Flexural strength and ductility of highway bridge I-girders fabricated from HPS-100W steel

High performance steel (HPS) for highway bridges has high strength in addition to good weldability, fracture toughness, and corrosion resistance. This research investigates the flexural strength and ductility of bridge I-girder made from HPS-100W, with a yield strength of 100 ksi (690 MPa). The AASHTO LRFD specifications limit the nominal flexural strength of steel I-girders made from steel with specified yield strength greater than 70 ksi (485 MPa) to the yield moment. This limit hinders the use of HPS-100W in highway bridges, and this study investigates whether this limit can be eliminated.; The experimental part of this research included testing of five I-girder specimens fabricated from HPS-100W steel. These I-girders were tested to failure under three-point loading simulating the condition of negative flexure at an interior pier of a continuous-span bridge girder. The experimental research included careful measurement of residual stresses and geometric imperfections before testing, and detailed analysis of the experimental data to study the complex stresses that developed in the specimens at failure.; The analytical part of this research included finite element simulations using ABAQUS [2002]. The purpose of these finite element simulations is to accurately predict both the strength and ductility of these I-girders. A simplified theoretical model for compression flange local buckling in the inelastic range was developed for the purpose of explaining the complex state of stresses that develops during local buckling. Finally, a parametric study was performed using finite element simulations to study the effect of various parameters on the flexural strength and ductility.; Comparison of the flexural strength of the experimental and parametric specimens with the nominal flexural strength, Mn, calculated according to the Draft 2004 AASHTO LRFD specifications shows that these specifications are also applicable for calculating the nominal flexural strength of HPS-100W I-girders when the strength is controlled by inelastic web and flange local buckling. It was also concluded that the procedures followed to execute the experiments proved to be valuable in achieving accurate experimental results, understanding of experimental results, and correlations with finite element simulations, including detailed results regarding the complex flange stresses developed at failure.