Experimental investigation on the hysteretic behavior of concrete-filled steel tubes with defects representing local corrosion

This paper investigated the hysteretic behavior of circular concrete-filled steel tubes (CFSTs) with local defects. Local defects on the steel tubes simulate localized corrosion encountered in engineering practice. Eight CFST specimens were tested under constant axial load and lateral cyclic load, including six specimens with defects and two intact specimens for comparison. The experimental study investigated the impact of local defects on the failure modes, hysteretic curves, skeleton curves, ductility, and energy dissipation capacity of CFSTs. The experimental results demonstrate that the local defects significantly degrade the hysteretic performance of CFSTs. Compared to intact specimens, CFSTs with defects exhibited reductions in initial stiffness by 6.9%, lateral ultimate strength by 16.5%, and ductility index by 29.8%. Furthermore, the defects induced asymmetry in the hysteretic curves and altered the failure modes. The degree of degradation in the lateral ultimate strength varied with the axial load ratio. At the axial load ratios of 0.35 and 0.5, specimens with defects failed by local buckling, with more pronounced reductions in lateral ultimate strength and ductility in the push loading direction. Finally, a calculation model is proposed to quantify the influence of the defect dimensions and axial load ratio on the degradation and asymmetry of the lateral ultimate strength in different loading directions.