Redistribution of Internal Torsional Moments Caused by Plastic Yielding of Structural Steel Members

Abstract

This paper analyses the influence of torsion on the structural stability behaviour of steel members. An integrated experimental and numerical simulation study is performed to obtain a thorough understanding of the structural behaviour of simple members in biaxial bending, axial compression and torsion. The behaviour is analysed in terms of load-deflection curves, plastic yielding of the cross section, ultimate capacities and failure modes. Additionally, the redistribution of the torsional loads within the cross section and on the member level was analysed as well as the influence of the load application type. The member resistance is severely affected by the yield-zone development and limited by the following failure criteria: cross section failure, eigenvalue-failure of the partially plastic system and eigenvalue-failure of the elastic system. The results of the study show that the structural behaviour of steel members exceeding the elastic limit is severely affected by the load redistribution of torsional internal forces caused by plastic yielding and the development of plastic hinges.