Fatigue behavior and failure mechanism of steel-concrete composite deck slabs with perforated ribs

This paper aims at investigating the variable-amplitude fatigue behavior and failure mechanism of the steel concrete composite (SCC) deck slab with perforated ribs. Firstly, two identical full-scale specimens were tested under different fatigue loading procedures. Test results reveal that the fatigue failure process starts with the initiation of cracks at the welding part between the steel plate and perforated rib, after which the slab could sustain tens or hundreds of thousands of load cycles until the crushing of concrete. As load amplitude increases by 54%, the crack propagation rate is accelerated by 300%, and the fatigue life from the crack initiation to the crushing of concrete is reduced by 79%. Higher load amplitude applied in the earlier service stage leads to the irreversible and a higher level of degradation on the stiffness, deformation recovery, and composite action. Further, the finite element (FE) model is established and verified, through which the stress state of the welding part is analyzed. It reveals that owing to the shear transfer between the steel members and concrete layer, the welding part is in the multiaxial stress condition where longitudinal normal stress, vertical normal stress, and shear stress coexist. Subsequently, the crack initiation position is predicted using the critical plane approach based on the SWT parameter, which shows good consistency with experimental results. Finally, by conducting the parametric analysis, the effects of geometric parameters and shear-span ratio on the SWT parameter of the welding part are clarified.