Numerical Simulation of Fatigue Crack Initiation and Propagation for In-plane Gusset Welded Joints

Welded built-up steel structures in service encounter many accidents caused by fatigue, and it is important for maintenance of social foundations and safeness to estimate their fatigue lives quantitatively. By considering that fatigue cracks cannot grow without the accumulation of alternating tensile / compressional plastic strain, one of authors identified that the effective stress intensity factor range ΔKRPG based on the Re-tensile Plastic zone Generating (RPG) load which represents the fatigue crack driving forces, and suggests that ΔKRPG should be applied as the parameter in order to describe the fatigue crack growth behavior. For predicting fatigue crack initiation and propagation, numerical simulation code “FLARP” based on ΔKRPG was developed. In this paper, it is confirmed that fatigue life estimation by FLARP gives accurate results by comparing the estimated fatigue crack growth curves with the experimental results for in-plane gusset welded joints which are used in many welded steel structures. Moreover, the effect of induced bending moment due to misalignment for the fatigue strength is investigated by the numerical simulations.