Distortional Lateral torsional buckling analysis of beams with overhangs

Abstract

The present study investigates the effect of web distortion on the lateral torsional buckling strength of Gerber systems. Towards this goal, a number of modifications are introduced into two finite element formulations for the distortional and non-distortional lateral torsional buckling analysis. The distortional formulation treats the web as a thin plate and the flanges as Gjelsvik members, and captures load height effects. The non-distortional formulation is based on the Vlasov beam kinematics and enables the enforcement of lateral restraints offset from the shear center while preserving the positive definiteness of the stiffness matrices. Both models are 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 where web distortion is considered to be insignificant, the present study indicates that web distortion heavily influences the lateral torsional buckling strength of Gerber beams.