Geometric Impact on the Behaviour of Composite Precast Prestressed Concrete Hollow Core Slab

Abstract

An experimental study was performed to evaluate the horizontal shear strength of precast pre-stressed concrete hollow-core units with cast-in-place concrete topping through load testing of three full-scale specimens. The specimens were divided into two groups, namely wide and narrow with nominal widths of 120cm and 55cm respectively. Cast-In-Place concrete was cast on top of the hollow-core units selected from the two groups to form a composite system. An additional specimen was tested with restraining mechanisms used at both ends to reduce the relative slip between the hollow-core unit and topping slab. It was found that the presence of cast-in-place concrete topping slab has significantly improved the behaviour of hollow-core units by increasing the flexural crack initiation and maximum load capacities as well as the stiffness. The loss of composite behaviour corresponds to an interfacial shear strength value smaller than the values of 0.55MPa and 0.52MPa limits specified by the (ACI, 2011) and (AASHTO, 2012) design guidelines. The results obtained in this study suggest that floor system made of cast-in-place concrete topping placed over the machine finished surface of precast concrete hollow-core units with no interfacial roughening does not offer the adequate interface shear strength required to develop a fully composite behaviour.