Experimental Study on Extremely Low-Cycle Material Fatigue Resistance for Two Types of Welded Structural Details

Abstract

Extremely low-cycle fatigue and fracture is one of the most critical damage types of the welded beam-to-column connections when the steel frame subjected to the strong earthquake excitation. The investigation on extremely low cycle fatigue behavior of welded structural details is useful for the fatigue design of welded structure. In the present study, extremely low cycle material fatigue tests were carried out to examine the fatigue failure mechanism of two types of welded structural details, which were the plate butt weld (PB) specimen and cruciform load-carrying groove weld (CLG) specimen. Fatigue tests were performed on 12 welded specimens under strain-controlled constant loading in the plastic range. The fitting S-N curves of the two types were presented. The fatigue S-N curves of the similar welded structural details in IIW Fatigue Recommendation was adopted to correlate the fatigue resistance of the two types of welded structural details. The results demonstrated that the failure mode of PB specimens was not the same as that of CLG specimens. The extremely low-cycle material fatigue strength of the investigated welded structural details was lower than expected high cycle fatigue S-N curves provided by IIW, showing shorter fatigue lives, which indicated that the cumulative damage of welded details involved ductile damage besides cyclic fatigue damage in extremely low-cycle fatigue situation.