Shear failure analysis of UHPC-NC composites interface with U-shaped studs

Given the extensive utilization of composite structures of ultra-high performance concrete (UHPC) and normal concrete (NC) in engineering applications, there has been a growing emphasis on studying the shear failure and mechanical properties analysis of the UHPC-NC interface. U-shaped studs assume a crucial role in reinforcing the UHPC-NC interface. A three-dimensional finite element model was constructed with different parameters to investigate the shear failure and mechanical properties of UHPC-NC incorporating U-shaped studs. The failure mode and the influences of diameter, internal span, stud number and concrete compressive strength on the shear characteristics of the UHPC-NC interface were analyzed. The numerical analysis indicates the final failure mode of the UHPC-NC interface with U-shaped stubs is the fracture of the U-shaped stud. The diameter and internal span of studs influence the interface shear capacity, while interface shear capacity is not sensitive to the compressive strength of UHPC and NC. Moreover, a calculation formula for the shear capacity of the UHPC-NC interface with U-shaped studs was proposed, considering the influence of stud diameter and internal span. An exponential function is recommended for predicting the interface shear slip and the stiffness corresponding to 0.55 times the shear capacity is adopted as the elastic shear stiffness. The interface shear slip model and the expression for elastic shear stiffness were established, providing a reference for approximate calculation without experimental data.