Elastic Lateral-Torsional Buckling Capacity of Wide Flange Beams with End Warping Restraints

Abstract

AbstractProviding end warping restraints is an effective means of increasing the elastic critical moment capacity of laterally unsupported beams subjected to transverse loading. Yet, design standards in Canada and the US do not have provisions to quantify the elastic critical moment for beams with such end details. In contrast, while the Australian standards and the Eurocode provide modifications factors that account for the beneficial effect of warping restraints, such factors are independent of the configuration and geometry of warping restraint details. Within this context, the present study investigates the effect of warping end restraints on the elastic lateral-torsional buckling capacity of single-span beams with doubly symmetric cross-sections. A parametric study based on 3D shell element models is conducted on beams with various end details aimed at restraining warping deformation at beam ends, namely (a) transverse stiffeners, (b) longitudinal stiffeners, (c) combinations of two transverse and a single inclined stiffener, (d) combinations of two transverse and two inclined stiffeners, and (e) combinations of two transverse and a longitudinal stiffener. The effectiveness of the various details is assessed in controlling end warping deformation and increasing the critical moments. A parametric study is conducted to assess the influence of plate thickness and length at end restraints on the critical moments attained. Comparisons against Australian standard and Eurocode provisions show that, depending on the type of warping detail adopted and its geometric parameters, standard provisions can either overestimate or underestimate the critical moment capacity.