength, static or dy-namic modulus of elasticity, the diameter of thecore should not be less than three times thenominal maximum size of aggregate. Warningshould be given against taking NX size (2 1/8-inchdiameter) cores in concrete containing 2- to 6-inchmaximum size aggregate. Due to the large aggre-gate size, these cores will generally be recovered

in short broken pieces. When drilling in poor-quality concrete with any size core barrel, thematerial will generally come out as rubble. Whendrill hole coring is not practical or core recovery ispoor, a viewing system such as a borehole camera,borehole television, or borehole televiewer may beused for evaluating the interior concrete condi-tions. In addition, some chemical tests may beperformed on smaller drilled powdered samplesfrom the structure, thus causing substantially lessdamage than that produced by coring, but thelikelihood of sample contamination is increasedand precision may be reduced.

b. Laboratory investigations. Once samples ofconcrete have been obtained, whether by coring,drilling, or other means, they should be examinedin a qualified laboratory. In general, the examina-tion will include one or more of the followingexaminations:

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(1) Petrographic examination. This type of ex-amination may include visual and microscopicinspection, x-ray diffraction analysis, differentialthermal analysis, x-ray emission techniques, andthin section analysis. These techniques may beexpected to provide information on the following:aggregate condition; pronounced cement-aggregatereactions; deterioration of aggregate particles inplace; denseness of cement paste; homogeneity ofthe concrete; depth and extent of carbonation;occurrence and distribution of fractures; character-istics and distribution of voids; and presence ofcontaminating substances.

(2) Chemical analysis. Chemical analyses ofhardened concrete or of selected portions (paste,mortar, aggregate, reaction products, etc.) may beused to estimate the cement content, originalwater-cement ratio, and the presence and amountof chloride and other admixtures. The chlorideanalysis is the most common of these analyses. Itis used to provide a quantitative measure ofchloride ion contamination and, thus, the potentialfor active steel corrosion at various levels in theconcrete deck. Samples for this test are usuallytaken by a rotary hammer drill. The “threshold”chloride content, or amount of chloride needed toinitiate corrosion, is approximately 2.0 pounds ofchloride content per cubic yard of concrete.

(3) Physical analysis. The following physicaland mechanical tests are generally performed onconcrete cores: density, compressive strength, mod-ulus of elasticity, Poisson’s ratio, pulse velocity,and volume change potential by freezing andthawing.

c. Nondestructive testing (NDT). The purpose ofNDT is to determine the various properties ofconcrete such as strength, modulus of elasticity,homogeneity, and integrity, as well as conditionsof strain and stress, without damaging the struc-ture. Some of the most commonly used tests arediscussed:

(1) Rebound number (hammer). Rebound num-bers may be used to estimate the uniformity andquality of in situ concrete. The rebound number isobtained by the use of a special “hammer” thatconsists of a steel mass and a tension spring in atubular frame. The measured rebound number canbe related to calibration curves which will give anindication of the in situ concrete strength. Therebound number increases with the strength of theconcrete. This method is inexpensive and allowsfor a large number of measurements to be rapidlytaken so that large exposed areas of concrete canbe mapped within a few hours. It is, however, arather imprecise test and does not provide a

reliable prediction of the strength of concrete. Themeasurements can be affected by: smoothness ofthe concrete surface; moisture content of the con-crete; type of coarse aggregate; size, shape, andrigidity of the specimen; and carbonation of theconcrete surface.

(2) Penetration resistance (probe). This test isalso used for a quick assessment of quality anduniformity of concrete. The apparatus most oftenused for penetration resistance is the WindsorProbe, a special gun which uses a 32-caliber blankwith a precise quantity of powder to fire a high-strength steel probe into the concrete. The depthof penetration of the probe into the concrete canthen be related by calibration curves to concretecompressive strength. A probe will penetratedeeper as the density, subsurface hardness, andstrength of the concrete decrease. It should not beconsidered for use as a precise measurement ofconcrete strength. However, useful estimates ofthe compressive strength may be obtained if theprobe is properly calibrated. This test does damagethe concrete, leaving a hole of about 0.32 inches indiameter for the depth of the probe, and may causeminor cracking and some surface spalling. Minorrepairs of exposed surfaces may be necessary.

(3) Ultrasonic pulse velocity. This method in-volves the measurement of the time of travel ofelectronically pulsed compressional waves througha known distance in concrete. These velocities canbe used to assess the general condition and qualityof concrete, to assess the extent and severity ofcracks in concrete, and to delineate areas ofdeteriorated or poor-quality concrete. Good-quality,continuous concrete will normally produce highvelocities accompanied by good signal strengths.Poor-quality or deteriorated concrete will usuallydecrease velocity and signal strength. Concrete ofotherwise good quality, but containing cracks, mayproduce high or low velocities, depending upon thenature and number of cracks, but will almostalways diminish signal strength. This method doesnot provide a precise estimate of concrete strength.Moisture variations and the presence of reinforc-ing steel can affect the results. Skilled personnelare required in the analysis of the results.

(4) Surface tapping (chain drag). Experiencehas shown that the human ear, used in conjunc-tion with surface tapping, is the most efficient andeconomical method of determining major delami-nation in bridge decks. Chain dragging is the mostcommonly used method for this purpose. This is,however, a very subjective test in that the opera-tor must be able to differentiate between soundand unsound regions, and the results cannot beeasily quantified.

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d. Steel corrosion assessment. The most com-monly used test for assessing the current state ofreinforcing steel corrosion is the half-cell potentialtest. This test involves measurement of the electri-cal potential of an embedded reinforcing bar rela-tive to a reference half-cell placed on the concretesurface. Potential differences more negative than- 0.35 volts indicates a high degree of probabilityof active corrosion of the reinforcing steel. Poten-tial readings of - 0.20 volts and lower indicate the

e. Load tests. Occasionally it may be necessaryto examine the overall behavior of an entire bridgestructure or section of a bridge. This may beachieved electronically by measuring the responseto dynamic loading with the aid of appropriatelypositioned accelerometers or alternatively monitor-ing the performance under static test loads. Themost common method however, is to measurestrains and deflections (with precise leveling orlasers) produced from static full-scale test loads.These tests are generally expensive but yield

probability of inactive or no corrosion, while read- valuable information as to the overall “health” ofings between -0.20 and -0.35 volts indicate the a structure. This type of test can be conducted onpossibility of active corrosion. any type of bridge, regardless of the material type.

Section II. STRUCTURAL STEEL

5-6. Physical and mechanical properties

a. Strength. Steel possesses tremendous com-pressive and tensile strength and is highly resis-tant to shear forces. Thin steel sections, however,are vulnerable to compressive buckling.

(1) Light. A light, loose rust formation pittingthe paint surface.

(2) Moderate. A looser rust formation scales orflakes forming. Definite areas of rust are discern-ible.

b. Ductility. Both the low-carbon and low-alloy (3) Severe. A heavy, stratified rust or rust

steels normally used in bridge construction are scale with pitting of the metal surface. This rustquite ductile. Brittleness may occur because of condition eventually culminates in the perforationheat treatment, welding, or through metal fatigue. of the steel section itself.

c. Durability. Steel, when protected properly, isextremely durable.

b. Cracks.

d. Fire resistance. Steel is subject to a loss ofstrength when exposed to high temperatures suchas those resulting from fire.

e. Corrosion. Unprotected carbon steel corrodes(rusts) readily. However, it can readily be pro-tected.

f. Weldability. Although steel is weldable, it isnecessary to determine the chemistry of the steeland to select a suitable welding procedure beforestarting welding operations on a bridge.

g. Others. Steel is elastic and conducts heat andelectricity.

(1) Cracks in the steel may vary from hairlinethickness to sufficient width to transmit lightthrough the member. The first visible evidence isnormally a crack in the paint film. Depending onthe location and the length of time the paint hasbeen open, there may be a thin line of rust stainemanating from the crack as shown in figure 5-12.Crack identification on unpainted A588 steel isparticularly difficult. There is no staining due tooxidation and the rough surface texture tends tohide the crack.

5-7. Indicators and classification of deteriora-tion

a. Rust. Rusted steel varies in color from darkred to dark brown. Initially, rust is fine grained,but as it progresses it becomes flaky or scaly incharacter. Eventually, rust causes a pitting of themember. The inspector should note the location,characteristics, and the extent of the rusted areas.The depth of heavy pitting should be measured andthe size of any perforation caused by rusting shouldbe recorded. Rust may be classified as follows:

(2) Any type of crack is obviously serious andshould be reported at once. Record the location andlength of all cracks and indicate whether thecracks are open or closed. The full length of thecrack may not be completely visible. A suitablenondestructive test such as the dye penetrant test(discussed in the following section) can help toestablish its full length.

(3) Cracks in fracture critical steel members(which should have been identified prior to theinspection) are especially serious and thereforethese members should be inspected with extremecare. Cracks of any size should be immediatelyreported to the appropriate authority.

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Figure 5-12. Rust stained crack in steel girder.

c. Buckles and kinks. These conditions developmostly because of damage arising from thermalstrain, overload, or added load conditions. Thelatter condition is caused by failure or the yieldingof adjacent members or components. Collision dam-age may also cause buckles, kinks, and cuts (figure5-13). Look for cracks radiating from cuts ornotches. Note the members damaged, the type,location, and extent of the damage, and measurethe amount of deformation, if possible.

d. Stress concentrations. Observe the paintaround the connections at joints for fine cracks asindications of large strains due to stress concentra-tions. Be alert for sheared or deformed bolts andrivets.

e. Galvanic corrosion. This condition will appearessentially similar to rust.

Figure 5-13. Buckled flange due to collision.

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5-8. Causes of deterioration

a. Air and moisture. Air and moisture causerusting of steel, especially in a marine climate.

b. Industrial fumes. Industrial fumes in theatmosphere, particularly hydrogen sulfide, causedeterioration of steel.

c. Deicing agents. While all deicing agents at-tack steel, salt is the most commonly encounteredchemical on bridges.

d. Seawater and mud. Unprotected steel mem-bers, such as piles immersed in water and embed-ded in mud, undergo serious deterioration and lossof section.

e. Thermal strains or overloads. Where move-ment is restrained, or where members are over-stressed, the steel may yield, buckle, or crack (orrivets and bolts may shear).

f. Fatigue and stress concentrations. Cracks maydevelop because of fatigue or poor details whichproduce high stress concentrations. Examples ofsuch details are: reentrant corners, abrupt andlarge changes in plate widths and/or thicknesses, aconcentration of heavy welds, or an insufficientbearing area for a support. Fatigue and stressconcentrations are very important factors in thefailure of steel structures. A thorough discussion ofthese factors is provided in the American Associa-tion of State Highway Transportation Officials(AASHTO) Manual, “Inspection of Fracture Criti-cal Bridge Members.”

g. Fire. Extreme heat will cause serious defor-mations of steel members.

h. Collisions. Trucks, over-height loads, derailedcars, etc., may strike steel beams or columns,damaging the bridge.

i. Animal wastes. These may cause rusting andcan be considered as a special type of directchemical attack.

j. Welds. Where the flux is not neutralized,some rusting may occur. Welds may crack becauseof poor welding techniques or poor weldability ofthe steel. Problems with welds will also be dis-cussed in more detail in chapter 6.

k. Galvanic action. Other metals that are incontact with steel may cause corrosion similar torust.

5-9. Assessment of deterioration

a. As discussed in paragraph 5-9, the deteriora-tion of steel members is mainly due to rusting orcracking. The determination of section loss due torusting is of primary importance for a proper loadrating assessment to be performed. This is usuallydone with precise mechanical (such as calipers) orelectrical (such as a “depth meter”) measuringdevices. The full assessment of cracks in steelmembers is very important since they can causerapid failure to some members. All of the cracks ina member should be located and their extent ofpropagation should be fully defined. In addition toa close visual examination, a wide variety ofnondestructive test methods exists for these pur-poses and several of the most common methods arebriefly discussed:

(1) Dye penetrant. This test is used to identifythe location and extent of surface cracks andsurface defects, such as hairline fatigue cracks. Itcannot be used to locate subsurface defects. Forthe test, the area must be thoroughly cleaned ofpaint, rust, scale, grease, and oily films. Then, anoil-based liquid penetrant is applied which isintended to be absorbed into any cracks present.After a specific amount of time, the excess is

Section Ill.

5-10. Physical and mechanical properties

a. Strength. Timber, while not as strong assteel, approximates ordinary concrete in compres-sive strength. Rated strongest in flexural strength,timber has an allowable compressive strength(parallel to grain) of about 75 percent of theflexural value. Perpendicular to the grain, com-pressive strength is only 20 percent of the flexuralstrength. Horizontal shear is limited to 10 percentof the flexural strength.

TM 5-600/AFJPAM 32-1088

wiped off and a developer applied. The developeracts as a blotter, drawing out a portion of thepenetrant which has seeped into the defect, caus-ing a bright red outline of the defect to appear inthe developer.

(2) Magnetic particle testing. In this test, amagnetic field is induced in the steel by means ofa moderately sized power source. Detection of aflaw is accomplished by application of inert com-pounds of iron which are attracted to the magneticfield as it leaves and then reenters the steel in thearea of the flaw. This test requires a highlytrained inspector.

(3) Radiographic inspection. This process in-volves the application of x rays to an area orspecimen in question. The ability of the specimento dilute the density of the x rays passing throughindicates its relative homogeneity. Any discontinu-ity, such as a fatigue crack, will show up on filmplaced behind the specimen as less dense than thesound material. This test method is most benefi-cial and has been used most successfully in analyz-ing welds for incomplete fusion, slag and otherinclusions, incomplete penetration, and gas pock-ets.

b. Tensile coupons. To perform an accurate anal-ysis of the bridge’s load capacity, the materialproperties of the steel must be known. In manyolder bridges, the type of steel, and thus itsproperties, may not be known. In these cases, thecutting of “coupons” for testing may be necessary.Since this operation causes considerable damage tothe member from which the coupon is taken,extreme care must be exercised. The location forthe coupon should be carefully chosen to providethe most accurate information while causing theleast structural damage to the structure. Guidancefrom a structural engineer should be obtained. Thesamples should be 9 to 12 inches long and 2 to 3inches wide. The actual coupons will be machinedfrom these samples.

TIMBER

b. Porosity. Being a cellular, organic material,timber is quite porous.

c. Anisotropy. As may be deduced from thedifferences in allowable compressive strengths,wood is anisotropic, i.e., it has different strengthproperties depending upon the manner and direc-tion of loading.

d. Impact resistance. Since timber is able towithstand a greatly increased load momentarily,neither impact nor fatigue are serious problemswith timber.

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e. Durability. Under certain conditions, andwhen properly treated or protected, timber is quitedurable. However, timber is not a particularlydurable material under all conditions. It should benoted that some preservative treatments reducethe strength of timber.

f. Fire resistance. Timber is very vulnerable todamage by fire.

g. Other. Timber is also elastic, low in thermaland electrical conductivity, and subject to volumechanges.

5-11. Deterioration: indicators and causes

a. Fungus decay. Fungi usually require somemoisture to exist. As a rule, fungus decay can beavoided only by excellent preservative treatment.Fungus decay is classified as follows:

(1) Mild. Mild fungus decay appears as a stainor discoloration. It is hard to detect and evenharder to distinguish between decay fungi andstaining fungi.

(2) Advanced. Wood darkens further andshows signs of definite disintegration, with thesurface becoming punky, soft and spongy, stringy,or crumbly, depending upon the type of decay orfungus (figures 5-14 and 5-15). It is similar todryrot of door posts and outside porches. Fruitingbodies of fungi, similar to those seen on oldstumps, may develop. The inspector should notethe location, depth of penetration, and size of theareas of decay. Where decay occurs at a joint orsplice, the effect on the strength of the connectionshould be indicated. A knife, icepick, or an incre-ment borer can be used to test for decayed wood.

Decay is very likely to occur at connections,splices, support points, or around bolt holes. Thismay be due to the tendency of such areas to collectand retain moisture or to bolt holes or cuts beingmade in the surface after the preservative treat-ment has been applied. Unless these surfaces aresubsequently protected, decay is very likely. Anyholes, cuts, scrapes, or other breaks in the timbersurface which would break the protective layers ofthe preservative treatment and allow access tountreated wood should be noted.

b. Vermin. The following vermin tunnel in andhollow out the insides of timber members for foodand/or shelter:

(1) Termites. All damage is inside the surfacesof the wood; hence, it is not visible. White mudshelter tubes or runways extending up from theearth to the wood and on the side of masonrysubstructures are the only visible signs of infesta-tion. If the timber members exhibit signs of exces-sive sagging or crushing, check for termite damagewith an ice pick or an increment borer.

(2) Powder-post beetles. The outer surface ispoked with small holes. Often a powdery dust isdislodged from the holes. The inside may becompletely excavated.

(3) Carpenter ants. Accumulation of sawduston the ground at the base of the timber is anindicator. The large, black ants may be seen in thevicinity of the infested wood.

(4) Marine borers. The inroads of marine bor-ers will usually be most severe in the area be-tween high and low water since they are water-borne, although damage may extend to the mud

Figure 5-14. Advanced wood decay in crosstie.

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Figure 5-15. Advanced wood decay in bent cap.

line. Where piles are protected by concrete ormetal shielding, the shields should be inspectedcarefully for cracks or holes that would permitentrance of the borers. Unplugged holes such asthose left by test borings, nails, bolts, and the like,also permit entrance of these pests. In such cases,there are often no outside evidences of borerattack. The inspector should list the location andextent of damage and indicate whether it is feasi-ble to exterminate the infestation and strengthenthe member or if immediate replacement is neces-sary.

(5) Mollusk borers (shipworms). The shipwormis one of the most serious enemies of marinetimber installations. The most common species ofshipworms is the teredo. This shipworm enters thetimber in the early stage of life and remains therefor the rest of its life. Teredos reach a length of 15inches and a diameter of 3/8 inch, although somespecies of shipworm grow to a length of 6 feet. Theteredo maintains a small opening in the surface ofthe wood to obtain nourishment from the seawa-ter.

(6) Crustacean borers. The most commonly en-countered crustacean borer is the linoria or woodlouse. It bores into the surface of the wood to ashallow depth. Wave action or floating debrisbreaks down the thin shell of timber outside theborers’ burrows, causing the linoria to burrowdeeper. The continuous burrowing results in aprogressive deterioration of the timber pile cross

section which will be most noticeable by thehourglass shape developed between the tide levels.

c. Weathering and warping. This is caused byrepeated dimensional changes in the wood, usuallydue to repeated wetting. It may be described asfollows:

(1) Slight. Surfaces of wood are rough andcorrugated, and the members may even warp(figure 5-16).

(2) Advanced. Large cracks extend deeply orcompletely through the wood (figure 5-16). Woodis crumbly and obviously deteriorated.

d. Chemical attack. Chemicals act in three dif-ferent ways: a swelling and resultant weakeningof the wood, a hydrolysis of the cellulose by acids,or a delignification by alkalis. Animal wastes arealso a problem. Chemical attack will resembledecay and should be classified similarly.

e. Fire. Timber is particularly vulnerable to fire.This type of damage is easily recognized andusually will have been reported prior to the inspec-tion.

f. Abrasion and mechanical wear. Wear due toabrasion is readily recognized by the gradual lossof section at the points of wear (figure 5-16). Thistype of wear is most serious when combined withdecay which softens or weakens the wood. Thedecks of bridges are especially vulnerable. Theinspector should report the location, the generalarea subject to wear, and the loss in thickness. Heshould also indicate whether immediate remedialaction is necessary.

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Figure 5-16. Slight and advanced wear on a timber deck (mechanical abrasion wear also present).

g. Collision or overloading damage. Damage willbe evident in the form of shattered or injuredtimbers, sagging or buckled members (figure5-17), or timbers with large longitudinal cracks(figure 5-18). The inspector should give the loca-tion and extent of damage and determine whetherimmediate remedial action is required.

h. Unplugged holes. Holes left by test borings,nails, bolts, etc. will inevitably allow attack frommany of the previously mentioned sources. Theirlocation and extent should be noted and recom-mendations should be made for their repair.

5-12. Assessment of deterioration

A chipping hammer, an ice pick, and an incrementborer are the primary tools used for assessment ofwood deterioration. The soundness of all timbersshould be first checked by tapping with the ham-mer and listening for a “hollow” sound. Whensuspect areas are found, the ice pick should beused to verify the existence of soft spots. If exten-sive damage is suspected, an increment borershould be used to take a test boring and fullydefine the extent of deterioration. Borings shouldbe taken very selectively to not further weakenthe already damaged timber, and borings shouldnot be made at all if no deterioration is evidenced.Once the boring has been made, save the boringsample and make sure that creosote plugs areinserted into the hole made by the borer.

Figure 5-17. Buckled timber pile due to overload.

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Figure 5-18. Longitudinal cracks in timber beam due to overload.

Section IV. WROUGHT AND CAST IRON

5-13. General

a. Wrought iron is a metal in which slag inclu-sions are rolled between the microscopic grains ofiron. This results in a fibrous material withproperties quite similar to steel, although tensilestrength is lower than it is in steel.

b. Cast iron is iron in which carbon has beendissolved. Other elements which affect the proper-ties of cast iron are silicon and manganese. Ingeneral, a wide range of properties are obtaineddepending upon the alloying elements used.

5-14. Physical and mechanical properties

a. Wrought iron.(1) Strength. Wrought iron has an ultimate

tensile strength of about 50,000 pounds per squareinch. However, the rolling process and presence ofthe slag inclusions make wrought iron anisotropic;wrought iron has a tensile strength across thegrain of about 75 percent of its longitudinalstrength. While this characteristic has beenlargely eliminated in the wrought iron made to-day, wrought iron in the old bridge will be aniso-tropic.

(2) Elasticity. Wrought iron has an elasticmodulus of 24,000,000 to 29,000,000 pounds persquare inch. This is nearly as high as steel.

(3) Ductility. Wrought iron is generally duc-tile, although its ductility depends, to large extent,upon the method of manufacture.

(4) Toughness and impact resistance. Wroughtiron is tough and resistant to impact.

(5) Corrosion resistance. The fibrous nature ofwrought iron produces a tight rust which is lesslikely to progress to flaking and scaling than isrust on carbon steel.

(6) Weldability. Wrought iron is welded withno great difficulty. However, care should be exer-cised when planning to weld the metal of anexisting bridge.

b. Cast iron.(1) Strength. The tensile strength of cast iron

varies from 20,000 to 60,000 pounds per squareinch, depending upon its composition. In dealingwith the iron in old bridges, it must be assumedthat the cast iron will be near the lower end of thescale. The compressive strength of cast iron ishigh, from 60,000 pounds per square inch higher.For this reason, cast iron was used for compressionmembers in the early iron bridges, while wroughtiron was used for tension members.

(2) Elasticity. Cast iron has an elastic modulusof 13,000,000 pounds per square inch.

(3) Brittleness. Cast iron is brittle.(4) Impact resistance. Cast iron possesses good

impact resistant properties.(5) Corrosion resistance. Cast iron, in general,

is more corrosion resistant than the other ferrousmetals.

(6) Weldability. Due to its high carbon con-tent, cast iron is not easily welded.

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5-15. Deterioration: indicators and causes iron is subject to defects such as checks (cracking

Both wrought iron and cast iron are subject to the due to tensile cooling stresses) and blowholes. The

same causes of deterioration as structural steel latter has a serious effect on both the strength and

(previously discussed). It should be noted that cast toughness of the cast iron.

Section V. STONE MASONRY

5-16. General

Stone masonry is little used today, except asfacing or ornamentation. However, some old stonestructures are still in use. The types of stonescommonly used in bridges are granite, limestone,and sandstone, although many smaller bridges orculverts were built of stones locally available.

5-17. Physical and mechanical properties

a. Strength. Stone has more than adequatestrength for most loads.

b. Porosity. While all stone is porous, sandstoneand some limestones are much more porous thangranite.

c. Absorption. Most stone is absorptive, espe-cially limestone.

d. Thermal expansions. Stone expands and con-tracts with temperature variations.

e. Thermal conductivity. Stone is generally apoor conductor of heat.

f. Durability. Stone is more durable than mostmaterials, although there is a wide range indurability between different varieties of stone.

g. Fire resistance. While not flammable, stonecan be damaged by fire.

5-18. Indicators of deterioration

The following terms should be used to describedeterioration of stone masonry structures. Thedescription, extent, and location of the deteriora-tion should be reported.

Section VI.

5-20. General

a. While aluminum has been widely used forsigns, light standards, railings, and sign bridges, itis seldom used as the principal material in theconstruction of vehicular bridges. While most prop-erties of aluminum are similar to those of steel,the following differences exist:

(1) Lightness. Aluminum weighs about one-third (1/3) as much as steel.

(2) Strength. Aluminum, while not as strongas steel, will be made comparable to steel instrength when alloyed.

a. Weathering. The hard surface degeneratesinto small granules, giving stones a smooth,rounded look.

b. Spalling. Small pieces of rock break out orchip away.

c. Splitting. Seams or cracks open up in therocks, eventually breaking them into smallerpieces.

5-19. Causes of deterioration

a. Chemical. Gasses and solids dissolved in wa-ter often attack rocks chemically. Some of thesesolutions can dissolve cementing compounds be-tween the rocks. Oxidation and hydration of somecompounds found in rock will also damage.

b. Seasonal expansion and contraction. Repeatedvolume changes produced by seasonal expansionand contraction will cause tiny seams to develop,thereby weakening the rock.

c. Frost and freezing. Water freezing in theseams and pores of rocks can split or spa11 rock.

d. Abrasion. Abrasions are due mostly to windor waterborne particles.

e. Plant growth. Lichens and ivy will attackstone surfaces chemically in attaching themselvesto the stone. Roots and stems growing in crevicesor joints exert a wedging force.

f. Marine borers. Rock-boring mollusks attackrock by means of chemical secretions.

ALUMINUM

(3) Corrosion resistance. Aluminum is highlyresistant to atmospheric corrosion.

(4) Workability. Aluminum is easily fabri-cated. However, welding requires special proce-dures.

(5) Durability. Aluminum is durable.

5-21. Deterioration: indicators and causes

a. Cracking. Aluminum may be subject to somefatigue cracking. Aluminum members should beexamined in areas near the bases of cantileverarms and in areas near complex welded and

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riveted connection. Weld cracking often occurs on fatigue caused from wind and vibration loadings.bridge signs due to stresses caused from the b. Pitting. Aluminum will pit slightly, but thismisalignment of prefabricated sections and due to condition rarely becomes serious.

Section VII. FOUNDATION SOILS

5-22. General

a. Most foundation movements are caused bymovement of the supporting soil. For this reason,it is desirable to give a brief description of thesemovements, although the basic theory involved isbeyond the scope of this manual.

b. Soil deformations are caused by volumechanges in the soil or by a shear failure. Slopeslides and bearing failures are good examples ofshear failures. Where loads are not large enoughto cause shear failure, settlements may still occuras a result of volume change. The length of timeand magnitude of the settlements depend upon thecomposition of the soil. Granular solids, such assand, will usually undergo a relatively smallvolume change in a short period of time. However,cohesive soils such as clay can undergo largedeformations or volume changes, which may con-tinue for years. This latter process is called consol-idation and is usually confined to clays and clayeysilts.

c. Substructures that are supported directly by acohesive soil may continue to settle for a longperiod of time. Consolidation usually producesvertical settlement.

5-23. Types of movement

For convenience, foundation movements may alsobe classified into the following categories:

a. Lateral movements. Earth-retaining struc-tures, such as abutments and retaining walls, aresusceptible to lateral movements, although pierssometimes also undergo such displacements.

b. Vertical movements (settlements). Any type ofsubstructure not founded on solid rock may besubject to settlement.

c. Pile settlements. While pile settlement couldbe listed under lateral or vertical movements, it ismentioned separately since there is a tendency toconsider piles as a panacea for all foundationproblems. In addition, some of the causes of failureare peculiar to pile foundations.

d. Rotational movement (tipping). Rotationmovement of substructures can be considered tobe the result of unsymmetrical settlements orlateral movements. It will be discussed under themovement that is typical of the various substruc-tures.

5-24. Effects on structures

The effects of foundation movements upon a struc-ture will vary according to the following factors:

a. Magnitude of movements. All foundations un-dergo some settlement, even if only elastic com-pression of ledge or piles. All sizable footingsprobably will experience a minute differentialsettlement. However, very small foundation move-ments have no effect. Simple structures, and thosewith enough joints, will tolerate even moderatedifferential displacements with little difficultyother than minor cracking and the binding of enddams. Movements of large magnitudes, especiallywhen differential, cause distress in nearly allstructures (paragraph 5-25b(2)). Large movementswill cause deck joints to jam; slabs to crack;bearings to shift; substructures to crack, rotate, orslide; and superstructures to crack, buckle, andpossibly, even to collapse. The larger the settle-ment to be accommodated within a given distance,the more structural damage can be anticipated.

b. Type of settlement.(1) Uniform settlement. A uniform settlement

of all the foundations of a bridge will have littleeffect upon the structure. Settlements of nearly 1foot have been experienced by small (70-foot),single-span bridges with no sign of appreciabledistress.

(2) Differential settlement. Differential settle-ment can produce serious distress in any bridge.Where the differential settlement occurs betweendifferent substructure units, the magnitude of thedamage depends on the bridge type and spanlength. Should a differential settlement take placebeneath the footings of the same substructure,damage can vary from an opening of the verticalexpansion joints between the wing wall and theabutment to severe tipping and cracking of wallsor other members (See figures 5-19 through 5-21).Scour can cause support settlement (figure 5-22)or complete failure (figure 5-23).

c. Type of structure.(1) Simple (determinant). As mentioned, the

strength of a simple, or determinant, structureusually is not affected by movements unless theyare quite large. There are usually enough joints topermit the movements without major damage tothe basic integrity of the structure. At most, somefinger joints or bearing may require resetting, or

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Figure 5-19. Differential settlement under an abutment.

Figure 5-20. Differential settlement.

beam supports may need shimming. However, pilebent or trestle bridges are very vulnerable since a

5-20

large settlement or movement of a bent couldcause the superstructure to fall off a narrow bridgeseat, leading to the loss of the bridge spans.

(2) Indeterminant. An indeterminant bridge isseriously affected by differential movements, sincesuch movements at supports will redistribute theloads, possibly causing large overstresses. For ex-ample, a fixed-end arch could be severely damagedif a foundation rotates. Most continuous bridgeshave fewer joints than simple-span bridges. Thesebridges are very likely to be damaged if subjectedto displacements which are greater in magnitude,or different in direction, from those that wereconsidered in the original designs.

5-25. Indicators of movement

Foundation movements may often be detected byfirst looking for deviations from the proper geome-try of the bridge. With the exception of curvedstructures, haunched members, and steeply in-clined bridges, members and lines should usuallybe parallel or perpendicular to each other. Whilenot always practical, especially for bridges span-ning large bodies of water or for those located inurban industrial areas, careful observation of theoverall structure for lines that seem incongruouswith the rest of the bridge is a good starting point.For a more detailed inspection, the following meth-ods are often useful:

a. Check the alignment. Any abrupt change orkink in the alignment of the bridge may indicate alateral movement of a pier or of bearings. Olderbridges are particularly vulnerable to ice pressureswhich can cause structural misalignment.

TM 5-600/AFJPAM 32-1088

Figure 5-21. Differential pier movement causing superstructure movement.

Figure 5-22. Movement due to scour.

b. Sight along railings. A sudden dip in the railline is often the result of settlement of a pier orabutment.

c. Run profile levels along the centerline and/orthe gutter lines. This inspection technique will notonly help to establish the existence of any settle-ment but will also identify any differential settle-

ments across the roadway. Normally, this kind ofinspection technique will be employed only forlarge bridges or where information concerning theextent and character of differential settlementmovement is required.

d. Check piers, pile bents, and abutment faces forplumbness with a transit. This inspection methodprovides an excellent check for the simpler tech-niques of plumbness determination. An out-of-plumb pier in either direction usually signifiesfoundation movement; it may also indicate a su-perstructure displacement. For small bridgesand for preliminary checks, the use of a plumb bobis an adequate means for determining plumbness.

e. Observe the inclination of expansion rockers orroller movements. Rocker inclinations inconsistentwith seasonal weather conditions may be a sign offoundation or superstructure movement. Of course,this condition may also indicate that the expan-sion rockers were set improperly. Out-of-plumbhangers on cantilevered structures are anotherindication of foundation shifting.

f. Observe expansion joints at abutments andwalls. Observe the expansion joints for signs ofopening or rotating. These conditions may indicatethe movement of subsurface soils or a bearingfailure under one of the footings.

g. Check deck joints and finger dams. Abnor-mally large or small openings, elevation differen-tial, or jamming of the finger dams can be causedby substructure movements. Soil movements underthe approach fills are also frequent occurrences.

h. Observe slabs, walls, and members. Cracks,buckling, and other serious distortions should be

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Figure 5-23. Abutment failure from scour.

noted. Bracing, as well as the main supportingsections, should be scrutinized for distortion.

i. Check backwalls and beam ends. Check thebackwalls for cracking which may be caused byeither abutment rotation, sliding, or pavementthrust. Check for beam ends which are bearingagainst the backwall. This condition is a sign ofhorizontal movement of the abutment.

j. Observe fill and excavation slopes. Slidescarps, fresh sloughs, and seepage are indicationsof past or imminent soil movement.

k. Scour. See “Waterways,” section VIII of thischapter.

l. Unbalanced postconstruction embankment orfills. Embankments or fills should be checked forbalance and positioning. Unbalanced embank-ments or fills can cause a variety of soil move-ments which may impair the structural integrityof the bridge.

m. Underwater investigation of all piling andpile bents. Underwater investigation of piling andpile bents should be undertaken periodically.Check all timber piles for insect attack and deteri-oration. Examine steel piles well below the watersurface. Steel piles protected in the splash zonecan rust between the concrete jacket and themudline. Examine prestressed piles below waterfor cracking or splitting.

5-26. Causes of foundation movements

The following causes of foundation movements,except as specifically noted, can produce lateraland/or vertical movements depending on the char-acteristics of the loads or substructures:

5-22

a. Slope failure (embankment slides). These areshear failures manifested as lateral movements ofhillsides, cut slopes, or embankments. Footing orembankment loads imposing shear stresses greaterthan the soil shear strength are common causes ofslides (figure 5-24, part a).

b. Bearing failures. Bearing failures are settle-ments or rotations of footings due to a shearfailure in the soil beneath (figure 5-24, part b).When bearing or slope failures take place on anolder structure, it usually indicates a change insubsurface conditions. This may endanger the se-curity of nearby structures and foundations.

c. Consolidation. Serious settlement can resultfrom consolidation action in cohesive soils. Settle-ment of bridge foundations may be caused bychanges in the groundwater conditions, the place-ment of additional embankments near the struc-ture, or increases in the height of existing em-bankments.

d. Seepage. The flow of water from a point ofhigher head (elevation or pressure) through thesoil to a point of lower head is seepage (figure5-24, part c). Seepage develops a force which actson the soil through which the water is passing.Seepage results in lateral movement of retainingwalls by:

(1) An increase in weight (and lateral pres-sure) of the backfill because of full or partialsaturation.

(2) A reduction in resistance provided by thesoil in front of the structure.

e. Water table variations. Large cyclic variationsin the elevation of the water table in loose granu-

TM 5-600/AFJPAM 32-1088

A. SLIDE FAILURE. B. BEARING FAILURE.

C. SEEPAGE FORCES AT AN ABUTMENT.D. DRAG FORCES ON PILES.

Figure 5-24. Causes of foundation movement.

lar soils may lead to a compaction of the upperstrata. The effects of noncyclic changes in the wa-ter table such as consolidations, slides, and seepagewere previously discussed. Changes in the watertable may also change the characteristics of thesoil which supports the foundation. Changes in soilcharacteristics may, in turn, result in the lateralmovement or the settlement of the foundation.

f. Frost action. Frost heave in soil is caused bythe growth of ice lenses between the soil particles.Footings located above the frost line may sufferfrom the effects of frost heave and a loss inbearing capacity due to the subsequent softeningof the soil. The vertical elements on light trestlebents may also be lifted by frost and ice actions.

g. Expansive soils. Some clays, when wet, absorbwater and expand, placing large horizontal pres-sures on any wall retaining such soil. Structuresfounded on expansive clay may also experiencevertical soil movements (reverse settlement).

h. Ice. Ice can cause lateral movement in twoways. Where fine-grained backfill is used in re-taining structures and the water table is above thefrost line, the expansion of freezing water willexert a very large force against a wall. The piers

of river bridges are also subject to tremendouslateral loads when an ice jam occurs at the bridge.

i. Thermal forces from superstructures. On struc-tures without expansion bearings, or where theexpansion bearings fail to operate, thermal forcesmay tip the substructure units. Pavement thrust isanother force that will have the same effect.

j. Drag forces. Additional embankment loads orvery slow consolidation of a subsurface compress-ible stratum will exert vertical drag forces on thebearing piles which are driven through such mate-rial. This may cause yielding or failure of the piles(figure 5-24, part d).

k. Deterioration, insect attacks, and constructiondefects. All piles may develop weaknesses leadingto foundation settlements from one or more ofthese causes:

(1) Timber, steel, and concrete piles are sub-ject to loss of section because of decay, rusting, anddeterioration.

(2) Timber piles are vulnerable to marineborers and ship worms.

(3) Construction defects include overdrivenpiles, underdriven piles, failure to fill pile shells

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completely with concrete, or imperfect casings of acast-in-place pile. Any of these defects will producea weaker pile. Settlement will probably be gradualin improperly driven piles or in piles with weak orvoided concrete. Piles suffering severe loss of sec-tion due to rust, spalling, chemical action, orinsect infestation may fail suddenly under anunusually heavy load.

l. Scour and erosion. Scour can cause extensivesettlement and/or structural failure as previouslyshown in figures 5-22 and 5-23. Since water willcarry off particles of soil in suspension, a consider-

able hole can be formed around piers or othersimilar structural objects. This condition results ina greater turbulence of water and an increasedsize of soil particles that can be displaced. Scour isa very important consideration and will be givenconsiderable attention in section VIII of this chap-ter. Erosion of embankments due to improperdrainage (figure 5-25) can also lead to approachand abutment settlements.

m. Earth or rock embankments (stockpiles). Post-construction placement of embankments maycause instability since it will produce greater loadsthan were included in the original design.

Figure 5-25. Embankment erosion due to improper drainage. (Sheet 1 of 2)

Figure 5-25. Embankment erosion due to improper drainage. (Sheet 2 of 2)

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TM 5-600/AFJPAM 32-1088

Section VIII. WATERWAYS

5-27. General

A typical flow profile through a bridge is shown infigure 5-26. Note that the presence of a bridge(obstruction) does significantly affect the flow.Waterways should be inspected to determinewhether any condition exists that could causedamage to the bridge or to the area surroundingthe bridge. In addition to inspecting the channel’spresent condition, a record should be made ofsignificant changes that have taken place in thechannel, attributable to natural or artificialcauses. When significant changes have occurred,an investigation must be made into the probableor potential effects on the bridge structure. Eventswhich tend to produce local scour, channel degra-dation, or bank erosion are of primary importance.

5-28. Types of movement and effects onwaterways

a. Scour. Scour is defined as the removal andtransportation of material from the bed and banksof rivers and streams as a result of the erosive

A. FLOW PROFILE

B. TYPICAL PLAN VIEW

Figure 5-26. Typical flow characteristics through a bridge.

action of running water. Some general scouring(figure 5-27) takes place in all streambeds, partic-ularly at flood stage. The characteristics of thechannel influence the amount and nature of scour.Accelerated local scouring (figure 5-28) occurswhere there is an interference with the stream-flow, e.g., approach embankments extended in theriver or piers and abutments constructed on theriver bottom. The amount of scour in such casesdepends on the degree to which streamflow isdisturbed by the bridge and on the susceptibility ofriver bottom to scour action. Scour depth mayrange from zero in hard rock to 30 feet or more invery unstable river bottoms. In determining thedepth of local scour, it is necessary to differentiatebetween true scour and apparent scour. As thewater level subsides after flooding, the scour holesthat are produced tend to refill with sediment.Elevations taken of the streambed at this timewill not usually reveal true scour depth. However,since material borne and deposited by water willusually be somewhat different in character fromthe material in the substrate, it is often possible todetermine the scour depth on this basis. If, forexample, a strata of loose sand is found overlyinga hard till substrate, it is reasonable to assumethat the scour extends down to the depth of thetill. This can often be confirmed by sounding orprobing, provided the scour depth is limited to afew feet. Where coarse deposits or clays are en-countered, sounding will probably be unsuccessful.Scour problems should be remedied as soon aspossible since every flood can destroy the bridgetotally. Typical situations which tend to lead toscour problems are as follows:

(1) Sediment deposits. The construction of anupstream dam, as seen in figure 5-29, will causesediment previously carried downstream to bedeposited in the reservoir, which acts as a settlingbasin. The increased scour capability of the down-stream flow may degrade the lower channel.

(2) Pier scour. Scour around piers (figure 5-30)is greatly influenced by the shape of the pier andits skew to the direction of the flood flow. Notethat the direction of flood flow will often bedifferent from that of normal channel flow.

(3) Loose riprap. Loose riprap (figure 5-31)piled around piers to prevent local scour at thepier may cause deep scour holes to form down-stream.

(4) Lined banks. Lined banks (figure 5-32)tend to reduce scour, but such a constriction mightincrease general scour in the bridge opening,especially at an adjacent or end pier.

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SECTION A-A

Figure 5-30. Pier scour.

Figure 5-27. General scour

Figure 5-28. Localized scour.

Figure 5-31. Loose riprap.

Figure 5-29. Sediment deposits.

Figure 5-32. Lined banks.

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(5) Horizontal of vertical channel constrictions.A firm or riprapped bottom or a horizontal con-striction can cause a deep scour hole downstreamwith severe bank erosion resulting in downstreamponding as shown in figure 5-33.

(6) Flooding. During flood (figure 5-34) thewaterway constriction may produce general scour-ing in the vicinity of the bridge.

(7) Protruding abutments. Protruding abut-ments (figure 5-35) may produce local scour. Deep-est scour usually takes place at the upstreamcorner. The severity of scour increases with in-creased constriction.

(8) Debris. Collection of debris around piers(figure 5-36), in effect, enlarges the size of the pierand causes increased area and depth of scour.

(9) River bends. As seen in figure 5-37, a highscour potential exists for bridges located in thebend of the channel.

Figure 5-33. Channel constrictions.

Figure 5-34. Flooding.

Figure 5-35. Protruding abutments.

Figure 5-36. Debris problems.

Figure 5-37. Bridge in a river bend.

b. Channel of streambed degradation. Stream-bed degradation is usually due to artificial ornatural alteration in the width, alignment, orprofile of the channel, upsetting the equilibrium orregime of the channel. These alterations may takeplace at the bridge site or some distance upstreamor downstream. A channel is in regime if the rateof flow is such that it neither picks up materialfrom the bed nor deposits it. In the course of years,the channel will gradually readjust itself to thechanged condition and will tend to return to aregime condition. Streambed degradation andscour seriously endanger bridges with foundationslocated in erodible riverbed deposits and where thefoundation does not extend to a depth below thatof anticipated scour. Removal of material adjacentto the foundation may produce lateral slope insta-bility causing damage to the bridge. Concreteslope protection (figure 5-38) or riprap (figure

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5-39) is often provided to prevent bank erosion orto streamline the flow. It is particularly importantwhere flow velocities are higher or where consider-able turbulence is likely. It may also be necessarywhere there is a change in direction of the water-way. Slope cones around abutments are very sus-ceptible to erosion and are usually protected.Situations which lead to channel degradation areas follows:

(1) Channel change. Changes in the channel(figure 5-40) steepen the channel profile and in-crease flow velocity. The entire upstream reachmay degrade.

(2) Removal of material. Removal of largequantities of material (figure 5-41) (such as bydredging or gravel borrow pits) from the down-

stream channel will cause increased upstream flowvelocities and thus degradation.

(3) Removal of obstruction. A downstream ob-struction (figure 5-42) will cause the flow underthe bridge to be deep and slow. Once the obstruc-tion is removed, the flow becomes more shallowand more rapid, causing degradation.

c. Waterway adequacy. Scour and streambeddegradation are actually the result of inadequatewaterway areas (freeboard). The geometry of thechannel, the amount of debris carried during highwater periods, and the adequacy of freeboardshould be considered in determining waterwayadequacy. Where large quantities of debris and iceare expected, sufficient freeboard is of the greatestimportance.

Figure 5-38. Concrete slope protection.

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Figure 5-39. Riprap slope protection.

Figure 5-41. Material removal.

Figure 5-40. Channel change.

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Figure 5-42. Obstruction removal.

5-30

CHAPTER 6

TM 5-600/AFJPAM 32-1088

BRIDGE REDUNDANCY AND FRACTURE CRITICAL MEMBERS (FCMs)

Section I. GENERAL

6-1. Introduction

Due to the nature of their construction and theirusage within the structure, some bridge members,referred to as fracture critical members or FCMs,are more critical to the overall safety of the bridgeand, thus, are more important from the inspectionstandpoint. Although their inspection is more criti-cal than other members, the actual inspectionprocedures for FCMs are no different. Therefore,the inspection of FCMs is not addressed separatelyin this manual and has been integrated into thenormal inspection procedures discussed in thismanual. The purpose of this chapter is to intro-duce the concept of FCMs and to provide guide-lines for their identification.

6-2. Fracture critical members

The AASHTO manual, “Inspection of FractureCritical Bridge Members,” states that “Membersor member components (FCMs) are tension mem-bers or tension components of members whosefailure would be expected to result in collapse ofthe bridge.” To qualify as an FCM, the member orcomponents of the member must be in tension andthere must not be any other member or system ofmembers which will serve the functions of themember in question should it fail. The alternatesystems or members represent redundancy.

6-3. Redundancy

With respect to bridge structures, redundancymeans that should a member or element fail, theload previously carried by the failed member willbe redistributed to other members or elementswhich have capacity to temporarily carry addi-tional load, and collapse of the structure may beavoided. Redundancy in this manual is dividedinto three parts as further described:

a. Load path redundancy. Load path redundancyrefers to the number of supporting elements, usu-ally parallel, such as girders or trusses. For astructure to be nonredundant, it must have two orless load paths (i.e., load carrying members), likethe bridges in figure 6-1 which only have twobeams or girders. Failure of one girder will usu-ally result in the collapse of the span, hence thesegirders are considered to be nonredundant andfracture critical. Examples of multiple load path

structures are shown in figure 6-2. There wouldbe no FCMs in these structures.

b. Structural redundancy. Structural redun-dancy is defined as that redundancy which existsas a result of the continuity within the load path.Any statistically indeterminant structure may besaid to be redundant. For example, a continuoustwo-span bridge has structural redundancy. In theinterest of conservatism, AASHTO chooses to ne-glect structural redundancy and classify all two-girder bridges as nonredundant. The current view-point of bridge experts is to accept continuousspans as redundant except for the end spans,where the development of a fracture would causetwo hinges which might be unstable.

c. Internal redundancy. With internal redun-dancy, the failure of one element will not result inthe failure of the other elements of the member.The key difference between members which haveinternal redundancy and those which do not is thepotential for movement between the elements.Plate girders, such as the one shown in figure 3-8,which are fabricated by riveting or bolting, haveinternal redundancy because the plates and shapesare independent elements. Cracks which developin one element do not spread to other elements.Conversely, plate girders fabricated by rolling orwelding, as shown in figures 3-7 and 3-8, are notinternally redundant and once a crack starts topropagate, it may pass from piece to piece with nodistinction unless the steel has sufficient tough-ness to arrest the crack. Internal redundancy isnot ordinarily considered in determining whethera member is fracture critical but may be consid-ered as affecting the degree of criticality.

6-4. Criticality of FCMs

The guidelines discussed above should be used toidentify bridges that warrant special attention dueto the existence of fracture critical members. Oncean FCM is identified in a given structure, theinformation should become a part of the perma-nent record file on that structure. Its conditionshould be noted and documented on every subse-quent inspection. The criticality of the FCMshould also be determined to fully understand thedegree of inspection required for the member.Criticality will be best determined by an experi-

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Figure 6-1. Nonload path redundant bridges. Figure 6-2. Load path redundant bridges.

enced structural engineer and should be basedupon the following criteria:

a. Degree of redundancy. This was previouslydiscussed in Section I.

b. Live load member stress. The range of liveload stress in fracture critical members influencesthe formation of cracks. Fatigue is more likelywhen the live load stress range is a large portionof the total stress on the member.

c. Propensity for cracking or fracture. The frac-ture toughness is a measure of the material’sresistance to crack extension and can be defined asthe ability to carry load and to absorb energy inthe presence of a crack. FCMs designed since 1978by AASHTO standards are made of steel meetingminimum toughness requirements. On olderbridges, coupon tests may be used to provide thisinformation. If testing is not feasible, the age ofthe structure can be used to estimate the steeltype which will indicate a general level of steeltoughness. Welding, overheating, overstress, ormember distortion resulting from collision may

adversely affect the toughness of the steel. FCMsthat are known or suspected to have been dam-aged should receive a high priority during theinspection, and more sophisticated testing may bewarranted.

d. Condition of the FCMs. A bridge that receivesproper maintenance normally requires less time toinspect. Bridges with FCMs in poor conditionshould be inspected at more frequent intervalsthan those in good condition.

e. Fatigue prone design details. Certain designdetails have been more susceptible to fatiguecracking. Table 6-1 and figure 6-3 classify thetypes of details by category. The thoroughness of afracture critical member inspection should be inthe order of their susceptibility to fatigue crackpropagation, namely from the highest (E) to thelowest (A) alphabetical classification.

f. Previous and predicted loadings. Repeatedheavy loading is a consideration in determiningthe appropriate level of inspection. While this isnot an exact science and new bridges have devel-

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Figure 6-3. Examples of details in table 6-1.

oped fatigue cracks, the longer the bridge has beenin service with a high volume of heavy loads, thegreater the risk. When the precise number of loadsexperienced is not available, the location and the

age is normally sufficient information to enablesomeone familiar with traffic in the area to makea reasonable estimate.

Section II. EXAMPLES

6-5. Two-girder system (or single-box girder)

a. Simple spans. A two-girder framing system isshown in figure 6-1. It is composed of two longitu-dinal girders which span between piers with trans-verse floorbeams between the girders. Floorbeamssupport longitudinal stringers. The failure of onegirder may cause the span to collapse. Thesegirders may be welded or riveted plate girders or

steel boxbeams. The fracture critical elements inall of these girders are in the bottom flange andthe web adjacent to the bottom flange as shown infigure 6-4, part a.

b. Anchor-cantilever. An anchor-cantilever spanarrangement induces tension in the top flange andadjacent portion of the web in the area over thesupport as shown in figure 6-4, part b.

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Table 6-1. Classification of types of details

c. Continuous spans. Continuous spans shouldbe reviewed by a structural engineer or bridgedesigner to assess the actual redundancy andconsequent presence of FCMs. In general, thefracture critical elements will be located nearthe center of the spans in the bottom of the gird-ers and over the supports in the top of the gird-ers.

6-6. Two-truss system

a. Simple spans. Most truss bridges have onlytwo trusses. A truss may be considered a special-ized girder with most of the web removed. Sincetension members are the critical elements, thebottom chord and its connections are of primary

concern. The diagonals and verticals which are intension are also of primary concern. These mem-bers should be identified by a qualified structuralengineer.

b. Anchor-cantilever. The anchor-cantilever in atruss system is similar to that in a girder system.In the area over an interior support (pier), the topchord is in tension. In the area near the endsupports (abutments), the truss is similar to asimple-span truss and the same principles ap-ply. From the center of the anchor span to theinterior support, the stress arrangement is morecomplex and should be analyzed by a structuralengineer.

c. Continuous spans. The statements regarding

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Table 6-1. Classification of types of details-Continued

continuous girders are also true regarding continu-ous trusses. In a continuous truss, the number ofmembers in tension varies with the loading. Con-sequently, the determination of which membersare in tension and which are fracture criticalshould be made by a structural engineer.

6-7. Cross girders and pier caps

The tension portions of simply supported crossgirders and steel pier caps, as shown in figure 6-5,are nonredundant. These members usually consistof I sections or box beams. Unlike floorbeamswhich support only a portion of the deck, crossgirders and steel pier caps support the entire endreactions of two longitudinal spans.

6-8. Supports and suspended spans

a. An example of a pin and hanger is shown infigure 3-15. Pin and hanger assemblies are asredundant as the framing system in which theyare used. Hangers in a two-girder framing systemoffer no redundancy while the same assembliesused in a multibeam system have a high degree ofredundancy.

b. An alternate support to the pin and hangerassembly is shown in figure 3-14. Portions of thisdetail (the short cantilever projection from thegirder to the right) are fracture critical becausepart of it is in tension, and its failure will causecollapse unless it is used in a redundant framingsystem.

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A. POSITIVE BENDING AT MIDSPAN

B. NEGATIVE BENDING OVER PIER

Figure 6-4. Portions of a girder in tension.

Figure 6-5. Steel cross girder on concrete piers.

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TM 5-600/AFJPAM 32-1088

CHAPTER 7

INSPECTION CONSIDERATIONS

Section I. TOOLS AND EQUIPMENT

7-1. Basic

For the inspection of bridges of any kind ofmaterial and structure, the bridge inspector shouldbe equipped with at least a basic tool kit whichincludes, but is not necessarily limited to, thefollowing: field books, inspection guide, sketch pad,paper, pencil, clipboard, keel marker, inspectionmirror on a swivel head and extension arm forviewing difficult areas, camera (35 mm/Polaroid)for recording observed defects, safety belt for indi-vidual protection, tool belt, flashlight for viewingdarkened areas, pocket knife, and binoculars.

7-2. Concrete inspection

In addition to the basic tools listed above, theconcrete inspection tool kit should also consist ofthe following: 100-foot tape for measuring longcracks and large areas, 6-foot folding rule with6-inch extender having 1/32-inch marking for mea-suring crack lengths and widths, piano wire formeasuring the depth of cracks, chipping hammerfor sounding concrete and removing deterioratedconcrete, whisk broom for removing debris, scraperfor removing encrustations, wire brush for clean-ing exposed reinforcements, calipers (inside andoutside) or micrometer for measuring exposed rein-forcing bars, and a tape recorder for recordingnarratives of deteriorated conditions.

7-3. Steel inspection

In addition to the basic tools listed above, the steelinspection tool kit should also consist of the follow-ing: 100-foot tape for measuring long, deformedsections; 6-foot folding rule with 6-inch extenderfor measuring sections and offsets of deformedmembers; chipping hammer for cleaning heavilycorroded areas; scraper for removing deterioratedpaint and light corrosion; center punch for mark-ing the end of cracks; calipers-dialed (inside andoutside) or micrometer for measuring loss of sec-tion in webs, flanges, etc.; feeler gauges for mea-suring crack width; dry film paint gauge formeasuring paint film thickness; large screwdriver;heavy-duty pliers; open-end wrench; wire brush forremoving corrosion products; corrosion meter; dyepenetrate kit and wiping cloths for examiningsmall cracks; magnifying glass for viewing sus-pected areas and small cracks along welds and

around connections; shovel for removing debris;ultrasonic testing device; testing hammer forchecking connections; and a cold chisel for mark-ing reference points.

7-4. Timber inspection

In addition to the basic tools listed above, thetimber inspection tool kit should also consist of thefollowing: industrial crayon; chipping hammer fordetermining areas of unsound timber; ice pick forprying and picking to determine the extent ofunsound timber; knife for prying and picking todetermine the extent of unsound timber; pryingtool for prying around fittings to determine, tight-ness, deterioration between surfaces, and extent oftimber defects (DO NOT use a screwdriver); incre-ment borer for taking test borings to determineextent of internal damage; creosoted plugs forplugging the holes made in the timber with theincrement borer; pocket tape for measuring aroundpiles or other members; 6-foot folding rule with6-inch extender having 1/32-inch markings formeasuring deteriorated areas; scraper for cleaningincrustations off pilings; 100-foot tape for measur-ing distances from reference points; whisk broomfor removing debris; straight edge to be used as areference point from which to measure section loss;calipers (inside and outside) or micrometer formeasuring loss of section; testing hammer; and acold chisel.

7-5. Cast iron, wrought iron, and aluminuminspection

In addition to the basic tools listed above, the toolkit should also consist of the following: 100-foottape for measuring long deformed sections, 6-footfolding rule with 6-inch extender for measuringsections and offsets of deformed members, chippinghammer for cleaning heavily corroded areas,scraper for removing deteriorated paint and lightcorrosion, center punch for marking the end ofcracks, calipers (inside and outside) or micrometerfor measuring loss of section, feeler gauges formeasuring crack width, large screwdriver, heavy-duty pliers, open end wrench, pocket knife, wirebrush for removing corrosion products, corrosionmeter, dye penetrate kit and wiping cloths forexamining small cracks, magnifying glass for

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viewing suspected areas and small cracks alongwelds and around connections, and a shovel forremoving debris.

7-6. Special equipment

Other specialty items which may be required are:ladders; scaffolds (travelers or cabling); “snooper”or “cherry picker” (truck-mounted bucket on ahydraulically operated boom (or on a platformtruck)); burning, drilling, and grinding equipment;sand or shot blasting equipment; boat or barge;diving equipment (scuba or hard hat); soundingequipment (lead lines or electronic depth finders);

Section II.

7-7. General

The safety of the bridge inspector is of the utmostimportance. While the work may be hazardous, theaccident probability may be limited by proceedingcautiously. Always be careful and use good judg-ment and prudence in conducting your activitiesboth for your own safety and that of others. Thesafety rules must be practiced at all times to beeffective.

7-8. Bridge site organization

a. General. The safety of personnel and equip-ment and the efficiency of the bridge inspectionoperation depend upon proper site organization.

b. Personnel. All individuals who are assignedto work aloft should be thoroughly trained in therigging and use of their equipment, i.e., scaffolds,working platforms, ladders, and safety belts. Theplans for inspection should give first considerationto safeguarding personnel from possible injuries.

c. Equipment. Inspection equipment, highwaytraffic barricades, and signs should be arrangedaccording to the plan of inspection to accomplishas little handling, unnecessary movement, andprepositioning as possible. Vehicles not directlyinvolved in the inspection process should beparked to prevent congestion and avoid interfer-ence in the areas of inspection.

d. Orderliness. Individuals should develop or-derly habits in working and housekeeping on thejob.

7-9. Personal protectiona. It is important to dress properly. Keep cloth-

ing and shoes free of grease. The following protec-tive equipment is recommended for use at alltimes:

(1) Hard hat with a chin strap.

7-2

transit, level, or other surveying equipment; tele-vision camera for underwater use on closed circuittelevision with video tape recorder; magnetic orelectronic locator for rebars; helicopters; air jetequipment; air breathing apparatus; mechanicalventilation equipment (blowers and air pipes);preentry air test equipment (devices to test oxygencontent and to detect noxious gasses); ultrasoundequipment; radiographic equipment; magnetic par-ticle equipment; and dye penetrants. Ultrasound,radiographic, magnetic particle, dye penetrant,and other nondestructive methods are beyond thescope of the average inspection.

SAFETY

(2) Goggles, face masks, shields, or helmets,when around shot blasting, cutting, welding, etc.

(3) Reflective vests or belts when working intraffic.

(4) Life preservers or work vests when work-ing over water.

(5) Shoes with cork, rubber, or some othernonslip soles.

b. If you wear glasses, wear them when climb-ing. The wearing of bifocals is an exception to thisrule. Only regular single-lens glasses should beworn while climbing. Where work requiring close-up viewing is to be performed, a separate pair ofglasses with lenses ground for this purpose shouldbe worn.

c. Do not drink alcoholic beverages before orduring working hours. They impair judgment,reflexes, and coordination.

7-10. Special safety equipment

a. A life line or belt must be worn whenworking at heights over 20 feet, above water, orabove traffic.

b. A life-saving or safety skiff should be pro-vided when working over large rivers or harbors;the skiff should have life preservers and life lineson board.

c. Warning signals, barricades, or flagmen arenecessary when the deck is to be inspected orwhen scaffolding or platform trucks are used foraccess to the undersides or bridge seat of astructure.

7-11. Climbing of high steel

a. General. It is preferable to work from atraveler, catwalk, or platform truck, if possible.NOTE: On old ladders and catwalks, proceed withcaution.

TM 5-600/AFJPAM 32-1088

b. Scaffolding. When using scaffolding, the fol-lowing precautions should be observed:

(1) Scaffolding and working platforms shouldbe of ample strength and should be secure againstslipping or overturning.

(2) Hanging scaffolds and other light scaffoldssupported by ropes should be tested before usingby hanging them 1 foot or so from the ground andloading them with a weight at least four times asgreat as their working load.

(3) Scaffolds should be inspected at least onceeach working day.

c. Ladders. Ladders should be used as workingplatforms only when it is absolutely necessary todo so. When using ladders, the following precau-tions should be observed:

(1) Make certain that the ladder to be used issoundly constructed. If made of wood, the materialshould be straight-grained and clear.

(2) Ladders should be tested to make surethey can carry the intended loads.

(3) Ladders should be blocked at the foot ortied at the top to prevent slipping.

(4) Personnel should be cautioned frequentlyabout the danger of trying to reach too far from asingle setting of a ladder.

d. Planks or platforms. Planks or platforms maybe used where necessary. The following precau-tions should be observed:

(1) Planks should be large enough for thespan.

(2) Never use a single plank. Two planks area bare minimum; they should be attached by leads18 inches apart.

e. Safety.(1) Keep all catwalks, scaffolds, platforms,

etc., free from ice, grease, or other slippery sub-stances or materials.

(2) Catwalks, scaffolds, and platforms shouldhave hand rails and toe boards to keep tools orother objects from being kicked off and become ahazard to anyone below.

(3) Always watch where you are stepping. Donot run or jump.

(4) Do not climb if you are tired or upset.

7-12. Confined spaces

a. General. In recent years there has been anincreasing use of hollow structural members of thetubular or box-section types large enough to per-mit a man to enter the interior of the member. Inbridge work, boxes are used both in large trussbridges and in girder bridges with rectangular ortrapezoidal box sections. In these types of mem-bers, the interior is often closed off at both ends,forming a closed box. This protected interior is

high in corrosion resistance even in the bare metalstate. In some closed sections, a closable, water-tight, and vapor tight access hole is provided topermit inspection of the interior. While the boxsection offers both structural and maintenanceadvantages over other types of sections, there arecertain health hazards of which the maintenanceinspectors, and others who may be involved withthese types of sections, should be aware.

b. Hazards. No health hazard exists in confinedspace if there is proper ventilation. However, ahazardous atmosphere can develop because of alack of sufficient oxygen or because of a concentra-tion of toxic gases. Oxygen deficiency can becaused by the low oxidation of organic matterwhich can become moistened. Toxic gasses mayseep into the confined space or may be generatedby such work processes as painting, burning, orwelding. The confined space may be of such smallvolume that air contaminants are produced morequickly than the limited ventilation of the spacecan overcome. Persons should not be allowed towork in confined spaces containing less than 19percent oxygen, unless provided with air breathingapparatus. However, as noted, a space with suffi-cient oxygen content can become unfit for humanoccupancy if the work conducted therein producestoxic fumes or gases. Such space should be occu-pied by the inspector only after adequate ventila-tion.

c. Safety procedures.(1) Preentry air tests.

(a) Tests for oxygen content should be con-ducted with an approved oxygen-detecting device.A minimum of two tests should be conducted.

(b) Where the presence of other gases issuspected, tests for such gases should be conductedusing approved gas-detecting devices. The follow-ing gases should be considered: carbon dioxide,carbon monoxide, hydrogen sulfide, methane, orany combustible gas.

(c) If the oxygen content of the air in thespace is below 19 percent or if noxious gasespresent are equal or in excess of 125 percent of theThreshold Limit Values established by the Ameri-can Conference of Government Industrial Hygien-ists (reference 6), no person should be allowed toenter such space until the oxygen content and gascontent meet these specified limits for a minimumperiod of 15 minutes.

(2) Ventilation during occupancy.(a) All confined spaces should be mechani-

cally ventilated continuously during occupancyregardless of the presence of gas, the depletion ofoxygen, or the conduct of contaminant-producingwork.

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TM 5-600/AFJPAM 32-1088

(b) Where contaminant-producing operationsare to be conducted, the ventilation scheme shouldbe approved by an industrial hygiene engineer,safety engineer, marine chemist, or others quali-fied to approve such operations.

(3) Air tests during occupancy.(a) If toxic gas presence or oxygen depletion

Section Ill. DOCUMENTATION OF THE BRIDGE INSPECTION

7-13. General

The field inspection of a bridge should be con-ducted in a systematic and organized procedurethat will be efficient and minimize the possibilityof any bridge item being overlooked. Notes mustbe clear and detailed to the extent that they canbe fully interpreted at a later date when a com-plete report is made. Sketches and photographsshould be included in an effort to minimize longdescriptions.

7-14. Planning and documenting the inspec-tion

Careful planning of the inspection and selection ofappropriate record keeping formats are essentialfor a well-organized, complete, and efficient inspec-tion. During the planning phase the followingitems should be considered:

a. The inspection schedule.b. The inspection type.c. The resources required: manpower, equip-

ment, materials, and special tools and instru-ments.

d. A study of all pertinent available informationon the structure such as plans, previous inspec-tions, current inventory report, and previous re-pairs.

e. Optional documentation methods:(1) Notebook. The inspection notebook is nor-

mally used as the sole documentation on struc-tures that are complex or unique. It should beprepared prior to the inspection and formatted tobest facilitate the systematic inspection and re-cording of the bridge.

(2) Bridge inspections. For small and simplebridges, it may be more convenient to preparechecklists. Suggested items for these inspectionsare provided in appendixes B and C. Sketches canbe drawn and additional comments provided asrequired. If available, standard prepared sketchesshould be attached with the coding of all membersclearly indicated. Where sketches and narrativedescriptions cannot fully describe the deficiency ordefect, photographs should be taken and should bereferred appropriately in the narrative. Prior to

7-4

is detected or suspected, air tests similar to thepreentry air tests should be conducted duringoccupancy at 15-minute intervals.

(b) Where contaminant-producing opera-tions are conducted, air tests should be conductedto determine the adequacy of the ventilationscheme.

the inspection, it should be determined whichitems are not applicable for the bridge to beinspected.

f. Coordination of resource requirements, partic-ularly that of specialist personnel and specialequipment.

g. The inspection procedure.h. The existence of fracture critical members.

As discussed in chapter 6, these members shouldbe identified prior to the inspection so that theycan be given special attention during the inspec-tion. These members should be specifically denotedin the inspector’s notebook prior to the inspection.

7-15. Structure evaluation

a. General. A bridge is typically divided intotwo main units, the substructure and the super-structure. For convenience the deck is sometimesconsidered as a separate unit. These basic unitsmay be divided into structural members, which, inturn, may be further subdivided into elements orcomponents. The general procedure for evaluatinga structure is to assign a numerical rating to thecondition of each element or component of themain units. A suggested numerical rating systemis provided in appendix C. These ratings may becombined to obtain a numerical value for theoverall condition of a member or of a unit.

b. Explanatory aids.(1) Narrative descriptions. Descriptions of the

condition should be as clear and concise as possi-ble. Completeness, however, is essential. There-fore, narratives of moderate length will sometimesbe required to adequately describe bridge condi-tions.

(2) Photographs. Photographs can be a greatassistance. It is particularly recommended thatpictures be taken of any problem areas that cannotbe completely explained by a narrative description.It is better to take several photographs that maybe unessential than to omit one that would pre-clude misinterpretation or misunderstanding ofthe report. At least two photographs of everystructure should be taken. One of these shoulddepict the structure from the roadway while the

TM 5-600/AFJPAM 32-1088

other photo should be a view of the side elevation. (4) Recommendations. The inspector should(3) Summary. An inspection is not complete list according to urgency any repairs that are

until a narrative summary of the condition of the necessary to maintain structural integrity andstructure has been written. public safety.

Section IV. INSPECTION PROCEDURE

7-16. General

The development of a sequence for the inspectionof a bridge is important since it actually outlinesthe plan for inspection. A well constructed se-quence will provide a working guide for the inspec-tor and ensure a systematic and thorough inspec-tion.

a. Factors. Some of the factors that influencethe procedure or sequence of a bridge inspectionare:

(1) Size of the bridge.(2) Complexity of the bridge.(3) Existence of fracture critical members.(4) Traffic density.(5) Availability of special equipment.(6) Availability of specialists.

b. Thoroughness of inspection. Thoroughness isas important as the sequence of the inspection.Particular attention should be given to:

(1) Structurally important members.(2) Members most susceptible to deterioration

or damage.c. Visual inspection. Dirt and debris must be

removed to permit visual observation and precisemeasurement. Careful visual inspection should besupplemented by appropriate special devices andtechniques. If necessary, use of closed circuit tele-vision, photography, and mirrors will increasevisual access to many components.

7-17. Inspection sequence

a. Average bridges. For bridges of averagelength and complexity, it is convenient to conductthe inspection in the following sequence:

(1) Substructure units.(a) Piles.(b) Fenders.(c) Scour protection.

(d) Piers.(e) Abutments.(f) Skewbacks.(g) Anchorages.(h) Footings.

(2) Superstructure units.(a) Main supporting members.(b) Bearings.(c) Secondary members and bracing.(d) Utilities.(e) Deck, including roadway and joints.(f) End dams.(g) Sidewalks and railings.

(3) Miscellaneous.(a) Approaches.(b) Lighting.(c) Signing.(d) Electrical.(e) Barriers, gates, and other traffic control

devices.b. Large bridges. While the sequence of inspec-

tion for large bridges will generally be the same asfor smaller bridges, exceptions may occur in thefollowing situations:

(1) Hazards. Climbing and other hazardoustasks should be accomplished while the inspectoris fully alert.

(2) Weather. Wind, extreme temperatures,rain, or snow may force the postponement ofhazardous activities such as climbing, diving, orwater-borne operations.

(3) Traffic. Median barriers, decks, deckjoints, traffic control devices, and approachesshould be inspected in daylight during periods ofrelatively light traffic to ensure inspector safetyand to avoid the disruption of traffic.

(4) Inspection party size. When the inspectionparty is large, several different tasks may beperformed simultaneously by different inspectorsor groups of inspectors.

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TM 5-600/AFJPAM 32-1088

CHAPTER 8

BRIDGE COMPONENT INSPECTION

Section I. SUBSTRUCTURES

8-1. General

All bridge components are defined and discussedin chapter 3 of this manual. Bridge constructionmaterials, their characteristics, and their associ-ated deterioration problems are discussed in chap-ter 5 of this manual. This chapter presents adetailed, systematic guide to the inspection of eachbridge component. Note that especially detailedinstructions will be given for the inspection ofFCMs. The guidelines provided in chapter 5 shouldbe used as a supplement to this chapter to helprecognize, describe, and assess problems with thevarious components.

8-2. Abutments

a. Check for scour or erosion around the abut-ment and for evidence of any movement (sliding,rotation, etc.) or settlement. Open cracks betweenadjoining wing walls or in the abutment stem,off-centered bearings, or inadequate or abnormalclearances between the back wall and the endbeams are indications of probable movement(figure 8-1). If substructure cracking or movementis evidenced, a thorough subaqueous investigationor digging of test pits should be ordered to deter-mine the cause of the problems.

b. Determine whether drains and weepholes areclear and functioning properly. Seepage of waterthrough joints and cracks may indicate accumula-tion of water behind the abutment. Report anyfrozen or plugged weepholes. Mounds of earthimmediately adjacent to weepers may indicate thepresence of burrowing animals.

c. Check bearing seats for cracking and spal-ling, especially near the edges. This is particularlycritical where concrete beams bear directly on theabutment. Check bearing seats for presence ofdebris and standing water.

d. Check for deterioration concrete in areas thatare exposed to roadway drainage. This is espe-cially important in areas where deicing chemicalsare used.

e. Check backwalls for cracking and possiblemovement. Check particularly the constructionjoint between the backwall and the abutment.

f. Check stone masonry for mortar cracks, vege-tation, water seepage, loose or missing stones,weathering, and spalled or split blocks.

8-3. Retaining walls

Inspection of most retaining walls should be simi-lar to that of an abutment. Crib walls are subjectto the same types of deterioration as other struc-tures of wood, concrete, and steel:

a. Timber cribs may decay or be attacked bytermites. However, the creosote treatment is usu-ally very effective in protecting the wood.

b. Concrete cribs are subject to shipping andspalling. In addition, the locking keys or flanges atthe ends of the crib pieces are sometimes brokenoff by vandals or inadvertently damaged by casualpassersby.

c. Settlement of soil under the embankment willlead to distortion and possible damage to a cribwall. If sufficient movement occurs, the wall mayfail.

8-4. Piers and bents

a. Check for erosion or undermining of thefoundation by scour and for exposed piles (figure8-2). Check for evidence of tilt or settlement asdiscussed in section VII of chapter 5. If problems ofthis type are evidenced, a thorough subaqueousinvestigation should be ordered to determine thecause of the problems.

b. Check for disintegration of the concrete, espe-cially in the splash zone, at the waterline, at thegroundline, and wherever concrete is exposed toroadway drainage (figure 8-3).

c. Check the pier columns and the pier caps forcracks.

d. Check the bearing seats for cracking andspalling.

e. Check stone masonry piers and bents formortar cracks, water and vegetation in the cracks,and for spalled, split, loose, or missing stones.

f. Check steel piers and bents for corrosion (rust,especially at joints and splices). Bolt heads, rivetheads, and nuts are very vulnerable to rust,especially if located underwater or in the base of acolumn.

g. Examine grout pads and pedestals for cracks,spall, or deterioration.

h. Examine steel piles both in the splash zoneand below water surface.

i. Investigate any significant changes in clear-ance for pier movement.

8 - l

TM 5-600/AFJPAM 32-1088

Figure 8-1. Abutment checklist items.

Figure 8-2. Concrete pier and bent checklist items.

j. Check all pier and bent members for struc-tural damage caused by collision or overstress.

k. Observe and determine whether unusualmovement occurs in any of the bent membersduring passage of heavy loads.

l. Where rocker bents (figure 8-4) are designedto rotate freely on pins and bearings, check to seethat such movement is not restrained. Restraintcan be caused by severe corrosion or the presenceof foreign particles.

8-2

Figure 8-3. Pier cap disintegration due to roadway drainage.

TM 5-600/AFJPAM 32-1088

Figure 8-4. Steel rocker bent.

m. Determine whether any earth or rock fillshave been piled against piers causing loads notprovided for in the original design and producingunstable conditions.

n. Inspect cross girder pier caps (figure 6-5).Their failure will generally cause collapse of theunsupported span. Therefore, they are consideredFCMs and should be closely inspected as follows:

(1) Riveted.(a) Check all rivets and bolts to determine

that they are tight and that the individual compo-nents are operating as one. Check for cracked ormissing bolts, rivets, and rivet heads.

(b) Check the member for misplaced holesor repaired holes that have been filled with weldmetal. These are possible sources of fatigue crack-ing.

(c) Check the area around the floorbeamand lateral bracing connections for cracking in theweb due to out-of-plane bending.

(d) Check the entire length of the tensionflanges and web for cracking which may haveoriginated from corrosion, pitting or section loss,or defects in fabrication (e.g., nicks and gouges inthe steel).

(e) Check entire length for temporary erec-tion welds, tack welds, or welded connections notshown on the design drawings.

(2) Welded.(a) Check all tranverse groove welds for

indication of cracks, especially near backup bars.(b) Check all tranverse stiffeners and con-

nection plates at the connection to the web, partic-

ularly at floorbeams and lateral bracing whereout-of-plane bending is introduced.

(c) If longitudinal stiffeners have been used,check any butt weld splices in the longitudinalstiffeners. The web at the termination of longitudi-nal stiffeners should also be checked carefully.

(d) If cover plates are present, check care-fully at the terminus of each for cracks.

(e) Observe any area of heavy corrosion forpitting section loss or crack formation.

(f) If girders have been haunched by use ofinsert plates, observe the transverse groove weld-ing between the web and insert plate.

(g) Check longitudinal fillet welds for possi-ble poor quality or irregularities that may causecracking to initiate. This is especially importantduring the first inspection of the member so thatdefects can be recorded and properly documentedon follow-up inspections.

(h) Check for cracks at any intersectingfillet welds. If triaxial intersecting welds are foundon an FCM, they should be reported and carefullyexamined in future inspections.

(i) Check any plug welds.(j) Check bolted splices for any sign of

cracks in girders or splice plates and look formissing or cracked bolts.

(k) Check the entire length of the tensionflanges and web for cracking which may haveoriginated from corrosion, pitting or section loss,or defects in fabrication.

(l) Check entire length for temporary erec-tion, tack welds, or welded connections not shownon the design drawings.

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TM 5-600/AFJPAM 32-1088

8-5. Pile bents

a. Concrete. Check for the same items as dis-cussed in paragraph 8-4.

b. Timber.(1) Check for decay in the piles, caps, and

bracing (figure 8-5). The presence of decay may bedetermined by tapping with a hammer or by testboring the timber. Check particularly at thegroundline, or waterline, and at joints and splices,since decay usually begins in these areas.

(2) Check splices and connections for tightnessand for loose bolts.

(3) Check the condition of the cap at thosepoints where the beams bear directly upon it andat those points where the cap bears directly uponthe piles. Note particularly any splitting or crush-ing of the timber in these areas.

(4) Observe caps that are under heavy loadsfor excessive deflections.

(5) Check for rotted or damaged timbers inthe backwalls of end bents (abutments), especiallywhere such conditions would allow earth to spillupon the caps or stringers. Approach fill settle-ment at end bents may expose short sections ofpiling to additional corrosion or deterioration.

(6) In marine evironments, check structuresfor the presence of marine borers and shipworms.

(7) Check timber piles in salt water to deter-mine damage caused by marine borers.

(8) Check timber footing piles in salt waterexposed by scour below the mudline for damagecaused by marine borers.

(9) Check timber piles in salt water at checksin the wood, bolt holes, daps, or other connectionsfor damage by marine borers.

c. Steel.(1) Check the pile bents for the presence of

rust, especially at the ground level line. Use achipping hammer, if necessary, to determine theextent of the rust. Over water crossings, check thesplash zone (2 feet above high tide or mean waterlevel) and the submerged part of the piles forindications of rust.

(2) Check for debris around the pile bases.Debris will retain moisture and promote rust.

(3) Check the steel caps for rotation due toeccentric (off-center) connections.

(4) Check the bracing for broken connectionsand loose rivets or bolts.

(5) Check condition of web stiffeners.

8-6. Dolphins and fenders

a. Steel. Observe the “splash zone” carefully forsevere rusting and pitting. The splash zone is thearea from high tide to 2 feet above high tide.Where there are no tides, it is the area fromthe mean water level to 2 feet above it. Rustingis much more severe here than at midtide eleva-tions.

b. Concrete. Look for spalling and cracking ofconcrete, and rusting of reinforcing steel. Be alertfor hour-glass shaping of piles at the waterline.

c. Timber. Observe the upper portions lyingbetween the high water- and mudline for marine

Figure 8-5. Timber bent checklist items.

8-4

TM 5-600/AFJPAM 32-1088

insects and decay (figure 8-6). Check the fenderpieces exposed to collision forces for signs of wear.

d. Structural damage. Check all dolphins orfenders for cracks, buckled or broken members,and any other signs of structural failures ordamage from marine traffic.

(1) Piling and walers require particular atten-tion, since these are areas most likely to bedamaged by impact.

(2) Note any loose or broken cable whichwould tend to destroy the effectiveness of thecluster (figure 8-6). Note whether they should berewrapped.

(3) Note missing walers, blocks, and bolts.e. Protective treatment. Note any protective

treatment that needs patching or replacing. Thisincludes breaks in the surface of treated timbers,cracks in protective concrete layers, rust holes ortears in metal shields, and bare areas where epoxyor coal tar preservatives have been applied exter-nally.

f. Catwalks. Note the condition of the catwalksfor fender systems. Figure 8-6. Deteriorated timber dolphins.

Section II. SUPERSTRUCTURES

8-7. Concrete beams and girders

a. All beams.(1) Check for spalling concrete, giving special

attention to points of bearing where friction fromthermal movement and high edge pressure maycause spalling (figure 8-7).

(2) Check for diagonal cracking, especiallynear the supports. The presence of diagonal crackson the side of the beam may indicate incipientshear failure. This is particularly important on theolder prestressed bridges. Cantilever bridges,

whether of prestressed or reinforced concrete, uti-lize a shiplapped joint in which the suspendedspan rests upon bearings located on the anchorspan (figure 8-8). The shiplap cantilevers withreentrant corners are fracture critical details andshould be inspected very carefully for signs ofcracking or other deterioration.

(3) Check for flexure (vertical) cracks or disin-tegration of the concrete, especially in the area ofthe tension steel. Discoloration of the concretesurface may be an indication of concrete deteriora-tion or the corrosion of the reinforcing steel. Insevere cases, the reinforcing steel may becomeexposed.

(4) Observe areas that are exposed to roadwaydrainage for disintegrating concrete.

(5) Check for damage caused by collision orfire.

(6) Note any excessive vibration or deflectionduring passage of traffic.

b. Box girders.(1) Examine the inside of box girders for

cracks and to see that the drains are open andfunctioning properly.

(2) Check the soffit of the lower slab and theoutside face of the girders for excessive cracking.

(3) Check diaphragms for cracks.Figure 8-7. Concrete beam checklist.

8-5

TM 5-600/AFJPAM 32-1088

Figure 8-8. Shiplapped cantilever joint.

(4) Examine the underside of the slab and topflange for scaling, spalling, and cracking.

(5) Note any offset at the hinges which mightindicate problems with the hinge bearing. Anabnormal offset should be investigated further todetermine the cause and the severity of the condi-tion.

c. Prestressed concrete members.(1) Check for longitudinal cracks on all flange

surfaces. This may occur on older prestressedbridges where insufficient stirrups were provided.

(2) Examine the alignment of prestressedbeams.

(3) Check for cracking and spalling in thearea around the bearings and at the cast-in-placediaphragms where differential creep and humpingof the beams may have some ill effects.

(4) On pretensioned deck units, either box-beams or voided units, check the underside duringthe passage of traffic to see whether any unit isacting independently of the others.

8-8. Steel beams and girders

It should be remembered that steel beams andgirders may qualify as FCMs (chapter 6). Anyserious problems found in an FCM should beaddressed immediately since its failure could causetotal collapse of the bridge. Immediate closure ofthe bridge may be warranted if the defect isdeemed serious. Regardless of the member’s FCMstatus, the following items should be inspected:

a. Check members for cleanliness and freedomfrom debris, especially on the top side of thebottom flange. Unclean members should be espe-

8-6

cially suspect since this indicates lack of mainte-nance and ideal conditions for deterioration.Cleaning may be necessary to properly inspect themembers for cracks and corrosion.

b. Inspect steel for corrosion and deterioration(figure 8-9) especially at the following places:

(1) Along the upper flange.(2) Around bolts and rivet heads.(3) At gusset, diaphragm, and bracing connec-

tions.(4) At cantilever hanger and pin connections.(5) Under the deck joints and at any other

points that may be exposed to roadway drainage.(6) At any point where two plates are in

face-to-face contact and water can enter (such asbetween a cover plate and a flange).

(7) At the fitted end of stiffeners.(8) At the ends of beams where debris may

have collected.c. If rusting and deterioration are evident, check

the members to determine the extent of reducedcross-sectional area, using calipers, rulers, corro-sion meters, or section templates.

d. Check all rivets and bolts to determine thatthey are tight and that the individual componentsare operating as one. Check for cracked or missingbolts, rivets, and rivet heads.

e. Check the entire length of the tension flangesand web for cracking which may have originatedfrom corrosion, pitting or section loss, or defectsin fabrication (such as nicks and gouges in thesteel).

f. Examine welds, weld terminations, and adja-cent metal for cracks, particularly at:

TM 5-600/AFJPAM 32-1088

Figure 8-9. Steel girder checklist items.

(1) Unusual types of weld connections or con-nections to which access would have been difficultfor the welder.

(2) Field welds, especially plug welds, oftencause stress concentrations and are thus prone tofatigue cracking.

(3) Connections transmitting heavy torsionalor in-plane moments to the members. Typicalconnections of this type are:

(a) Floorbeam-to-girder connections (see fig-ure 8-10).

(b) Brackets cantilevered from the fasciabeams (or any cantilever connection from a beam).

(c) Moment splices.(d) Joints in rigid frames.

(4) Sudden changes in cross section or configu-ration or other locations subject to stress concen-trations or fatigue loadings. Several specific areasin this category are:

(a) Termination points of welded coverplates (figure 8-11).

(b) Longitudinal welds along the length ofcover plates, especially intermittent welds asshown in figure 8-12.

(c) Welds of insert plates in haunched gird-ers (figure 8-13).

(5) The potential crack locations for longitudi-nal and transverse web stiffeners are summarizedin figure 8-14. Note in figure 8-14 (sheet 3) thatthe crack is due to an improperly made butt weld.

(6) The intersection of horizontal and verticalfillet welds such as that shown in figure 8-15.

(7) Horizontal connection plates used to con-nect lateral bracing, as shown in figure 8-16.

(8) Areas where vibration and movementcould produce fatigue stress.

(9) Coped sections/reentrant corners (figure8-17).

(10) Connections of boxbeams to columns(figure 8-18).

g. Check the general alignment by sightingalong the members. Misalignment or distortionmay result from overstress, collision, or fire dam-age. If such a condition is present, its effect onstructural safety of the bridge should be fullyinvestigated.

h. Check for wrinkles, waves, cracks, or damagein the web flanges of steel beams, particularlynear points of bearing. This condition may indicateoverstressing. Check the stiffeners for straightnessand determine whether their connections are bro-ken, buckled, or pulled from the web.

i. Determine whether any unusual vibration orexcessive deflections occur under the passage ofheavy loads.

j. Check the wind locks (figure 3-14) for bind-ing, jamming, improper fit, or excessive movementbefore engaging.

k. Thoroughly check the inside of box girders forall of these problems.

l. In composite construction, stud type shearconnectors are utilized between the upper flange ofthe beam or girder and the deck slab. In this case,the underside of the top girder flange should bechecked for cracks as shown in figure 8-19. This is

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TM 5-600/AFJPAM 32-1088

SECTION A SCHEMATIC OF CRACK IN GIRDER WEB AT FLOORBEAMCONNECTION PLATES

SCHEMATIC SHOWING CRACK IN GIRDER WEE ATFLOOR BEAM CONNECTION PLATES AT SUPPORTS

A. BOTTOM OF CONNECTION PLATE. B. TOP OF CONNECTION PLATE.

Figure 8-10. Floorbeam connection plates.

only necessary in the areas spanning over piersupports; i.e., the negative moment region.

8-9. Pin and hanger connections

a. Hanger plates. These plates (figure 3-15) areas critical as the pin in a pin and hanger connec-tion. It is, however, easier to inspect since it isexposed and readily accessible; and the followingsteps are required:

(1) Try to determine whether the hanger-pinconnection is frozen, since this can induce largemoments in the hanger plates. Check both sides of

8-8

the plate for cracks due to bending of the platefrom a frozen pin connection.

(2) Observe the amount of corrosion buildupbetween the webs of the girders and the back facesof the plates.

(3) Check the hanger plate for bowing orout-of-plane movement from the webs of the gird-ers. If the plate is bowed, check carefully at thepoint of maximum bow for cracks which might beindicated by broken paint and corrosion.

(4) All welds should be checked for cracks.b. Pin. Rarely is the pin directly exposed in a

TM 5-600/AFJPAM 32-1088

ELEVATION

SQUARED SQUARED END ROUNDED SECTION A-AEND WELDED NOT WELDED CORNERS

TAPERED END SECTION A-A

NOTES: * POSSIBLE CRACK LOCATION** POSSIBLE BUT UNLIKELY

CRACK LOCATION

OVER SIZED SECTION A-ANOT END WELDED

LOOKING DOWNON BOTTOM FLANGE

Figure 8-12. Intermittent welds.

Figure 8-11. Cracks in ends of cover plates.

Figure 8-13. Insert plates in haunched girders.

pin and hanger connection, and as a result itsinspection is difficult but not impossible. By care-fully taking certain measurements, the apparentwear can be determined. If more than 1/8-inch netsection loss has occurred, it should be consideredcritical and given immediate attention. Severaltypes of pins and hangers and the manner for Figure 8-14. Attachments. (Sheet 1 of 3)

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TM 5-600/AFJPAM 32-1088

Figure 8-14. Attachments. (Sheet 2 of 3)

SCHEMATIC OF GIRDER SHOWING LONGITUDINAL STIFFENERS

IN TENSION STRESS REGION WIYH BUTT WELDED SPLICE

Figure 8-14. Attachments. (Sheet 3 of 3)

measuring wear on each are discussed in thefollowing paragraphs:

(1) Girder pin and hanger. Wear to the pinsand hangers will generally occur in two locations,at the top of the pin and top of the hanger on thecantilevered span, and the bottom of the pin andbottom of the hanger on the suspended span.Sometimes wear, loss of section, or lateral slippagemay be indicated by misalignment of the deckexpansion joints or surface over the hanger connec-tion. The following inspection procedure should beused. Figure 3-16 can be used as a referencesketch.

(a) Locate the center of the pin.

(b) Measure the distance between the centerof the pin and the end of the hanger.

(c) Compare to plan dimensions, if avail-able. Remember to allow for any tolerances, sincethe pin was not machined to fit the hole exactly.Generally, this tolerance will be 1/32 inch. If plansare not available, compare to previous measure-ments. The reduction in this length will be the“apparent wear” on the pin.

(2) Fixed pin and girder. Wear will generallybe on the top surface of the pin due to rotationfrom live load deflection and tractive forces. Thefollowing steps should be used with figure 3-16 asa reference:

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TM 5-600/AFJPAM 32-1088

Figure 8-15. Intersecting welds.

Figure 8-16. Flange and web attachments.

(a) Locate the center of the pin.(b) Measure the distance between the center

of the pin and some convenient fixed point, usuallythe bottom of the top flange.

(c) Compare this distance to the plan dimen-sions and determine the amount of section loss.

(3) Truss pin and hunger. Pin and hangerarrangements are slightly different when used intrusses. Usually the hanger plates are compactmembers similar to a vertical or diagonal. Thehanger then slips between gusset plates at boththe upper and lower chords. It is more difficult to

find a fixed reference point because the gussetplate dimensions are not usually given on designplans, but two recommended options are the inter-section of the upper or lower chord and the nearestdiagonal or the edge of the gusset plate along theaxis of the hanger. Both these points will providereadily identifiable reference points which can berecreated easily by the next inspection team. Forthis reason, measurements should be carefullydocumented along with the temperature andweather conditions. The inspection procedureshould include:

(a) Locate center of pin.

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TM 5-600/AFJPAM 32-1088

a. COPED SECTION IN FLANGES

c. CUTOUTS IN GUSSET PLATES

b. ACCEPTABLE AND UNACCEPTABLE COPES.

d. BEAM TO GIRDER CONNECTIONS.

Figure 8-17. Copes and reentrant corners.

Figure 8-18. Boxbeam to column connections.

(b) Measure to reference point to determinesection loss.

(c) Compare to plans or previous inspectionnotes.

Figure 8-19. Cracks near shear studs.

8-10. Floor systems

a. Floorbeams. See figure 8-20.(1) The end connections of floorbeams should

be checked carefully for corrosion. This is particu-larly critical on truss bridges where the endconnections are exposed to moisture and deicingchemicals from the roadway.

(2) The top flange of floorbeams should bechecked for corrosion especially near the end con-nections and at points of bearing.

(3) The floorbeams should be checked to deter-mine if they are twisted or swayed. This situationoccasionally develops as a result of the longitudi-nal forces that are exerted by moving vehicles on

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TM 5-600/AFJPAM 32-1088

Figure 8-20. Steel floorbeam checklist items.

the floorbeams. It occurs primarily on older struc-tures where the floorbeams are simply supportedand where the stringers rest upon the floorbeams.

(4) The connections on the end floorbeamsshould be examined thoroughly for cracks in thewelds and for slipped rivets or bolts.

b. Stringers.(1) Steel.

(a) Check for rust or deterioration, espe-cially around the top flange where moisture mayaccumulate from the floor above and at the endconnections around rivets, bolts, and bearings.

(b) Check for sagging or canted stringers.(c) Inspect all stringer connections for loose

fasteners and clip angles (figure 8-21). Wherestringers are seated on clip angles, check forcracks in the floorbeam web.

(2) Timber.(a) Check for crushing and decay, especially

along the top where the decking comes in contactwith the stringer and at points at which thestringer bears directly upon the abutment andbent caps.

(b) Check for horizontal cracks and split-ting, especially at the ends of stringers, wherethey are often notched.

(c) Check for sagging or canted stringers.(d) Check the bridging between the string-

ers to determine whether it is tight and function-ing properly.

(e) Check for accumulations of dirt and de-bris.

8-11. Diaphragms and cross framesa. Steel.

(1) Check for loose or broken connections be-tween the web of the beam or girder and thediaphragm (figure 8-22).

(2) Check for rust or other deterioration, espe-cially around rivets and bolts, and those portionsof the end of the diaphragms which come incontact with the bridge floor. These may be partic-

Figure 8-21. Clip angle stringer connection

Figure 8-22. Diaphragm checklist items.

ularly susceptible to corrosion from roadway mois-ture and from deicing agents.

(3) Look for buckled or twisted cross frames.This situation may be an indication of overstressof the bracing.

b. Timber.(1) Check for cracking or splitting, especially

in end diaphragms that are supporting the floor.(2) Check for decay along the top of the

diaphragms where they may come in contact withthe floor.

c. Concrete. Check for cracks, spalls, and forother forms of deterioration.

8-12. Trusses

a. Steel trusses.(1) Rust and deterioration. On through

trusses, moisture and deicing chemicals from theroadway are often splashed on the lower chordmembers and the member adjacent to the curb.The moisture and chemicals are retained at the

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connection and between the adjacent faces of eye-bars, pin plates, etc. leading to rapid deteriorationof the member. On riveted trusses, the horizontalsurfaces and connections of lower chord members(figure 8-23) are especially susceptible to corro-sion. Debris tends to accumulate causing moistureand salt to be retained. Note any deformationcaused by expanding rust on the inside surfaces oflaminated or overlapping plates.

(2) Alignment of truss members. End posts andinterior members are vulnerable to collision dam-age from passing vehicles. Buckled, torn, or mis-aligned members may severely reduce the load-carrying capacity of the truss. Misalignment canbe detected by sighting along the roadway rail orcurb and along the truss chord members. Investi-gate and report any abnormal deviation.

(3) Over-stressed members. Local buckling indi-cates overstress of a compression member. Wrin-kles or waves in the flanges, webs, or cover platesare common forms of buckling. Overstress of aductile tension member could result in localizedcontraction in the cross section area of the mem-ber. This is usually accompanied by flaking of thepaint.

(4) Loose connections. Cracks in the paint ordisplaced paint scabs around the joints and seamsof gusset plates and other riveted or bolted connec-tions may indicate looseness or slippage in thejoints. Check rivets and bolts that appear defec-tive.

(5) Pins. Inspect pins for scouring and othersigns of wear. Be sure that spacers, nuts, retaining

Figure 8-23. Lower chord of a riveted truss.

caps, and keys are in place. Refer to paragraph8-9 for a detailed inspection procedure.

(6) Noise. Note clashing of metal with thepassage of live loads.

(7) Riveted or bolted tension members.(a) Check each component to see that the

loads are being evenly distributed between themby attempting to vibrate the members by handand that batten plates are tight. If the loads arebeing unevenly distributed, one component mightbe loose or not have the right ring to it whenstruck with a hammer.

(b) Check carefully along the first row ofbolts or rivets for cracking as the first row carriesmore load than succeeding rows. The first row isthat closest to the edge of the gusset plate andperpendicular to the axis of the member.

(c) Check for nicks, gouges, and tears due toimpact from passing vehicular traffic. This type ofdamage can initiate future cracks.

(d) Observe carefully any tack welding usedeither in construction or repair since this is apotential source of cracks. Any tack welds shouldbe specially noted in the report for future observa-tion and consideration in stress rating.

(e) If any misplaced holes or holes used forreconstruction have been plug welded, check care-fully for fatigue cracks.

(8) Welded tension members.(a) Check the full length of all longitudinal

welds of each tension member for cracks.(b) Check all joints at the ends of the

members, including gussets.(c) Check all transverse welding including

internal diaphragms in box members.(d) If connections are welded at gusset

plates, carefully check these welds, particularly ifany eccentricities observable by eye are involved.

(e) As with bolted or riveted members,check carefully for nicks, gouges, and tears due toimpact damage and for any repairs made usingtack welding.

(f) Box sections or other sections weldedwith backup bars should be checked carefully fordiscontinuity in the backup bars.

(g) Portions of fracture critical tension mem-bers which are difficult to access must be checkedfor corrosion using mirrors, fiberscopes, or boro-scopes.

(h) Members should be examined carefullyfor any sites of arc strikes.

(i) Check carefully any holes that have beenfilled with weld metal since those are a source offatigue cracking.

(9) Eyebar members. Whether or not thesebars are fracture critical is dependent upon the

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TM 5-600/AFJPAM 32-1088

number of eyebars per member. During the inspec-tion process, the inspector should:

(a) Inspect carefully the area around the eyeand the shank for cracks (figure 8-24). This iswhere most failures occur in eyebars.

(b) Examine the spacers on the pins to besure they are holding the eyebars in their properposition.

(c) Examine closely spaced eyebars at thepin for corrosion buildup (pack rust). These areasdo not always receive proper maintenance due totheir inaccessibility.

(d) Evaluate weld repairs closely.(e) Check to determine if any eyebars are

loose (unequal load distribution) or if they arefrozen at the ends (no rotation).

(f) Check for any unauthorized welds andinclude their locations in the report so that theseverity of their effect on the member may beassessed.

(10) Counters.(a) Check the looped rod for cracks where

the loop is formed.(b) Observe the counters under live load for

abnormal rubbing where the counters cross, andcheck this area carefully for wear (figure 8-25).

(c) Examine the threaded rods in the area ofthe turnbuckle for corrosion and wear.

(d) Test the tension in each rod to be surethey are not over-tightened or undertightened. Therelative tension can be checked by pulling trans-

versely by hand. The inspector should not adjustthe turnbuckle but report the problem.

b. Timber trusses.(1) Check for weathering, checking, splitting,

and decay. Decay is often found at joints, caps, andaround bolts holes. Decay is also common on thebridge seat.

(2) Check for crushing at the ends of compres-sion chord and diagonal members.

(3) Examine splices carefully for decay. Notewhether bolts and connections are tight.

(4) Check for decay at joints where there arecontact surfaces, caps, where moisture can enter,and around holes through which truss bolts arefitted.

(5) Check end panel joints for decay.(6) Check for dirt or debris accumulation on

the bridge seat.(7) Investigate the roof and sides of covered

bridges for adequacy of protection afforded thestructure members from the elements of weather.

(8) Check the alignment of the truss. Saggingof the truss may be due to the partial failure ofjoints or improper adjustment of steel verticalrods.

(9) Be particularly aware of fire hazards un-der the bridge, such as:

(a) Brush or drift accumulating.(b) Storage of combustible material.(c) Parking of vehicles.(d) Signs of fires built.

Figure 8-24. Broken eyebar.

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Figure 8-25. Worn counters due to rubbing.

8-13. lateral bracing portals and sway frames

a. Check all bracing members for rust, espe-cially on horizontal surfaces such as those oflateral gusset plates and pockets without drains orwith clogged drains.

b. Check for rust around bolts and rivet heads.c . Look for loose or broken connections.d. Check all upper and lower bracing members

to observe whether they are properly adjusted andfunctioning satisfactorily.

e. Check for bent or twisted members. Sincemost of these bracing members work in compres-sion, bends or kinks could significantly reducetheir effectiveness. Since portals and sway bracesnecessarily restrict clearances, they are particu-larly vulnerable to damage from high loads.

f. Where lateral bracing is welded to girderflanges, inspect the weld and flanges for cracking.

g. Observe transverse vibration or movement ofthe structure under traffic to determine adequacyof lateral and sway bracing.

8-14. Tied arches

The stability of these types of arches is dependentupon the structural tie which is in tension. There-fore, the tie is always classified as a fracturecritical member. The tie is the box memberstretching horizontally between bearings. The ma-jority of tied arch bridges built in the last decadehave experienced some problems in the tie.

a. Riveted or bolted members. As with any FCM,the advantage of a riveted or bolted member is

8-16

that they areshould include:

(1) Observe

internally redundant. Inspection

built-up members to assure thatthe load is being evenly distributed to all compo-nents and that batten plates, lacing, and ties aretight. If members are loose or do not ring properlywhen struck with a hammer, loads may be distrib-uted unevenly.

(2) Check the bolts or rivets at all connections(hangers, floorbeams, and end reactions) for cracks.All tack welds and/or strikes should be brought tothe attention of the engineer for proper evaluation.

(3) Observe if any repairs or construction tech-niques have made use of tack welding and checkcarefully for cracks. All tack welds and/or strikesshould be brought to the attention of the engineerfor proper evaluation.

(4) Check the area around the floorbeam con-nection for cracks due to out-of-plane bending ofthe floorbeam and for cracks in rivet and boltheads due to prying action.

(5) Check for corrosion sites with potentialloss of section. This is particularly important inthe inside of box-shaped members.

b. Welded members. These members must bethoroughly inspected from the inside as well as theoutside. The key locations in the tie girder are thefloorbeam connections, the hanger connections,and the knuckle area (area at the intersection ofthe tie girder and the arch rib). The inspectionsteps should include the following:

(1) Check all welds carefully for the entirelength of the member. This applies primarily tothe corner welds where the web and flange plates

are joined. Depending on the results of the cornerweld inspection, it may be desirable to remove thebacking bars and reexamine the welds. All filletwelds inside the girder should be inspected visu-ally as accessible. Wire brushes should be used toclean the welds as necessary. The inspector shouldlook for triaxial intersecting welds, irregular weldprofiles, and possible intermittent fillet weldsalong the backup bars.

(2) Locate and inspect all the internal dia-phragms and transverse butt welds. It may benecessary to clean the welds using a power wirebrush.

(3) Check transverse connections at floorbeamwith particular care. The usual location of thecrack is near the corners, particularly if there isany gap between the floorbeam diaphragm and theweb plates. This is a good place to clean with apower wire brush and use a dye penetrant test toascertain the presence of cracks.

(4) If the box section has been welded withbackup bars in the corners, as is often the case,the backup bars should be carefully examined forany breaks or poor splices.

(5) Portions of members that are difficult toaccess must be checked for corrosion using mirror,fiberscopes, or boroscopes.

(6) Hanger connections should each receive athorough and detailed check. The purpose is tolocate cracks or local distortions and to evaluatethe extent of rusting or deterioration. These con-nections are where the support from the arch rib

TM 5-600/AFJPAM 32-1088

connects to the tie and, ordinarily, the floorbeamsat the same location.

(7) The knuckle area at the intersection of thearch tie and arch rib is extremely complicatedstructurally and physically. Considerable studymay be necessary to determine how to inspect allof the necessary locations in this area. Again, itmay be necessary to use mirrors or devices. Also,dye penetrant testing should be used in this areaif any suspicious crack-like formations are ob-served.

(8) At floorbeam connections and any splicepoints where the splices have been made withbolts, all of the bolts should be checked for tight-ness.

8-15. Metal bearings

In examining these types of bearings, determineinitially whether they are actually performing thefunctions for which they have been designed.Bearings should be carefully examined after un-usual occurrences such as heavy traffic damage,earthquakes, or batterings from debris in floodperiods. Bearings should be inspected for the fol-lowing (refer to figure 8-26):

a. Check to ensure that rockers, pins, and roll-ers are free of corrosion and debris. Excessivecorrosion may cause the bearing to “freeze” orlock and become incapable of movement. Whenmovement of expansion bearings is inhibited, tem-perature forces can reach enormous values.

b. Check rocker bearings where slots are pro-vided for anchor bolts to ensure that the bolt is notfrozen to the bearing.

Figure 8-26. Metal bearing checklist items,

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c. Check for dirt and corrosion on the bearingsurfaces of rockers and rollers and the deflectionslots around pins.

d. Determine whether the bearings are inproper alignment, in complete contact across thebearings surface, and that the bearing surfaces areclean.

e. Check barriers that require lubricants forproper functioning to ensure adequate and properlubrication.

f. In those cases where bronze sliding plates areused, look for signs of electrolytic corrosion be-tween the bronze and steel plates. This conditionis common on bridges that are located in salt-airenvironments.

g. Detection of bearing rattles under live loadconditions usually indicates that the bearings areloose. Determine the cause of this condition.

h. Check anchor bolts for looseness or missingnuts.

i. Measure the rocker tilt to the nearest 1/8-inchoffset from the reference line as shown in figure8-26. The appropriate amount of rocker tilt de-pends upon the temperature at the time of obser-vation. Most rockers are set to be vertical at 68°Ffor steel bridges. Record the temperature at thetime of inspection.

j. Measure the horizontal travel of the slidingbearings to the nearest 1/8 inch from the referencepoint. The two punch holes are aligned verticallyat the standard of temperature used (usually68°F). Record the temperature at the time ofinspection.

k. On skewed bridges, bearings and lateralshear keys should be checked to determine ifeither are binding or if they have suffered damage

from the creep effect of the bridge.

8-16. Elastomeric bearings

a. Check for splitting or tearing either verti-cally or horizontally. This is often due to inferiorquality pads (figure 8-27).

b. Check for bulging caused by excessive com-pression. This may be the result of poor materialcomposition.

c. Check for variable thickness other than thatwhich is due to the normal rotation of the bearing.

d. Note the physical condition of the bearingpads and any abnormal flattening which mayindicate overloading or excessive unevenness ofloading.

8-17. Decks

a. Concrete decks. Check for cracking, scaling,and spalling of the concrete and record the extentof the deterioration. Refer to chapter 5 for guid-ance in recognizing and describing concrete deteri-oration.

(1) Deck surface. Note the type, size, andlocation of any deck deterioration.

(2) Deck underside. Inspect the underside ofthe deck for deterioration and water leakage. Thepassage of water through the deck usually causessome leaching of the concrete which forms grayish-white deposits of calcium hydroxide in the area ofthe leak known as efflorescence (figure 8-28).Extensive water leakage may indicate segregatedor porous concrete or a general deterioration of thedeck. Areas of wet concrete are additional indica-tions of defective concrete.

(3) Wearing surface. Examine the wearing sur-face covering the concrete deck for reflection crack-

Figure 8-27. Elastomeric pad checklist items

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ing and for poor adherence to the concrete. Deteri-orated concrete beneath the wearing surface willoften be reflected through the surface in the formof map cracking. Poor adherence leads to develop-ment of potholes. If deterioration is suspected,remove a small section of the wearing surface tocheck the condition of the concrete deck.

(4) Wear. Determine whether the concrete sur-face is worn or polished. When softer limestoneaggregates are used in the concrete, fine aggre-gates and paste will be worn away, exposing the

surface of the coarse aggregates to the polishingaction of rubber tires. The resulting slippery sur-face becomes increasingly hazardous when thesurface of the limestone is wet.

(5) Stay-in-place forms. If deterioration is sus-pected, remove several panels of the forms topermit examination of the underside of the deck.Rusty forms (figure 8-29), water dripping frompinholes in the form, or the separation of portionsof the forms from the deck are reliable indicationsof deck cracking.

Figure 8-28. Efflorescence on the underside of a concrete deck.

Figure 8-29. Rusted stay-in-place forms underneath a concrete deck.

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(6) Reinforcing steel. Note whether there areany stains on the concrete which would indicatethat the reinforcing steel is rusting. Note whetherany of the reinforcing steel is exposed.

b. Timber decks.(1) Deterioration. Check for loose, broken, or

worn planks, for loose fasteners, and for presenceof decay particularly at the contact point with thestringer where moisture accumulates. Check as-phalt overlays for the presence of potholes andcracking as a result of weak areas in the deck.

(2) Traffic response. Observe the timber deckunder passing traffic for looseness or excessivedeflection of the members.

(3) Slipperiness. Timber decks are sometimesslippery, especially when wet. Observe the tractionof vehicles using the bridge for signs of thiscondition.

(4) Utilities. If utilities are supported by thebridge, note the effects on the bridge.

c. Steel decks.(1) General. Check for corrosion and cracked

welds. Maintenance of an impervious surface overa steel deck is an important safeguard againstcorrosion of the steel. Check to determine if thedeck is securely fastened. Note any broken weldsor clips. Determine if there is any loss of sectiondue to rust or wear.

(2) Slipperiness. Note whether decks are slip-pery when wet.

(3) Utilities. If utilities are supported by thebridge, note any effect on the bridge.

d. Open-grating decks.(1) Cracks. Examine the grating, support

brackets, and stringers for cracking or welds.(2) Slipperiness. Note whether decks are slip-

pery when wet. Small steel studs may be welded tothe grating to improve traction.

8-18. Expansion joints

a. Check all expansion joints for freedom ofmovement, proper clearance, and proper verticalalignment (figure 8-30). There should be sufficientroom for expansion, but the joint should not beunduly open. Closed or widely opened joints or a

bump at the back wall can result from substruc-ture movements. Joints should be cleaned, filledand sealed to prevent seepage of water into thesubgrade. This seepage causes subgrade failureand allows earth or debris to plug the joints andprevent closing in hot weather. The crowding ofabutments against the bridge ends is common andcan cause severe damage to the bridge. Properopening size depends on the season, the type ofjoint seals, the temperature range, and the amountof slab expansion that must be accommodated bythe joints. Normal temperature is usually assumedto be 65 to 70°F. Table 8-1 lists some general datafor various types of expansion joints. The expan-sion length in table 8-1 is the portion of deck orstructure expansion that must be accommodatedby the joints. This distance may extend from theend of the bridge to the nearest fixed bearing, or itmay be the sum of the distance on both sides ofthe joint. Multiplying the expansion length by thedifferential between the temperature at the partic-ular moment and 68°F and this product by0.0000065 will give the approximate change injoint opening from the values listed. Very often,construction plans will give useful data concerningthe setting of expansion devices.

Figure 8-30. Expansion joint checklist items.

Table 8-1. Expansion joint data

Joints Expansion Lengths

Steel finger dams 200-foot minimum

Steel expansion plates 200-foot maximum

Compression seals 135-foot maximum

Poured sealants and joint fillers 120-foot maximum

Joint Openings at 69°F

3 inches min.

2 inches

1 5/8 inches

1½ inches

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TM 5-600/AFJPAM 32-1088

b. Check seals for water tightness and generalconditions. Look for:

(1) Seal or sealant pulling away from theedges of the joints.

(2) Abrasion, shriveling, or other physical de-terioration of the seal.

(3) Stains and other signs of leakage under-neath the deck. Leaking seals permit water andbrine to flow onto the bridge seat and pier capcausing corrosion of the bearings, disintegration ofthe concrete, and staining. Joints not properlysealed should be cleaned and resealed.

c. Check to see that expansion joints are free ofstones and other debris. Stones lodged in the jointscan create localized stresses which may causecracking and spalling of the deck. Large amountsof debris cause jamming, thus rendering the jointsineffective.

d. Examine steel finger-type joints and slidingplate joints for evidence of loose anchorages, crack-ing or breaking of welds, or other defective details.Sometimes the fingers may be damaged by trafficor by cracks which have developed at the base ofthe fingers.

e. Verify that surfacing material has notjammed the finger joints on bridges that have beenresurfaced several times.

f. Examine specifically the underside of theexpansion joint, regardless of accessibility, to de-tect any existing or potential problem.

g. Sound the concrete deck adjacent to all ex-pansion devices for voids or laminations in thedeck.

8-19. Railings, sidewalks, and curbs

a. Railings.(1) Inspect all railings for damage caused by

collision and for weakening caused by some formof deterioration.

(2) Check concrete railings for cracking, disin-tegration, and corrosion of rebars.

(3) Check steel and aluminum railings forloose posts or rails and for rust and other deterio-ration. In particular, check the condition of theconnections of the posts to the decks, including thecondition of the anchor bolts and the deck areaaround them.

(4) Check timber railings for decay, loose con-nections, and for missing or damaged rails.

(5) Check the vertical and horizontal align-ment of all handrails for any indications of settle-ment in the substructure or any bearing defi-ciencies.

(6) Examine all handrail joints to see thatthey are open and functioning properly.

(7) Examine all handrails to see that they areof adequate height, secure, and relatively free ofslivers or any projections which would be hazard-ous to pedestrians.

(8) Check for rust stains on the concretearound the perimeter of steel rail posts which areset in pockets. Remove grout from around theposts and determine severity of corrosion if ruststains indicate such action is warranted.

(9) Note whether barrier railings on the ap-proaches to the bridge extend beyond the end ofthe bridge railing or parapet end and are anchoredto the inside face (figure 8-31). This featurereduces the severity of vehicle collision. In situa-tions where parapet ends are unprotected and noapproach rail exists, a flared, tapered approachrailing should be installed. On two-way bridges,this type of railing should be installed at bothends of the existing railings or parapet.

(10) Examine barrier railings for traffic dam-age and alignment.

(11) Check concrete barrier railings for cracks,spalls, and other deterioration.

(12) Check for corrosion in the metal portionsof barrier railings and determine whether theanchor bolts and nuts are tight.

Figure 8-31. Unprotected parapet end of a bridge.

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b. Sidewalks.(1) Check concrete sidewalks and parapets in

the same manner as the bridge decks for cracks,spalls, and other deteriorations.

(2) Examine the condition of concrete side-walks at joints, especially at the abutments, forsigns of differential movement which could openthe joint.

(3) Check steel sidewalks for corrosion and tosee that all connections are secure.

(4) Check timber sidewalks for soundness ofthe timber. Determine whether the floor planksare adequately supported.

(5) Check timber sidewalks for hazards topedestrians such as loose or missing planks, largecracks, decay or warping of the planks, protrudingnails, or other hazardous conditions.

(6) Check slickness of surfaced timber duringwet or frosty weather conditions to determinewhether any corrosive action is necessary.

(7) Check sidewalk drainage for adequatecarryoff. Examine the sidewalk surface for rough-ness or other conditions that may make walkinghazardous or difficult.

(8) Check structural integrity of sidewalkbrackets.

c. Curbs.(1) Check concrete curbs for cracks, spalls,

and other deterioration.(2) Check timber curbs for splitting, warping,

and decay.(3) Report any curbs or safety walks which

project into the roadway or a narrow shoulder ofthe roadway, since they are safety hazards.

(4) Note any loss of curb height resulting fromthe buildup of the deck surface.

(5) Examine timber wheel guards includingscupper blocks for splits, checks, and decay.

(6) Check timber wheel guards to see whetherthey are bolted securely in place.

(7) Note condition of the painting of timberwheel guards where paint is used to improvevisibility.

8-20. Approaches

a. At the joint of the bridge backwall.(1) Vertical displacement. Laying a straight

edge across the joint will record any differences inelevation across the joint not caused by the grade.If the deck is lower than the approach, or if thestraight edge indicates a rotation, then foundationsettlement or movement may have occurred, andother indications of such action should be checked.

(2) Joint width (horizontal displacement).(a) Incorrect opening. Measure the joint

width for increased or decreased openings. Eithercondition indicates foundation movement. A de-creased opening could also be caused by pavementthrust. Other parts of the bridge affected by suchoccurrences should also be investigated.

(b) Clogged joints. Where joints are cloggedor jammed with stones and hard debris, the expan-sion joints will be unable to function properly, andpavement thrust will develop. Make particularnote of this condition.

(c) Joint seal. The integrity of the jointsealant is critical to protecting the soil or portionsof the bridge under the joint, particularly thebridge seat, from water. The seal may be damagedby either weathering, traffic abrasion, or move-ment of the seal itself.

b. Other transverse joints near the bridge. Exam-ine these joints for closing or clogging, since theyare liable to the same difficulties as the backwalljoints. The inspector should note the relativemovements (if any) of the joints, any clogging withstones or other debris, and any failure, deteriora-tion, or slippage of the joint seal. The extent ofthese defects should be reported.

c. Approach slabs. Check for cracking or tippingof the approach slabs. These are indications of poorbackfill compaction (although on a skewed bridge,it would not be unusual for an acute corner tocrack).

d. Shoulders and drainage. Check the shouldersand determine whether they are maintained at thesame height as the pavement. There should beadequate provisions to carry off drainage in thecatch basins or ditches, especially if water isallowed to flow off the bridge deck (see figure8-25).

e. Approach slopes. Check the approach slopesfor adequacy and report any condition or othersurface defects that make the approach unusuallyrough or indicate approach settlement.

f. Pavement approaches. Report any potholes,severe cracks, surface unevenness, or other surfacedefects that make the approach unusually roughor indicate approach settlement.

8-21. Bridge drainageAlmost all of the drainage problems encounteredby an inspector are caused by the failure of thedrainage system to carry water away. Poor deckdrainage usually leads to deck disintegration. Thefollowing items should be checked:

8-22

TM 5-600/AFJPAM 32-1088

a. Clogging or inadequate drainage openings.Check the deck and the deck inlets for signs ofclogging or inadequate drainage openings. Thesedeficiencies will be manifested by debris on oraround the inlet after a storm. Scaling and con-crete deterioration around the inlet are additionalsigns of an inadequate inlet.

b. Water stains. Observe the bridge beams,piers, and abutments for water stains. These mayindicate leaky pipes, filled gutters, or scupperdischarge pipes that are too short. However,stained abutments and piers could also meanleaky joints.

c. Drain outlets. Check to see that deckdrainoutlets (scuppers) do not discharge water where itmay be detrimental to other members of thestructure, cause fill and bank erosion, or spill ontoa roadway below.

d. Damaged pipes. Look for pipes damaged byfreezing, corrosion, or collision. These will showcracks, holes, or stains.

e. Clogged pipes. Check pipes, if possible. Openthe cleanout at bottom of pipes to see whetherpipes are open all the way through.

f. Sand or soil accumulations. Check for layersof sand or soil on the bridge deck. Presence ofeither of these will retain moisture and brine andwill accelerate deck scaling. Soil or sand depositsare clear indications of poor deck drainage (figure8-32).

Figure 8-32. Debris accumulation on bridge deckindicating drainage problem.

Section III. MISCELLANEOUS INSPECTION ITEMS

8-22. Waterways

a. Maximum water level. Ideally, waterwaysshould be inspected during and immediately fol-lowing periods of flood, since the effects of highwater will be most apparent at these times. Sincethis is not always possible, a knowledge of theheights of past major floods from stream gaug-ing records or from other sources, together withobservations made during or immediately follow-ing high water, are helpful in determining theadequacy of the waterway opening. Other sourcesare:

(1) High water marks or ice scars left ontrees.

(2) Water marks on painted surfaces.(3) Debris wedged beneath the deck of the

bridge or on the bridge seats.(4) Information from established local resi-

dents.b. Insufficient freeboard. This is a prime charac-

teristic of inadequate waterways. In addition tothe signs mentioned previously, lateral displace-

ment of old superstructures is a prime indicationof insufficient freeboard.

c. Debris. Debris compounds the problems of ascanty freeboard. Check for debris deposits alongthe banks upstream and around the bridge.

d. Obstruction. Debris or vegetation in the wa-terways, both upstream and downstream, mayreduce the width of the waterway, contribute toscour, and even become a fire hazard. Sand andgravel bars formed in the channel may increasestream velocity and lead to scour near piers andabutments.

e. Scour.(1) Channel profile. In streambeds susceptible

to scour and degradation, a channel profile shouldbe taken periodically. Generally, 100-foot inter-vals, extending to a few hundred feet upstreamand downstream, should be sufficient. This infor-mation, when compared with past records, willoften reveal such problems as scour, shifts in thechannel, and degradation.

(2) Soundings. Soundings for scour should be

8-23

TM 5-600/AFJPAM 32-1088

taken in a radial pattern around the large riverpiers.

(3) Shore and bank protection.(a) Examine the condition and adequacy of

existing bank and shore protection.(b) Check for bank or levee for erosion

caused by improper location or skew of the bridgepiers or abutments.

(c) Note whether channel changes are im-pairing or decreasing the effectiveness of thepresent protection.

(d) Determine whether it is advisable to addmore channel protection or to revise the existingprotection.

f. High backwater. Be particularly alert for loca-tions where high fills and inadequate or debris-jammed culverts may create a very high backwa-ter. The fill acts as a dam, and with the possibilityof a washout during rainfall, a disastrous failurecould result.

g. Wave action. Observe the effect of wave ac-tion on the bridge and its approaches.

h. Existing or potential problems. Observe theareas surrounding the bridge and its approachesfor any existing or potential problems, such as icejams.

i. Spur dikes. Observe the condition and func-tioning of existing spur dikes.

8-23. Painta. Examine all paint carefully for cracking or

chipping, scaling, rust pimples, and chalking. Lookfor evidence of “alligatoring.” If the paint film hasdisintegrated, note whether the prime coat or thesurface of the metal is exposed. Note the extentand severity of the paint deterioration. If extensive“spot” painting will be required, probably theentire structure should be repainted; otherwise,spot painting will most likely be sufficient.

b. Look for paint failure on upper chord horizon-tal surfaces, or those surfaces which are mostexposed to sunlight or moisture. Give particularattention to areas around rivets and bolts, theends of beams, the seams of built-up members, theunwelded ends of stiffeners, and any other areasthat are difficult to paint or that may retainmoisture.

8-24. Signing

This section is concerned with the presence andeffectiveness of bridge signing. Since some bridgeson military installations must carry both militaryand civilian traffic, signing may be necessary forboth types of traffic. The required regulatorysigning for the bridge to be inspected should bedetermined prior to the inspection. The absence of

8-24

required signing and the condition of the existingsigns should be noted during the inspection. Forcivilian traffic, the AASHTO “Manual on UniformTraffic Control Devices” should be consulted forspecific information with regard to signing. Mili-tary signing should be inspected according to thefollowing guidelines:

a. Type of signs. When inspecting a bridge forsigning, not only should the presently posted signsbe inspected, but it should also be determinedwhether additional signs are needed because ofchanged bridge or roadway conditions. The typesof warning and regulatory signs normally requiredare:

(1) Weight limit. This is the most importantinspection item, particularly for the older anddeteriorated bridges. The weight limit should bedetermined by the bridge classification procedureoutlined in chapter 9. Depending upon the bridgetype and expected traffic, the bridge may needboth military and civilian load classifications. Typ-ical military load classification signs are shown infigure 8-33. Civilian load limit signs should be inaccordance with the local legal requirements andwith AASHTO “Manual on Uniform Traffic Con-trol Devices.”

(2) Overhead clearance. Minimum overheadclearances for military vehicles (as summarized intable 8-2) should be checked. When the overhead

a. b.

Figure 8-33. Typical military load-class signs.

Table 8-2. Minimum overhead clearances for bridges

Bridge Class Minimum Overhead Clearance

4-70 14’ 0”

71-over 15’ 6”

clearance is less than the values prescribed in thetable, the actual clearance must be indicated bythe use of a telltale sign as shown in figure 8-34.Civilian traffic bridges with clearance restrictionsshould be marked as shown in figure 8-35. Forcivilian traffic, any clearance that is less than 1foot higher than the local legal height and roadlimit should be posted with a “Low Clearance”sign. Where existing civilian signs are in placeand are sufficiently clear, additional clearancesigns (vertical or horizontal) for military vehiclesare not required.

(3) Roadway width. Bridge width limitationsoften limit the maximum class of military vehiclefor the bridge. Minimum lane widths for specificbridge classes are summarized in table 8-3 andshould be checked during the inspection. Manynew bridges are narrower than they should be. Forcivilian bridges, “Narrow Bridge” signs andstriped paddleboards (figure 8-35) should be usedwhen the bridge width is less than that of theapproach roadway. If the superstructure or parapetend extends above the curb, it should be stripedand a reflectorized hazard marker should be at-tached.

(4) Narrow underpass. Where the roadwaynarrows at an underpass or where there is a pierin the middle of the roadway, striped hazard

TM 5-600/AFJPAM 32-1088

markings should be placed on the abutment wallsand on pier edges of civilian bridges. Reflectivehazard markers should also be placed on the piersand abutments, and the approaching pavementshould be appropriately marked to warn the ap-proaching traffic of the hazard.

(5) Speed and traffic markers. These types ofsigns should be checked to ascertain whether theyare appropriate. Speed restrictions should be care-fully noted to determine whether such restrictionsare consistent with bridge and traffic conditions.Additional traffic markers may be required tofacilitate the safe and continuous flow of traffic.

b. Details of military signs.(1) Circular signs. Both military and civil

bridges should be marked with circular signs indi-cating the military load classification. They shouldhave a yellow background with black inscriptions,as large as the diameter of the sign allows. Thesesigns should be placed at both ends of the bridgein a position that is clearly visible to all oncomingtraffic. The required sizes and appearance forthese signs are summarized in figure 8-33.

(2) Rectangular signs. Additional instructionsand technical information are inscribed on rectan-gular signs. These signs should be a minimum of16 inches in height or width and have a yellowbackground upon which the appropriate letters,figures, or symbols are inscribed in black. Thesesigns, other than those indicating height restric-tions, should be placed immediately below thebridge classification signs. Height restriction signsshould be placed centrally on the overhead ob-struction.

c. Details of civilian signs.(1) Location. The weight limit sign, being

regulatory, should be located just ahead of the

Figure 8-34. Typical telltale indicating overhead clearance of bridge.

8-25

TM 5-600/AFJPAM 32-1088

Figure 8-35. Appropriate markings for clearances on civilian bridges.

Table 8-3. Minimum lane widths for bridges

BridgeClass

4-12

13-30

31-60

61-100

Minimum Width Between Curbs

One Lane Two Lane

9' 0" 18' 0"

11' 0" 18' 0"

13' 2" 24' 0"

14' 9" 27' 0"

bridge. Lateral clearance of the sign should bedetermined by the requirements of the highwaytype. On heavily traveled roads (such as freeways),side-mounted signs should be:

(a) Positioned 30 feet from the edge of thetravel way.

(b) Located behind a barrier, guardrail.(c) Affixed to a breakaway installation.

On less traveled roads, signs should preferably belocated behind a barrier guardrail or be affixedto a breakaway standard. Any sign support ofsufficient mass to be a hazard, which does notmeet the preceding criteria, should be noted andreported.

(2) Condition. It is important that all cautionsigns be in good condition. Evaluation of thecondition and adequacy of the signing will dependupon the conditions prevailing in a given area. Itis suggested that the AASHTO “Manual on Uni-form Traffic Control Devices” be consulted forspecific information with regard to signing. Signsshould be checked for:

(a) Reflectorization. Adequate reflectoriza-

8-26

tion and/or painting are required for night visibil-ity.

(b) Legibility. Note whether the legend isdifficult to read. This may be because of dirtencrustment, dulled paint, inadequate lettering, orinadequate sign size. Refer to the AASHTO“Manual on Uniform Traffic Control Devices” forguidelines as to criteria to be followed in evaluat-ing sign legibility.

(c) Vandalism. Bullet holes, paint smears,campaign stickers, etc. should be noted.

(d) Minimum sizes. In general, most warn-ing signs are diamond-shaped and measure atleast 30 by 30 inches. “Low Clearance” signs are36 by 36 inches. The “Weight Limit” signs arerectangular with minimum dimensions of 18 by 24inches.

(e) Vegetation. On minor roads, heavy vege-tation growth may obscure signs. Note the typeand location of such vegetation so that it may betrimmed or removed entirely. If relocation of thesign(s) is necessary, include such remarks in theinspection report.

(f) Sign support damage. Note whether signsupports are bent, twisted, or otherwise damaged.

8-25. Utilities

a. Check pipe, ducts, etc., for leaks, breaks,cracks, and deteriorating coverings.

b. Check the supports for signs of corrosion,damage, loose connections, and general lack ofrigidity. If utility mounts rattle during passage oftraffic, especially on steel bridges, note need forpadding.

TM 5-600/AFJPAM 32-1088

c. Check the annual space between pipe andsleeve or between the pipe and the blocked-up areafor leaks where utilities pass through abutments.

d. Check for leaky water or sewer pipes fordamage.

e. Inspect the area under water or sewer pipesfor damage.

f. Determine whether mutually hazardous trans-mittants, such as volatile fuels and electricity, aresufficiently isolated from each other. If such utili-ties are side-by-side or in the same bay, report thiscondition for auxiliary encasement or future relo-cation.

g. Check utilities that are located beneath thebridge for adequate roadway clearances.

h. Determine whether any utility obstructs thewaterway area or is positioned so that it hindersdrift removal during periods of high water.

i. Check the encasement of pipes carrying fluidsunder pressure for damage, and check vents ordrains for leaks.

j. Check for the presence of shutoff valves onpipelines carrying hazardous pressurized fluids,unless the fluid supply is controlled by automaticdevices.

k. Note whether any utility is located wherethere is a possibility that it may be struck anddamaged by traffic or by ice and debris carried byhigh water.

l. Determine whether utilities are adequatelysupported and whether they present a hazard toany traffic which may use or pass under thebridge.

m. Check for wear or deteriorated shielding andinsulation on power cables.

n. Check for adverse effect utilities may have onthe bridge, e.g., interferences with bridge mainte-nance operations or an impairing of structuralintegrity.

o. Check whether vibration or expansion move-ments are causing cracking in the support mem-bers.

p. Check supporting members of the bridge forpaint damage.

q. Note any adverse aesthetic effect utilitiesmay have on the bridge.

8-26. Lighting

a. Whitewuy lighting.(1) Collision. Note any light poles that are

dented, scraped, cracked, inclined, or otherwisedamaged.

(2) Fatigue. Aluminum light standards andcastings are most likely to suffer from fatigue.Check for cracking in:

(a) Mast arms and cast fitting on standards.

(b) At the base of standards, especially thecast elements.

(3) Corrosion. Check steel standards for rust-ing and concrete standards for cracking and spal-ling.

b. Electrical systems. This part of the inspectionshould be made by or with the assistance of aqualified electrician.

(1) Wiring. Observe any exposed wiring forsigns of faulty, worn, or damaged insulations. Noteand report the following:

(a) Bad wiring practices.(b) Bunches of excess wires.(c) Loose wires.(d) Poor wire splices.(e) Inadequate securing of groundlines.

(2) Junction boxes. Check inside junctionboxes for excessive moisture, drain hole, poor wiresplices, and loose connections. Note the conditionof wiring and insulation. Where the base of thelight standards contains a junction box, examinethis as well. Note whether the junction box, outletbox, or switch box covers are in place.

(3) Conduit. Check conduits for rust or miss-ing sections. Check the curbs and sidewalks forlarge cracks that might have fractured the conduitimbedded in them. Note whether the conduitbraces and boxes are properly secured.

(4) Whiteway current. On those structureswhere the whiteway current is carried over anopen line above the sidewalks, check for hangingobjects such as fishing lines and moss.

c. Lamps or damaged standards. Note any miss-ing or damaged standards. A cover placed over theelectric eye controller will turn on the lights. Notethe number and the locations of those lights thatdo not illuminate.

d. Sign lighting. Inspect sign lighting for thesame defect as conventional lighting.

e. Navigation lights.(1) Lights. Check to determine whether all of

the required navigation lights are present andproperly located. For fixed bridges, a green naviga-tion light is suspended from the superstructureover the channel centerline and red lights areplaced to make the channel edges. When piers aresituated at the channel edges, the red lights arepositioned on the piers or fenders. For movablespans, navigation lighting requirements vary ac-cording to the bridge type. When in doubt as tothe requirements, refer to Section 68 of the CoastGuard Pamphlet CG204, “Aids to Navigation.”

(2) Lighting devices. Check the overall condi-tion of lighting and devices to determine whetherthey are rusted, whether any of the lenses are

8-27

TM 5-600/AFJPAM 32-1088

broken or missing, and whether the lights are points of the superstructure. For longer struc-functioning correctly. tures, the red lights should be placed at 150- to

(3) Wiring. Check the condition of wiring, 600-foot intervals, while sets of at least threeconduits, and securing devices to determine flashing red beacons should be mounted atop thewhether they are loose or corroded. peaks of widely separated high points such as

f. Aerial obstruction lights. For short bridges suspension bridge towers, truss cusps, etc. Check(less than 150 feet), there should be at least two these lights for proper maintenance and function-continuous glow red lights mounted at the high ing.

Section IV. INSPECTION OF RAILROAD BRIDGES

8-27. General

a. The construction of railroad bridges is thesame as that for all of the previously discussedroadway bridges. Their construction may also befrom steel, concrete, masonry, or wood. As a result,most aspects of their inspection are the same,including inspector qualifications, frequency of in-spection, and the required thoroughness of inspec-tion.

b. Thorough inspection of the track portion ofrailroad bridges is usually conducted separatelyand by different personnel and inspection stan-dards. Therefore, track inspection is only brieflycovered in this manual. The primary emphasis forthe bridge inspector should be on the supportingbridge structure itself.

c. If, during the inspection, the inspector findsany condition that he considers serious enough topossibly result in collapse of the bridge, he shouldimmediately close the bridge and notify the properauthorities.

8-28. Railroad deck typesRailroad bridge decks are generally of two differ-ent types: open deck and ballast deck. An opendeck bridge has bolts securing the ties to stringerswhich in turn are attached to a pile bent or piercap. On a ballast deck bridge, the deck is a solidfloor with a regular ballast section placed on top ofthe floor.

8-29. Track inspection

As previously noted, a thorough track inspection isgenerally performed separately from the bridgeinspection. However, a thorough bridge inspectionshould include a minimal inspection of the tracksince track defects can adversely affect the integ-rity of the bridge structure itself. The followingitems relating to the track should be inspected asa minimum:

a. Check the alignment of the track, both verti-cally and horizontally. State whether the track islevel or on grade and if alignment is tangent orcurved. If on a curve, note how the superelevation

8-28

is provided, whether by cutoff in the bents or bytaper in the caps or in the ballast section. Note thelocation of the track with reference to the chordsfor uniformity of loading.

b. Where track appears out of line or surface,note the location, degree of misalignment, and theprobable cause.

c. Check the condition of the embankment atthe bridge ends for fullness of crown, steepness ofslopes, and depth of bulkheads. Note whether thetrack ties are fully ballasted and well bedded.

d. Record the weight and condition of the trackrails and inside guardrails. Check the condition ofany rail joints, fastenings, and tie plates.

e. Any rail anchors found on track over opendeck bridges are to be removed immediately. An-chors on open deck bridges are particularly dan-gerous because the ties form an integral part ofthe bridge structure. Should the rail start to run,the rail anchors will put longitudinal forces intothe ties which will be transferred to the remainderof the bridge structure, possibly causing structuraldamage. Where anchors are used on track ap-proaching open deck bridges, every third tieshould be box anchored (four anchors per tie) for atleast two rail lengths off each end of the bridge.Very importantly, no anchors are to be applied onthe bridge itself.

8-30. Deck inspection

a. Guardrails are installed to guide derailedequipment and prevent it from leaving the track.All bridges and their approaches should beequipped with guardrails which extend at least 50feet past the ends of the structure. The conditionof the guardrails should also be closely inspected.Look for loose or missing spikes, joint bars, trackbolts, or tie plates.

b. On ballast deck bridges, check the ballast tosee if it is clean and in full section. The ballastshould be measured from the base of the rail ateach end of bridge. The ballast section should beclean, free-draining, and free of vegetation, soil

TM 5-600/AFJPAM 32-1088

(mud), and other foreign materials. The ballastmaterials should not be at a level above the top ofthe ties.

c. Ballast deck bridges are normally equippedwith drainholes to allow water to drain from thebridge deck. Check these holes to make sure theyare open and free draining.

d. Walkways or walkboards along an open deckbridge should be maintained to allow for safewalking over the structure. Check for loose, bro-ken, deteriorated, or missing boards.

e. The ties should be inspected as follows:(1) Note the size, spacing, and uniformity of

bearing of all ties. In a ballast deck bridge, makesure all of the ties are fully ballasted and wellbedded. Bolts that secure the ties to the bridge

stringers in open deck bridges should be checkedfor deterioration and sufficient tightness. Any tiethat is not materially defective (paragraph8-30e(2)), but does not fully support both rails,should be noted and recommended for tamping upand respiking.

(2) Typical tie defects are shown in figure8-36 and a tie should be considered defective (andnoted) if it is:

(a) Broken through.(b) Split or otherwise impaired to the extent

that it will not hold spikes or other rail fasteners.(c) So deteriorated that the tie plate can

move laterally more than ½ inch relative to thecrosstie.

(d) Cut by the tie plate more than 2 inches.

Figure 6-36. Examples of good and defective cross-ties.

8-29

TM 5-600/AFJPAM 32-1088

(e) Cut by wheel flanges, dragging equip-ment, fire, etc. to a depth of more than 2 incheswithin 12 inches of the base of the rail, frog, orload-bearing area.

(f) Rotted, hollow, or generally deterioratedto a point where a substantial amount of thematerial is decayed or missing.

(3) The occurrence of consecutive defective tiesin categories 1 and/or 2 requires operating restric-tions as specified in table 8-4.

(4) All track joints should be supported by atleast one nondefective tie whose centerline iswithin 18 inches of the rail ends as shown infigure 8-37. At any location where a rail joint isnot supported by at least one nondefective tie,operations should not exceed 10 miles per hour(mph).

(5) If the existing tie spacing averages greaterthan 22 inches within the distance of a rail length,the desired spacing should be established duringthe next major maintenance cycle. For track con-structed with an average tie spacing greater than22 inches, the desired spacing should be estab-lished during the next track rehabilitation.

(6) Missing or skewed (crooked) ties are unde-sirable in track. At any location where the center-to-center tie spacing measured along either railexceeds 48 inches, operations shall not exceed 10mph until additional tie support is provided, orskewed ties should be straightened during thenext track rehabilitation.

8-31. Superstructure inspection

The inspection procedures for the superstructureportion of railroad bridges are the same as those

Table 8-4. Operating restrictions

Number ofConsecutive

Defective Ties

0 to 2

3

4

5 or more

Operating Restrictions

None

Limit maximum speed to 10 mph

Limit maximum speed to 5 mph

No operation

previously discussed for roadway bridges with thefollowing exceptions:

a. When possible, the movement of the super-structure during passage of a train should beobserved. Note excessive movements, rattles, andvibrations.

b. Observe all members to determine if any arebroken or moved out of proper position andwhether all fastening devices are functioning prop-erly.

c. Check all stringers for soundness and surfacedefects. Note their size and type and the numberused in each panel. Note if the bearing is soundand uniform, if all stringers are properly chordedand securely anchored, and if all shims and block-ing are properly installed. Note whether packersor separators are used and the condition of allchord bolts.

d. With timber trestles, fire protection is veryimportant. The following items should be in-spected:

(1) Note whether the surface of the groundaround and beneath the structure is kept clean ofgrass, weeds, drift, or other combustible material.

A T E A C H J O I N T . A T L E A S T O N E T I E W I T H I NT H I S A R E A M U S T B E N O N - D E F E C T I V E .

Figure 8-37. Required tie support at track joints.

8-30

(2) Where rust-resisting sheet metal is used asa fire protection covering for deck members, notethe condition of the metal and its fastenings.

(3) Note if any other method of fire protectionhas been used, such as fire retardant salts, exter-nal or surface protective coatings, or fire walls.Record such apparent observations as are perti-nent to the physical condition and effectiveness ofsuch protective applications.

(4) Where water barrels are provided, note thenumber, condition, if filled, and if buckets forbailing are on hand. If sand is used, note whetherbins are full and in condition to keep the sand dry.

(5) Note if timber, particularly top surfaces ofties and stringers in open deck bridges, is freefrom frayed fiber, punk wood, or numerous checks.

8-32. Substructure inspection

The inspection procedures for the substructureportion of railroad bridges are the same as thosepreviously discussed for roadway bridges with thefollowing exceptions:

a. When possible, the movement of the substruc-ture during passage of a train should be observed.Note excessive vibration, deflection, side sway, andmovement at pier supports.

b. Examine all bents and towers for plumbness,settlement, sliding and churning, and give anaccurate description of the nature and extent ofany irregularities. Note particularly whether capsand sill have full and uniform bearing on thesupports.

c. Note the number and kind of piles or posts inthe bents or towers. Note the uniformity of spacingand the location of any stubbed or spliced mem-

TM 5-600/AFJPAM 32-1088

bers, especially if the bridge is on a curve or thebent is more than 15 feet in height.

d. Check all fastening devices for physical con-dition and tightness.

8-33. Recommended practices

The inspector’s outline of repairs should be basedon the following recommended practices. Refer tochapters 11 through 13 of this manual for specificdetails for these repairs:

a. Posting of the outside piles should not bepermitted on bridges on curves where bents exceed12 feet in height or on tangents where bents areover 20 feet in height.

b. On high-speed track where traffic is heavy,not more than two posted piles in any one bentshall be permitted. If more than two piles are poor,all piles should be cut off to sound wood belowgroundline and a framed bent installed or pilesredriven.

c. All posts should be boxed, in addition to toenailing, to prevent buckling.

d. When individual caps, sills, braces, or strutshave become weakened beyond their ability toperform their intended function, renewal is theonly remedy.

e. When only an individual stringer is materi-ally deteriorated, an additional stringer may beinstalled, inside or outside of the chord, to aid theweakened member.

f. Where piles are decayed at the top they maybe cut off and double capped; a single pile may becorbelled.

g. Shimming of stringer to provide proper sur-face and cross level should be done with a singleshim under each chord. If possible, avoid multipleshimming.

Section V. BOX CULVERTS

8-34. Types of distress

A culvert is generally used where its constructionwould permit a fill to substitute for a bridgewithout any loss of vital waterway area. Thiscombination of high earth loads, long pipe-likestructures, and running water tends to produce thefollowing types of distress:

a. The basic causes and actions of foundationmovements are discussed in chapter 5. Here, theyneed only be listed:

(1) Settlement of the box. This may be eithera smooth sag, or it may be differential settlementat the expansion joints.

(2) Tipping of wing walls.(3) Lateral movements of sections of the box.

b. High embankments may impose very heavyloads on the top and bottom slabs. These earthpressures can cause either shear or flexural fail-ures in the top slabs.

c. Construction defects can lead to structuraldistress.

d. Undermining is a form of scour attack on theupstream and downstream ends of box culverts.When sheeting or a concrete cut-off wall is notprovided or is not deep enough, the stream maywash away the soil under the ends of the floorslab, the apron, or the wing wall footings, leadingto settlements and culvert cracking.

e. Plugging may result from debris collectingover the mouth of the culvert. This can cause

8-31

TM 5-600/AFJPAM 32-1088

flooding and flotation and displacement of part, orall, of the box.

f. Water leaving the box at high velocities maycause downstream scour at the streambed.

8-35. Inspection

a. Check for sag of the culvert floor. In times oflight flow, this may be noted by location ofsediment. Where there are several feet of water inthe box, a profile of the crown may be taken.

b. Check for sag in the profile of the roadwayoverhead.

c. Check for vertical differential settlement atthe expansion joints.

d. Check for transverse and longitudinal differ-ential settlements at the expansion joints.

e. Check for widely opened expansion joints.Water may be seeping through joints from soiloutside.

f. Check for canted wingwalls. This conditionmay be due to settlement, slides, or scour.

g. Check for slide failures in the fill around the

box. Such slides are likely to affect the box aswell.

h. Check for cracks and spalls in the top slab.Longitudinal cracks indicate shear or flexure prob-lems; transverse cracks indicate differential settle-ment. Cracks in the sides may be from settlementor from extremely high earth pressures. Note thesize, length, and location of the crack. Look forexposed or rusty rebars.

i. Where there is no bottom slab, look for under-mining of side footings.

j. Check for undermining at the ends of the boxand under the wings.

k. Examine the inside of the box for largecracks and debris. This may indicate the need fora debris rack. Check the inlet end of the culvertfor debris. Note whether vegetation is obstructingthe ends of the culvert.

l. If the culvert floor is visible, check it forabrasion and wear.

m. Note any other signs of deterioration of theconcrete box, especially those which suggest designerror or construction omissions.

8-32

TM 5-600/AFJPAM 32-1088

CHAPTER 9

FINAL DOCUMENTATION

9-1. Annual (Army) and biannual (Air Force)inspection documentation

The results from these inspections are used to planand coordinate preventative maintenance opera-tions on the bridges. The inspection documentationshould include, but not be limited to the following:

a. Jobsite inspection documentation. This docu-mentation will generally be the bridge inspectionnotebook as discussed in chapter 7 or a copy of thesuggested format as shown in appendix B.

b. Photographs and sketches. Photographs orsketches of problem areas and of item requiringmaintenance should be included in the report.

c. Cost estimation. Cost estimation for each re-paired item should be provided so that installationengineers and maintenance personnel are able touse it for their maintenance and budget planning.

d. Remarks and recommendations. A brief sum-mary of the inspection findings should be made bythe inspector. Problem areas, those requiring im-mediate attention, and those requiring additionalattention from a structural engineer should bepointed out in this section.

9-2. Triennial (Army) and every third biannual(Air Force) bridge inspection documentation

The results from these inspections are used both toplan and coordinate preventative maintenance op-erations on the bridges and to insure their overallsafety. The documentation should generally beprepared by a qualified engineer who participatedin the inspection. The inspection documentationshould include, but not be limited to the following:

a. Paragraph 1: Introduction and Background.This paragraph must contain all the pertinentinformation for an inspection of a bridge:

(1) The official request for conducting an in-spection.

(2) Individual conducting the inspection(name, position, and qualifications).

(3) Criteria for an inspection (references anddocumentation).

b. Paragraph 2: Load Classification Summary.Load classification should be performed by a quali-tied engineer.

c. Paragraph 3: Bridge Repair Cost Summary.The bridge repair costs in this paragraph are forthe recommended maintenance and repairs whichshould be accomplished over the next 2 years. Theestimated costs are based on the cost of materialsand labor required to complete the job.

d. Paragraph 4: Bridge Data. This paragraphshould provide the following information:

(1) Bridge data. Provide as follows:(a) Installation.(b) Bridge number. The official number as-

signed to bridge.(c) Date of inspection.(d) Inspected by.(e) Location. Usually described by route

number, county and log mile.(f) Design load. The live loading for which

the bridge was designed will be stated if it isknown. A structure widened or otherwise alteredso that different portions have different live loaddesigns is to have each live load specified.

(g) Military load classification.(h) Date built.(i) Traffic lanes. State the number of traffic

lanes.(j) Transverse section. Include items noted

b e l o w . ” (k) Roadway width. This shall be the mini-

mum clear width between curbs, railings, or otherrestrictions. On divided roadways, such as is foundon freeways under overcrossings, the roadwaywidth will be taken as the traveled way betweenshoulders, but the shoulders and median widthwill also be given.

(l) Sidewalks. If only one is present, the sideshall be noted thus: “1 @ 5.0’ (east).” Measure-ment is recorded to the nearest one-tenth of 1 foot.Sidewalks on both sides are noted thus: “2 @5.0’.” If there are no sidewalks, note “None.”

(m) Clearances. A clearance diagram shouldbe made for each structure which restricts thevertical clearance over the highway, such as over-crossings, underpasses, and through truss bridges.The minimum number of vertical measurementsshown on the diagram will be at each edge of thetraveled way and the minimum vertical clearancewithin the traveled way. The report will state theminimum roadway clearance. This will includeeach roadway on a divided highway. When astructure is of a deck or point truss type so that novertical obstruction is present, the vertical clear-ance shall be noted on the report as “unimpaired.”Vertical measurements are to be made in feet andinches and any fraction of an inch will be droppedback to the nearest inch, i.e., a field measurementof 15 feet, 7 3/4 inches will be recorded as 15 feet,7 inches. Horizonal measurements are to be re-

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TM 5-600/AFJPAM 32-1088

corded to the nearest one-tenth of 1 foot.(n) Total length. This shall be the overall

length to the nearest foot and shall be the lengthof roadway which is supported on the bridgestructure. This will normally be the length frompaving notch or between back faces of backwallsmeasured along centerline.

(o) Spans. The number of spans shall belisted in the same direction as the log mile. Spanscrossing state highways will be normally listedfrom left to right looking ahead on route. Spansare noted as follows: e.g., “1 @ 24.0”’ or “3 @45.0”’ or “1 @ 36.0’, 5 @ 50.0’, 1 @ 36.0’, 27.0’,12.0’.” Span lengths shall be recorded to thenearest one-tenth of 1 foot and it shall be notedwhether the measurement is center to center (c/c>or clear open distance (clr) between piers, bents, orabutments. Measurements shall be along center-line.

(p) Skew. The skew angle is the angle be-tween the centerline of a pier and a line normal tothe roadway centerline. Normally, the skew anglewill be taken from the plans, and it is to berecorded to the nearest degree. If no plans areavailable, the angle is to be estimated. If the skewangle is 0 feet, it should be so stated.

(q) Plans available. State what plans areavailable, where they are filed, and if they are “asbuilt.”

(r) Inspection records. Record the year in-spected, inspector, and qualification. Under de-scription, briefly give all pertinent data concerningthe type of structure. The type of superstructurewill generally be given first followed by the type ofpiers and type of abutments along with theirfoundation. If the bridge is on piles, the type ofpiles should be stated. If data are available,indicate type of soil upon which footings arefounded, maximum bearing pressures, and pilecapacities.

(2) Bridge component rating. Each componentof the bridge should be numerically rated. Asuggested format and rating system are providedin appendix C.

(3) Recommendations and repair costs. The

final portion of appendix C provides a space forrecommendations regarding deficient bridge com-ponents.

(4) Sketches.(a) Overall sketch. The first sketch schemat-

ically portrays the general layout of the bridge,illustrating the structure plan and elevation data.The immediate area, the stream or terrain obsta-cle layout, major utilities, and any other pertinentdetails should also be included.

(b) Bridge component sketches. These arenecessary for a component condition rating of “6”or “7” (refer to appendix C).

(c) Substructures. Sketches or drawings ofeach substructure unit should be included. Inmany cases it will be sufficient to draw typicalunits which identify the principal elements of thesubstructure. Each of the elements of a substruc-ture unit should be numbered so that they can becross referenced to the information appearing onthe data page on the left-hand side of the sketch.Items to be numbered include piling, footings,vertical supports, lateral bracing of members andcaps.

(d) Special sketches. Additional sketchesmay have to be prepared of critical areas of certainbridges.

(5) Photos. At least two photographs of eachbridge, one showing a roadway view and oneshowing a side elevation view, should be provided.Other photos necessary to show major defects orother important special features also may be in-cluded. A photo showing utilities on the structureis desirable. All signs of distress, failure, or defectsworthy of mention, as well as description of condi-tion and appraisal, should be noted with sufficientaccuracy so that another inspector at a future datecan easily make a comparison of condition or rateof disintegration. Photographs and sketches shouldbe used freely as needed to illustrate and clarifyconditions of structural elements. Good photos andpictures are very helpful at future investigationsin determining progression of defects and to helpdetermine changes and their magnitude. All rec-ommendations and directions for correspondingrepair and maintenance should be included.

9-2

CHAPTER 10

TM 5-600/AFJPAM 32-1088

GENERAL PREVENTIVE MAINTENANCE, REPAIR, AND UPGRADE

Section I. INTRODUCTION

10-1. General 10-3. Replacement

With the cost of constructing and replacing bridgesescalating every day, it is imperative that wemake the most out of our existing bridges. Theformula for doing this is: properly maintainingeach bridge to extend its service life, immediatelyrepairing any structural damage or deteriorationof the bridge to prevent increased damage ordeterioration, and upgrading the load capacity ofthe structure to meet the future increased trafficrequirements. The specific categories of bridgemaintenance, repair, and upgrade are discussed inthe following paragraphs.

The replacement of bridge member components isbased on the material of the existing member,equipment availability, and the training level ofthe repair crews. More detailed considerationsfor the replacement of each type of bridge memberare provided in section III of chapters 11 through13.

10-4. Repair

10-2. Preventive maintenance

Maintenance is the recurrent day-to-day, periodic,or scheduled work that is required to preserve orrestore a bridge to such a condition that it can beeffectively utilized for its designed purpose. Itincludes work undertaken to prevent damage to ordeterioration of a bridge that otherwise ‘would bemore costly to restore. The concept of preventivemaintenance involves repair of small or potentialproblems in a timely manner so that they will notdevelop into expensive bridge replacements. Pre-ventive maintenance activities can be divided intotwo groups: those performed at specified intervalsand those performed as needed.

Bridge repair is actually an extension of a goodmaintenance program. It involves maintaining thebridge’s current structural load classification. Se-lection of the correct repair technique for a bridgeof any type and material depends upon knowingthe cause of a deficiency and not its symptoms. Ifthe cause of a deficiency is understood, it is morelikely that the correct repair method will beselected and that the repair will be successful. Ageneral procedure to follow for designing andexecuting a repair involves the evaluation anddetermination of the causes for the deficiency andthe methods, materials, and plans to be used inthe execution of the repair.

a. Evaluation. The first step is to evaluate thecurrent condition of the structure. Items to includein the evaluation are:

a. Specified interval maintenance. This groupincludes the systematic servicing of bridges on ascheduled basis. The interval varies according tothe type of work or activity. Tasks identified asinterval maintenance can be incorporated into amaintenance schedule for that bridge. Examplesare:

(1) Review of design and construction docu-ments.

(2) Review of structural instrumentation data.(3) Review of past bridge inspections.(4) Visual examination, nondestructive test,

and laboratory test.

(1) Cleaning drainage facilities.(2) Cleaning and resealing expansion joints.(3) Cleaning expansion bearing assemblies.

b. As-needed maintenance. These activities areperformed when the need is foreseen for remedialwork to prevent further deterioration or the devel-opment of defects. The need for this type ofmaintenance is often related to the environment oridentified during inspections. Example activitiesinclude:

b. Relate observations to causes. Evaluation in-formation must be related to the mechanism ormechanisms that caused the damage. Since manydeficiencies are caused by more than one mecha-nism, a basic understanding of the causes ofdeterioration is needed to determine the actualdamage causing mechanism.

c. Select methods and materials. Once the under-lying cause of the structural damage is deter-mined, selection of appropriate repair materialsand methods should be based on these consider-ations:

(1) Sealing concrete decks.(2) Painting steel members.(3) Snow and ice removal.

(1) Determine prerepair adjustments or modi-fications required to remedy the cause, such aschanging the water drainage pattern, correcting

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TM 5-600/AFJPAM 32-1088

differential foundation subsidence, and eliminatingcauses of cavitation damage.

(2) Determine constraints such as access tothe structure, the operating schedule of the struc-ture, and weather.

(3) Determine permanent/temporary repair ad-vantages/disadvantages.

(4) Determine the available repair materialsand methods and the technical feasibility of usingthem.

(5) Determine the most economically viable,technically feasible methods and materials. Selectthe combination that ensures a satisfactory job.

d. Prepare design memoranda, plans, and speci-fications. This step should be based on existingguide specifications, enhanced by incorporatingexperience gained from similar projects, and allow-ing as much flexibility with regard to materials aspossible.

e. Execute the repair. The success of the repairdepends on the degree to which the repair isexecuted in conformance with the plans and speci-fications.

10-5. Bridge upgrade

a. General. The upgrading of existing bridges isusually required where they are to carry heavierlive loads than those for which they were de-signed. Upgrading or strengthening may also berequired because of inadequate design or as theresult of localized deterioration. The decision toupgrade a bridge or to replace it should take intoaccount the age of the structure, the material ofwhich the various members are made, the fatigueeffect of the live loading, the comparative esti-mated cost, the added service life of the upgradedbridge, and the possible future increase in the liveloading.

b. Upgrade levels. The upgrade of a bridgestructure can be carried out at three levels.

(1) Strengthening of the existing individualcomponents of the bridge to provide a moderateincrease of the bridge’s load carrying capacity.

(2) Redesigning the structure by adding com-ponents (stringers, piers, load bearing decks, etc.).

(3) Redesigning the structure by a combina-tion of strengthening existing components andadding components to increase the load capacity.

Section II. COMMON MAINTENANCE TASKS

10-6. General

There are numerous different types of bridges andmaterials of which these bridges are constructed.However, there are some maintenance tasks thatare common to all bridges despite their individualdesigns and construction materials. These tasksare incorporated into standardized maintenanceoperating procedures and generally involve keep-ing the bridge clean and conducting work andminor repairs to prevent bridge deterioration.

10-7. Cleaning deck drains

Drains and scuppers should be open and clear toensure that the deck drains properly and thatwater does not pond. Ponding of water on the deckincreases the dead load on the bridge and presentsa hazard to drivers in the form hydroplaning.Proper drainage also helps prevent water fromleaking through the deck or deck joints and caus-ing deterioration of other superstructure compo-nents.

10-8. Ice and snow removal

The primary reason for the removal of snow andice is to provide a safe bridge for motorists.Bridges are generally the first portion of the roadnetwork to ice over and require immediate atten-tion in freezing weather. The primary means to

10-2

combat the accumulation of snow and ice is plow-ing the snow from the traffic lane of the bridge,spreading abrasives (crushed rock, sand, cinders,etc.) to improve the wheel traction, and chemicals(see table 10-1) to lower the freezing point of thewater on the deck. When deicing salts (calciumchloride or sodium chloride) are used as part ofthis process, it is imperative that the maintenanceschedule includes cleaning the bridge in the springto remove any lasting effects of the salts. Anyabrasives used on the structure should be removedas soon as possible after the snow period is over toreduce wear on the deck.

10-9. Bank restoration

Bank restoration involves the area in and aroundthe abutments and up to the waterline. Erosion isthe biggest problem and a maintenance programshould include filling in washouts and seeding orusing riprap to help prevent erosion. For a moredetailed description on the use of fill and riprap,refer to paragraph 10-18d.

10-10. Traffic control items

It is important that traffic control items (clear-ances, load classifications, speed signs, centerlines,etc.) be maintained on a regular basis to controlthe traffic across the bridge. It is especially impor-

TM 5-600/AFJPAM 32-1088

Table 10-1. Chemical application rates

note: Chemical application is in pounds per mile of 2-lane road or 2 lanes of divided.

tant for moveable bridges that navigation lights,traffic control systems, and protective fender sys-tems be monitored regularly. This is a safety morethan a structural issue; however, it constitutes animportant component in providing a completemaintenance program.

10-11. Bearings and rollers

All rockers, pins, and rollers are to be kept free ofdebris and corrosion, lubricated where necessary,and maintained in good working order. Dependingon the type of bearing (fixed or expansion), theyshould permit the superstructure to undergo neces-sary movements without developing harmful over-stresses. A “frozen” or locked bearing that be-comes incapable of movement allows the stressesgenerated to become excessive and may even causea major failure in some affected member.

10-12. Debris and removal

a. Superstructure. Any debris left on the super-structure due to traffic or high water should beremoved for safety reasons and to prevent deterio-ration in areas were the debris will trap moistureonto the superstructure.

b. Substructure. The substructure is susceptibleto debris or floating ice that forms drifts againstits components. This can cause premature deterio-ration of these components and place excessivelateral loads on the whole structure. The tech-niques available to remove drifts are:

(1) Clear small debris with a pole or hook.

(2) Pull large pieces of debris clear with acrane.

(3) Clear large and small pieces of debris witha powerboat.

(4) Blast large jams to break them up.

10-13. Bridge joint systems

a. General. Joints are designed to provide forrotation, translation, and transverse movements ofthe superstructure under live loading and thermalexpansion. The system should also prevent waterleakage onto the components below the bridgedeck. The two common joint systems are open andclosed joints.

b. Open joints. The open joint provides for longi-tudinal movement of the superstructure. The jointconstruction is not watertight and should permittraffic to cross smoothly.

(1) Finger joints. Interlocking steel fingers at-tached to a steel plate allow longitudinal butrestrict transverse deck movements.

(a) Clogged joint and drain trough. Fre-quently flush and clean the joint and drainagesystem to remove debris accumulation in thesystem. This will also help prevent corrosion andconcrete deterioration.

(b) Loose joints. Remove loose or faulty boltsor rivets, reposition the expansion device, andrebolt. It may be necessary to countersink thebolts or rivets to avoid future problems.

(c) Broken finger joints. Weld replacementfingers onto the joint.

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TM 5-600/AFJPAM 32-1088

(d) Fingers closed. Trim the expansion fin- common failure associated with this joint sealantgers or remove the system, reposition, and rein- and requires replacement of the deficient compres-stall. sion joint sealant (figure 10-1).

(2) Armored joints. These consist of steel an-gles at concrete edges which are left open or filledwith a mastic or other material to prevent intru-sion of debris. If the joints are clogged, clean outthe joint, repair any broken angles, and apply aliquid polyurethane or preformed compression jointsealant for waterproofing and to prevent debrisintrusion.

10-14. Scour protection

(3) Sliding plate. A horizontally positionedsteel plate is anchored to the deck and allowed toslide across an angle anchored to the opposite faceof the opening.

The excavation or removal of the soil foundationfrom beneath the substructure undermines theload carrying capacity of the bridge. It can alsocause excessive settlement if proper preventivemaintenance is not practiced. A foundation may beprotected against scour in the initial design andafter construction has been completed.

a. Design.

(a) Clogged expansion gap. Remove any dirt,debris, or asphalt from the gap to ensure thatsliding plate interacts properly with its angle seat.

(b) Joint closed. Trim the steel plate.c. Closed joints. The closed joint is a watertight

arrangement of various materials which allowlongitudinal movement of the superstructure.

(1) Elastomeric. A sealed, waterproof joint sys-tem which uses steel plates and angles moldedinto neoprene coverings to provide an anchorageand load transfer (figure 10-1).

(a) Faulty section. Remove and replace.(b) Inadequate seal. Apply new sealant or

remove and reinstall using proper sealing tech-niques.

(1) Locate bents and piers parallel to thedirection of the water flow.

(2) Use long piles driven to a depth whichprovides sufficient bearing and accounts for scour-ing.

(3) Drive a row of closely spaced fender pilesperpendicular to the stream flow at the upstreamend of the substructure. This may not protect thedownstream end since eddies and increased veloc-ity may produce erosion on the downstream end.Their greatest effectiveness is for narrow piers andlarger spans structures.

b. After construction.(1) Place sandbags around the base of bents,

piers, and abutments, particularly at the upstreamend.

(c) Loose or broken bolts. Remove brokenbolts and replace with “J” bolts.

(2) Compression seal. Extruded neoprene withcross-sectional design and elasticity to provide forretention of its original shape. Leakage is the most

(2) Place riprap consisting of stones weighingat least 50 pounds or bags filled with stones orcement.

(3) Divert drainage lines when scouring is dueto local ground drainage or drainage from the deckitself.

MODEL INCORPORATING A GLANDTYPE OF JOINT SEALANT.

COMPRESSION JOINT SEALMODIFIED WITH CORNER CLIPS

Figure 10-1. Examples of closed joints.

Section III. COMMON REPAIR TASKS

10-15. General

Just as in maintenance tasks there are severalrepair tasks that apply to almost all bridgesdespite the materials used in construction. Thepurpose of bridge maintenance is to bring a bridge

10-4

back up to original design load after damage ordeterioration to the structure. These repairs caninvolve the strengthening, replacing, or addingsupport to the existing components of the struc-ture. In the case of common repair tasks, these

tasks generally involve repair to the foundation orsubstructure of the bridge.

10-16. Abutment stability

a. In addition to providing end support for thebridge deck, an abutment also acts as a retainingwall and is subject to horizontal earth pressures.These pressures coupled with the dynamic loadingof vehicle traffic has the tendency to push out theabutment. If the abutment is unstable, it may beshored or fixed using guylines from shore anchor-ages or a deadman tie-back system.

b. The procedure for this process is as follows(figure 10-2): Emplace a deadman or drive a pileanchor approximately 3 feet on either side of theapproach to the bridge. These anchors should befrom 60 to 100 feet from the face of the existingabutment. Drill a hole in the wing-wall on bothsides of the abutment and in a position outsideand in line with the abutment cap. Run a restrain-ing rod or cable from the deadman through thehole in the wall. Place a beam (example: steelwafer) on the outside of the cap. The beam mustextend a distance at least greater than the posi-tion of the drilled holes in the wingwall on bothsides of the abutment cap. Connect the retain-ing rod or cable to the beam and place tensionon the rods or cables. This technique can be usedon smaller abutments to help draw the abutmentback to its original position and to hold it in place.

10-17. Drift and floating ice

Drift and floating ice place forces on the piers andframe bent of bridges. They can also cause struc-tural damage to the cross section of the piles or

TM 5-600/AFJPAM 32-1088

columns of the system from the impact of thedebris on the substructure. A common repair tominimize this problem is to install dolphins and/orfender systems upstream of the piers to adsorb theenergy of the physical contact with the drift and tohelp break it up.

a. Pile cluster dolphins. This type of dolphinconsists of a cluster of piles with the tops pulledtogether and fixed into position (figure 10-3).Dolphins can be constructed from:

(1) Timber. The top is lashed together withwire rope. Timber piles can be protected fromimpact damage by banding the piles with sheetmetal.

(2) Steel tube. Dolphin system is connectedwith bracing and fender arrangement.

(3) Caisson. Sheet-pile cylinders of large diam-eter filled with sand or concrete and topped with aconcrete slab. Fendering can also be attached tothe outside sheets, if needed.

b. Fenders. Fenders are designed to divert theflow of drift and ice around the piers. Thesefenders generally form a wedge on the upstreamside of the pier to divert the flow.

(1) Timber/steel bents. A series of piles withtimber wales and braces are attached to the topportion of the bent system. The steel piles may betied together using a concrete slab (figure 3-19).

(2) Steel or concrete frames. Steel or concreteframes are sometimes cantilevered from the pierand faced with timber or rubber cushioning toreduce collision impact from surface craft anddebris.

(3) Timber grids. Timber grids, consisting ofpost and wales, are attached directly to the pier(figure 3-19).

Figure 10-2. Abutment held in place with a deadman.

10-5

TM 5-600/AFJPAM 32-1088

Figure 10-3. Typical use of dolphins.

10-18. Scour

When scour undermines the existing foundation,methods must be undertaken to reestablish thefoundation. Scour can effectively reduce the bear-ing of piles, undermine pier footings and abut-ments, and cut into the bank.

a. Piles. When scour reduces the effective bear-ing of the piles in a pier:

(1) Additional piles can be added to the baseof the pier to make up for the lost bearing and rip-rap added to prevent future scouring (figure 12-12).

(2) A concrete footing can be added to the baseof the pier to make up for the lost bearing asfollows (figure 10-4). Place a tremie encasementaround the bottom of the pier. Inject concrete ormortar into the encasement. The concrete willdisplace the water from within the encasement.The formwork or encasement can be removed afterthe concrete is cured. Nails or spikes can be driveninto timber piles, shear studs or bolts placed onsteel piles, and rebar placed in drilled holes or theouter surface chipped on concrete piles to provide abetter bond between the pile and the footing.

b. Pier footings. When footings are undermined,the most common repair method is to fill the voidfoundation area with a concrete grout or crushedstone. To place grout, some type of formwork mustbe used to confine the grout.

(1) Concrete grout.(a) Tremie encasement. This is a steel, wood,

or concrete form that is placed around the existingfooting to reestablish the foundation. The form

10-6

allows the concrete grout to be pumped under theeroded footing and displaces the water in theencasement through vents (figure 10-4).

(b) Confinement walls. Walls of stone, sand-bags, or bags filled with riprap are placed alongthe faces of the footing and extending through themud layer of the river bottom. The grout is inject-ed into the cavity below the footing and the wateris displaced through the voids in the wall. Thegrout penetrates into the voids in the wall andseals the confinement wall. The cavity is filled withgrout and the foundation is reestablished (figure10-5).

(c) Flexible fabric. A closed bag of canvas,nylon, etc., with grout injection ports is positionedunder the footing. Grout is pumped into the bagand it expands to fill the cavity. The injection portis then closed and fabric confines the grout until itcan cure (figure 10-5).

(2) Backfill.(a) Dry footing. In this case the footing is

not under water and may have been eroded byservice runoff or flooding. A good structural fillmaterial can be compacted into the erosion cavityto fill the void. If the streambed is eroded belowthe base of the footing, the compacted fill will beextended on a slope of 2 to 1 from the currentstreambed to the base of the footing. Riprap willthen be placed around the footing to preventfurther scouring.

(b) Wet footing. Crushed stone is used as thefill material (figure 10-6).

c. Abutments. Scour around the base of abut-ments can be repaired in a similar fashion as thepier footing as follows (figure 10-7):

(1) Shore up the abutment to prevent settle-ment during the repair,

(2) Remove any loose material from thescoured area,

(3) Set bolts into the abutment face along thelength of the abutment. These bolts should extend3 to 6 inches from the abutment face and bespaced 2 feet apart. Use the bolts installed in step3 to connect an expansion shield to the abutment.Place concrete behind the shield to fill the erosioncavity and the space between the shield andabutment face. Place riprap on a 2 to 1 slope toprevent future scouring.

d. Bank slope. Erosion under and around aconcrete slope protector can be repaired using ariprap till or may require extending the protector.

TM 5-600/AFJPAM 32-1088

(1) Riprap (figure 10-8). Fill the scour holewith riprap. Extend the riprap above the face ofthe concrete to protect from future scouring. Slopethe riprap level down from the edge of the protec-tor to the face of the concrete protector.

(2) Protector extension (figure 10-9). Removeloose material from the scour hole. Backfill withsand or gravel. Form a ground mold in the backfillfor the extended slope protector. Place concreteinto the ground mold. Add the following steps foran undermine protector: cut a hole in the protectorabove the erosion cavity, backfill or grout throughthis hole, and repair the holes.

10-19. Settlement

Foundation settlement usually is caused bystructural failure of the foundation material orscour.

Figure 10-4. Forming a footing with a tremie encasement.

Figure 10-5. Alternate methods for confining grout under footings.

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TM 5-600/AFJPAM 32-1088

NOTE: THE USE OF THIS SIZE CRUSHED STONE MAY BEPROHIBITIVE IF STREAM CURRENTS ARE STRONG

Figure 10-6. Use of crushed or structural fill to repair scour damage.

Figure 10-7. Repair of scour around concrete abutments.

Figure 10-8. Bank repair using riprap,

Figure 10-9. Concrete bank protector extension.

10-8

a. Minor settlement. This can be corrected byjacking up the structure and inserting steel shimsbetween stringers and cap or between bearingplates and pedestal. Hard wood shims can be usedunder wooden members.

b. Major settlement. The pier is tilted or hassettled to a point that it can no longer safely carryits design load.

(1) Piles. Correct the cause of the settlementby adding piles or a footing (Refer to relatedparagraphs in the following chapters for specificmethods). Jack the deck to its proper position.Enlarge or replace the existing cap. Level the deckand remove jacks.

(2) Pier footings. Correct the cause of thesettlement. Jack the deck to its proper position.Construct a level bearing surface for the super-structure. For bents, enlarge or replace the exist-ing cap. For walls, enlarge the stem of the pier byplacing a form around the stem and placingconcrete. The concrete formwork should extend tothe top of the pier to provide a level bearingsurface (figure 10-10). Then cure, level the deck,and remove the jacks.

10-20. Waterway

Some waterways withplains have a tendency

TM 5-600/AFJPAM 32-1088

flat gradients and floodto shift channel locations.

Such channel shifts may deposit eroded material:against the bridge piers, erode pier foundations, orattack the approach. This can be controlled bydikes of earth, rock, or brush mats.

(a) SECTION THRU PIER STEM SHOWINGFIRST STAGE OF REPAIR

(b) SECTION THRUSTEM SHOWINGSECOND STAGEOF REPAIR

NOTE: THIS REPAIR SHOULD BE UNDERTAKEN ONLYIF THE STABILITY OF THE PIER AND OTHERATTENDANT DAMAGES ARE JUDGED TO BEACCEPTABLE AND AMENABLE TO REPAIR

Figure 10-10. Settlement repair of a concrete wall pier.

Section IV. COMMON METHODS TO UPGRADE EXISTING BRIDGES

10-21. General

There are several methods available to upgradeexisting bridges. Some of the more common meth-ods involve shortening the effective span length,adding stringers, strengthening the piers, reducingthe dead load, and strengthening individual struc-tural members. This section will discuss a few ofthe techniques involved with these upgrade meth-ods.

10-22. Shortened span lengths

a. Bearing point. Shifting the bearing point canachieve a slight increase in bridge strength andcan be used in conjunction with other upgrademethods to obtain a total bridge upgrade. Thebearing point is shifted in toward the span, andthe strength increase is limited by the size of thebearing surface on the abutment or pier cap. Theshift can be accomplished by:

(1) Jacking the stringer off the bearing pointand moving the existing point out on the bearingface.

(2) Placing a new bearing point in front of theexisting point and using wedges to transfer theload to the new point.

b. Intermediate piers. The greatest bridgestrength can be achieved by adding intermediatepiers between the existing piers and abutments.The original span acts as a continuous beam andthe negative movement must be checked over theintermediate pier.

c. A-Frame. For short spans, the A-frame pro-vides an expedient substitute for installing anintermediate pier. The legs of the frame areanchored to the existing pier footings or footingsare constructed for this purpose. These footingsmust be designed or reinforced to carry the lateralthrust transmitted through the frame’s legs. Theapex of the A-frame supports a cap which has abearing surface for the bridge stringers. The use ofthe A-frame reduces the clearance below thebridge and may require additional horizontal rein-forcement against seasonal floods (figure 10-11,part a).

d. Knee-braces. Knee-braces may be used to

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TM 5-600/AFJPAM 32-1088

function in nearly the same manner as A-frames.However, the reaction of the span is not that of acontinuous span and must be analyzed as supportbracing (figure 10-11, part b).

10-23. Add stringers

The addition of stringers may require respacingexisting stringers. The procedure increases thecapacity of the existing deck and redistributes theloads carried by the stringers. When the deck isnot replaced, special techniques must be used toplace the new stringers. With the increase of theload carrying capacity of the superstructure, it isimperative to check the substructure for the sameloading conditions.

10-24. Strengthen piers

a. Add piles. Drive additional piles and tie intothe existing pier system.

b. Add or increase a footing. Once the footing isestablished, columns can be added between thenew footing and the existing cap to provide agreater column strength in the pier.

c. Add or enlarge columns. The load carryingcapacity of a pier or bent system can be increasedby adding more columns or by adding material tothe existing column cross sections.

10-25. Reduce deadload

The live load capacity of a bridge can be increasedby reducing the applied dead load, thereby allow-

ing existing capacity to be used for carryingincreased live load. Significant dead load reduc-tions can be obtained by removing an existingconcrete deck and replacing it with a lighter deck.A reinforced concrete deck 8 inches thick weighsapproximately 100 pounds per square foot. Thisweight is compared to the weights of lightweightdecks in table 10-2.

10-26. Posttensioned bridge components

Posttensioning can be used to:a. Relieve tension, shear, bending, and torsion

overstress.b. Add ultimate strength to the bridge struc-

ture.c. Reverse displacements.d. Change simple span to continuous span be-

havior. Various methods and configurations forposttensioning are shown in table 10-3.

10-27. Strengthen individual members

In many cases the bridge classification can beincreased by strengthening the individual mem-bers of the structure. The drawbacks to thismethod are that it generally increases the deadload of the structure and the added material shallbe considered effective in carrying the added deadload and live load only. Methods for strengtheningindividual members are dependent upon the mate-rial type and are thus discussed in the followingchapters.

A. A-FRAME B. KNEE-BRACES

Figure 10-11. Expedient methods of span length reduction.

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TM 5-600/AFJPAM 32-1088

Table 10-2. Lightweight decks

Lightweight Deck

Open-grid steel deck

Concrete-filledsteel grid

Exodermic deck

Laminated Timberdeck

Transverse Or ien ta t ion

Lightweight concretedeck

Orthotropic platedeck

Description

Steel stringers connected by a weldedsteel plate grid that provides the decksurface. Spans 5-9 feet.

Half-filled: S-inch deck with concreteplaced in the top half of the grid.Full-depth fill: S-inch deck withconcrete placed full depth in the grid.

A 3-inch prefabricated concrete slabjoined to a steel grating. Spans 16feet.

Vertically laminated 2-inch-diameterlumber bonded togetherinto structral panels 48in. wide with a depthfrom 3 l/8 to 6 3/4 in.

Long i tud ina l Or ien ta t i on

Concrete mix uses lightweight aggregate(expanded shale, slate, or clay).These decks can be cast in place orfactory precast.

Aluminum alloy plates with a skid-resistant polymer wear surface rein-forced by extrusions. The deck boltsto the existing beams using hold-downbrackets.

Steel plates - No standard design.

lb/sq ft

15-25

46-51

76-81

40-60

10.4-22.5

75

20-25

45-130

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TM 5-600/AFJPAM 32-1088

Table 10-3. Bridge posttensioning configurations

Method

Eccentric TendonIncludes axialcompression andnegative bending

Concentric TendonRelieves tensionmembers by applyingaxial compression.

Polygonal TendonInduces axial com-pression,nonuniformnegative bending in theposttensioned region,and shear opposite toload shear.

Polygonal Tendon with aCompression Strut

Similar to polygonal butdoesn't add axialcompression into theexisting structure.

King PostCombination of eccen-tric and polygonal ten-don configurations. Themoment to axial forceratio is large due tothe king post.Queen Post-uses 2 post.

External StirrupTimber - Sec t . 13-7c(2)

Concrete - Sec t . 14-72(1)

Box beam - Sec t . 14-7e(2)

Beam/StringerConfiguration

Truss Configuration

10-12

CHAPTER 11

TM 5-600/AFJPAM 32-1088

STEEL BRIDGE MAINTENANCE, REPAIR, AND UPGRADE

Section I. PREVENTIVE MAINTENANCE FOR CORROSION

11-1. General

Rust and corrosion are the greatest enemies ofsteel. When rust is allowed to progress withoutinterruption, it may cause a disintegration andsubsequently complete loss of strength in a bridgemember. The corrosion also causes other problemssuch as pressure or friction between the surfaces.

11-2. Structural steel

Preventive maintenance of steel bridge compo-nents consists mainly of measures to protect thesteel from corrosion. The preservation of steelinvolves protection from exposure to electrolytes,such as water or soil. When deicing salt is addedto the electrolyte, there is a dramatic increase inthe rate of corrosion of the structural steel. Corro-sion is usually easily spotted by visual inspection.Protection from corrosion can take various forms:

a. Weathering steel. This special type of steelforms its own protective coating and theoreticallydoes not need painting. However, many statehighway departments have indicated poor perfor-mance from their bridges constructed with thistype of steel. Therefore, members constructed fromweathering steel should be monitored for excessivecorrosion and painted if necessary.

b. Paint. Typical painting requirements arebased on whether the steel is new or is to berepainted. The following steps are usually neces-sary:

(1) New steel. One prime coat applied in theshop, one prime coat applied in the field, two colorcoats applied in the field.

(2) Repainting (depends on the condition of theexisting paint). If cleaned to bare metal, use oneprime and two color coats. If cleaned to prime coat,use two color coats. If no prime exposed, use onecolor coat.

(3) Paint seal. The intersections and edges ofmetal surfaces can be protected from corrosionwith a paint seal. This is a paste paint thatprevents moisture penetration between the metalparts.

(4) Notes.(a) When removing lead-based paint, pre-

cautions must be taken to protect against leadinhalation, ingestion, and pollution.

(b) Schedule field painting at the end ofmaintenance projects to avoid damage to the freshpaint.

(c) Separate cleaning and painting opera-tions to avoid contaminating the fresh paint.

(d) Protect cleaned steel until paint can beapplied.

(e) Apply paint to a dry surface that is nottoo hot. This ensures a good bond that does notblister (ambient temperature greater than 40 o F,relative humidity less than 85 percent).

c. Cathodic protection. Zinc or aluminum anodesare attached to H piles to abate corrosion of steelin salt or brackish water (figure 11-1). Small zincanodes are used when less than 8 linear feet ofpile is exposed. Large zinc or aluminum anodesare used when greater than 8 linear feet of thepile is exposed.

d. Good housekeeping. Steps to follow:(1) Keep drains open to remove standing wa-

ter from steel surfaces.(2) Keep deck joints watertight to prevent

water leakage onto steel members.(3) Keep exposed areas clean by pressure

washing.(4) Spot paint and repaint as necessary.(5) Maintain steel cables by removing foreign

objects from the cable support system, cleaningand lubricating cable supports, tightening andreplacing stirrups, and repairing cable wrapping.

Section II. REPAIR AND STRENGTHEN

11-3. General

a. Repair decision. Each repair decision mustcarefully weigh the long-term operational require-ments and existing environmental factors that canhelp accelerate corrosion prior to evaluating initial

and life cycle costs. The physical condition of thestructure must first be determined by a detailedinspection. The structural capacity of the steelshould be known. Once the physical condition ofthe bridge is evaluated, a determination of

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TM 5-600/AFJPAM 32-1088

Figure 11-1. Anodes placed on steel H piles for corrosion protection

whether damaged bridge components should berepaired or replaced is made.

b. Common repairs. The most common steelrepairs are:

(1) Adding metal to strengthen cross sectionsthat have been reduced by corrosion or externalforces.

(2) Welding or adding cover-plates to repairstructural steel cracks caused by fatigue and vehi-cle loads.

(3) Retrofitting connections.c. Rules for adding steel. When steel members

are strengthened to carry a specified load, thepermissible stresses in the added material mustcomply with the load design stresses. To properlyanalyze and design repairs that involve adding

11-2

metal, the following rules are applied:(1) Metal added to stringers, floorbeams, or

girders shall be considered effective in carrying itsportion of the live loads only.

(2) New metal added to trusses, viaducts, etc.,shall be considered effective in carrying its portionof the live load only. The exception is when: Thedead load stress is temporarily removed from thesemembers until the new metal is applied, or thedead load stress is applied to the new metal whenit is applied.

(3) The added material shall be applied toproduce a balanced section, thus eliminating orminimizing the effect of eccentricity on thestrengthened member. Where balanced sectionscannot be obtained economically, the eccentricity

TM 5-600/AFJPAM 32-1088

of the member shall be taken into account indetermining the stresses.

(4) Strengthened members shall be investi-gated for any decrease in strength resulting fromtemporary removal of rivets, cover plates, or otherparts. In some cases falsework or temporary mem-bers may be required. Where compression mem-bers are being reinforced, lacing bars or tie platesshall be replaced before allowing traffic over thebridge.

11-4. Connections

Primary connections involve the use of welds,bolts, or rivets. However, pin connections andthreaded fasteners are used commonly in tensionmembers.

a. Welds. Electric arc welding may be employedsubject to the approval of the engineer. In general,welding can be used to repair broken or crackedwelds, strengthen rivet connections, and add metalto existing steel members.

(1) Broken or cracked welds. Remove all dirt,rust, and paint for a distance of 2 inches from thedamaged weld. File or grind down the damagedweld to ensure the weld will bond with the steelsurfaces being welded together. For cracks, grinddown the cracked weld until the crack is no longervisible then check the weld with dye penetrant toensure the crack has been completely ground out.Replace the weld. Apply paint or a corrosionprotector to welded area.

(2) Welded rivet connections. Remove all dirt,rust, and paint for a distance of 2 inches from thesteel surfaces in which the weld is to be applied.Apply welds to join the steel surfaces. Whereoverstressed rivets/bolts can carry the dead load,the weld is designed to carry the impact and liveloads. Where overstressed rivets/bolts cannot carrythe dead load, the weld is designed to carry thetotal load. Apply paint or a corrosion protector towelded area.

(3) Added metal for strength. Clean the steelsurfaces in which metal is to be added and removeany severely damaged or corroded steel portions.Use welds to fill cracks and holes, to replaceremoved steel portions, or to add coverplates tostrengthen individual members. With cracks, en-sure the weld penetrates the full depth of thecrack. With holes, work the weld from the steelsurface to the center of the hole ensuring no voidsare allowed in the weld. Replace removed steelportions with steel of the same strength, and, if atorch is used to cut the steel, ensure the edges areground smooth to ensure a good welding surface.When adding coverplates that will be subjected tocompression, ensure the maximum clear spacing

distance (d) is less than 4,000 multiplied by tdivided by Fy, where t = plate thickness in inchesand Fy = yield stress in pounds per square inch.This prevents local buckling of the attached platewhen loaded in compression (figure 11-2). Applypaint or a corrosion protector to welded area andadded steel.

b. Rivets. Riveted connections can be repairedusing many different methods. The most commonrepair requirements are for loose or missing rivetsor an understrength connection. The repair tech-niques for each are as follows:

(1) Loose or missing rivets. Clean workingsurface. Replace all missing rivets with high-strength bolts of the same size and draw the nutup tight. This will help support the connectionduring the repair operations. Tighten or removeand replace loose rivets with high-strength bolts ornew rivets. Work on only one rivet at a time tohelp maintain the proper load distribution to therivets. Remove and replace high-strength boltswith rivets, one at a time, if the engineer requiresrivets for the repair work (high-strength bolts canbe substituted for rivets). Check all bolts and/orrivets to ensure tightness. Apply paint or corrosionprotector.

(2) Understrength connection. Several optionsexist for an understrength connection:

(a) Rivets or bolts can be added to theexisting connection plate.

(b) A longer connection plate can be addedto allow for more rivets.

(c) Larger rivets or bolts can be substitutedfor the existing ones.

(d) Welds can be added to the connectionplate of sufficient strength to carry impact andlive loads or the total load depending on thecondition of the connection.

c. Pin connection. The pin connections discussedherein refer to those used in tension members andmilitary assault bridges. The repair of such con-

Figure 11-2. Local buckling under compression.

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TM 5-600/AFJPAM 32-1088

nections may involve the pin itself or the pinhousing. To repair or replace the pin or housing,the load must be shifted from the connectionthrough use of jacks or winches. The pin can thenbe removed from the housing. Repair the housingusing welds or by adding metal to build up theconnection, as necessary. The pin can either bereplaced or a bolt of the same size can be used.The pin connection should be replaced with awelded or riveted connection if it is functioning asa fixed connection or if the bridge is considered apermanent structure.

d. Threaded fastener. Threaded fasteners areused primarily in conjunction with a tension rod orcable. Typical problems with these fasteners in-volve stripped threads, a rust frozen shaft, or abroken threaded shaft.

(1) Stripped threads. Remove the threadedshaft and rethread if necessary. Drill out thethreads in the female housing. Place the rethread-ed shaft through the female housing and retightenthe fastener with a bolt on the backside of thehousing.

(2) Rust frozen shaft. Clean the shaft andhousing of external rust and apply a lubricant tothe threads. Attempt to rotate the shaft; if theshaft still refuses to rotate, the fastener must bereplaced. Cut the threaded portion of the shaftfrom the tension member and splice a newthreaded shaft to the member. Remove the frozenportion of the shaft from the housing using atorch. Place a bolt on the backside of the housingand pull the tension member tight.

(3) Broken shaft. Splice the shaft as shown infigure 11-3.

11-5. Repair of structural members

Structural steel members are generally classifiedby the function they perform. The primary mem-bers are tension members, compression members,beams, and beam-columns. The repair of variousstructural members is discussed in the followingparagraphs.

a. Bars. Structural bars can be either round orrectangular and have a pin or threaded connec-tion. Repair of the bar itself involves tighteningthe bar to account for elongation, adding metal tothe eye of a pin connection, or splicing the bar torepair breakage.

(1) Tightening adjustable connections or turn-buckles. Clean the components and attempt totighten the bar. If adjustments cannot be made,adjustments can be made to the eyes or turnbuck-les can be added as follows:

(a) Adjustments to the eyes. For slack of lessthan 1 inch, the pin connection can be shimmed totake up any slack between the pin and the eye ofthe bar. Shimming is accomplished by removingthe pin from the housing and placing a metalsleeve snugly around the pin and the inside of theeye of the bar. The metal sleeve will take up theslack between the pin and the eye of the bar.

(b) Add turnbuckle. A turnbuckle can beadded to a round bar which previously had noadjustable tension system (figure 11-3). This isaccomplished by cutting a section out of theexisting bar, threading both adjacent ends of thecut, and screwing on a turnbuckle.

(2) Broken/damaged bars. Repair broken ordamaged bars as follows:

(a) Add turnbuckle. Cut out the damagedarea and use the same technique discussed inparagraph 11-5a(1)(b) above.

(b) Splice bars. Broken bars can be splicedby welding bars or plates on both sides of thedamaged area as shown in figure 11-3. Bolts andrivets can also be used if desired.

(3) Reinforcement of eyebars with loop bars.Eyebars can be reinforced with loop bars in thefollowing manner. Release tension from the eye orconsider the added metal for carrying live load andimpact loading only. Weld a plate onto the exist-ing eyebar. This plate can be used to attach asupplemental eye (loop or forged bar which rein-forces the eye of the bar). Place loop bars aroundthe pin and weld to the steel plate (figure 11-4,part a). Reapply tension and paint repaired area.

Figure 11-3. Repairing tie rods with splices or turnbuckles.

11-4

TM 5-600/AFJPAM 32-1088

A. US ING A F ILL PLATE B . U S I N G A C U T P L A T E T O R E D U C E W I D T H

Figure 11-4. Strengthening pin connections using a supplementary eye.

(4) Reinforcement of eyebars with steel plates(figure 11-4, part b). Eyebars can be reinforcedwith steel plates by the following procedure. Re-lease tension from the eye. Place a supplementaleye around the existing eyebar. Slide a new platebetween the arms of the supplemental eye. Thethickness of the new plate should be equal to thatof the supplemental eye. Its width should be equalto the diameter of the pin for the approximatelength of the arms of the supplemental eye, andthen it should widen to a width greater than theexisting eyebar. Its length should be determinedby the load carrying capacity requirements of thewelds. Weld the supplemental eye, new plate, andeyebar together. Replace the pin, reapply tension,and paint the repair.

b. Hanger plates. Pin and hanger connectionsare especially vulnerable to corrosion, which mayfreeze the connection and increase the internalstresses in the hanger, causing cracks to form. Ifthe hanger must be removed for cleaning orrepair, a technique which can be used is:

(1) Fashion a temporary hanger to support thedead load normally carried by the hanger. Thiscan be accomplished as follows:

(a) Place a steel plate across the expansiondam on the road surface. The plate should havetwo holes running the length of the dam and at adistance slightly greater than the flange width ofthe girder apart.

(b) Run two threaded bars capped with nutsthrough the holes to the bottom of the girder’sbottom flange.

(c) Attach a plate to the bars below thebottom flange.

(d) Tighten the nuts on the top plate todraw the bottom plate up tight to the bottomflange and adjust the tension on the hanger.

(2) Once the temporary hanger is in place, theconnection can be cleaned and repaired as follows:

(a) Attach a safety cable to the outsidehanger and remove the hanger from the pins.

(b) Clean the pins and hanger thoroughlyand repair any damage to these components.

(c) Spot paint the inside face of the hangerwith light layers of paint and allow time for thepaint to dry while working on the pins.

(d) Lubricate the pins and replace thehanger.

(e) Repaint the outside face of the hanger.(f) Repeat the procedure for the inside

hanger.(3) Remove the temporary hanger.

c. Cable. The most common damage that occursto cable is fraying of the steel wires forming thecable. Any repair requiring strengthening thedamaged portion of the cable involves removingthe tension on the cable. There are three repairtechniques that can be used on damaged cables.

(1) If the cable still retains adequate strengthto carry its design loading despite the frayed area,then clip off the frayed wires, clean any rust anddebris from the cable, and paint or wrap thedamaged portion of the cable with a protectivecoating.

(2) If the cable requires strengthening, thenreplace the cable, run an additional cable parallel

11-5

TM 5-600/AFJPAM 32-1088

to the existing cable to carry the balance of theload, or cut the cable and emplace a turnbuckle.

d. Rolled sections or plate girders. The mostcommon repairs to these sections are repairingcracks in welds and strengthening the sectionswith cover plates. In some cases, bent steel sec-tions are repaired using a technique called struc-tural steel flame straightening.

(1) Crack repair. The typical cracks that occurin rolled sections and plate girders are caused byfatigue and overloading. The cracks generally be-gin in the flange and propagate through the flangeinto the web. To properly repair these cracks, thecracks must first be closed and then a weldapplied. The importance of closing the crack is toensure that the dead load is properly transferredacross the entire cross section of the steel member.There are various methods which can be used toclose these cracks:

(a) Posttensioning the member (see para-graph 11-10).

(b) Jacking the load off the member (seeparagraph 12-7).

(c) Using a heated cover plate across thecrack and following these steps. Weld a cover plateto the member along only one side of the crack.Heat the cover plate to expand the plate’s length.While still heated, weld the opposite side of theplate to the member and allow the plate to cooland contract. This will pull the crack together.Weld the crack and apply a continuous fillet to thecover plate.

(2) Cover plates. The cover plate is a relativelyeasy and inexpensive technique to use in steelrepair. It can be used to bridge over a crack andtransfer the dead load throughout the cross sectionof the steel member or to just add strength to themember’s cross section. A key dilemma whenadding steel cover plates is the method used tointroduce dead load stresses into the new material.The most common method used with major mem-bers (i.e., W-sections) is to calculate the amount ofshorting required to produce the dead-load stressesin the existing member. Holes are drilled into theold and new members in such a way that the newmembers will be shortened by drifting, as thesections are bolted together. Another method isheating the cover plate after welding one end andthen welding the expanded plate into place asdiscussed. As the plate cools and contracts,stresses will be added to the cover plate. Examplesof various uses of the cover plate are:

(a) Extending an existing cover plate tobridge a welded crack (Refer to paragraph11-4a(3)).

(b) Building up the bottom flange, top

11-6

flange, or the web of the member to increase theload capacity of a steel member.

(c) Bridging or strengthening steel sectionsdamaged by corrosion or collisions (figure 11-5).

(3) Rules for using cover plates.(a) When one or more cover plates must be

renewed, consideration must be made for replacingthe defective plates with one plate of adequatesize.

(b) Cover plates should be connected bycontinuous fillet welds, high-strength bolts, orrivets.

(c) Where the exposed surface of old platesare rough or uneven from corrosion and wear, theyshould be replaced with new plates.

(d) Welded cover plates should be of suffi-cient thickness to prevent buckling without inter-mediate fasteners.

(e) Where the web was not originally splicedto resist moment, it may be spliced by addingcover plates or side plates.

(f) Where fatigue cracking can occur at thetop of welds on the ends of the cover plate, it isrecommended that bolting be used at the coverplate ends.

(g) When cover plates are used in compres-sion members, care must be taken to maintainsymmetry of the section to avoid eccentrical load-ings.

(4) Alternative to cover plates. Where the costof removal and replacement of the deck would beexcessive, as in ballasted-deck bridges, flange sec-tions may be increased by adding full-length longi-tudinal angles, plates, or channels just below theflange angles. First remove the stiffener anglesand then replace them with new stiffeners afterthe flange steel is added (figure 11-6).

(5) Stiffeners. Stiffeners are used to reinforceareas of the beam which are suspectable to webbuckling (intermediate transverse stiffeners), con-centrated loads greater than allowable stresses(bearing stiffeners), and web buckling due to bend-ing (longitudinal stiffeners).

(a) Intermediate stiffeners. Additional stiff-eners may be added by riveting, high-strengthbolting, or welding angles or metal plates perpen-dicular to the top flange and web. These stiffenersshould not be connected to the tension flange ofthe member.

(b) Bearing stiffeners. These stiffeners canbe reinforced by adding angles or plates to theexisting stiffeners, grinding the bearing ends ofthe new parts to make them fit closely, or weldingthe bearing ends to the flanges.

(c) Longitudinal stiffeners. Stiffness may beadded to the member by bolting or welding longi-

TM 5-600/AFJPAM 32-1088

Figure 11-5. Use of cover plates on rolled steel sections.

ELEVATION SECTION A-A

Figure 11-6. Iowa DOT method of adding angles to steel I-Beams.

tudinal angles to the web of the steel mem-ber.

(6) Piles.(a) When steel piles require additional sup-

port or protection, an integral pile jacket can beplaced around the steel piling. The encasement ofthe steel piles is accomplished by filling a fiber-glass form with Portland-cement grout. After theconcrete hardens, the fiberglass form remains inplace as part of the jacket. The integral jacketprovides protection to steel piles above and belowthe water. If the pile has deteriorated to the point

that additional steel support is required, coverplates can be added to the pile prior to placing thejacket or a reinforced concrete jacket can bedesigned.

(b) A procedure for installing an integralpile jacket follows (figure 11-7). Sandblast thesurfaces clean of oil, grease, dirt, and corrosion(near white metal). Place the pile jacket formaround the pile. Ensure standoffs are attached tothe form. Seal all joints with an epoxy bondingcompound and seal the bottom of the form to thepile. Brace and band the exterior of the form to

11-7

TM 5-600/AFJPAM 32-1088

DETAIL OF STANDARD TREATMENT OF TOP 12” OF PILING

Figure 11-7. Integral pile jacket for steel piles.

hold the form in place. Dewater the form. Fill thebottom 6 inches of the form with epoxy groutfiller. Fill the form to within 6 inches of the topwith a Portland-cement grout filler. Cap the formwith a 6-inch fill of epoxy grout. Slope the cap toallow water to run off. Remove the externalbracing and banding and clean off the form of anydeposited material.

(7) Flame straightening. Flame straighteninghas been used for over 40 years to straighten bentbeams or align members for proper connections.This process involves using “V” heats or triangleheats on flanges in conjunction with jacking de-vices to shrink the beam in the desired direction.The “V” heat is not heated completely, nor is itgone over again until cooled. The base of the “V”heat should not exceed 6 inches to avoid warpingof the flange. The heat used in the process shouldnot exceed 1,200 o F and in most areas will proba-bly be less. It is usually necessary to heat thewebs of damaged beams in conjunction with theflange. Overheating and jacking can cause theflange to exceed its yield strength and movevertically, instead of the desired horizontal direc-tion. For these reasons, this process should beconducted with trained and qualified operatorsonly to direct and monitor all heats, jack place-ments, and to supervise the program’s sequence ofevents.

e. Built-up sections. These sections are primarilyused to form truss systems. Cracks due to fatigueand overloading are repaired in the same manner

11-8

as rolled sections discussed previously. A combina-tion of cover plates, plates, angles, and other rolledsections can be used to reinforce or strengthen thebuilt-up member. Adding metal to these sectionsincreases the cross-sectional steel area in tensionmembers, reduces the slenderness ratio in com-pression members, and increases the sectionalmodulus in beams. Examples of strengthenedmembers are shown in table 11-1.

f. Composite sections. Composite action is devel-oped when two load-carrying structural memberssuch as a concrete deck and the supporting steelbeams are integrally connected and deflect as asingle unit. To ensure that no relative slippageoccurs between the slab and beam, the beam’sflange is imbedded into the concrete or shearconnectors are used to develop a composite actionbetween the surfaces. Three areas may requirerepair on a composite bridge: the concrete deck,the steel beam, or the composite action betweenthe deck and beam.

(1) Concrete deck. Concrete deck damage orfaults can decrease the bridge’s load capacity byreducing the composite action of the section. Theconcrete maintenance and repair techniques dis-cussed in chapter 13 should ensure that the deckwill carry the compressive forces required by thecomposite action.

(2) Steel beam. Any cracks or damage to thesteel section should be repaired (paragraph11-5d(1)) to ensure that, the correct compositeaction is received.

TM 5-600/AFJPAM 32-1088

Table 11-1. Built-up members

(3) Composite action. Several repair tech-niques exist to address the loss of compositeaction:

(a) Allow for noncomposite action. Build upthe steel beam to carry the load neglecting com-posite action. Angles can be added to the bottom ofthe top flange, cover plates can be added to thebottom flange, and/or stiffeners can be used tooffset web buckling.

(b) Repair shear connectors. The compositeaction of the section can be reactivated by repair-ing the shear connectors in the following manner.Use bridge diagrams and plans to determine thelocation and type of the shear connectors. Remove

the concrete from around the shear connector.Repair the existing connectors or replace withwelded studs. If welding is not feasible, high-strength bolts can be used as the shear stud asdemonstrated in figure 11-8. High-strength boltsmay also be added to increase the compositeaction.

(c) Deck replacement. The deck can be com-pletely replaced to renew the bond between theconcrete and the shear connectors. A new deck canbe poured or a new precast deck can be emplacedwith holes cast for the connectors, using grout inthe holes around the connectors (paragraph 11-9).Note that the composite action is normally de-

l l - 9

TM 5-600/AFJPAM 32-1088

Figure 11-8. Details of double-nutted bolt shear connector.

signed for live and impact loading, unless the deadload is distributed during the concrete curingprocess.

g. Steel grid decks. Steel decks are often used toincrease the live load capacity of bridges whenused to replace concrete decks. The primary main-tenance and repair problems with steel decks aredeterioration from exposure to the weather, weldfailure, and skid resistance. Repairs for corrosionand welds are the same for steel decking as withany other structural steel member.

(1) Concrete fill. Another method of repaircommonly used is to fill or partially fill the steelgrid with concrete. The concrete filled grid acts asa reinforced concrete deck. The steel grid provides

the steel reinforcement and the concrete fill pro-vides stiffness to help carry the load. This repairtechnique has several advantages: increased deckstrength, reduction in the effect of weathering bylimiting the water penetration, support of thewelded grid joints, and increased skid resistance.A wearing surface can be added to the deck toprovide additional skid and weather resistance.Recommended wearing surfaces are: latex modifiedconcrete (l-inch thickness), asphalt (1.75inchthickness), concrete overfill (1.75inch thickness),or epoxy asphalt (5/8-inch thickness).

(2) Exodermic deck.(a) This deck consists of a thin upper layer

(3-inch minimum) of precast reinforced concretedeck panels joined to the steel grating. The panelscan be precast and placed on a bridge or added toan existing steel deck using shear connectorswelded to the steel grid.

(b) The emplacement procedure follows.Weld shear studs/connectors to the steel grid.Precast concrete deck panels with holes for theshear studs. Place a thin metal, wood, or card-board plate with a diameter greater than theprecast stud hole around the stud. Place theprecast concrete deck panels on the steel grid andgrout the stud holes. Seal the cracks between theconcrete panels.

Section III. MEMBER REPLACEMENT

11-6. Tension members

Any tension in the member must be transferred toa temporary cable support system prior to remov-ing the damaged member (figure 11-9). Attach acable/turnbuckle system to the supporting frameparallel to the member to be replaced. Transferthe load carried by the steel member to the cableby tightening the turnbuckle. Remove and replacethe damaged steel member. Remove the temporarycable support system.

11-7. Compression members/columnsThe primary method to support the compressiveload during replacement is block and bracing.Emplace a steel or wood section parallel to themember to be removed. Jack the load off thedamaged member and place wood or steel shims onthe temporary support to transfer the load to thetemporary support. In some cases the shims maybe driven between the temporary support and theframe to transfer the load. A cable support systemwrapped around the temporary support and theframe can be used to hold the member in placeduring the replacement operation. Remove and

11-10

Figure 11-9. Method for relieving stress in tension members.

replace the damaged compression member. Re-move the shims and temporary support.

11-8. Beams

The addition or replacement of a stringer is nor-mally performed in conjunction with the replace-ment of the deck. If the deck is not removed themember must be replaced. from under the bridge.The beam replacement method will depend upon

TM 5-600/AFJPAM 32-1088

whether the beam/deck system is composite ornoncomposite.

a. Noncomposite beams. Place jacks under thedeck or under the beams that are not beingreplaced and jack the deck off the beam to beremoved. Remove beam or repair the damaged endof the beam. The beam may be cut to facilitateremoval. The beam may be jacked out of positionor a lift truck used to lower the beam. Lift or jackthe replacement beam into place. To use a lifttruck or cable system, a hole must be cut or drilledinto the deck to run the cable through. Positionthe beam on the bearing plates, jack the deckdown onto the new beam and check for distress inthe beam and deck. Remove jacks, temporarysupports, and repair any holes in the deck.

b. Composite beams (figure 11-10). Use jacks tolift the composite beam off its bearing. Burn or cut

the lower portion of the beam (web and bottomflange) from the fixed top flange. Grind the cutarea of the top flange smooth. Weld a new stringerto the old stringer top flange for continuity.

Figure 11-10. Replacement of a steel beam in acomposite section.

Section IV. UPGRADE STEEL BRIDGES

11-9. Creation of a composite action

The overall strength of a noncomposite stringer/deck configuration can be greatly increased bymaking the deck and stringers work together as asingle unit using composite action.

a. Concrete deck. The condition of the deckdetermines how to obtain composite action be-tween the deck and the stringers. If the concretedeck does not need replacing, create a compositeaction between the deck and stringers by theintroduction of shear connectors or studs acrossthe interface of the two materials. If the deck isbadly deteriorated, remove the deck and emplaceshear connectors or high strength bolts as dis-cussed in section II of this chapter. Another alter-native to recasting the deck is to precast concretepanels to be used as bridge decking (figure 11-11).This method reduces the interruption of traffic byallowing the upgrade to be conducted in stagesand not having to wait for a recast deck to cure.

b. Steel grid deck. A varying amount of strengthcan be added to a structure by welding the grid tothe top flange of the stringers. The strengthincrease is based on the stiffness that can begenerated by the deck to resist bending. If the gridis filled with concrete, it would act as a concretedeck with the welds providing the interface nor-mally achieved by shear connectors.

11-10. Posttensioning

Posttensioning can be applied to an existing bridgeto meet a variety of objectives. It can relievetension overstresses with respect to service load

NOTE: SHEAR STUDS SHOWN AREACTUALLY ADDED AFTERPRECAST DECK IS POSITIONED.

Figure 11-11. Precast deck with holes.

and fatigue-allowable stresses, reduce or reverseundesirable displacements, and add ultimatestrength to an existing bridge. Posttensioning fol-lows established structural analysis and designprinciples. A design procedure to posttension steeland composite stringer follows:

a. Determine the standards to which the bridgeis to be strengthened (loads, allowable stresses,etc.).

b. Determine loads and loads fractions for allstringers (dead load, long-term dead load, live load,impact load).

c. Compute moments at all critical locations fordead load, long-term dead load, and live andimpact loading.

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TM 5-600/AFJPAM 32-1088

d. Compute section properties as required.e. Compute stress to be relieved by posttension-

ing at all critical locations.f. Design posttensioning (tendon force, tendon

eccentricity, distribution of axial forces and mo-ments, and tendon length).

f = FF (P/A) + MF (Pet/I) (eq 11-1)where:

f = stress at extreme fiberP = tendon forceA = area of stringer (composite area if bridge

is composite)e = eccentricity of tendon with respect stringer

or bridge

I c = distance to extreme fiber

= stringer moment of inertia (composite sec-tion moment of inertia)

FF = force fraction (similar to load fraction forlive load)

MF = moment fraction (similar to load fractionfor live load)

g. Select tendons, accounting for losses andgains:

P adjusted = P / (1 - losses % + gains %) (eq 11-2)Assume a 4-percent loss for relaxation of tendonsteel, 7-percent loss for potential error in distribu-tion fractions, 2-percent loss for an approximate10°F temperature differential between tendonsand bridge. Assume a 25-percent gain from trucklive load.

h. Check stresses at all critical locations.i. Design anchorages and brackets. Typical ones

are shown in figure 11-12. Experience has shownbrackets should be about 2 feet long.

j. Check other design factors (beam shear, shearconnectors, fatigue, deflection, beam flexuralstrength, other, as required).

11-11. Truss systems

These systems can be strengthened by adding sup-plementary members to change to a stiffer systemor superposition another system onto the existingstructure. In cases where the dead load is increased,the substructure must be checked to ensure that itis adequate for the new loading requirements.

a. Add supplementary members. This techniqueis most often applied to Warren and Pratt trusses(figure 11-13). The most common use of supple-mentary members is to reduce the unbraced lengthof the top chords in the plane of the truss.Additional lateral bracing may be required toreduce the effective length in the plane perpendic-ular to the truss. The load capacity of the topchords in compression can be increased by 15 to 20percent using this technique.

b. Doubling a truss.(1) Steel arch superposition on a through truss.

A method of upgrading through-truss bridges is toreinforce the existing truss with a steel arch(figure 11-14). A lightweight arch superimposedonto the truss carries part of the dead and liveloads normally carried by the truss alone. Thetruss provides lateral support to the arch. Thereare two methods of attaching the steel arch to thetruss and both methods may require the end panelverticals to be strengthened to ensure adequatelateral support to the arch. In method 1, theexisting floorbeams and stringers are assumedadequate to carry the increased live load. In this

A. TENDON DESIGN B. BRACKET DESIGN

Figure 11-12. Design of posttensioning.

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TM 5-600/AFJPAM 32-1088

(A) EXISTING TRUSS

(B) MODIFIED TRUSS

Figure 11-13. Adding supplementary members to a truss frame.

Figure 11-14. Arch superposition scheme.

case, the arch support system is attached to thetruss at the existing truss verticals. A conserva-tive design includes the dead load of the arch andthe truss, along with the full live load. In method2, the existing floorbeams and stringers will notcarry the increased loading. This requires addi-tional floorbeams at the midpoints of existingfloorbeams to increase the capacity of the string-ers. The existing stringers can be analyzed astwo-span continuous beams, with the new floor-beams providing midspan support. Hangers areattached to the new floorbeams, and the arch isconnected to the existing verticals. In the determi-nation of the load-carrying capacity of the rein-forced system, the analysis of the arch and trussshould be conducted separately, with the two-spancontinuous stringers providing the loads to each.As an alternative to these methods, the arch canbe posttensioned along the bottom chords. Postten-sioning will reduce horizontal forces transferred bythe arch to the abutments.

(2) Superimposing a bailey bridge. Superim-posing Bailey trusses onto pony or through-trussbridges is a temporary upgrading method. Normally the Bailey trusses are a few feet longer than

the existing truss and are supported by the abut-ments. The Bailey trusses are connected by hang-ers to the existing floorbeams (additional floor-beams may be added and connected to the Baileytruss if the stringers are inadequate). The hangerbolts are tightened until the existing truss showssome movement, indicating complete interactionbetween the Bailey truss and the existing truss(figure 11-15). The Bailey truss is placed insidethe existing truss and blocked and braced againstthe existing truss to provide lateral bracing to theBailey truss. This may restrict sidewalk or road-way width. Design data for the Bailey bridge trussare provided in Army TM 5-312. A design proce-dure for this upgrade is as follows:

(a) Determine additional moment capacityrequired of the Bailey truss.

(b) Determine initial Bailey truss assemblythat meets required moment capacity (Army TM5-312).

(c) Replace the existing truss with a beamequivalent flexural rigidity.

(d) Replace the selected Bailey truss with abeam of equivalent flexural rigidity.

(e) Consider adding additional floorbeamsbetween existing beams if the stringers are inade-quate, and connect the Bailey truss to the old andnew floorbeams.

(f) Connect the two trusses rigidly at thepoints of application of the loads so that theydeflect simultaneously an equal amount. The loadscarried by each truss can then be determinedbased on deflected values and flexural rigidity. Ifthe Bailey is inadequate, select another trussconfiguration with greater moment capacity.

(g) Check required shear capacity.(h) Design hangers, lateral bracing, and

bearing supports. If separate bearing supports areused as shown in figure 11-15, the Bailey trussadds no additional dead load to the structure.

Figure 11-15. Reinforcing a pony truss with Bailey trusses.

11-13

CHAPTER 12

TM 5-600/AFJPAM 32-1088

TIMBER BRIDGE MAINTENANCE, REPAIR, AND UPGRADE

Section I. PREVENTIVE MAINTENANCE

12-1. General

When adequately protected, timber is a very dura-ble building material. The preventive maintenanceprogram for timber involves protection from waterand insect damage and the repair of damage fromthese sources and mechanical abrasion.

a. Water damage. Timbers placed on the groundor at the waterline and continually exposed to wetand dry cycles are subject to rotting. It is helpfulto elevate these members with concrete footings orenclose them in concrete. To prevent water frompenetrating the wood, the timber itself must betreated as well as any holes or sawed ends of thetimber.

(1) Preservatives for timber treatments. Thepenetration of the preservative normally rangesfrom 1 to 3 inches into the surface.

(a) Creosote pressure treatment. This is themost effective method of protection for bridgetimbers.

(b) Pentachlorophenol (penta-oil treatment).This is a heavy oil solvent applied using pressuremethods.

(c) Inorganic salt solutions. The salt solutionis applied using pressure and provides less waterrepelling than other treatments. The salt solutioncan corrode any hardware used to construct thebridge.

(2) Holes. Anchor bolts, drift pins, and lagbolts create holes where decay and deteriorationoften begins. These holes should be protected frommoisture penetration by swabbing with hot as-phalt or treating with creosote using a pressurebolt-hole technique.

(3) Timber ends. The natural opening in thegrain of timber ends allows easier water penetra-tion. If the end is cut, it should be painted with apreservative or swabbed with hot asphalt. Theends of the exposed members should be cappedwith a thin sheet of aluminum, tin, or similarmaterial (figure 12-1).

(4) Pile ends. Two options exist for treatmentof pile ends.

(a) Drill ¾-inch holes evenly spaced into thepile top 1½ inches deep, fill holes with creosote,and cap with lead sheeting (figure 12-1).

(b) Clamp an iron ring around the top of thepile, pour hot creosote into the ring, and allow the

pile to absorb the creosote, remove the ring, andcap the pile.

(5) Debris. Accumulated debris should be re-moved from any timber surface. Debris holds mois-ture which will penetrate into the timber member.

(6) Bark. The bark of native logs should beremoved if it is not removed during construction.This prevents moisture from being trapped be-tween the wood and bark.

b. Insect attack. The insects that attack timbercan be classified as either dry land insects (ter-mites, carpenter ants, and powder-post beetles) ormarine borers (wood louse or limnoria). The mostcommon treatment for dry land insects is topressure treat the wood with the proper poison andkeep careful watch for reinfestation. Marine borerscommonly enter the wood through bruises, breaks,or unplugged bolt holes. The area of infestationgenerally runs from the mudline to the water levelat high tide. The best method of control of marineborers is prevention of infestation. Preventivemaintenance for marine borers is conducted forseveral different stages of infestation.

(1) Prevent bruises. Install buttresses to pro-tect the structural members from damage by waveaction, current flow, or floating debris.

(2) Treat damaged wood. Plug or coat allholes, bruises, and freshly sawed ends with heavycreosote.

(3) Flexible barrier. Install a flexible PVCbarrier when a pile loses approximately 10 to 15percent of its cross-sectional area.

(a) Piles. Piles should be protected 1 footbelow the mudline and 1 foot above high tide(figure 12-2, part a). Sheath the pile with a 30-milPVC sheet. A half-round wood pole piece is at-tached to the vertical edge of the PVC sheet tohelp in the wrapping process. (Note: A pile withcreosote bleeding from its surface must first bewrapped with a sheet of polyethylene film prior toinstalling the PVC wrap to prevent a reactionbetween the PVC and the creosote.) Staple lengthsof polyethylene foam, ½ by 3 inches, about 1 inchfrom the upper and lower horizontal edges of thesheet. Fit the pole pieces together with one in-serted into a pocket attached to the bottom of theother pole. Roll the excess material onto thecombined pole pieces and tighten around the pile

12-1

TM 5-600/AFJPAM 32-1088

Figure 12-1. Protective covers for timber members.

with a special wrench. Secure the wrap and poleswith aluminum alloy rails. Nail rigid plastic bandsat the top and bottom directly over where thepolyethylene foam is located under the wrap.Install additional bands on equal distance centersbetween the top and bottom bands.

(b) Braces. Use wrapping when the braceshave light damage or to prevent damage fromoccurring. Remove the bolt which secures thebrace to the pile. Wrap the freed end with 20-milflexible PVC sheeting. Drive the bolt through thewrapping and existing hole. Rebolt the brace tothe pile. Wrap the remainder of the brace in thesheeting. Wrap bolt connections as shown in thefirst steps.

(4) Concrete barrier. When the pile has lost 15

A. FLEXIBLE PVC BARRIER

to 50 percent of its cross-sectional area, a concretebarrier can be poured around an existing pile toprovide compressive strength and a barrier tomarine borers (figure 12-2, part b). To accomplishthis, clean the pile to remove foreign materials.Place a tube form (fiberglass, metal, plastic, etc.)around the pile and seal the bottom of the form.Pump concrete grout into the form from thebottom to the top, thus forcing the water out of theform as the grout is placed.

c. Mechanical abrasion and wear.(1) This is an important consideration when

timber is used as piles or decking material. Pilesare subject to abrasion and wear from the currentand tidal flow and the effect of debris carried bythese flows. Methods available to help preventproblems in this area are:

(a) Emplace buttresses on the upstream sideof the piles.

(b) Encase the pile in concrete or steel.(2) Decks are susceptible to wear and abrasion

at locations where sand and gravel are trackedonto the bridge. Two methods to protect the wooddeck are:

(a) Treadways. Sheet plates or wood planksare placed in the wheel lines to provide a wearingsurface.

(b) Bituminous surface treatment. A liquidasphalt is applied to the deck and covered withgravel. This protects the deck from wear; it alsoseals between the planks and contributes to water-tightness. Note that the asphalt wearing surfacewill not bond to freshly creosoted timber. It isrecommended that the deck should be surfacedonly after a period of at least 1 year. This permits

B. FORM FOR A GROUTED BARRIER

Figure 12-2. Flexible PVC barrier installed on a timber pile.

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TM 5-600/AFJPAM 32-1088

the creosote to leach from the surface before the bucket to distribute water can be placed in con-asphalt is applied. venient locations. The danger of fire can also be

12-2. Fire protection reduced by a thin coating of tar or asphalt covered.To prevent tire, covered water barrels with a with sand, gravel, or stone chips.

Section II. REPAIR AND STRENGTHEN TIMBER MEMBERS

12-3. General

Repair methods for wood and timber structures aregenerally directed at correcting one or more of thefollowing problem areas: fungi and/or insect at-tack, deterioration, abrasion, and overload. Themost common repairs for timber structures areretrofitting timber connections, removing the dam-aged portion of the timber member and splicing ina new timber, and removing the entire memberand replacing it with a new member. Commonrules for timber repair are:

a. There should be at least 1/8-inch clearancesbetween timbers to allow the timber to dry prop-erly.

b. When native logs are used for construction,all bark should be removed to reduce moisturepenetration into the logs.

c. Green or wet timber shrinks considerablywhen seasoned. Repeated wetting and drying alsocauses dimension changes as great as 5 to 10percent in the direction perpendicular to thegrowth rings. Frequent renailing and tightening ofbolts is necessary.

d. Care should be taken when using new andsalvaged wood together to carry loads because of adifference in the sag and shrinkage of the mem-bers. The repair should avoid using new and oldstringers in the same panel.

e. Wood shims or wedges should be made fromheart cypress, redwood, douglas fir, or of the samematerial as the member.

f. Replacement members must have the samedimensions as the existing member accounting forshrinkage.

g. Always treat drill holes and cut ends, toprevent water or insect damage.

12-4. Connections

The typical timber connection relies on some typeof hardware to connect timber members. However,with the improvements made in glues and lamina-tion, glues are becoming a viable option that canbe used to enhance the connection. They provide abond between the wood surfaces and prevent mois-ture penetration into the connection.

a. Bolts, drift pins, and screws. The two mostcommon repairs required for these connections are

the replacement of the bolts due to rust or damageand retrofitting the bolt hole in the timber. Afterremoval and inspection of the existing bolt orscrew, proceed as follows:

(1) No deterioration (provides a snug fit forthe bolt). Inject a wood preservative into the holeand replace the bolt.

(2) Slight deterioration (loose fit for the bolt).Drill out the hole to a size that provides a goodwood surface. (Note: The diameter of the holeshould not be increased to the extent that thewood cross section will no longer carry the designload.) Inject a wood preservative. Replace the boltor screw with a larger size to tit the increased holediameter.

(3) Moderate deterioration (hole provides nobearing on the bolt and boring out the hole wouldreduce the connections load capacity). Remove thedeteriorated wood from around the edge of thehole. Inject a wood preservative, and, if possible,coat with tar or creosote. Attach steel plates withholes corresponding with those in the timber con-nection across the connection to bridge the dam-aged area. Place bolts through holes in the platesand tighten.

(4) Heavy deterioration (connection is beyondrepair). Cut off the damaged portion of the mem-ber and splice on a new portion, or replace themembers which form the connection.

b. Wood scabbing. Scabbing is used to join mem-bers together or splice repaired timber membersinto existing components. Exterior plywood can beused for light loads. However, in most casesstandard sawed timbers are used. The first step inany repair of this nature is to check the scabbingfor soundness and replace if required. If the scab-bing is in good shape, it can be tightened invarious ways:

(1) Remove loose nails or screws and replacewith larger size.

(2) Add nails or screws to the existing scab-bing.

(3) Drill through the scabbing and memberand emplace bolts.

c. Steel connector plates. Connection plates aremade of light-gauge galvanized steel plates inwhich teeth or plugs have been punched. If the

12-3

TM 5-600/AFJPAM 32-1088

plate must be replaced, the wood surface may betoo damaged for the teeth of the new plate toprovide a shear interface. In this case, woodscabbing can be used to replace the steel plate or anew steel plate can be emplaced using nails toprovide the interface. A loose plate can also betightened and strengthened by adding nails orscrews to the plate.

d. Nails, spikes, and screws. These are the mostcommon hardware items used to form wood con-nections. When these items become loose the onlyoptions are to:

(1) Replace the nail or screw with a largerone.

(2) Drive or screw the connector back in place,and add nails or screws to help carry the load ofthe loose connector.

e. Deck connectors. Timber decking is connectedto steel stringers with floor clips (figure 12-3) ornails driven into the under side of the decking andbent around the top flange of the steel member(figure 12-3). Composite action is achieved be-tween a concrete deck and timber stringers byeither castelled dapping, consisting of ½ to ¾-inchcuts in the top of the stringer; castelled dapping inconjunction with nails or spikes partially driveninto the top of the stringer; lag bolts at a 45-degree inclination to horizontal; or epoxies.

12-5. Repair of graded lumber

When lumber is damaged to the point that thestructural integrity of the member is in question,scabbing or slicing of the member may be requiredto bridge the damaged area.

a. Scabbing. Scabbing can be used when themember is moderately damaged and the additionof the scabbing allows the member to carry itsdesign load. The method of scabbing used dependsupon the type of timber member:

(1) All members. Clean and treat damagedarea. Relieve the member of any load, if possible.Place scabbing on the sides and/or the top andbottom of the member to transmit the load acrossthe damaged area. The scabbing can be of a likewood, steel plate with bolt holes, or a steel plateconnector.

(2) Beams and stringers. A steel plate can bescabbed onto these members to repair longitudinalcracks as follows (refer to figure 12-4): drill holesthrough the deck on either side of the stringer at aminimum distance equal to the beam depth pastthe damaged area; drill an additional set of deckholes past the other end of the damaged area;place draw-up bolts through the holes that extendpast the bottom of the existing beam (use washersor support straps to help prevent pull through);place a steel retaining plate on the bottom of thestringer and hold it in place with support strapsand nuts on the draw-up bolts; and tighten theretainer plate in place. This process willstrengthen the damaged area by providing a steelcover plate across the damage, closing any slits orcracks in the wood, and by creating a compositeaction between the stringer and the deck.

(3) Piles. A reinforced concrete scab or jacketcan be placed around a partially deteriorated pileto restore the strength. The procedure is the sameas placing protective cover around a pile with the

Figure 12-3. Common deck connectors.

12-4

TM 5-600/AFJPAM 32-1088

exception that reinforcing bars are placed insidethe form for added strength (see paragraph 12-1).

(4) Caps. Caps can be scabbed to extend thebearing area where the bottoms of stringers orlaminated decking has deteriorated over the cap.The repair consists of attaching 6-inch-thick tim-bers with a depth equal to the cap to each side ofthe existing cap as follows (figure 12-5). Use atemplate to lay out 4-inch O-ring connectors on thecap and scabs. Cut O-rings and drill ¾-foot holesthrough the cap and scabs. Insert O-rings in thecap. Position scabs and clamp or bolt into place.Insert bolts through scabs and cap using O.G.washers on both ends of the bolt, and tighten intoplace.

b. Splicing. Splicing is required when the lum-ber is too severely damaged to carry its designload (figure 12-6). To splice, remove the damagedportion of the wood member. Treat the freshly cutend of the member and the replacement member.Then, nail, screw, or bolt scabbing onto the exist-ing timber and replacement to join them together.

12-6. Repair of piles

When piles are damaged or deteriorated to thepoint that the structural integrity of the pile is inquestion, it may be more advantageous to repairthe existing pile than to drive a replacement. Thekey to pile repair is that the existing pile musthave good bearing as part of the foundation. The

Figure 12-4. Repair of cracked or split stringers

Figure 12-5. Timber cap scabs provide additional bearing.

12-5

TM 5-600/AFJPAM 32-1088

Figure 12-6. Stringer splice.

method of repair chosen depends upon the type ofpile damage:

a. Pile damage extending below the waterline.(1) Single-pile steel reinforced splice (figure

12-7, part a). Sever the pile approximately 2 feetbelow the mudline. Cut a stub pile the length ofthe defective portion. Connect the ends of the stubpile and the existing pile with a center drift pin ordowel with a ¾-inch diameter and 18 inches long.Reinforce the joint by placing three angle sections2 feet long (1.5 inches by 1.5 inches or 2 inches by2 inches) at each third point around the circumfer-ence of the pile connection. The angles will be heldin place by a minimum of four lag screws (4 incheslong) per angle.

(2) Multiple pile steel reinforced splice (figure12-7, part b). Sever the piles about 2 feet belowthe mudline. Place a mudsill on the portion of thepiles left in place. Secure even bearing on thepiles. Tamp earth between piles for an even sillsupport. Ensure that the cross section of mudsillequals the bent cap and extends 3 feet beyond thepiles. Connect pile stubs between the mudsill andcap using the drift pins and angles described forthe single pile. If the pile damage extends abovethe waterline, sever the pile about 2 feet below thedamage and proceed as previously described for abelow-water single pile. Seal the joint with creo-sote or asphalt.

b. Single pile damage above the groundline(figure 12-8). Remove the soil around the pile tobelow moisture line. Construct cribbing or placestruts for support jacks. Place jacks and jack up

12-6

cap ½ inch to 1 inch. Cut the dowel connecting thecap to the pile. Cut the deteriorated pile off belowthe permanent moisture line. Make cut at a rightangle to the centerline of the pile. Cut the newpile ¼ inch longer than the removed section. Placethe concrete form and reinforcing bars into posi-tion. The form must allow a minimum of 6 inchesof cover around the pile. The form can be madefrom steel culvert or steel drums and need not beremoved. Place the new pile section on the exist-ing pile stump. Ensure an even contact at thebearing points and check to make sure the rebarhas not shifted. Pour Class II concrete into theform and slope the top of the pour to allow waterto run off. Reattach the cap to the pile with adowel or an exterior steel plate.

c. Settlement and bearing loss of a pile due todeterioration. Place cribbing or struts adjacentto the pier and jack the stringers off the cap toan elevation ½ inch higher than desired. Cutthe tops off the decayed pile. Cut a shim ¼ inchless than the space between the cap and the pilehead and treat the pile head and shim. Placethe shim into position. Lower jacks and fix theshim into position (figure 12-9). Toenail the shimto the pile. Dowel through the cap and repair. Nailfish plates across the repair and remove thecribbing.

d. Damage to fender piles. Piles that have beenbroken between the top and bottom wales (figure12-10) can be repaired as follows: cut off the pilebelow the break; install a new section, securedwith epoxy; fit a strongback into position behind

TM 5-600/AFJPAM 32-1088

Figure 12-7. Timber pile repair.

Figure 12-8. Concrete jacket supporting a timber pile splice.

the pile with bolts; and connect a metal wearingshoe on the front side of the pile.

12-7. Repair of posts

Damaged bent posts can be repaired in much thesame way as single piles or through splicing acrossthe damaged section.

12-8. Repair of sway bracing

Repairs involving sway bracing may include theerection of bracing to help stabilize a pier or thereplacement of existing bracing. When bracing isdesired, measurements should be taken and thetimber cut and treated prior to the repair opera-tion.

a. Installation of bracing. Temporarily attachbracing to piling in its final position using galva-nized nails. Locate and drill bolt holes through thebracing and pile. The holes should be the samediameter as the bolts. Treat all holes with a hot oilpreservative. Install bolts, washers, and nuts andtighten into place.

b. Repair sway bracing. Locate the end of thedeteriorated or damaged brace. Cut off the dam-aged portion to the nearest pile. Take the requiredmeasurements for the new bracing and cut thetimber to size. Drill bolt holes in the new bracing,rebolt the bracing to the piling using existingholes when possible, and drill new holes in thepiles to realign bracing. Treat all timber cuts andholes with hot oil preservatives followed by acoating of hot tar.

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TM 5-600/AFJPAM 32-1088

Figure 12-9. Shimming timber piles.

Figure 12-10. Fender pile repair.

Section III. MEMBER REPLACEMENT

12-9. Replacement of tension timber compo-nents

These members can be replaced using the sameprocedures outlined in paragraph 11-6 for steelmembers.

12-10. Replacement of compression timbercomponents

a. Piles. There are three methods that can beused to replace a damaged pile:

(1) Pull the existing pile and drive a new pile.(2) Drive a new pile along side the existing

pile as follows (figure 12-11, part a): locate thecenterline of the stringers nearest to the pile to bereplaced, cut a hole through the deck to drive thenew pile, remove bracing which interferes withpile driving. Set pile at a slight batter so that it isplumb when pulled into position. Drive to a speci-fied bearing. Install U clamps and blocking aroundthe pile being replaced or on adjacent piles if theexisting pile has no load carrying capacity. Place a

12-8

jack on the block system, and jack the cap off thepiles. Cut the new pile ¼ inch below the cap, andplace copper sheeting on the pile head. Pull thepile into position. Lower jacks and dowel or strapthe cap to the pile. Repair and replace bracing anddeck.

(3) Leave the existing pile in place and addnew piles as follows (figure 12-12): cut holes in thedeck to drive piles, and drive piles on either side ofthe damaged pile, perpendicular to the bent. Thenew pile should off set at least one pile width toone side of the damaged pile. Cut the tops of thenew piles and place a support across the tops ofthe new piles to form a cap under the existing pilecap. The two caps should be in contact with eachother. Use wedges to ensure that the load istransferred to the new bent.

b. Bent post. Replace as follows: install a tempo-rary support parallel to the damaged post, removethe existing post, install a new post and wedgeinto place to ensure proper load transfer, drive a

TM 5-600/AFJPAM 32-1088

drift pin through the pile cap, wedge into the postto secure into position or nail the wedge into place,cut the wedges off flush with the cap, post andconnect the post to the sill, and cap with scabs.

c. Caps. To replace caps, temporary or falsebents should be constructed to support the deckand floor during the replacement operation (figure12-11). The new caps should be given a free, evenbearing on each pile or post support. The capshould be fastened to each post or pile by drift pinsand spikes.

12-11. Replacement of flexural timber compo-nents (stringers)

Stringers should be lined up to a true plane fornew or replacement wood (figure 12-13). Stringersin good condition and of proper size may besalvaged and reused. New and salvaged stringersshould not be used together in any one panelbecause of differences in sag and shrinkage be-

A. JACKING FROM CRIBBING.

tween the new and old stringers. When selectingmaterial for new stringers, it should be of thesame width and depth as the other stringers in thepanel; however, in case of emergency, the bestavailable size may be used temporarily. Thestringers should be wedged as tightly against thedeck at the center of the span as they are at theend; do not attempt to fit to the deck sag byadzing. As the new stringers acquire sag, thewedges will be tightened to compensate. The proce-dure for adding or replacing stringers is as follows:

a. Under-the-deck method (figure 12-13). Placetwo jacks on each cap in adjoining bays next to thestringer being replaced. Use steel plates betweenthe jack faces and the timber. Stop traffic duringthe jacking operation and jack the deck up ¼ to ½inch to clear the stringer. Cut a wedge out of oneend of the stringer, and bevel the corners on theother end. If the replacement timber is warped,place the camber up to provide bearing on all thedeck members. Place the stringer’s wedged end on

B. JACKING FROM A BENT PILE.

Figure 12-11. Jacking methods for timber cap replacement.

Figure 12-12. Pile replacement methods.

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its cap, and push it far enough onto the cap toallow the opposite end to be placed on its cap.Lift the beveled end of the stringer onto the cap.Anchor a “come-along” to the cap under thebeveled end, and attach the cable to the wedgedend of the replacement stringer. With the come-along, pull the new stringer into a final positionthat provides an equal bearing on each cap andwedge the under side of the stringer to providecontact with the deck. Remove the support equip-ment, and nail the wedge into position in such afashion that the nails can be removed and thewedges adjusted to account for sag.

b. Above-the-deck method. Cut the deck alongeach side of the stringer to be replaced. Removeenough decking to allow one end of the stringer torotate on the cap enough for the other end to clearthe far side cap when it is lifted. Lift the far end ofthe stringer with a cable through a precut hole inthe deck clear of the cap. Jack or pull the stringerinto final position. Replace the decking.

12-12. Replacement of timber decking

a. Timber flooring. Floor planks should be laidwith the heart side down because it is more resis-tant to decay. A ¼-inch spacing should be providedbetween planks for drainage, expansion, and aircirculation. Structural grade hardwood planks, 6to 10 inches wide, are preferred as decking mate-rial because wider planks have a tendency to curl.All nails or spikes should be driven so that theirheads are imbedded into the plank. Planks of thesame thickness should be placed adjacent to eachother with a full, even bearing on the stringers.Wedges should not be used to level flooring be-cause they are easily dislodged and leave theflooring in a loose and uneven condition.

b. Wheel guards. Replacements should use thesame size sections as the original and be fastenedwith the same bolt spacing. The bolts should beextended through the riser or scupper blocks andfloor planks (figure 12-14).

NEWSTRINGER

TYPICAL JACKING ARRANGEMENT ERECTION SCHEME

Figure 12-13. Belowdeck timber stringer replacement.

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TM 5-600/AFJPAM 3 2 - 1 0 8 8

Figure 12-14. Splicing in a wheel curb.

Section IV. TIMBER BRIDGE UPGRADE

12-13. Strengthen intermediate supports(piers)

a. Bent post. Bent posts can be strengthened bynailing 2-inch thick planks to the cap and sill andthe post between them. The planks should beapproximately the width of the pier component towhich it is nailed. This has the effect of increasingthe cross sectional wood area carrying the com-pressive loads of the bridge.

b. Concrete encased piles. Paragraph 12-4 dis-cusses the process of encasing a timber pile inconcrete to shore up a timber splice. The sametype of technique can be used to extend thereinforced concrete casing the full length of thetimber pile. The procedure involves the same stepsrequired in jacketing steel or concrete piles (Referto paragraphs 11-4 and 13-5).

c. Helper bents.(1) This system can be used to strengthen an

entire pier section. It is used when existing pilinghave lost their bearing and settlement occurs,when the load capacity of the piling is in question,or when the load bearing capacity of an existingpier is increasing. Timber piles are driven throughthe deck parallel and adjacent to the pile bent andtopped with a cap to interface with the stringers.In essence, a new pier is constructed adjacent tothe existing pier to help carry the loads (figure12-15).

(2) Helper bents are installed in the followingmanner. Locate the centerline of stringers or

beams and mark the positions of the helper bentpiles parallel to the pier. Cut holes in only onetraffic lane at a time. For timber decks, make acut along the centerline of the stringers andremove enough decking to drive the pile. Forreinforced concrete decks, remove sufficient con-crete in a square pattern to drive the piles. Cutthe reinforcing steel at the center of the hole andbend out of the way. Set the piling and drive tothe required bearing. Cut the pile ¼ inch abovethe existing cap (make allowances for grade differ-entials due to settlement). Place cover plates overthe deck holes and move to the next position.Repeat the same operation until all the piles aredriven. Jack up the superstructure ½ inch usingthe existing pier. Place a timber cap onto thepilings. Lower the superstructure onto the caps ofthe new piers and strap the caps to the pilings.Shim between the superstructure and the cap asrequired to obtain the proper bearing. Remove thedeck plates and repair the deck. Construct cross-bracing on the new pile bents and between thebents for intermediate bents.

12-14. Shorten span length

The strength increase obtained from shortening atimber span is fairly large due to the short spansgenerally associated with timber bridges. Shorten-ing is accomplished by adding one of the following:

a. Intermediate piers. Paragraph 10-22b.b. A-Frame. Paragraph 10-22c.c. Knee brace. Paragraph 10-22d.

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Figure 12-15. Diagrams of an intermediate helper bent.

12-15. Posttensioning

Many types of posttensioning can be applied totimber structures. The most common and effectivemethods are the king post, which counteractsbending, and the external stirrup, which reducesshear effects.

a. King post.(1) In effect, the king post shortens the effec-

tive length of the reinforced span. One techniquethat can be used to install the king post to atimber bridge is as follows (figure 12-16):

(2) Install a ¾-inch threaded steel eyeboltthrough the stringer at an equal distance fromeach end of the member. Steel plates with a holefor the eyebolt should be used under the eye-bolt nuts to help prevent pull through. Note thatthe eyebolts should be positioned in a low mo-ment area of the stringer and the internal mo-ments generated by posttensioning should bechecked. Run a steel cable through the eye of theeyebolt and use u-bolts to tie the cable to theeyebolt. Attach a king post to the underside of thebeam at midspan. The king post can be of steel orwood and should have an eye to run a steel cablethrough. Run a cable through the eye of the kingpost, and connect the ends of the cable to thecables from the eyebolts using a turnbuckle.Tighten the turnbuckle to provide posttensioningto the stringer.

b. External stirrups. External stirrups can beapplied to timber stringers to provide shearstrengthening in much the same way as stirrupsare used to reinforce concrete. Small channels orangles are used as tie plates across the top andbottom of the stringer, and threaded bars tight-ened into holes in the tie plates form the externalreinforcement (paragraph 13-7).

12-16. Add stringers

Additional stringers can be installed in an existingbridge to redistribute the bridge loading. The sametechnique used to replace stringers can be used toinstall additional stringers under an existing deck(paragraph 12-10).

Figure 12-16. Timber beam strengthened using king postposttensioning.

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12-17. Strengthen individual members

Timber members can be strengthened by the addi-tion of steel cover plates to counteract flexure andshear as follows (figure 12-17): Apply a fieldpreservative treatment to the timber and paint thesteel cover plates. Attach the flexural cover plateto the timber member using lag screws. Attachshear cover plates to both sides of the memberusing through bolts. Note that proper spacing oflag screws or bolts will ensure that compositeaction between the plate and timber stringeroccurs.

Figure 12-17. Steel cover plates used to reinforce atimber beam.

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CHAPTER 13

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CONCRETE BRIDGE MAINTENANCE, REPAIR, AND UPGRADE

Section I. PREVENTIVE MAINTENANCE

13-1. General

Preventing concrete deterioration is much easierand more economical than repairing deterioratedconcrete. Preventing concrete deterioration beginsin the design of the structure with the selection ofthe proper materials, mixture proportions, concreteplacement, and curing procedures. Even a welldesigned concrete will generally require follow-upmaintenance action. The primary types of mainte-nance for concrete are surface protection, jointrestoration, and cathodic protection of the reinforc-ing bars. Surface maintenance involves the appli-cation of coatings for protective purposes. Jointproblems are usually treated with one of a varietyof types of joint sealers, and cathodic protectioninvolves the use of anodes connected to the rein-forcing bars which will deteriorate in place of thereinforcing bar.

13-2. Surface coating

a. General. Surface coatings are applied to con-crete for protection against chemical attack byalkalies, salt solutions, or other chemicals. Theactual need for a coating must first be established,and then the cause and extent of any deteriora-tion, rate of attack, and environmental factorsmust be considered for selecting the right coatingfor the job. A variety of coatings and sealants areavailable for waterproofing and protecting concretesurfaces. Among the products are several types ofoil and rubber resins, petroleum products, sili-cones, and other inorganic and organic materials.Some of these products have been successful inprotecting new concrete from contamination bydeicing salts and other harmful environmentalagents. They have generally been unsuccessful atstopping the progression of already contaminatedconcrete.

b. Surface water repellents. This type of coatinghelps prevent or minimize scaling from the use ofdeicers. This is a low-cost treatment that providesa degree of protection for non-entrained concrete oris added insurance for air-entrained concreteplaced in the fall and subject to deicing saltsduring the first winter.

(1) Linseed oil. A mixture of 50 percent lin-seed oil and 50 percent mineral spirits is normallyused. The mixture is applied in two applications

on a dry, clean concrete surface. The surfacecoating should be less than 5 mils, and a test stripshould be used to help determine the applicationrate. The normal application rate is 40 squareyards per gallon for the first application and 65square yards per gallon for the second application.This treatment should last for 1 to 3 years.

(2) Silicone. Silicone has been used on con-crete to minimize water penetration. Care must betaken where moisture has access to the backside ofthe wall and carries dissolved salts to the frontface where it is trapped by the silicone. Siliconeoxidizes rapidly and is somewhat water soluble.Treatments are required every 1 to 5 years.

c. Plastic and elastomeric coatings. These coat-ings form a strong, continuous film over theconcrete surface. To be effective in protectingconcrete, the coating must have certain basicproperties: the adhesive bond strength of the coat-ing to the concrete must be at least equal to thetensile strength of the surface concrete; the abra-sion resistance must prevent the coating frombeing removed; chemical reactions must not causeswelling, dissolving, cracking, or embrittlement ofthe material; the coating should prevent the pene-tration of chemicals that will destroy the adhesionbetween the coating and concrete; for proper adhe-sion, the concrete must be free of loose dirtparticles, oil, chemicals that prevent adhesion,surface water, and water vapor diffusing out of theconcrete.

(1) Epoxies. Epoxies are used, with a solidcontent from 17 to 100 percent as a clear sealant,with coal or tar mixed as a mortar. As with mostthin coatings and sealants, a protective overlay orcover is required if they are exposed to traffic wearor abrasive forces.

(2) Asphalt. Asphalt is used as a protectiveoverlay for bridge decks. This surface provideswater protection and a protective wearing surface.

13-3. Joint maintenance

Little maintenance is required for buried sealantsbecause they are not exposed to weathering. Mostfield-molded sealants require some type of periodicmaintenance if an effective seal is to be main-tained. Minor touchups in field-molded sealantscan usually be made with the same sealant. Where

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the failure is extensive, it is necessary to removeand replace the sealant. The sealant can be re-moved using handtools or on large projects byrouting or plowing using suitable tools. Sawingcan be used to enlarge the joint to improve theshape factor for the new sealant. After the jointhas been cleaned it can be resealed. For moreinformation on joints see paragraph 12-12.

13-4. Cathodic protection

The only remedial procedure other than replace-ment that has proved effective in stopping thecorrosion process in contaminated concrete is ca-thodic protection. Compared with the cost of re-placement, it is normally much less expensive.There are two types of cathodic protection systemsthat can be used to prevent corrosion in reinforc-ing bar. The systems are the impressed currentsystem and the galvanic system.

a. Impressed current system. This system useslow-voltage, high-amperage direct current from anexternal power source to make the reinforcing barinto a cathode. This system is most effective wheninstalled during the construction of decks, piers,

stringers, and abutments. During the installationensure that the reinforcing bars are in goodcontact with one another; this will allow thecurrent to flow through the reinforcing system.This system can be used to protect the exposedreinforcing bar; however, it is usually not aneconomical option in this special case. A commonpower source used in the system is a rectifierwhich provides DC power from an AC source.

b. Galvanic system. This system requires noexternal power source but uses anodes of a specialalloy to generate the current required to suppressthe corrosion process. Three common alloys arezinc, magnesium, and aluminum. A procedureused to protect exposed reinforcing bars in con-crete piles follows (figure 13-l): Clean an areaon the exposed reinforcing bar on which to attacha zinc anode (figure 13-1, part a). Attach one7-pound anode to every 6 feet of reinforcing barexposed to brackish or salt water (figure 13-1,part b). Note that additional site testing may berequired to adjust the weight of the anode toensure a 2-year life for the anodes. Less brackishwater or fast moving water will affect this lifeexpectancy.

a. ZINC ANODE REBAR ATTACHMENT b. ANODE ATTACHMENT SPACING

Figure 13-1. Cathodic protection for reinforced concrete piles.

Section II. REPAIR AND STRENGTHEN

13-5. General

The repair and strengthen methods discussed inthe following paragraphs apply only to convention-ally reinforced concrete and specifically do notapply to prestressed concrete. Refer to paragraph13-17 for a discussion of prestressed concretemembers. In concrete repair it is imperative that

the causes and not the symptoms of the problemare dealt with. The types of concrete damage, thecauses, and the means of determining the causesare discussed in chapters 5 and 8. The repair ofdeteriorated concrete can be categorized into re-pairs suited for cracking and those suited forspalling and disintegration. Repair of deterioratedconcrete is required when: (1) The deterioration

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affects the structural design performance of thebridge; (2) The deterioration exposes the reinforc-ing steel to corrosive action; (3) The lack of arepair will make the bridge unsafe for trafficunder normal operating conditions. (Examples: pot-holes, extensive spalling of the deck, damagedparapets, etc.)

13-6. Crack repairs

The large variety of crack types prevents a singlerepair method. Active cracking may requirestrengthening of the concrete across the crack toprevent further crack expansion and the applica-tion of a flexible sealant that will expand with thecrack. Dormant cracks basically require bondingacross the crack for the load carrying portion ofthe concrete and sealing in all other areas.

a. Conventional reinforcement. This method isprimarily used to bridge isolated cracks in theload-bearing portion of the structure for active anddormant cracks. This repair bonds the crackedsurfaces together into one monolithic form (figure13-2). Proceed as follows: clean and seal theexisting crack with an elastic sealant applied to athickness of 1/16 to 3/32 inch and extending at least¾ inch on either side of the crack, drill ¾-inchholes at 90 degrees to the crack plane, fill the holeand crack plane with epoxy pumped under lowpressure (50 to 80 psi), and place a reinforcing bar(No. 4 or No. 5) into the drilled hole with at leastan 18-inch development length on each side of thecrack.

b. Prestressing steel. This technique uses pre-stressing strands or rods to compress the crack toclose it. (Refer to paragraph 13-12c).

c. Drilling and plugging. This repair consists ofdrilling down the length of the crack and groutingthe hole to form a key that resists transversemovement of the section. This technique is most

effective on isolated cracks that run in a straightline and are accessible at one end (figure 13-3). Toaccomplish, proceed as follows: drill a hole (2- to3-inch diameter) centered on and following thecrack its full depth, and clean out the drill hole.The specifics of the remaining procedure are givenfor:

(1) Dormant cracks. Fill the drill hole andcrack with a cement grout. If watertightness isrequired over the bond transfer, fill the hole withasphalt or a like material. When both watertight-ness and a keying action is required, drill twoholes along the crack and fill one with grout andthe other with asphalt.

(2) Active cracks. Fill the hole with precastconcrete or mortar plugs set in bitumen. Thebitumen is used to break the bond between theplug and the hole to prevent cracking of the plugby subsequent movement of the crack.

d. Dry packing. This process consists of ram-ming or tamping a low water content mortar intoa confined space. This technique is effective inpatching holes with a high depth-to-area ratio ordormant cracks. To accomplish, proceed as follows:Undercut the area to be repaired so that the basewidth is slightly greater than the surface width.For dormant cracks, a slot should be cut along thesurface of the crack 1 inch wide and 1 inch deepwith a slight undercut. A sawtooth bit is a goodtool to use for this purpose. Clean and dry the slot.Apply a cement slurry bond coat of equal parts ofcement and fine sand to the faces of the slot. Placedry pack mortar in the slot in 3/8-inch layers andcompact each layer with a hard wood stick work-ing from the middle out or a T-shaped rammer forlarger areas. If the mortar becomes spongy duringthe compaction process, allow the surface of thedry pack to stiffen and then continue the compac-tion. Fill the slot completely and strike flush with

Figure 13-2. Reinforcing bars inserted 90 degrees to the crack plane.

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TM 5-600/AFJPAM 32-1088

Figure 13-3. Crack repair by drilling and plugging.

the concrete surface using a board or the hardwoodcompaction stick.

e. Epoxy injection.(1) Cracks as narrow as 0.002 inch can be

bonded by injection of epoxy along the crack(figure 13-4). This technique also has been used torepair delamination in bridge decks.

(2) To accomplish, proceed with the followingsteps. Clean the crack of all oil, grease, dirt, orsubstances that may retard the bonding process.Seal the surface of the crack by brushing an epoxyalong the surface of the crack and allowing it toharden. If high-pressure injection is required, cut aV-shaped groove along the crack ½ inch deep and¾ inch wide, and fill the groove with epoxy. Installepoxy injection ports. There are three proceduresin current use for the installation of injectionports:

(a) Drilled holes with fittings. This methodis used in conjunction with V-grooves and involvesdrilling ¾-inch-diameter holes to a depth of ½ inchbelow the apex of the groove. An injection fitting(small-diameter pipe, plastic tubing, valve stem,etc.) is bonded into the hole.

(b) Bonded flush fittings. When cracks arenot V-grooved, injection ports are bonded flushwith the concrete face. This type of port would beseated directly into the crack, and the face of theport would be flush with the concrete face.

(c) Interruption in seal. A portion of the sealis omitted from the crack. For this method, theepoxy injector must have a gasket system thatcovers the unsealed portion of the crack and allowsthe epoxy to be injected into the gap withoutleaking.

(3) After installation of the injection ports,mix the epoxy to conform to the current AmericanSociety of Testing and Materials specification forType I, low-viscosity grade epoxy. Inject the epoxy

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Figure 13-4. Epoxy injection used to seal cracks.

into the crack using hydraulic pumps, paint pres-sure pots, or air-actuated caulking guns. Verticalcracks should be injected starting with the port atthe lowest elevation and working up. Horizontalcracks can proceed from either end of the crackand run to the far end of the crack. Remove theepoxy seal by grinding or some other means andpaint over the injection ports with an epoxypatching compound.

f. Flexible sealing. This repair method involvesrouting and cleaning the crack and fitting it witha field-molded flexible sealant. It is used for activecracks in which the crack is the indication of ajoint requirement in the concrete, and the forma-tion of a joint does not impair the capacity of thestructure. To install, proceed as follows (figure13-5): Rout out the active crack to the dimensionsthat comply with the width and shape factorrequirements of a joint having the same move-ment. Clean the crack and routed area by sand-blasting and/or water jetting. Apply a bondbreaker at the bottom of the slot to allow thesealant to change shape without forming a stressconcentration on the bottom of the sealant. Com-mon bond breakers are polyethylene strips andpressure sensitive tape. Fill the slot with a suit-able field-molded flexible sealant in accordancewith the proper American Concrete Institute (ACI)specification. Narrow cracks can be sealed withoutrouting by applying a bond breaker over the crackand overlapping the sealant across the bondbreaker to seal the crack (figure 13-5).

g. Routing and sealing. This method is used toseal dormant cracks that do not affect the struc-tural integrity of the bridge member. The sealprevents water from reaching the reinforcing steel.Proceed as follows (figure 13-6): Rout along the

TM 5-600/AFJPAM 32-1088

Figure 13-5. Flexible seals used in concrete crack repair

Figure 13-6. Conventional procedure for sealing dormant cracks.

crack to provide a minimum surface width of ¼inch. Clean the cut and allow the surface of thecut to dry. Apply sealant (ACI 504R).

h. Grouting (hydraulic-cement). Dormant crackscan be repaired with portland cement containingslag or pozzolans for strength gain. The grout canbe sanded or unsanded. Proceed as follows: Cleanthe concrete along the crack. Install built-up seats(grout nipples) at intervals astride the crack toprovide contact with the pressure injection appara-tus. Seal the crack between the grout nipples witha cement paint or grout. Pump grout into thecrack through the nipples. Maintain the pressurefor several minutes to ensure good penetration ofthe grout. The grout should have a water-cementratio of one part cement to one to five parts water.The water-cement ratio can be varied to improvethe penetration into the crack. Chemical groutscan also be used. They consist of solutions of twoor more chemicals that react to form a gel or solidprecipitate as opposed to cement grouts that con-sist of suspensions of solid particles in a fluid.Guidance regarding the use of chemical grouts canbe found in EM 1110-2-3504.

i. Stitching.

(1) Stitching is the process of drilling holes onboth sides of the crack and grouting in stitchingdogs (U-shaped steel bars with short legs) thatbridge the crack (figure 13-7). Stitching is used toreestablish tensile strength across the crack. Adja-cent sections to the cracked section may requirestrengthening to prevent a crack from forming inthe adjacent sections of the concrete.

(2) Install stitching as follows: Drill a hole ateach end of the crack to blunt it and relieve thestress concentrations. Clean and seal the crack,use a flexible seal for active cracks. Drill holes onboth sides of the crack. The holes should not be ina single plane and the spacing should be reducednear the ends of the crack. Clean the holes andanchor the legs of the dogs in the holes with anonshrink grout or an epoxy. The stitching dogsshould vary in length and orientation to preventtransmitting the tensile forces to a single plane.

(3) The following considerations should bemade when using stitching: Stitch both sides ofthe concrete section where possible to preventbending or prying of the stitching dogs. Bendingmembers may only require stitching on the ten-sion side of the member. Members in axial tension

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Figure 13-7. Reinforcement of a crack using stitching.

must have the stitching placed symmetrically.Stitching does not close the crack, but can preventits propagation. Stitching that may be placed incompression must be stiffened and/or strengthenedto carry this force, such as encasement of thestitching dogs in a concrete overlay.

13-7. Spall repair

Spa11 is repaired primarily by removing the deteri-orated concrete and replacing it with new concreteof similar characteristics. The process involves thefollowing:

a. Analyze the structure to determine the effectof removing the deteriorated concrete down tosound concrete will have on the structure. Deter-mine the need for and the design of any shoringand bracing required to support the structureduring the repair.

b. The concrete must be removed down to soundconcrete or to a depth where the patch is at least¾ inch thick. Sharp edges, at least 1 inch deep,should be formed around the area to be patched toavoid feather-edging the concrete patch. It is alsoadvantageous to make the bottom of the removedconcrete areas slightly wider than the surface toform a keying effect with the new concrete patch.If a large surface area is to be overlaid with newconcrete, a minimum of ¼ inch should be removedfrom the surface. The edges of the overlay shouldbe chipped or cut at about 45 degrees to prevententrapping air under the overlay. Tools that canbe used to remove concrete are: jackhammers,diamond saws, rotary head cutters, high-pressurewater jets, thermal lances, and hydraulic splitters.Clean sound surfaces are required for any repairoperation, and the absolute minimum amount of

13-6

concrete to be removed is all unsound concrete,including all delaminated areas.

c. The patch area must be cleaned to remove alldebris from the concrete removal process. Theexisting concrete surface and reinforcing steelshould then be blast cleaned. The repair is cleanedagain and inspected. Any aggregate particles thathave been cracked or fractured by scarifying orchipping should be removed to sound concrete.

d. Patches should be reinforced with wire meshattached either to reinforcing bars or dowels tosecure the patch to the old concrete. Loose rein-forcing bars should be tied at each intersectionpoint to prevent relative movement of the bars andrepaired concrete due to the action of traffic inadjacent lanes during the curing period. If newreinforcement is required, an adequate length toattain a lap splice (30 times the bar diameter)must extend from the existing section. If a propersplice is not possible, holes must be drilled into theexisting concrete and dowels or anchors installed.

e. An interface must be established between theexisting and new concrete. Options for this in-clude:

(1) Epoxy bonding. Ensure the surface isclean, dry, and free of oil. Apply the epoxy agentto the prepared surface.

(2) Grout or slurry. Clean the prepared surfaceand saturate with water. Remove all freestandingwater with a blast of compressed air, and apply athin coat of grout.

f. After surface preparation, the new concretemust be promptly applied to the repair and fin-ished.

g. The new concrete should be moist cured for aminimum of 7 days to prevent drying shrinkage

and to allow proper strength development. This ismost easily accomplished by covering the patchwith plastic or wet burlap.

h. Shotcrete can also be used to replace concretein spalled areas. Shotcrete is a mixture of portlandcement, sand, and water shot in place by com-pressed air. It is best used for thin repair sections(less than 6 inches deep) or large irregular sur-faces. Shotcrete requires a proper surface treat-ment similar to that required for a concrete over-lay and no form work is needed to confine the mix.This makes shotcrete useful in the repair ofvertical walls, beams, and the underside of decks.This technique requires specialized training andguidance on the use of shotcrete as a repairmaterial is given in EM 1110-2-2005.

13-8. Joint repairThe maintenance and minor repair of joints iscovered in chapter 10 of this manual. Deteriora-tion around a joint in concrete may require arepair of the concrete around the joint in conjunc-tion with resetting the joint. Some of the special-ized joint repairs are as follows:

a. Joint sealant repair. This repair can be usedwhen the sealant has failed, but the premoldedjoint filler is still in good condition. The repairprocedure is as follows: remove the existing seal-ant (with tools such as a mechanical joint cleaneror joint plow); score the joint walls with a pave-ment saw; clean the joint with a mechanical brush

TM 5-600/AFJPAM 32-1088

and remove debris; place sealant in accordancewith the manufacturer’s installation procedure.

b. Expansion joint seal. This seal can be used toseal open joints, replace failed preformed jointmaterial, and reseal joints sealed with elastomericseals. The installation procedure is as follows.Determine the required elastomeric seal size inaccordance with the guidelines in table 13-l:

Table 13-1. Elastomeric seal size guidelines

Clean the joint. A high pressure water jet is usefulin removing any debris or existing joint materialin the joint. Saw cut the joint across the bridge toprovide a uniform dimension in the repair joint(figure 13-8, part a). Blow out the joint withcompressed air to remove any standing water, dirt,gravel, etc. Brush an adhesive/lubricant onto theinner joint faces. Position the seal over the joint(figure 13-8, part b). Compress the bottom portionof the seal and press into the joint. Ensure the sealis seated to its proper depth and alignment. Tomake an upward turn with the seal, proceed as

a. SAW CUT DETAILS OF A JOINT. b. SEAL INSTALLATION IN EXPANSION JOINTS

c. UP-TURN AND DOWN-TURN DETAILS

Figure 13-8. Expansion joint repair with elastomeric seals.

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follows (figure 13-8, part c). Drill three ½-inch-diameter holes on line in the elastomeric seal. Theholes should be spaced at intervals of 1/3H (H =height of the seal) on lines 2/3H from the bottom ofthe seal. Cut the lower section of the seal from thebottom, and seal the hole in all three locations.Bend the seal in the desired position and installfollowing normal sealing procedures. To make adownward turn with the seal, proceed as follows(figure 13-8, part c). Drill a M-inch hole along theseal at the location of the bend in the seal in aposition 2/3H from the bottom of the seal. Cut awedge from the underside of the seal by makingtwo intersecting angled cuts (45 degrees) from thebottom of the seal to the ½-inch hole. Bend theseal down and install using normal sealing proce-dures.

c. Expansion joint seals with an asphalt overlay.The installation procedure is as follows (figure13-9). Saw cut along lines parallel to and 1 foot oneither side of the joint at a 60-degree angle awayfrom the joint. Remove the asphalt inside the cutarea and clean the concrete deck. Place a filler inthe joint to maintain an area between the jointand asphalt. Apply an epoxy bonding compound tothe cleaned concrete surface. Place latex modifiedconcrete in the cut area and finish off flush withthe existing asphalt. After the concrete has set,saw cut a joint to the required width and depth.Remove all debris and filler from the joint. Applyadhesive to the joint faces and install the seal.

d. Expansion dam repair.(1) Open armored joint. This repair method

can be used to spot repair a loose expansion damor across the full length of armored, finger, andsliding joints. The repair involves removing a

small portion of concrete, welding a steel strap tothe dam and the deck’s reinforcing steel, andreplacing the concrete (figure 13-10, part a). Theprocedure is as follows. Identify the loose portionsof the expansion joints requiring repair. Mark 12-by 8-inch rectangles immediately adjacent to thedam on 18-inch centers, and saw cut around theperimeter of the rectangle to a l-inch depth.Remove the concrete inside the rectangle to adepth required to expose the deck’s reinforcingsteel with an air hammer. Cut a slot 1 inch wideinto the dam and weld a ¼- by l- by 12-inch steelZ-strap into the slot and to the deck’s reinforcingsteel. Sandblast the rectangular opening in theconcrete and blow out all debris. Apply an epoxybonding compound to the exposed concrete and fillthe rectangle with a compacted latex modifiedportland cement concrete.

(2) Sliding joint. This repair can also be usedon armored and finger joints. The repair placesl-inch diameter bolts on 2-foot centers through thebridge deck and the bolt is welded to the expan-sion dam. The bolt is anchored to the bottom of thedeck with a steel plate, wedge washer, and nut(figure 13-10, part b). The repair procedure is asfollows. Burn holes through the top flange of theexpansion dam on 2-foot centers across the area tobe repaired. Below the holes in the top flange, drill1¼-inch hole through the deck at a 45-degreeangle. Saw cut a 6- by 6-inch area, 1 inch deeparound the exit of the drilled hole on the under-side of the deck. Remove the concrete inside thescored area to the reinforcing steel. Place a l-inch-diameter bolt through the hole in the flange andthe deck. Cut the head of the bolt flush with thetop flange and weld to the flange with a fullpenetration weld. The bolt should extend through

END DAM SYSTEM FOR

END BENT JOINT SEALS

Figure 13-9. Placing an elastomeric seal in an asphalt overlay.

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A. WELDED Z-STRAP REPAIR. B. ANCHOR BOLT REPAIR.

Figure 13-10. Expansion dam repairs.

the deck. Place a ½-inch-thick layer of latexmodified concrete in the drilled hole around thebottom of the bolt. Position a ¼- by 4- by 4-inchsteel plate with a 1¼-foot hole, add the wedgewasher (45-degree wedge) and nut, then tighten.Apply an epoxy bonding compound to the 6- by6-inch area and fill with latex modified concrete.Drill and tap the flange close to the bolt locationand install a zerk fitting. Pump epoxy through thefitting to fill the voids under the expansion damand around the bolt. Remove the zerk fittings andweld the hole closed. Grind the top flange smooth.

13-9. Abutments and wingwalls

The concrete in abutments and wingwalls maydeteriorate from the effects of water, deicing chem-icals, freeze cracking, or impact by debris whichresults in breaking off the edges or portions of theface. These conditions require that repairs bemade to prevent continued deterioration, particu-larly increased spalling due to moisture reachingthe rebar and causing corrosion. The followingsteps in the rehabilitation procedure are normallyrequired (figures 13-11 and 13-12). Establish traf-fic control, as necessary. Excavate as required toset dowels and forms. Remove deteriorated con-crete by chipping and blast cleaning. Drill and settie screws and log studs to support the form work.Set reinforcing steel and forms. Apply epoxy-bonding agent to the concrete surface. Place con-crete, cure, and remove forms. Install erosioncontrol material as necessary.

13-10. Bridge seats

Problems often found in concrete bridge seatsinclude deterioration of concrete, corrosion of thereinforcing bars, friction from the beam or bearingdevices sliding directly on the seat, and the im-proper design of the seat which results in shearfailure. During the preliminary planning stage,

Figure 13-11. Repair of abutment and wingwall facesusing a jacket.

the specific cause of the problems should be deter-mined to properly repair the damage. A detailedplan of the jacking requirements should be made.Several repair procedures are as follows:

a. Abutment and cap seats (figure 13-13). Re-move traffic from structure during jacking opera-tions. Lift jacks in unison to prevent a concentra-tion of stress in one area and possible damage tothe superstructure. Restrict vehicle traffic duringthe repair as much as possible. Saw cut aroundconcrete to be removed and avoid cutting reinforc-ing steel. Remove deteriorated concrete to thehorizontal and vertical planes ensuring that soundconcrete is exposed. Add reinforcing steel as re-quired and construct forms to confine the newconcrete. Apply bonding material to the preparedsurface that will interface with the new concrete.Place and cure new concrete. Service, repair, orreplace bearings as necessary.

b. Concrete cap extension. This repair restoresadequate bearing for beams that deteriorated orsheared at the point of bearing by anchoring anextension to the existing cap. The procedure is asfollows (figure 13-14). Locate and drill 6-inch-deepholes to form a grid in the existing cap and install

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FRONT VIEW SECTION A-A

Figure 13-12. Repair of broken or deteriorated wingwalls.

concrete anchors that will accept a ¾-inch bolt.Place ¾- by 9-inch bolts 4 inches into the concreteanchors. Wire a reinforcing steel (No. 4 bars) gridto the inside head of the anchor bolts. Construct aform around the reinforcing steel grid with aminimum of 4 inches cover around the sides of thebolts and a minimum of 2 inches cover for the faceof the extension. Place roofing paper against thebottom of the beam and place Class IV concrete inthe form. Remove forms after 3 days. The exten-sion should not carry any load during curing.Repair any damage to the end of the beam.

c. Beam saddle. The saddle restores bearing forbeams and caps where they have deteriorated orbeen damaged in the bearing area. The procedureis as follows (figure 13-15). Obtain measurementsof the cap and beam width, and have an engineerdesign the saddle. Prepare the top of the cap andthe beams for good bearing contact with thesaddle. Use neoprene bearing pads for contactpoints between the saddle and the beam and cap.Place saddle members in contact with the capacross the cap on each side of the beam. Drop onebolt through a hole at each end of the two saddlecap contact members, and bolt the saddle bearingmembers in place under the beam. Place neoprenebearing pads under the beam, and tighten thebolts in place. Install and tighten the remainingbolts.

13-11. 13-11. Columns and piles

The typical repair involving concrete columns andpiles is to place a concrete jacket around the

member to protect it from further deterioration orto restore the structural integrity of the member.The repair can be made with a standard wood ormetal form work which is removed after curing ora fiberglass form that remains in place and helpsprotect the surface of the member.

a. Standard formwork. This repair method isused for piles that have been damaged or deterio-rated to the point that structural integrity of themember is in question. In this procedure, the pileis encased with a concrete jacket reinforced withepoxy coated reinforcing steel (figure 13-16). Theconstruction procedure is as follows. Remove alldeteriorated concrete to a sound base. Clean thepile to ensure proper bonding with the jacket.Sand-blast rebars to remove corrosion and rust.Place a rebar cage around the pile to reinforce thepile. Treat the inside face of the forms with arelease agent, and set the forms for the concretejacket around the rebar cage and pile. Dewater theforms and place Class III concrete. Allow a mini-mum of 72 hours for curing.

b. Fiberglass forms. These forms can be used toprevent further deterioration or restore structuralintegrity to piles and columns. The repair involvesthe encasement of the pile or column in thefiberglass form and filling the form with epoxygrout, cement grout, or Class III concrete. Thefiberglass forms should be a minimum of 1/8-inchin thickness with noncorrosive standoffs and acompressible sealing strip at the bottom. Installa-tion procedures will vary depending upon thedegree and location of damage and the specificjacket manufacturer’s recommendations. The basic

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SECTION A-A

Figure 13-13. Typical repair of concrete bridge seats.

procedure for using fiberglass forms is as follows.Clean pile surfaces of materials which preventbonding. Remove deteriorated concrete down to asound concrete base. Sandblast exposed rebar to a“near-white metal” finish. Place the jacket formwork around the pile. The form should have builtin standoffs, concrete blocks attached to the insideface, or double-nut bolts placed through drilledholes to provide the proper standoff. Seal theform’s joints and bottom with an epoxy compound.Place external bracing and bonding materials tohelp prevent form movement and bulging. De-water form and fill the space between the pile andform with the appropriate tiller. Cure, removeexternal bracing and banding, and clean any fillermaterial from the form’s faces.

13-12. Stringers and beams

Spall in beams can be dealt with in a similarmanner as walls by constructing a form aroundthe damaged area and replacing the lost concrete(paragraph 13-10a). Shotcrete is an excellent ma-terial to use in this type of repair. The majorproblem caused by concrete deterioration is theloss of effective reinforcing bar diameter due tocorrosion. This is also true of cracks which allowwater to penetrate to the reinforcing steel. Due tothe criticality of reinforcing bars in beams, it isimportant to repair or replace any damaged rein-forcing bars. There are three methods available toreestablish the reinforcing steel required forproper beam performance:

a. Conventional repair. Refer to paragraph 13-7.b. Conventional reinforcement. Refer to para-

graph 13-6a.c. Prestressing steel. This method can be used to

close a crack and/or provide external reinforcingsteel to support the beam loading (figure 13-17).Install as follows. Clean the crack and any exposedrebar. Drill holes through the side of the beam(missing existing rebar) for the prestressing anchorat both ends of the beam. Install anchors on bothsides and at both ends of the beam by runningbolts through prepared holes in the anchors andbeam. The anchor should be designed by an engi-neer and generally consist of a reinforced anglesection with holes in the flanges to receive thethrough bolts and the tension tie. Connect thetension tie to each set of anchors on either side ofthe beam. Apply tension to the ties using aturnbuckle or torquing nuts. Tension should beapplied across both sides of the beam evenly.Increase tension until the crack closes and sealwith a flexible seal. This method can also be usedin conjunction with a patch to replace deterioratedsteel.

13-13. Decks

a. Spall. Spa11 repair on bridge decks can bebroken into three categories based on the overallcondition of the deck, as is shown further into thisparagraph. The categories are identified accordingto the amount of spall, the extent of total deterio-ration (spall, delaminations, and corrosion poten-

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a. FRONT VIEW OF CAP EXTENSION b. CROSSSECTION OF CAP EXTENSION

Figure 13-14. Concrete cap extension to increase bearing surfaces.

Figure 13-15. Typical beam saddle design using standard steel W-sections.

tials over -0.35 volts), and total percentage ofconcrete samples containing at least 2 pounds ofchloride per cubic yard of concrete:

(1) Extensive active corrosion.(a) Spa11 covers more than 5 percent of total

deck area.(b) Deterioration covers more than 40 per-

cent of total deck area.(c) Chlorides high in over 40 percent of

samples.

(2) Moderate active corrosion.(a) Spa11 covers from 0 to 5 percent of total

deck area.(b) Deterioration covers from 5 to 40 percent

of total deck area.(c) Chlorides high in 5 to 40 percent of

samples.(3) Light to no active corrosion.

(a) No spa11 present.

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Figure 13-16. Standard concrete pile jacket with steel reinforcing cage.

Figure 13-17. External prestressing strands used to closea crack.

(b) Deterioration covers from 0 to 5 percentof total deck area.

(c) Chlorides high in from 0 to 5 percent ofsamples.In many cases the identifying characteristics ofthe moderate category will overlap with the othertwo categories, and a best judgment based onengineering, economics, and other factors must beused to establish the appropriate repair for thebridge. The deck repair procedures for each ofthese categories are outlined in table 13-2.

b. Cracks. Cracks in decks can be repaired asdiscussed in paragraph 13-6. In composite decksystems, prestressing techniques can be employedto help close cracks in the deck. The repair

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Table 13-2. Bridge deck restoration procedures

13-14

consists of placing a tie rod across the deck crack.The tie rod is emplaced through drilled holes inthe beams on either side of the cracked deck. Thetorquing nuts or turnbuckles on the tie rods arethen tightened to close the crack in the deck(figure 13-18).

13-14. Replacement of concrete members

a. Decks. After the deteriorated portion of thedeck has been removed, replacement decks can becast in place or precast sections can be fixed intoposition. The advantage to using precast sectionsis that no form work is required, and smallerportions of the deck can be removed and replaced,thereby minimizing traffic disruption. The proce-dures for both types of deck replacement areoutlined:

TM 5-600/AFJPAM 32-1088

(1) Cast in place. Remove the deteriorateddeck. Construct the form work for the new deck.Shore the form work to carry the dead load of thedeck. Install reinforcing steel. Place the concreteand allow to cure long enough to achieve itsdesign strength.

(2) Precast. Remove the deck area to be re-placed with the precast section. Place the precastsections with a crane, being careful to overlapextended rebar when placing adjacent panels andwire together. Form around the connection be-tween adjacent panels and apply an epoxy agent tointerface between the sides of the panels and thenew concrete.

b. Piles. Piles which cannot be jacketed can bereplaced in much the same manner as timber piles(chapter 12).

Figure 13-18. Closing a crack in a deck using prestressing steel.

Section III. UPGRADE CONCRETE BRIDGES

13-15. General upgrade methods

a. Substructure upgrade. The strength of thesubstructure can be increased by adding piles/columns to the pier or by placing a concrete jacketaround the existing piles.

(1) Jacketing (figure 13-19, part a). The jacket-ing procedures for strengthening columns andpiles are basically the same as the repair proce-dures discussed in section II of this chapter. Forstrengthening, the jacket must be extended thefull length of the column and connected to the capand footing. The jacket is connected to the existingcap and footing by grouting dowels into drilledholes.

(2) Jacketing with spiraled reinforcement(figure 13-19, part b). This method is used toimprove the lateral strength of circular columns. It

involves wrapping tensioned prestressing wirearound the existing column or applying a series ofM-inch-diameter reinforcing bar hoops with turn-buckles at each end to pretension the hoops. Acover of shotcrete or cast-in-place concrete is thenapplied to the reinforcing steel.

(3) Partial jacketing (figure 13-19, part c).This technique involves attaching precast sectionsto the existing column using bolts or the casting ofany additional reinforced concrete to the existingcolumn that does not completely encase the col-umn.

b. Span reduction. The common methods ofshortening spans discussed in chapter 10 alsoapply for concrete bridges. These methods includeintermediate piers, A-frames, or knee braces.

c. Posttensioning. All the posttensioning tech-niques shown in table 10-3 can be applied to

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concrete bridges. The connections and componentsfor these systems should be designed by a struc-tural engineer.

d. Add stringers. Additional concrete stringerscan be cast in place under the deck and connectedto the deck with dowels. The added dead load mayreduce the benefit of the additional stringers andmay prove uneconomical to construct. Anotheralternative is the addition of steel stringers be-tween each of the existing concrete stringers. Theabutments and caps can have seats constructed onthem for the steel members.

13-16. Strengthen individual members

Individual concrete members can be strengthenedby jacketing, inserting reinforcing bars, prestress-ing, or by external reinforcement. Members aregenerally strengthened to counter increases inshear or flexural forces.

a. Shear reinforcement of beams.(1) External reinforcement (figure 13-20). In-

stall external reinforcement as follows. Run chan-nel sections across the top of the beam or attachchannel sections to either side of the upper portionof the beam using through bolts in drilled holes.Run channel sections across the bottom of thebeam and place tie rods through prepared holes inthe top and bottom channels. Use torque nuts oneither end of the rods to prestress the rods. Theprestressed rods installed at specified spacingsprovide an increase in the shear capacity of thebeam.

(2) Reinforcing bar insertion (figure 13-2). In-sert bars as follows. Seal all cracks with siliconerubber. Mark the girder centerline on the deck.Locate the transverse deck reinforcement. Drill45-degree holes avoiding the reinforcing bars.Pump epoxy into the holes and cracks, and insertthe reinforcing bars into the epoxy-filled holes.

a. STANDARD TECHNIQUE b. SPIRAL REINFORCEMENT c. PARTIAL JACKETING

Figure 13-19. Jacketing of concrete columns.

a. ADDITION OF EXTERNAL STIRRUPS b. ATTACHMENT OF VERTICAL STIRRUPSUSING STEEL SECTIONS AS SIDEMEMBERS

Figure 13-20. External shear reinforcement for concrete beams.

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b. Shear reinforcement of box beams.(1) External reinforcement (figure 13-21). In-

stall as follows. Drill holes for the tendons throughor just outside the web of the box beam. Countersink the drill holes. Install the prestressing ten-dons. Inject epoxy into any existing cracks.Tighten the nuts on the tendon to prestress thebeam, carefully following design specifications toavoid overstressing the beam. Inject epoxy aroundthe tendons, and dry pack the countersink holesflush with the concrete surface.

(2) Web reinforcement (figure 13-22). Install asfollows. Locate and drill holes on the inside face ofthe web of the box-beam. Clean the holes of dustand debris, and set concrete anchors in place.Place anchor bolts with a spacer and steel plateattached. Weld rebar to the steel plate on eitherside of the bolt. Attach horizontal reinforcing barsto the vertical rebar.

Figure 13-22. Web reinforcement of boxbeams.

c. Flexural reinforcement of beams. The twomost common methods of strengthening concretebeams in flexure are adding steel cover plates tothe beam’s tension face and partial encasement ofthe beam in reinforced concrete.

(1) Steel channel cover plate (figure 13-23).Install as follows. Remove dirt and any foreignmaterial, sand blast, and then remove any debriswith compressed air. Locate the beam’s stirrupsand longitudinal steel. Mark the location of thedrill holes to miss the reinforcing steel and still beabove the bottom row of longitudinal steel. Drillholes through the concrete beam. Drill or cut holesin the steel channel to match the holes in thebeam. Position the channel into place and installbolts to hold it in place. Inject epoxy resign intothe remaining holes and install the bolts. Take outthe positioning bolts, inject epoxy, and reinstall.Seal between the channel and the concrete beam.

Figure 13-23. Steel channel used to reinforce beams

reinforcing bars are held in place by the verticalbars that are attached to the existing beam (figure13-24, part a), placed through the beam (figure13-24, part b), or run through the existing deck(figure 13-25, part c). The concrete cover can becast in place or shotcreted.

(3) External plates.

(2) Partial jacketing. The purpose of the jack-eting in this case is to provide cover for theadditional reinforcing bars which are positioned tohelp carry the flexural load. The longitudinal

(a) This method involves bonding mild steelplates to the concrete member. This compositesystem relies on the effectiveness of the bondsbetween the concrete/adhesive and the adhesive/steel surfaces. This technique should not be usedon members with reinforcement corrosion or highconcentrations of chloride ions.

INSIDE THE WEB OUTSIDE THE WEBINSIDE THE HOLLOW BOX

Figure 13-21. Reinforcing boxbeams for shear.

(b) Design considerations to avoid brittlecracking of the concrete cover are as follows: usesteel plates with a minimum width/thickness ratioof 40 to reduce horizontal shears; limit the nomi-nal elastic horizontal shear stress in the adhesiveto the tensile capacity of the concrete for anapplied safety factor.

(c) This strengthening method should beconducted by trained personnel using the followingprocedure. Clean and sandblast the steel platesand apply an epoxy primer paint adhesive. Sand

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Figure 13-24. Concrete beams reinforced with concrete sleeves.

blast the concrete to remove the surface laitanceand to expose coarse aggregates. Drill holes inthe slab or beam to emplace anchor bolts forthe ends of the steel plates. Mix adhesive andapply to the steel plate with a thickness between1/16th to 1/8th inch. The adhesive should be thickeralong the centerline of the plate to prevent airpockets from forming between the plate and con-crete faces. Place the steel plate on the undersideof the beam or slab and bolt the ends to hold intoplace. Supplemental bolting is used at the plateends to reduce peel failures and hold the plate inplace in case of failure. Apply pressure along thefull length of the plate using secondary supportsand wedges. Tighten the end bolts into place andallow the adhesive to cure (normally 24 hours).Remove secondary supports and paint the steelplate.

13-17. Prestressed concrete members

By design, prestressed concrete members behavedifferently than conventionally reinforced mem-bers. As a result, many of the methods discussedin the preceding paragraphs do not apply toprestressed concrete members. Due to its complex-ity, the repair of prestressed concrete members isnot covered in this manual. The following reportsby the Transportation Research Board should bereferred to for the evaluation and repair of pre-stressed concrete members:

(1) National Cooperative Highway ResearchProgram (NCHRP) Report Number 226, “DamageEvaluation and Repair Methods for PrestressedConcrete Bridge Members.”

(2) NCHRP Report Number 280, “Guidelinesfor Evaluation and Repair of Prestressed ConcreteBridge Members.”

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APPENDIX A

REFERENCES AND BIBLIOGRAPHY

A-1. References

Government Publications

Departments of the Army, Navy, and Air Force

AR 420-72 Surfaced Areas, Bridges, Railroad Track and AssociatedAppurtenances

FM 5-446 Military Nonstandard Fixed BridgingTM 5-628 Railroad Track StandardsFM 5-277 Bailey Bridge

Coast Guard

Pamphlet CG204 Aids to Navigation

Department of Transportation, Federal Highway Administration

Bridge Inspector’s Training Manual 70Inspection of Fracture Critical Bridge Members

Nongovernment Publications

American Association of State Highway Transportation Officials (AASHTO), 444 North CapitolStreet, Washington, DC 20001

Standard Specifications for Highway Bridges, Fourteenth Edition, 1989Manual on Uniform Traffic Control DevicesManual for Maintenance Inspection of Bridges

National Cooperative Highway Research Program (NCHRP), Transportation Research Board,National Research Council, Washington, DC

Report 280 Guidelines for Evaluation and Repair of PrestressedConcrete Bridge Members, December 1985

Report 293 Damage Evaluation and Repair Methods for PrestressedConcrete Bridge Members, November 1980

A-2. Bibliography

ManualsAASHTO Maintenance Manual, 1987. American Association of State Highway and Transportation

Officials, Washington, DC (1987).AASHTO Manual for Bridge Maintenance, 1987. American Association of State Highway and Transporta-

tion Officials, Washington, DC (1987).American Concrete Institute (ACI) Manual of Concrete Practice, 1988. American Concrete Institute, Detroit,

MI.Annual Book of American Society for Testing and Materials (ASTM) Specification, 1990. American Society

for Testing and Materials, 1961 Race Street, Philadelphia, PA.Guide Specifications for Strength Evaluation of Existing Steel and Concrete Bridges, 1989. American

Association of State Highway and Transportation Officials, Washington, DC (1989).Guide Specifications for Fracture Critical Non-Redundant Steel Bridge Members, 1978. American Associa-

tion of State Highway and Transportation Officials, Washington, DC (1989).Manual for Railway Engineering, American Railway Engineering Association (AREA), Washington, DC

(1989).Manual for Bridge Maintenance Planning and Repair Methods, Volume I. Florida Department of

Transportation, State Maintenance Office.

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Technical Publications-Departments of the Army, Navy, and Air Force

FM 5-742 Concrete and MasonryFM 5-551 CarpentryTM 5-744 Structural Steel WorkTM 5-622/MO-104/AFM 91-34 Maintenance of Waterfront Facilities

Reports

National Cooperative Highway Research Program, Report 293. “Methods of Strengthening ExistingHighway Bridges.” Transportation Research Board, National Research Council, Washington, DC,September 1987.

National Cooperative Highway Research Program, Report 333. “Guidelines for Evaluating CorrosionEffects in Existing Steel Bridges.” Transportation Research Board, National Research Council,Washington, DC, December 1990.

Journal ArticlesAmerican Concrete Institute Committee 201, “Guide to Durable Concrete,” Journal of the American

Concrete Institute, Number 12, Proceedings Volume 74, pages 573-609, December 1977.

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APPENDIX B

SUGGESTED ITEMS FOR ARMY ANNUAL AND AIR FORCE BIANNUALBRIDGE INSPECTIONS

BRIDGE INSPECTION ITEMS

Include the following items:1. Installation.2. Bridge number.3. Location.4. Date inspected.5. Existing bridge classification (if applicable).

For the following components, address each appropriate inspection item and make notes of any observeddeficiencies and recommendations:

A. Timber Abutments1. Signs of settlement.2. Rusting of steel rods.3. Decay of end dam, wingpost, post, and/or cap.4. Deterioration of block (bearing and anchor).5. Decay of sill and footing.6. Loose timbers.7. Decay of breakage of piles (wing or bearing).

B. Steel Pile Abutments1. Settlement.2. Rusting of end dam, pile and/or cap.3. Section loss of steel members.4. Missing, loose, or rusting bolts.

C. Concrete Abutments, Wingwalls, and Retaining Walls1. Settlement.2. Proper function of weep holes.3. Cracking or spalling of bearing seats.4. Deterioration of cracking of concrete.5. Exposed reinforcing steel.

D. Timber Piers and Bents1. Settlement.2. Decay of caps, bracing, scabbing, or corbels.3. Missing posts or piles.4. Decay of posts or piles.5. Debris around or against piers.6. Section loss of sills or footings.7. Erosion around piers.8. Rusting of wire-rope cross bracing.9. Loose or missing bolts.10. Splitting or crushing of the timber when:

a. The cap bears directly upon the cap, orb. Beam bears directly upon the cap.

11. Excessive deflection or movement of members.

E. Steel Piers and Bents1. Settlement or misalignment.2. Rusting of steel members or bearings.

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3. Debris.4. Rotation of steel cap due to eccentric connection.5. Braces with broken connections or loose rivets or bolts.6. Member damage from collision.7. Need for painting.8. Signs of excessive deflection or movement of members.

F. Concrete Piers and Bents1. Settlement.2. Deterioration or spalling of concrete.3. Cracking of pier columns and/or pier caps.4. Cracking or spalling of bearing seats.5. Exposed reinforcing steel.6. Debris around piers or bents.7. Section loss of footings.8. Erosion around piers.9. Collision damage.

G. Concrete (girders, beams, frames, etc.)1. Spalling (give special attention to points of bearing).2. Diagonal cracking, especially near supports.3. Vertical cracks or disintegration of concrete, especially in the area of the tension steel.4. Excessive vibration or deflection during vehicle passage.5. Corrosion or exposure of reinforcing steel.6. Corroded, misaligned, frozen, or loose metal bearings.7. Tearing, splitting, bulging of elastomeric bearing pads.

H. Timber (trusses, beams, stringers, etc.)1. Broken, deteriorated, or loose shear connectors.2. Failure, bowing, or joint separation of individual members of trusses.3. Loose, broken, or worn planks on the timber deck.4. Improper functioning of members.5. Rotting or deterioration of members.

I. Steel (girders, stringers, floor beams, diaphragms, cross frames, portals, sway frames, lateralbracing, truss members, bearing and anchorage, eyebars, cables, and fittings)

1. Corrosion and deterioration along:a. Web flange.b. Around bolts and rivets heads.c. Under deck joints.d. Any other points which may be exposed to roadway drainage.e. Eyebars, cables, and fittings.

2. Signs of misalignment or distortion due to overstress, collision, or fire.3. Wrinkles, waves, cracks, or damage in the web and flange of steel beam, particularly near points of

bearing.4. Unusual vibration or excessive deflection occurring during the passage of heavy loads.5. Frozen or loose bearings.6. Splitting, tearing, or bulging in elastomeric bearing pads.

J. Concrete Appurtenances1. Cracking, scaling, and spalling on the:

a. Deck surface.b. Deck underside.c. Wearing surface (map cracking, potholes, etc.).

NOTE: If deterioration is suspected, remove a small section of the wearing surface in order to check thecondition of the concrete deck.

2. Exposed and/or rusting reinforcing steel.3. Loose or deteriorated joint sealant.

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4. Adequacy of sidewalk drainage.5. Effect of additional wearing surfaces on adequacy of curb height.

K. Timber Appurtenances1. Loose, broken, or worn planks.2. Evidence of decay, particularly at the contact point with the stringer where moisture accumulates.3. Excessive deflection or loose members with the passing of traffic.4. Effect of additional wearing surfaces on adequacy of curb height.

L. Steel Appurtenances (including but not limited to decks, gratings, curbs, and sidewalks)1. Corroded or cracked welds.2. Slipperiness when deck or steel sidewalk is wet.3. Loose fasteners or loose connections.4. Horizontal and vertical misalignment and/or collision damage.

M. Masonry Bridges1. Settlement.2. Proper function of weep holes.3. Collision damage.4. Spalling or splitting of rocks.5. Loose or cracked mortar.6. Plant growth, such as lichens and ivy, attaching to stone surfaces.7. Marine borers attacking the rock and mortar.

N. Miscellaneous1. Existence and appropriateness of bridge classification signs.2. Condition of approachments.3. Leaks, breaks, cracks, or deterioration of pipes, ducts, or other utilities.4. Damaged or loose utility supports.5. Wear or deterioration in the shielding and insulation of power cables.

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TM 5-600/AFJPAM 32-1088

APPENDIX C

SUGGESTED ITEMS FORARMY TRIENNIAL AND EVERY THIRD AIR FORCE BIANNUAL

BRIDGE INSPECTIONS

BRIDGE INSPECTION ITEMS

Include the following items:

A. General Information to Include1. Bridge name.2. Location.3. Date of inspection.4. Design load (if known).5. Military load classification (if known).6. Date built.7. Traffic lanes.8. Transverse section (describe or sketch).9. Structure length.10. No. of spans.11. Plans available.12. Inspection records.

a. Year inspected.b. Inspector.c. Qualification.

13. Bridge description.a. Floor system.b. Beams.c. Girders.d. Stringers.e. Trusses.f. Suspension.g. Piers.h. Abutment A.i. Abutment B.j. Foundation.k. Piers or bents.

(1) Caps.(2) Posts or columns.(3) Footings.(4) Piles.(5) Other.

l. Deck:(1) Wearing surface.(2) Curb.(3) Railings.(4) Sidewalk.(5) Other.

B. Bridge Components Rating InformationThe following items may be rated using the suggested ratings from part C of this appendix. Descriptiveremarks may also be included.

1. Traffic safety features.a. Bridge railing.

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TM 5-600/AFJPAM 32-1088

b. Transitions.c. Approach guardrail.d. Approach guardrail terminal.

2. Deck.a. Wearing surface.b. Deck structural condition.c. Curbs.d. Median.e. Sidewalk.f. Parapet.g. Railings.h. Drains.i. Lighting.j. Utilities.k. Expansion joints.

3. Load bearing components.a. Bearing devices.b. Stringers.c. Girders or beams.

(1) General.(2) Cross frames.(3) Bracing.

d. Floor beams.e. Trusses.

(1) General.(2) Portals.(3) Bracing.

f. Paint.4. Abutments.

a. Wings.b. Backwall.c. Bearing seats.d. Breast wall.e. Weep holes.f. Footing.g. Piles.h. Bracing.i. Erosion or scour.j. Settlement.

5. Piers/bents or pile bents.a. Caps.b. Bearing seats.c. Column, stem, or wall.d. Footing.e. Piles.f. Bracing.g. Erosion or scour.h. Settlement.

6. Channel and channel protection.a. Channel scour.b. Embankment erosion.c. Drift.d. Vegetation.e. Fender system.f. Spur dikes and jetties.

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g. Rip rap.h. Adequacy of opening.

7. Approach.a. Alignment.b. Approach.c. Relief joints.d. Approach.

(1) Guardrail.(2) Pavement.(3) Embankment.

C. Suggested Component Ratings1. Traffic Safety Features.

Code Description0 Inspected feature DOES NOT currently meet acceptable standards or a safety feature is

required and NONE IS PROVIDED.1 Inspected feature MEETS currently acceptable standards.N NOT APPLICABLE

2. Superstructure, Substructure, Channel and Channel Protection, and Approach.Code DescriptionN NOT APPLICABLE9 EXCELLENT CONDITION8 VERY GOOD CONDITION-no problems noted.7 GOOD CONDITION-some minor problems.6 SATISFACTORY CONDITION-structural elements show some minor deterioration.5 FAIR CONDITION-all primary structural elements are sound but may have minor sec-

tion loss, cracking, spalling or scour.4 POOR CONDITION-advanced section loss, deterioration, spalling or scour.3 SERIOUS CONDITION-loss of section, deterioration, spalling or scour have seriously af-

fected primary structural components. Local failures are possible. Fatigue cracks in steelor shear cracks in concrete may be present.

2 CRITICAL CONDITION-advanced deterioration of primary structural elements. Fatiguecracks in steel or shear cracks in concrete may be present or scour may have removedsubstructure support.Unless closely monitored it may be necessary to close the bridge until corrective action istaken.

1 “IMMINENT” FAILURE CONDITION-major deterioration or section loss present in crit-ical structural components or obvious vertical or horizontal movement affecting structurestability. Bridge is closed to traffic but corrective action may put back in light service.

0 FAILED CONDITION-out of service-beyond corrective action.

3. Supplemental for Channel and Channel Protection (Use in conjunction with part 2 above).Code DescriptionN NOT APPLICABLE bridge is not over a waterway.9 There are no noticeable or noteworthy deficiencies which affect the condition of the chan-

nel.8 Banks are protected or well vegetated. River control devices such as spur dikes and em-

bankment protection are not required or are in a stable condition.7 Bank protection is in need of minor repairs. River control devices and embankment pro-

tection have little minor damage. Banks and/or channel have minor amounts of drift.6 Bank is beginning to slump. River control devices and embankment protection have wide-

spread minor damage. There is minor stream bed movement evident. Debris is restrictingthe waterway slightly.

5 Bank protection is being eroded. River control devices or embankment have major dam-age. Trees and brush restrict the channel.

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Code Description4 Bank and embankment protection is severely undermined. River control devices have se-

vere damage. Large deposits of debris are in the waterways.3 Bank protection has failed. River control devices have been destroyed. Stream bed aggra-

dation, degradation, or lateral movement has changed the waterway to now threaten thebridge or approach roadway.

2 The waterway has changed to the extent the bridge is near a state of collapse.1 Bridge is closed because of channel failure. Corrective action may put it back in light ser-

vice.0 Bridge is closed because of channel failure. Replacement is necessary.

4. Supplemental for Approach Roadway Alignment (Use in conjunction with part 2 above):Code Description8 Speed reduction is NOT required.6 A VERY MINOR speed reduction is required.3 A SUBSTANTIAL speed reduction is required.

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The proponent agency of this publication is the Office of theChief of Engineers, United States Army. Users are invited tosend comments and suggested improvements on DA Form 2028(Recommended Changes to Publications and Blank ‘Forms) toHQUSACE (CEPW-ER), WASH DC 20314-1000.

By Order of the Secretaries of the Army and the Air Force:

Official:

GORDON R. SULLIVANGeneral, United States Army

Chief of Staff

MILTON H. HAMILTONAdministrative Assistant to the

Secretary of the Army

OFFICIAL

JAMES E. MCCARTHYMajor General, United States Air Force

The Civil Engineer

DISTRIBUTION:

Army: To be distributed in accordance with DA Form 12-34-E, blocknumber 0721, for TM 5-600.

Air Force: F

*U.S. G.P.O.:1994-386-731:120