Torsion-bending analysis of continuous thin-walled beams

Abstract

This paper indicates the analytical difficulties which arise when thin-walled open sections are used as elements of continuous rigid-jointed structures. Although there has been much research carried out in the field of thin-walled structures it has, in general, been directed towards the behaviour of individual thin-walled structural elements. Until recently, comparatively few papers have been devoted to the particular problems of continuous rigid-jointed, thin-walled structural systems. The principal aim of this paper is to illustrate how approximate methods of torsion-bending analysis can be used in the determination of stress distributions in continuous rigid-jointed structures comprising thin-walled elements. The particular problem of a three-span continuous beam is examined and initially a closed-form solution is obtained. The two alternative approximate solutions, particularly useful for design purposes, are then presented and the limitations of these solutions, which can only be truly evaluated in the light of exact results obtained from the closed form solution, are discussed. The paper also includes details of experimental investigations carried out on two different continuous beam test specimens. Details are given of the test rig employed; in particular, of the forms of support adopted and the method of applying the loads. Longitudinal strains due to bending and torsion measured during these tests are compared with theoretically predicted values. The paper concludes by indicating how the present work will be extended to consider thin-walled, rigid-jointed structures, other than continuous beams, which are subjected to the action of combined bending and torsion.