Experimental Investigation on Low-Cycle Fatigue Performance of Butt-Welded Steel Connections

Abstract

Welded steel connections have been extensively used in practical engineering for the superiority of welding. However, many welded structures under complex disaster conditions have exhibited significant low-cycle fatigue damage, resulting in catastrophic accidents and tremendous economic losses. In this study, the low-cycle fatigue performance of steel welded connections was experimentally investigated based on full-field strain collected by a 3D-digital image correlation (DIC) system. Analysis of fatigue life, failure mode, force-displacement hysteresis curve, strain-time curve, and strain distribution of butt-welded steel connections under low-cycle fatigue loading was implemented. The failure process under low-cycle fatigue was investigated based on the strain distribution and variation of the weld zone and heat-affected zone and further explained from the point of micromechanisms. Results reveal that the strains of the weld zone were higher with the increase of loading cycles than that of other positions. Hence, the final failure of the specimens had a preference for the weld zone where the weld metal exhibited tensile and compressive plastic strain asymmetry and cyclic softening characteristics. The plastic strain accumulation of the weld zones and heat-affected zones should be the main reason for the failure of specimens under low-cycle fatigue.