Structural stainless steel design by advanced analysis with CSM strain limits

Advanced structural analysis is commonly carried out using finite element models constructed using beam elements. Beam elements are incapable of capturing the effects of local buckling. However, disregarding local buckling can lead to overestimations of system strengths leading to unsafe design. In traditional design approaches, time-consuming semi-empirical design calculations are carried out on individual members. However, with improvements in computational power and advances in software, system-level advanced analysis is now viable for widespread use in design. A proposal is made herein, in which strain limits, defined by the Continuous Strength Method, are applied to simulate local buckling in beam element models, thereby controlling the extent to which spread of plasticity, moment redistribution and strain hardening can be exploited. Strains are averaged over a finite length of member to reflect the fact that local buckling requires a finite length over which to develop and to allow for local moment gradient effects. The paper includes a numerical assessment of the proposed method for design at member level, with both I-sections and hollow sections considered. Comparisons against current design methods confirm the significant benefits of the proposed approach. Application of the approach is particularly appropriate for stainless steel structures due to the high material value and the complexities presented by the nonlinear material stress-strain response for traditional design treatments.