Influence of cyclic hardening characteristic on seismic performance of cold-formed S30408 austenitic stainless steel RHS and SHS bracing members

Prior research has demonstrated that the cyclic hardening characteristic of austenitic stainless steel is strongly influenced by loading history, exhibiting significant strain memory effects, which may substantially influence the cyclic performance of stainless steel structures. Given the limited investigations into the seismic behavior and design of stainless steel members, this paper explores the effects of cyclic hardening characteristics on the behavior of square and rectangular hollow-section (SHS/RHS) bracing members under a variety of loading conditions. A novel constitutive model that accounts for complex mechanical features, including the strain memory effect and hardening-coupling effect, was employed in this study to accurately predict the cyclic behavior of S30408 stainless steel under various loading conditions. Finite element (FE) models for the S30408 austenitic stainless steel SHS/RHS tubes were established and verified against test data. Extensive parameter studies were then conducted to assess how loading history, cross-sectional slenderness, and global slenderness influence the seismic performance of these members. The findings revealed that the load capacities and deformation behaviors of the stainless steel braces were highly dependent on the loading history. In particular, the pronounced cyclic hardening of S30408 stainless steel had a substantial impact on their seismic performance. Furthermore, existing design codes, including the European Code (EC3), ASCE 8–02 (ASCE), CECS 410 (CECS), and the Continuous Strength Method (CSM), tend to undervalue the ultimate strength of SHS/RHS bracing members subjected to seismic loads. Additionally, a seismic deformation capacity design formula based on the compressive ductility coefficient was proposed. • Investigate the effects of cyclic hardening on the seismic performance of cold-formed austenitic stainless steel braces. • The influences of the width-to-thickness ratio, member slenderness, and loading protocols are investigated. • The current design approaches for predicting buckling and post-buckling strength of stainless steel members are evaluated.