High performance steel bridge girders: Performance and design

High Performance Steel (HPS) has quickly gained popularity in United States bridge applications due to its high yield strength and better weldability, toughness, ductility, and weathering characteristics when compared to conventional grades of 50 ksi (345 MPa) structural steel. However, a great deal of information is missing from the body of knowledge on HPS performance and design criteria, especially concerning HPS-70W (485W) produced by thermo-mechanical controlled processing (TMCP). This research examines material characteristics and fatigue performance of HPS-70W (485W) TMCP, as well as its potential performance in inelastic loading ranges within representative bridge systems.; Data from 96 tensile tests show that yield and ultimate strengths of HPS-70W (485W) TMCP is dependent upon plate thickness and orientation. 75 Charpy V-Notch (CVN) specimens were tested, and all met the ASTM A709 requirement for minimum toughness.; Twenty-nine specimens were tested to investigate the fatigue resistance of HPS-70W (485W) continuous plate with punched holes. Specimen thickness, hole diameter, and method used for creating the holes were varied to examine their effect upon fatigue resistance of punched connections utilizing high performance steel. Results from this investigation suggest that current restrictions mandated by some state DOTS concerning punching holes are not overly restrictive when HPS-485W (70W) is utilized. Performance of drilled and sub-punched and reamed specimens met or exceeded AASHTO (2004) requirements for Category B details.; Performance of Submerged Arc Weld (SAW) and Narrow Gap Improved Electroslag Weld (NGI-ESW) welded butt-splices utilizing HPS-70W (485W) were examined. Five SAW and five NGI-ESW specimens were tested in fatigue and all reached infinite life. All ten specimens performed considerably better than predicted by the AASHTO fatigue life equation. Results from this study suggest that it is reasonable to include HPS-70W (485W) welded butt-splices created using NGI-ESW in the AWS D1.5 specification (2001).; Inelastic moment redistribution properties were also examined through an extensive finite element investigation completed in conjunction with an inelastic AASHTO analysis. All analyses dealt with a full-length girder from an HPS-70W (485W) TMCP bridge located near Lancaster, Ohio. The HPS-70W (485W) TMCP girder exhibited comparable inelastic moment redistribution when finite element results and results predicted using the AASHTO inelastic redistribution approach were examined. Peak moment capacity was found to be significantly lower for model results than for AASHTO predictions, and this difference is likely attributable to low yield strengths and roundhousing in thicker HPS-70W (485W) TMCP plates.