Fatigue life evaluation of welded joints in steel bridge considering residual stress

Abstract

Welded joints are widely used to connect structural components in steel truss bridges. Weld residual stresses (WRS) and weld residual stresses relaxation (WRSR) have notable influences on fatigue crack propagation in welded joints, and therefore affect the fatigue life of welded joints. Failing to properly consider the effect of WRS and WRSR in fatigue evaluation may lead to inaccurate results. This study presents a fatigue life prediction model based on the elastic fracture mechanics, with consideration of the WRS and WRSR. The solution for stress intensity factor caused by cyclic loading and WRS is derived. The WRS-induced stress intensity factor is calculated using a weight function technique. Fatigue tests of eight welded joint specimens are implemented, and the fatigue failure analysis of specimens is conducted. The proposed fatigue life prediction model is validated against fatigue test results of welded joints. By considering both WRS and WRSR, the model provides a prediction of fatigue life with a maximum error of 14%. Finally, the validated model is employed to investigate the fatigue life of a real bridge. The fatigue life is underestimated by 17% by considering WRS but not considering WRSR; the fatigue life is overestimated by 49% by neglecting WRS and WRSR.