Z-type shear connector for interface of hollow-core slab and cast-in-place topping concrete

Precast hollow-core slabs (PHSs) are widely used in precast construction due to their relatively low dead weight and easy assemblage. Cast-in-place topping concrete (TC) is utilized to obtain composite sections and to enhance in-plane stiffness of the slab system. Shear transfer between the layers of a composite slab can be provided by the upper face roughness of PHS. However, the roughening process may not be preferred in some plants. This paper evaluates the efficiency of Z-type shear connectors applied in the interface between PHS and TC. Three dissimilar interface conditions (i.e., Z-reinforced, smooth and rough) were studied experimentally in full-scale specimens. Push-off loading was applied to evaluate the interface shear transfer capability of the specimens, and Z-type shear connectors were found to be the most effective when they are applied at each joint between PHSs. The achievements of some code equations to assess interface shear strength were also investigated, and an alteration for the interface shear capacity equation of ACI 318M is proposed.