Shear Behavior and Capacity of UHPC Double-Keyed Joints Subjected to Direct Shear Loading

Ultra-high-performance concrete (UHPC) epoxy joints are extensively employed in precast ultra-high-performance concrete segmental bridges (PUSBs). The performance and operation of the PUSB structure are largely determined by the shear behavior of UHPC keyed joints, which require in-depth investigations to clarify the shear behavior and capacity of the joints. In this study, five UHPC double-keyed joints (including four epoxy joints and one dry joint) with double-sided shear specimens were cast and tested, and the effects of joint type, confining stress, and keyed reinforcement on the shear behavior were analyzed. The test results presented that the load-relative displacement responses of the UHPC double-keyed epoxy joint specimens were divided into four stages, while the failure mode of the dry joint specimens differed from those of the epoxy joints due to the lack of bonding of the epoxy resin adhesive. The cracking load and ultimate shear strength of epoxy joints increased as confining stress increased, and residual shear capacity was approximately linearly related to the confining stress. The key teeth reinforcement effectively enhanced the ultimate shear capacity of the double-keyed epoxy joint. Then, based on the existing methods for calculating the shear capacity of the UHPC keyed joints, the angle of the diagonal compression bar in the key tooth region was amended by the test results. The shear contribution of the key tooth region was expressed as an equation related to the uniaxial tensile strength of the UHPC, and the comparative results showed that the predicted equation agreed with the test data.