Distortional Lateral Torsional Buckling Analysis of Beams with Overhangs

Abstract

The present study investigated the effect of web distortion on the lateral torsional buckling strength of Gerber systems. Toward this goal, a number of modifications were introduced into two finite-element formulations for the distortional and nondistortional lateral torsional buckling analysis. The distortional formulation treated the web as a thin plate and the flanges as Gjelsvik members and captured load height effects. The nondistortional formulation was based on the Vlasov beam kinematics and enabled the enforcement of lateral restraints offset from the shear center while preserving the positive definiteness of the stiffness matrices. Both models were validated against shell finite-element solutions and then utilized to develop moment gradient coefficients for Gerber beams, assess the web distortional effects, and quantify the influence of various lateral bracing scenarios on the elastic lateral torsional buckling strength. Unlike rolled simply supported beams in which web distortion was considered to be insignificant, the present study indicated that web distortion heavily influences the lateral torsional buckling strength of Gerber beams.