Low cycle fatigue strength assessment of butt and fillet weld connections

Abstract

The paper presents the analysis of the low cycle fatigue strength of axially tensioned welded connections between I- or H-profile and gusset plate, in which butt and fillet welds cooperate in transmitting the load. The presented approach is based on the local strain state at the notch directly. The method of stress analysis was presented, which was divided into global finite element analysis at the geometrical stress level, coupled with a local finite analysis of the notch area. Local elastic–plastic stress–strain behaviour at the notch root was evaluated from Neuber’s rule and load–life curves were established for such connections from equation based on Langer’s formula. Although in steel structures the applied nominal load does not vary in fully cyclic type, material anisotropy developed during first plastic strain in notch area can lead after unloading to fully reversed plastic stress. In some cases, the first crack can occur after a small number of load cycles.