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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 Chain of Events Since the I-35W Bridge collapse in Minnesota VDOT’s Approach to Load Rating Gusset Plates 2 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 3 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 4 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 5 Chain of Events Since the I-35W Bridge collapse in Minnesota 6 Chain of Events Since the I-35W Bridge collapse in Minnesota 7 Chain of Events Since the I-35W Bridge collapse in Minnesota 8 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 9 VDOT’s Approach to Load Rating Gusset Plates Typical Connection 10 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) 11 VDOT’s Approach to Load Rating Gusset Plates Tension and Compression Checks for Gusset Plate at Member Ends 12 VDOT’s Approach to Load Rating Gusset Plates MathCAD Sample Calculations 13 VDOT’s Approach to Load Rating Gusset Plates MathCAD Sample Calculations 14 VDOT’s Approach to Load Rating Gusset Plates MathCAD Sample Calculations 1 = Inventory Rating 2= Operating Rating 15 VDOT’s Approach to Load Rating Gusset Plates MathCAD Calculations for Members Fastener Capacity Check Block Shear Capacity Check 16 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 17 VDOT’s Approach to Load Rating Gusset Plates Typical Connection 18 VDOT’s Approach to Load Rating Gusset Plates MathCAD Sample Calculations 19 VDOT’s Approach to Load Rating Gusset Plates MathCAD Sample Calculations 20 VDOT’s Approach to Load Rating Gusset Plates Gusset Plate Rating Summary At each member 21 VDOT’s Approach to Load Rating Gusset Plates Truss Member Rating Summary At each member 22 VDOT’s Approach to Load Rating Gusset Plates Final Summary Controlling Gusset Plate Controlling Truss Member 23 VDOT’s Approach to Load Rating Gusset Plates 24 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! 25 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