Ultimate shear resistance of ultra-high performance fiber reinforced concrete-normal strength concrete beam

The composite element of ultra-high performance fiber reinforced concrete (UHPFRC) and normal strength concrete (NC) is an effective way to take full advantage of the material properties of UHPFRC and NC. In this paper, the calculation method for UHPFRC-NC composite beams with stirrups based on ultimate equilibrium theory is proposed. The shear resistance of composite beams is divided into three parts: compression zone, stirrups and UHPFRC layer. The shear contribution of stirrups and compression zone is calculated according to the force equilibrium state of the free body of the composite beam. The shear contribution of the UHPFRC layer is calculated based on the fracture pattern of the single hinge in the UHPFRC layer. Then the calculation method is modified considering the size effect. Subsequently, the shear experiment of the UHPFRC-NC composite beams is conducted to test the validity of the calculation method and study the influence of the UHPFRC layer, longitudinal reinforcement and size effect on the composite beams. Meanwhile, the universality of the method is verified based on the cantilever shear experiments of other researchers.