FHWA Webinar: Load Rating of Gusset Plates in Steel Truss Bridges by Other States Presented By: Anwar S. Ahmad, P.E. Assistant State Bridge EngineerDate: October 8, 2009

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Presentation Outline

About VDOT

Chain of Events Since the I-35W Bridge collapse in Minnesota

VDOT’s Approach to Load Rating Gusset Plates

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About VDOT

VDOT maintains the 3rd largest state-owned road system in the U.S.

57,867 miles of sate maintained roadway system

20,918 Structures (Bridges and Large Culverts)- 19,390 Maintained by VDOT- 1,528 Maintained by Localities

9 Districts and one Central Office

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Chain of Events Since the I-35W Bridge collapse in Minnesota

Worked with FHWA to identify all bridges with similar design type to the I-35W Bridge (Deck Truss Type)– Total of 11 bridges were identified

Both FHWA and VDOT reviewed the latest inspection reports of the 11 bridges and did not find anything out of the ordinary– All bridges were inspected within the last 2 years of the review date– Some were inspected as early as May 2007

Assigned the inspections of all 11 bridges to the 3 engineering consulting firms– Inspection completed September 30, 2007

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Chain of Events Since the I-35W Bridge collapse in Minnesota

Identified all FCM bridges and reviewed the last inspection reports (305 total)

Re-inspected 36 of the 305 FCM structures for QA measures

Restricted permit vehicles from crossing truss bridges

Identified 113 truss bridges with gusset plates

Developed standard procedure for analyzing gusset plates in accordance with FHWA latest guidelines

Completed the load rating for 106 of the 113 truss bridges

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Chain of Events Since the I-35W Bridge collapse in Minnesota

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Chain of Events Since the I-35W Bridge collapse in Minnesota

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Chain of Events Since the I-35W Bridge collapse in Minnesota

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VDOT’s Approach to Load Rating Gusset Plates

VDOT decided to follow FHWA - LFR Guidelines

VDOT decided to develop examples in MathCAD

Analyze up to 5 members at a joint

Analyze gusset plates and member ends

Separate MathCAD sheet for splice plate

10Typical Connection

VDOT’s Approach to Load Rating Gusset Plates

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MathCAD Calculations for Gusset Plates at Member Ends Tension & Compression Check

Fastener CapacityBlock Shear CapacityTension / Compression Capacity (Whitmore Section)

VDOT’s Approach to Load Rating Gusset Plates

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Tension and Compression Checks for Gusset Plate at Member Ends

VDOT’s Approach to Load Rating Gusset Plates

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VDOT’s Approach to Load Rating Gusset PlatesMathCAD Sample Calculations

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VDOT’s Approach to Load Rating Gusset PlatesMathCAD Sample Calculations

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1 = Inventory Rating

2= Operating Rating

VDOT’s Approach to Load Rating Gusset Plates

MathCAD Sample Calculations

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MathCAD Calculations for Members Fastener Capacity CheckBlock Shear Capacity Check

VDOT’s Approach to Load Rating Gusset Plates

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MathCAD Calculations For Gusset Plates at Sections A-A, B-B and C-CUnsupported Length to Thickness RatioGross and Net Section Shear Yielding Resistance

VDOT’s Approach to Load Rating Gusset Plates

18Typical Connection

VDOT’s Approach to Load Rating Gusset Plates

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VDOT’s Approach to Load Rating Gusset Plates

MathCAD Sample Calculations

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VDOT’s Approach to Load Rating Gusset PlatesMathCAD Sample Calculations

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Gusset Plate Rating SummaryAt each member

VDOT’s Approach to Load Rating Gusset Plates

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Truss Member Rating SummaryAt each member

VDOT’s Approach to Load Rating Gusset Plates

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Final SummaryControlling Gusset PlateControlling Truss Member

VDOT’s Approach to Load Rating Gusset Plates

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VDOT’s Approach to Load Rating Gusset Plates

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VDOT’s Approach to Load Rating Gusset Plates

Example of Gusset Plate Analysis can be found at the following weblink

http://www.virginiadot.org/business/bridge-FRP.asp

Thank you!

FHWA Webinar: Load Rating of Gusset Plates in Steel Truss Bridges by Other States Presented By: Anwar S. Ahmad, P.E. Assistant State Bridge EngineerDate: October 8, 2009