Distortion Analysis of Till -Walled Box Girders

Abstract

Thin-walled structural components of closed profiles, although economical and effective in bearing torsional and bending loads, give rise to warping and distortion due to the thinness of the walls. The conventional method of predicting warping and distortional stresses is by the BEF analogy, which ignores the effect of shear deformations. In the present work, the variation principle was employed on the assumptions of Vlasov's theory to derive a fourth order differential equation of distortional equilibrium for thin-walled box girder structures. Unlike the BEF analogy, this formulation took into consideration shear deformations which were reflected in the equation of equilibrium by second derivative terms. BEF analogy is also shown to be a particular case of the present formulation when shear deformations are disregarded. Numerical analysis of a single cell box subjected to distortional loading was carried out using the present formulation and the BEF analogy, and values of the distortional displacement, distortional normal warping stress, and distortional shear compared. The results show that the effect of shear deformations can be substantial and should not be disregarded under distortional loading.