Structural performance of elliptical hollow section (EHS) steel tubular braces under extremely low cycle fatigue loading - a finite element study

A comprehensive non-linear analysis of EHSs under extremely-low-cycle fatigue (ELCF) loading is necessary to accurately assess their cyclic energy dissipation, which is one of the primary factors in the selection of brace parameters, for enhanced seismic performance. This study emphasizes the cyclic response of twenty EHS finite element modeled steel braces of constant cross-sectional steel area, A and wall thickness, t, by employing a non-linear combined isotropic/kinematic hardening material model in Abaqus. Cross-sectional aspect ratio (major to minor axis diameter ratio, a/b) and non-dimensional global slenderness (λ¯) ranging between 1-2 and 0.3-2 respectively, are considered. Parametric studies are conducted to investigate the hysteresis behaviour of EHS models at various displacement ductility levels under cyclic axial displacement loading history based on the recommendations of ECCS. It is observed that cross-sectional aspect ratio has less significance on compressive resistance and energy dissipation values at cyclic displacements of higher displacement ductility levels for sections with non-dimensional global slenderness ratio greater than ~0.8. Design curves for post-buckling compressive resistance of HSS braces at various displacement ductility levels as per AISC LRFD methodology are also proposed.