Flexural and shear behavior of ultra-high performance concrete segmental joints

Abstract

The purpose of this study is to determine the optimum shape of ultra-high performance concrete (UHPC) segmental joints under flexural conditions and to investigate the flexural and shear capacities of UHPC segments connected by optimum segmental joints. A series of nonlinear finite element (FE) analyses is first performed to define the optimal shape and dimensions of the joint. The FE analysis results show that the most effective joint shape is the 45° key joint, as it does not induce an overly high stress concentration at the joint. Therefore, fourteen UHPC segments connected with optimal joint configurations are prepared and tested under bending and shear loads. Several parameters, such as prestressing force, joint depth, the number of shear keys, and the presence of dowels, that affect the flexural and shear capacities of the UHPC segment are experimentally examined. The experimental results indicate that by inducing the prestressing forces, both flexural and shear performance predominantly increase, and higher ductile behavior in the UHPC segments can be achieved. Moreover, the presence of dowel bars and double shear keys can significantly retard crack opening at the joints under flexure and shear loading, respectively. This is because both dowel bars and key joints can facilitate the transfer of higher stresses across the joint. Additionally, the joint depth contributes positively to the stiffness and loading capacity of the UHPC segmental joints.