On the distortion and warping of cantilever beams with hollow section

Abstract

This paper deals with the stress analysis of a cantilever box beam subjected to static or fluctuating torsional moment loading. Such beams may have multiple critical locations from the strength point of view; one interesting detail is the cross section where the loading is imposed. However, such details can be typically designed to possess smooth shapes, resulting in moderate stress concentrations, which mean that fatigue failures can be avoided. However, the distortional deformation of the cross section induces transverse bending stresses, which may be detrimental, particularly in welded box beams. In addition, the fixing location where the beam is typically welded to an end plate may become a critical point. This paper presents an analytical approach for calculating the longitudinal stresses due to the warping of the cross section as well as the distortion-induced transverse and longitudinal stresses in rectangular hollow sections. Finite element analyses (FEAs) are carried out to verify the analytical approach to shed light on the critical points in the end plate details with different degrees of weld penetration using the effective notch stress (ENS) concept and to suggest design proposals for an efficient structural detailing of diaphragm plates to decrease the warping behavior.