Effect of weld residual stress relaxation on evolutionary properties of multiple cracks in orthotropic steel deck

Abstract

Welding residual stress is a key factor leading to the initiation of multiple cracks in orthotropic steel decks. However, the effects of welding residual stress on evolutionary properties of multiple cracks in welded joints remain unclear. This study proposes a multiple cracks growth analysis method considering welding residual stress relaxation. Subsequently, the influence mechanism of welding residual stresses and multiple crack effects on fatigue life is investigated. Finally, the evolutionary properties of multiple cracks were revealed through experiments. The results show that fatigue life prediction result considering welding residual stress tend to yield conservative results, while incorporating its relaxation effects proves more consistent with experimental data. Welding residual stress accelerates the occurrence of multiple crack merging behavior. As crack depth increases, the effect of residual stresses on crack growth in the depth direction gradually decreases, while the merging behavior of multiple cracks becomes the critical driving force for structural fracture. Reverse analysis of beach marks indicates that the macrocracks observed on the fracture surface originate from the merging behavior of high-density microcrack clusters. The fatigue crack density at the rib-to-deck weld is severely underestimated, and numerous cracks have merged before reaching observable dimensions. This research provides a theoretical basis for comprehensively assessing the fatigue performance of orthotropic steel decks.