Behaviour of reinforced concrete dapped-end beams

The test results of 24 reinforced concrete dapped-end beams are reported. The main variables studied were the compressive strength of concrete, the shear span-to-depth ratio and the horizontal load. The test results indicate that the shear strength of dapped-end beams increases with an increase in concrete compressive strength. The shear strength of dapped-end beams also increases with decreases in shear span-to-depth ratio and horizontal load. The smaller the shear span-to-depth ratio of dapped-end beams, the greater their stiffness and ultimate load. Both the stiffness and the ultimate load of dapped-end beams increase with increasing concrete compressive strength, but decrease with an increase in horizontal load. The extension of the softened strut-and-tie model for predicting the shear strength of dapped-end beams with a shear span-to-depth ratio greater than unity is examined in this paper. The shear strength predicted by the proposed model, the strut-and-tie model of the American Concrete Institute (ACI) and the approach of the Precast/Prestressed Concrete Institute (PCI) are compared with available test results. The comparison shows that the proposed model and the strut-and-tie model can predict the shear strength of reinforced concrete dapped-end beams more accurately than the PCI approach.