Experimental and numerical analysis on shear performance of single embedded nut bolted shear connectors in prefabricated steel-UHPC composite structures under cyclic loading

Replacing conventional stud shear connectors with single embedded nut bolts (SENBs) in prefabricated steel-UHPC composite structures (SUCSs) was an effective solution to reduce the welded work and to address the challenge of dissembling and recycling the structural components at the end of service period. In such innovative structural system, SENBs were the most crucial component to transfer the shear stress along the steel-concrete interfaces, which further ensured the monolithic action of composite structures. In addition, the structures might suffer from seismic action in practices, resulting in reversed cyclic loading conditions for the SENBs. However, existing investigations on SENBs primarily focused on their shear performances under monotonic loading rather than those subjecting to cyclic loading. Against this background, this paper presented systematic experimental and numerical analysis work on shear performance of SENBs within prefabricated SUCSs subjected to cyclic loading. The experimental results indicated that SENBs with larger diameter exhibited improved ultimate shear strength, ultimate slip capacity, initial stiffness, and energy dissipation. In addition, the specimens subjected to cyclic loading showed a more pronounced degradation in both ultimate shear strength and ultimate slip capacity compared to those under monotonic loading. Finite element analysis revealed that the UHPC damage region could be categorized into shear-compression region, tension-splitting region, tension-prying region and tension-compression region. The existing models in design codes and earlier researches were unable to accurately predict the shear strength of SENBs subjected to cyclic loading.