Effect of crack-inclusion interaction on fatigue behavior of rib-to-deck joints in orthotropic steel deck

There are various types of initial defects in weld joints of orthotropic steel deck, which significantly impact the fatigue crack growth behavior of the welds. The traditional single-crack growth model is not appropriate to be utilized for the fatigue investigation of welds containing multiple defects. This study analyzed the dynamic evolution behavior of crack-inclusion interactions in the weld toe of rib-to-deck joints based on the fracture mechanics theory. The influence of defect-related parameters on crack fatigue life was discussed. Numerical simulations and fatigue test were conducted to investigate the dynamic interaction behavior of the crack-inclusion under fatigue loading. A merging criterion for multiple inclusions was proposed to simply the fatigue life analysis of coupled cracks. The numerical results show that the stiff inclusion has a shielding effect on the crack growth. The effect is affected by the relative depth of the crack and inclusion (a0/R), the interaction spacing of defects (S), and the burial depth of the inclusion (h). The shielding effect becomes negligible under the condition a0/R≥3. The fatigue life of the interactive crack increases by up to 23 % compared to single crack. Fully buried inclusions have a limited impact on crack growth. The fatigue life of the interactive crack shows a non-monotonic increase with the quantities of inclusions, with double inclusion clusters. It is demonstrated that the highest shielding effect will increase the fatigue life by 26 %. The proposed merging criterion simplifies the prediction of the fatigue life for welded joint containing multiple inclusions. The numerical result provides a referencing database for fatigue life evaluation of steel structures with multiple welding defects.