Finite-Element Modeling of Heat-Curved I-Girders

Heat curving is extensively used for fabricating structural steel girders for bridges. Current American Association of State Highway and Transportation Officials (AASHTO) specifications limit usage to Grade 345 steel $(F_y=50\mathrm{ksi})\text{,}$ ruling out Grade 485 $(F_y=70\mathrm{ksi})$ high performance steel (HPS). This paper presents results of a three-dimensional finite-element analysis to assess the applicability of existing AASHTO provisions for HPS 485W sections. The finite-element package NASTRAN was used to conduct the analysis and the model calibrated against experimental data obtained from full-scale tests conducted previously by U.S. Steel Corporation. Comparisons include curvatures, lateral deformations, and residual stresses. The calibrated model was used to predict the performance of an identical HPS girder subjected to the same heat/cool cycles. The three-dimensional analysis predicted smaller curvatures as compared with Grade 250 $(F_y=36\mathrm{ksi})$ or Grade 345 $(F_y=50\mathrm{ksi})$ steel. Comparable curvatures could be obtained by using higher temperatures.