On non-uniform plastic torsion of steel I-section cantilevers: Fid-Bau Portal

On non-uniform plastic torsion of steel I-section cantilevers

Gonçalves, Rodrigo / Henriques, David / Antão, Armando / Ritto-Corrêa, Manuel

Abstract This paper aims at contributing towards a better understanding of the non-uniform elastoplastic torsion mechanism of I-section beams. The particular case of cantilevers subjected to an end torque is analysed, which constitutes a simple yet interesting problem, since the maximum torque is very close to the so-called Merchant upper bound (MUB), with added independent maximum bishear and Saint-Venant torques. Consequently, it turns out that the maximum torque can be significantly higher than that for uniform plastic torsion. Besides the MUB, several solutions are presented and compared, namely (i) a stress resultant-based solution stemming from the warping beam theory differential equilibrium equation and (ii) solutions obtained with several beam finite elements that allow for a coarse/refined description of warping. It is found that all models are in very close agreement in terms of maximum torque (including the MUB) and stress resultants. However, the beam finite elements that allow for bishear, even with a simplified warping function, are further capable of reproducing quite accurately the stress field, as a comparison with a 3D solid finite element solution shows. Although the paper is primarily concerned with the small displacement case, the influence of considering finite rotations is also addressed.

Highlights • A contribution towards a better understanding of non-uniform plastic torsion is presented. • A simple but accurate stress resultant-based solution is proposed. • The Merchant upper bound provides very good estimates for short cantilevers. • Even beam elements with a simplified warping function provide acceptable solutions. • Beam elements with bishear deformation can predict quite accurate stress distributions.