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

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

presentation outline
Presentation Outline
  • About VDOT
  • Chain of Events Since the I-35W Bridge collapse in Minnesota
  • VDOT’s Approach to Load Rating Gusset Plates
about vdot
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
chain of events since the i 35w bridge collapse in minnesota
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
chain of events since the i 35w bridge collapse in minnesota5
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
vdot s approach to load rating gusset plates
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
vdot s approach to load rating gusset plates11
VDOT’s Approach to Load Rating Gusset Plates

MathCAD Calculations for Gusset Plates at Member Ends

  • Tension & Compression Check
    • Fastener Capacity
    • Block Shear Capacity
    • Tension / Compression Capacity (Whitmore Section)
vdot s approach to load rating gusset plates12
VDOT’s Approach to Load Rating Gusset Plates

Tension and Compression Checks for Gusset Plate at Member Ends

vdot s approach to load rating gusset plates15
VDOT’s Approach to Load Rating Gusset Plates

MathCAD Sample Calculations

1 = Inventory Rating

2= Operating Rating

vdot s approach to load rating gusset plates16
VDOT’s Approach to Load Rating Gusset Plates

MathCAD Calculations for Members

  • Fastener Capacity Check
  • Block Shear Capacity Check
vdot s approach to load rating gusset plates17
VDOT’s Approach to Load Rating Gusset Plates
  • MathCAD Calculations For Gusset Plates at Sections A-A, B-B and C-C
    • Unsupported Length to Thickness Ratio
    • Gross and Net Section Shear Yielding Resistance
vdot s approach to load rating gusset plates21
VDOT’s Approach to Load Rating Gusset Plates
  • Gusset Plate Rating Summary
    • At each member
vdot s approach to load rating gusset plates22
VDOT’s Approach to Load Rating Gusset Plates
  • Truss Member Rating Summary
    • At each member
vdot s approach to load rating gusset plates23
VDOT’s Approach to Load Rating Gusset Plates
  • Final Summary
    • Controlling Gusset Plate
    • Controlling Truss Member
vdot s approach to load rating gusset plates25
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!

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