Experimental and numerical investigation on ultra-low cycle fatigue performance of LCCST members

Given that localized corroded circular steel tube (LCCST) members are more prone to ultra-low cycle fatigue (ULCF) failure under seismic action, this study first conducts electrochemical accelerated corrosion tests to simulate the localized corrosion of circular steel tube (CST) members. Subsequently, ULCF tests are performed on 13 CST members to analyze the effects of different parameters on the failure modes and ULCF performance. The test results show that the hysteresis curves of the LCCST members are clearly asymmetric, and that corrosion could seriously affect the ULCF performance of the CST members. As the corrosion ratio increases, the load-bearing capacity and stiffness significantly decrease. In addition, the specimens are mainly characterized by buckling instability failure in compression and fracture owing to damage accumulation in tension. For members with a large slenderness ratio, the post-buckling segment decreases linearly, whereas that of members with a small slenderness ratio decreases nonlinearly. With an increase in the corrosion and circumferential corrosion ratios, the post-buckling segment gradually transforms from nonlinear to linear. Finally, a finite element (FE) model of the LCCSTs is established, and the verified FE model can better simulate the failure modes and ULCF performance of the specimens. The parametric analysis shows that the corrosion location has a limited effect on the ultimate load-bearing capacity but affects the location of the fracture. The length of longitudinal corrosion has a limited effect on the ultimate load-bearing capacity.