Load carrying capacity of composite slabs with various end constraints

Abstract

In many cases, the load carrying capacity of composite slabs depends on the shear-bond resistance at the sheet-concrete interface. At the ultimate state, the tension forces in the hogging region of a continuous composite slab are mainly transferred by the negative bending reinforcement and the shear-bond resistance in the region do not significantly influence the load carrying capacity of the slab. To identify the shear-bond action in composite slabs, seven simply supported one-span composite slabs and two continuous composite slabs were tested. Different end restraints had been used in the simply supported slabs. The slabs with end anchorage of steel shear connectors were found to bear a higher shear-bond strength than that of slabs without end anchorage. The shear-bond strength was calibrated based on a linear regression of the test results of the one-span composite slabs with end anchorage. The prediction of the shear-bond resistance was also found in close agreement with the vertical shear force at the onset of the initial shear-bond slip in the two-span continuous composite slabs. It is suggested that the shear-bond slip model be reasonable to predict the shear-bond resistance of a continuous composite slab. However, the shear span of the continuous composite slabs must be related to the sagging region, which could be derived on an elastic analysis base, or simply taken as 0.8 L for the side span and 0.6 L for the interior span. At the onset of the initial shear-bond slip, the mean ratios of the vertical shear force to shear-bond resistance (VeVu) are 1.065 for the one-span slabs and 1.165 for the two-span continuous composite slabs, which are on the safe side. Because of the shear-bond failure at the sheet-concrete interface, composite slabs would not be capable of developing full plastic moments in the spans.