Reassessment of the Lateral Torsional Buckling Resistance of I-Section Members: Uniform-Moment Studies

Abstract

The I-section member lateral torsional buckling (LTB) resistance equations of the unified provisions underlying the current AISC and AASHTO specifications are a fit to a large body of experimental test data. It has been observed that finite-element (FE) test simulations commonly predict smaller capacities than the AISC/AASHTO LTB equations, especially in the inelastic LTB region. One reason for this disconnect is the fact that the residual stresses and geometric imperfections are often approximated by conservative nominal values in test simulations. Another reason for the discrepancy is the common lack of consideration of inelastic effective length effects within calibrations to experimental test results. This paper recommends improvements to the current LTB resistance equations to address these shortcomings. The impact of inelastic end restraint in representative beam LTB experimental tests is illustrated through FE test simulations. In addition, extensive test simulation results are presented, based on reduced residual stresses and geometric imperfections determined in separate research, which illustrate the quality of the proposed prediction equations for I-section members of various cross section types subjected to uniform moment.