Exploration of shear transfer strength of ultra-high performance concrete with shear reinforcement

The shear transfer behaviour of concrete was an important mechanical property, which can be applied to evaluate the shear load-bearing capacity of concrete beams and the connection behaviour among concrete components. However, with the application of ultra-high performance concrete (UHPC) in civil engineering, the studies on the shear transfer strength of UHPC were rare. In this paper, 36 Z-typed UHPC specimens were tested under direct shear load to explore the shear transfer behaviour of UHPC. The investigated parameters included the compressive strength of UHPC, the volume fraction of steel fibres, and the ratio of shear reinforcement. The test results showed that compared with the specimens without steel fibres or shear reinforcement, the failure modes of the specimens with steel fibres or shear reinforcement under direct shear loads changed from brittle failure to ductile failure. The compressive strength of UHPC, the volume fraction of steel fibres, and the ratio of shear reinforcement had positive relationships with shear transfer strength of UHPC. The ratio of shear reinforcement was the most important factor affecting the shear transfer strength of UHPC, followed by the volume fraction of steel fibres, and finally the compressive strength of UHPC. Based on the theoretical analysis, the shear transfer mechanism of UHPC and the dowel action of shear reinforcement were analyzed. The prediction model for evaluating the shear transfer strength of UHPC with shear reinforcement was proposed. By comparing the predicted results and test results from previous studies, the prediction models were suitable for evaluating the shear transfer strength of concrete, which the compressive strength of concrete in the range of 14.8 MPa similar to 166.38 MPa.