Lateral‐Torsional Buckling of Thin‐Walled I‐Beams

Abstract

An experimental study is presented on the interaction of local and lateral‐torsional buckling of thin‐walled I‐shaped beams. Welded beams with four different cross‐sectional sizes are tested under a concentrated load at the center of the simply supported span. The flange width‐thickness ratios are 14.7 and 17.5, and those of the web vary from 62.3–96.0. The slenderness ratios about the minor axis are approximately 50, 70, and 100. For the beams with intermediate length, the combined failure mode of local flange and lateral‐torsional buckling is obtained, while the long beams fail only by lateral‐torsional buckling. Though local flange buckling with a short wavelength occurs only near the span center of the beams, the ultimate strengths are considerably lower than those of stocky beams. By comparing the experimental ultimate strength and the nominal design strength of the specifications in North America, it is found that the design approaches based on the effective width concept give reasonable estimates for the test results.