Research on shear behavior and resistance of UHPFRC-RC composite beam

Abstract

Ultra-high performance fiber reinforced concrete (UHPFRC) is a material with high strength, ductility and impermeability, and it can be applied for strengthening concrete structure to form UHPFRC-RC composite structure. To study the shear mechanism of composite beams and establish calculation formula for shear resistance. At first, the shear test including one reinforced concrete(RC) beam and four UHPFRC-RC composite beams was designed to study the influence of UHPFRC layer, longitudinal reinforcement and shear span-to-depth ratio on shear resistance. Then, the test was conducted in three-point loading mode and the results showed that both UHPFRC layer and longitudinal reinforcement can effectively increase the shear resistance, and UHPFRC layer can improve the overall ductility of the structure. As for the local part, such as interface and UHPFRC layer, the near interface cracking(NIC) zone appeared in the concrete element and UHPFRC layer appeared plastic hinges in the failure stage, they were special aspects for composite beams. Furthermore, the strain condition of reinforcement was recorded and the corresponding failure mechanism was analyzed in this paper. Finally, the calculation formula was established based on the truss-arch model and above works, and to verify this model, the test results from this paper and literatures were adopted to calculate the prediction values and compare them with test values, the results proved the calculation formula can predict shear resistance of UHPFRC-RC composite beams accurately.