Large-Scale Experimental Lateral Torsional Buckling Tests of Welded I-Section Members

The AISC 360 Specification Chapter F I-section member flexural resistance equations are a central part of structural steel design in the US. Analytical studies and experimental tests subsequent to the implementation of "unified" provisions have raised a level of concern that the flexural resistance equations may not meet the target β = 2.6 for welded I-section members within the inelastic Lateral Torsional Buckling (LTB) range in certain cases. However, the experimental test data is quite sparse within much of this design space. This paper presents the results of twelve large scale experimental tests aimed at providing additional data to ascertain the level of reliability inherent in various LTB design resistance equations. This study also provides valuable experimental data complementing analytical simulation based research aimed at improving the AISC Specification characterization of Tension Flange Yielding (TFY) limit states and to investigate the effect of early yielding on the shear resistance for welded singly symmetric I-section members. Various aspects of the experimental test design, the test procedures, and the experimental measurements are discussed, including minimization of incidental restraint, measurement of strain and displacement fields via digital image correlation, laser measurement of initial imperfect geometry, and measurement of specimen residual stresses via hole drilling.

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