Consistent formulation for LTB of welded beams incorporating an advanced residual stress approach

Abstract

In the structural stability design of steel structures, the effects of imperfections arising from steel members' fabrication must be adequately accounted for. In the case of welded members, residual stresses have a substantial impact on the structural performance due to the high thermal energy input during production and subsequent non-uniform cooling. In simplified design methods for steel beams, these imperfections are taken into account by assigning the members to buckling curves and the associated imperfection factors. A review of simplified design methods and their structural efficiency for welded members is timely, given the latest results on residual stresses. This paper presents a study on the lateral torsional buckling behaviour of welded steel beams and the subsequent consequences of the findings for simplified design methods. A comprehensive numerical study analysed the load-bearing behaviour of steel beams made of S235 to S690. Residual stresses were taken into account using the residual stress approach according to current standards, as well as a state-of-the-art approach. The numerical study confirmed that residual stresses have a lesser influence on the structural performance of members made from higher steel grades. To take the identified effects into account for structural designs, an adjustment of the imperfection factors is proposed in this paper.