Shear behaviour of embedded nut-bolted connectors in precast steel-concrete composite beams: Experimental investigations and numerical analyses

Precast steel-concrete composite beam (PSCCB) has been applied extensively in bridge constructions owing to its excellent mechanical properties. Employing demountable embedded nut-bolted connectors (ENBCs) in PSCCBs has become a competitive solution to conveniently replace deteriorated components and to further extend their service life. However, investigations pertaining to shear behaviours of ENBCs in PSCCBs are limited. Hence, economical push-out tests are conducted for investigating the ENBC performance in PSCCBs. Experimental re- sults show that increasing bolt diameters significantly improves the shear performance of ENBCs. Increasing the ring width enhances the initial shear stiffness slightly, minimally affects the ultimate shear capacity, and significantly reduces the slip capacity. Additionally, a finite element model is developed based on the present experimental results to capture the nonlinear response and damage processes of the ENBCs. Subsequently, a validated model is used for parametric studies. Results of numerical analyses show that larger bolt diameters and higher grades improve the shear behaviour of the ENBCs. In addition, steel beams and concrete with lower strengths increase the slip capacity. The pretension degree of the bolts significantly affects the initial shear stiffness of the composite beams. However, the embedded nut angle minimally affects the shear behaviour of the ENBCs. Additionally, the model provided in Eurocode 4 yields slightly conservative predictions for calculating the ultimate shear capacity of ENBCs, thus, a reliable predicted model was proposed for hexagonal-ENBC. Based on experimental analyses, the mechanism associated with the shear and internal stress variations of the ENBCs are revealed via the verified model.