1

Donald W. Harvey, Jr.Atkinson‐Noland & AssociatesBoulder, Coloradowww.ana‐usa.com

Structural Engineers Association of Ohio Annual ConferenceSeptember 11, 2014

Atkinson‐Noland & Associates

Forensic Engineering Firm founded in 1975

Specializing in Masonry Structures

Non‐Destructive and Material Testing

www.ana‐usa.com

Angkor Wat, Cambodia

Infrared Thermography

Shear Testing

Modifications – Causes and Implications

Strength & Evaluation of Existing Masonry

Strengthening of Masonry

Common Modifications and Repairs

Moisture & Thermal Modifications

Case Study

Building Changes

Load Changes

Code References

Building Changes

Open up interior spaces

Addition (pop top)

Add an opening

Enhance performance

Load Changes

Occupancy

Wind/Hurricane

Seismic

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International Building Code

International Existing Building Code

MSJC Empirical Requirements

ASCE 41‐06 guidelines

For many years…

25% ‐ 50% ruleProject cost <25% of building worth? Upgrades negotiable

25% to 50%? All new work to meet code

> 50%? Bring entire building into code compliance

Chapter 34: Existing Structures

Primary goals“Dangerous” conditions must be mitigated

New work cannot introduce “dangerous” conditions

New work must meet code

Repair using like materials

OK to meet IEBC instead

Chapter 5: Empirical Design of MasonrySeismic Design Category A, B, C only

Building height < 35 feet

Basic wind speed <110 mph 

Simple rules of thumb to checkLateral stability

Compressive strength

Wall thickness

Wall connections TMS 402/ACI 530/ASCE 5

Table 5.5.5.1 Wall lateral support requirements

Thicknesst

Hei

ght

h

Late

ral L

oad

Wall Construction Max. h/t

Bearing wallsSolid units or fully groutedOther than solid units or fully grouted

2018

Nonbearing wallsExteriorInterior

1836

Parapets: max. h/t = 3

Bonding

Headers4% of wall face

Extending 3” into each wythe

24” max spacing

Steel, concrete, masonry, wood

Types of tests

How many tests?

Default material properties

Strengthening methods

3

Bearing – Stress Concentrations (f′m)

Out‐of‐Plane Flexure (Tension)

Shear Capacity

Post‐Installed Anchors General

Compressive Strength

Shear Strength

Flexural Bond

Anchors & Other

What information is needed?

As‐built configuration

Current condition

Material CharacterizationType

Engineering Properties

Visual

Ground Penetrating Radar

Pulse velocity

Impact‐echo

Tomographic imaging

Sounding

Infrared thermography

X‐ray

Metal location

Borescope

ASTM C805, Standard Test Method for Rebound Number of Hardened Concrete

Variations in original materials

Quality control: mortar joint repointing

Damage:Fire

Weathering

Pendulum Hammer

Stress wave transmissionUltrasonic

Sonic (mechanical pulse)

Parameters of interestArrival time: velocity

Amplitude: attenuation

Frequency: attenuation, reflections from subsurfaceanomalies

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BLIND HEADERCOURSE

CRACKED HEADER

VOID COLLARJOINTS

Concrete: ASTM D 4580, Practice for Measuring Delaminations in Concrete Bridge Decks by Sounding

Chain drag, hammer

Sounding

Sensitive to dielectric variations Voids

Cracks

Embedded metals

Moisture

Salts

Microwave radar scanning

Cooper HallSterling, Kansas

Nondestructive Evaluation: Impulse Radar

BACK OF WALLSIGNIFICANTVOIDING

Figure 3 – GPR scan 030 from location #7

MODERATE VOIDING

Christ Church, Greenwich, CT

Locate internal voids, steel

Concrete masonrygrout quality

Hol

low

Hol

low

Hol

low

Hol

low

Hol

low

Hol

low

Reb

ar,

Gro

uted

Reb

ar,

Gro

uted

Hol

low

Grout detection by measuring heat flow through walls

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Evaluation of anchor condition with a fiber‐optic borescope

Earl Warren Federal Courthouse, San Francisco

Engineering propertiesExisting stress: ASTM C1196

Compressive strength:   ASTM C1197

Shear strength:  ASTM C1531

Bond strength: ASTM C1072

Anchor capacity:  ASTM E 488

Flatjacks: thin hydraulic pressure cell

ASTM C1197, In‐Situ Deformability

Usually: Minimum of 3 tests per each

masonry type for each 5000 ft2

wall area

Coupons of Block

Cores of Grout

Mortar Chemical Tests (Usually Negligable)

Why Not Cut Prisms?

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Externally

Internally

Compatibility

External methods

Internal methods

“CIF” Injection

Incorporate masonry’s strengths

Injection techniques

Internal reinforcement

Post‐tension repairs

Masonry = strong in compression

Frame into wallsNeed supplemental beam support

• Frame Members• Wall Attachment

New concrete pilasters, buttresses Reinforced shotcrete overlay

Continuous or pilasters?

Bond?

Windows and doors?

Mass increase

Foundations?

Russian Masonry Designer’s Manual (1968)

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External ApproachesReversible

Cost effective

but

Visible

Disruptive and Space‐Consuming

Internal ApproachesAppearance not affected

but

Not easily reversible

Often more expensive

Adding VerticalReinforcement (Old Method)

Cut vertical slot

Tie steel in place

AddingReinforcement (New Method)

Core holes through existing masonry

80 ft.  Vert. 

100’s of ft. Horiz.

Grout reinforcing in place (sometimes with socked bars)

Form board

Pour or inject grout

Conventional masonry groutSelf-consolidating grout

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Vertical post-tension forceadded to prevent pier rocking

Void and crack injection

Mix design:Highly fluid

“Stable” 

CompatibilityStrength

Stiffness

Water vapor transmission

Strength and stiffness must match original materials

Facing: stone or face brick

(Stiff)

Fill: rubble or common brick

(Soft)

Compatible Repair:even stressdistribution

Voids: uneven stress distribution

High strength fill: inappropriate

stress redistribution

CIF Material

Stabilize multi‐wythe masonry

Repair cracks

Fill voids

Reduce water penetration

Adding Windows and Doors

Crack Repair

Repointing

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New window or door?

Temporary access

Replacing corroded lintels

Partial rebuilding

Arched opening?

Arch abutments resist lateral thrust, vertical loads

Structural window frame?

1. Divide arc ABCD into 3 equal parts by C and D

2. Extend DB so DB = BE

3. E defines edge of abutmentCooper Hall

Sterling CollegeSterling, Kansas

Cooper HallSterling CollegeSterling, Kansas

“Hinges” forming

Tie rod

Strengthen barrelDiagonal rods

Plates

6’-4

”

Cooper HallSterling CollegeSterling, Kansas

“Hinges” forming

Tie rod

Strengthen barrelRods

Plates

Strengthen abutments

Buttress

Post‐tension rods

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Needle beams, temporary shoring

How far apart can your supports be?Depends on masonry quality

2 feet apart? 6 feet apart?

Rely on (temporary)arching action

Use masonry arching action to span between supports

Consider loads within 45° triangle above opening

Angle lintels

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New externalstructure

University of Colorado Theatre Renovation

External steel

Hang from structure

above

Making a reinforced masonry lintel

New horizontal reinforcement

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Think perpendicular to the crack

Address root cause FIRST!

Compatibility is KEY!

Strength is SECONDARY! UNIMPORTANT!

Thermal Mass

Insulation at Interior Surface

Barrier vs. Drainage Cavity Systems

Energy plays increasingly large role in exterior wall design

Thermal MassCode Provisions

COMCheck – Roof Insulation

Insulation at Interior of MasonryComplications – freezing, condensation

Bottom Line – NO Batts Insulation

Publication: Building America Report – 1105 buildingscience.com

Moisture: Barrier vs. Drainage Cavity Systems

Spray Testing Results

CIF and Grouting for Moisture ResistanceCaution Regarding Mortar Joints

4-Hour Test

Before After repair

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New Orleans Pump Stations

DiagnosticsNDE, in situ tests

Laboratory 

StabilizationHelical anchors

Injection

StrengtheningVertical reinf.

Horizontal reinf.

29 August 2005

Category 3 Hurricane wind over 125 mph (off shore)

Storm Surge – Flooding

Areas in New Orleans more than 9 ft below sea level

1800 deaths

Damage: 81 billion US Dollars 

Revealed weakness in levee and pumping system

United States Army Corps of Engineers (USACE) 

Stations pump water out of New Orleans up into Lake Pontchartrain

Most originally constructed between 1890 and 1920 and expanded multiple times

Construction is multi‐wythe (typically 3 or 4) clay brick masonry load bearing walls with riveted steel roof trusses.

Tested existing masonry, soft lime mortar f’m approx. 700 psi

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USACE Design RequirementsFull‐strength category 4 hurricane 

Wind 156 mph 

Category IV Importance Factor (Additional 15%)

Flood loading to 5 ft. 

Large out‐of‐plane loads

Strengthening required

Stations house large pumps that are tightly spaced and require access on all sides

Many pipes and utilities directly adjacent to wall interior

MUST REMAIN IN OPERATION THROUGHOUT CONSTRUCTION

Bracing – would cover historic appearance

Internal stiffback bracingExisting equipment, power controls, 

Pumps

Overhead crane rails

Could not keep Pump Stations operational 

Shotcrete at wall interior – same as above

Solution: add internal reinforcement to walls

Condition surveyCracks, deterioration

Microwave radar: interior voids, metals

Borescope: interior voids

Pachometer: metals

Typical wall sections

Typical conditions: roof anchors, steel lintels

In situ testsExterior face wythe

Interior common brick wythes

Flatjack (compression): ASTM C1197

Shear: ASTM C1531

Flexural bond: ASTM C1072

Anchor tension: ASTM E488

Anchor shear: ASTM E488

Masonry compression behaviorIn situ flatjack tests: ASTM C1197

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Masonry shear strengthASTM C1531

Mortar‐unit flexural bond strengthASTM C1072 “bond wrench” (field adaptation)

AnchorageASTM E488: tension, shear

0

500

1000

1500

2000

2500

3000

3500

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16

Load

 (lb)

Displacement (inch)

Anchor Bolt Tension

PropertyAverage Load/Strength

Conservative Design Load/Stress

Common Wythe

Face WytheCommon Wythe

Face Wythe

Masonry compressive strength f’m (psi)

260 390 240 290

Masonry compression modulus Em (psi)

86,000 1,000,000 N/A N/A

Masonry flexural tensile strength, normal to bed joints (psi)

7 9 4 6

Masonry shear strength (psi) 25 64 20 43Anchor tensile strength (lb) 3,340 8351

Anchor shear strength (lb) 2,140 5351

Table 9. Engineering Design Values: Construction Typology 1, Multi-Wythe Brick Masonry, No Visible Header Courses, Construction Era 1898 – 1930’s

1Factor of safety of 4 applied to average ultimate load values.

ComponentsCompatible Injection Fill: CIF grout injection

Helical Wall Ties 

Enhancement rods – hollow stainless steel reinforcing

Placed in holes, cored vertically and horizontally 

Tapered anchor conditions at wall base

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91

Dry coring – no water involved

Hollow, cold‐rolled stainless steel bars

Tapered foundation anchorageDevelops bar strength with shorter anchorage

Useful for older, weak masonry construction

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How do you make sure the wall is injected properly?

Microwave radar

Borescope Radar Scan

Pre-injection

Post-injection

Many void collar joints

Over 85,000 sq ft. (1050 m2) of wall area

Over 1200 US Tons CIF grout injected

Approx. 8 % of wall volume was void

Over 30,000 linear ft. (9.200 m) of stainless steel reinforcing bars

No visible change to structure

No service interruption

Earn your CEU’s! Technical sessionsSocial eventsMason certification courseDesign seminar

12th North American Masonry ConferenceMasonry: Science • Craft • Art

Denver, Colorado  May 17 – 20, 2015

Tivoli Student CenterUniversity of Colorado, Denver

www.masonrysociety.org/NAMC

12NAMC@masonrysociety.org

Donald W. Harvey, Jr.dharvey@ana‐usa.com

303‐444‐3620

Notes: