Mechanical properties and design method of composite slab with concrete shear keys

Abstract

A new type of prefabricated composite concrete slab with shear keys arranged in a rectangular grid (CSWSK) is proposed. Its advantages are that it needs fewer steel reinforcing bars, and it does not require temporary support when being installed. We physically tested CSWSK and created finite element models (FEMs) to investigate bending performance, failure mode, influential factors and shear force distribution among shear keys under load. We derived simplified equations to calculate yield load and ultimate bearing capacity. CSWSK had a similar failure mode to a cast-in-place slab and a comparable bearing capacity (<4% difference). The row spacing, column spacing and cross-sectional area of the shear keys were the main factors influenced their mechanical behaviour. When these parameters were separately varied, yield load maximally varied by 12.1%, 14.4% and 13.4%, separately, and corresponding yield displacement maximally varied by 40.6%, 161% and 81.2%. The compressive strength of the upper layer of the composite slab and the coefficient of friction had little effect after a certain number of shear keys had been used. Shear force was greater for shear keys closer to the support than those nearer the centre of the slab. The derived simplified equations were accurate: the difference in results between the equations and physical test or FEM was <8%.