Shear behavior of joints in precast UHPC segmental bridges under direct shear loading

Abstract

The joints in precast ultra-high-performance concrete (UHPC) segmental bridges (PUSBs) play significant roles in the structural performance of PUSBs, which require systematic investigation to establish a thorough understanding of their shear behavior. To this end, the push-off tests for 11 UHPC joints, including 9 epoxy joints and 2 dry joints, were carried out to obtain the failure modes, crack distribution, and the load-relative vertical displacement relationships. The confining stress, number of shear keys, and joint types were the critical test parameters considered in this study. Experimental results show that the failure mode of flat epoxy joints was the spalling of the epoxy, and no visible damage was observed on the surface of joints. For the keyed epoxy joints, the brittle shear-off of shear keys led to the failure of joints. However, dry joint specimens showed severe damage and spalling of UHPC. The shear capacity of UHPC joints effectively improved as the confining stress and number of keys increased, and the epoxy joints exhibited a higher shear capacity than the dry joints. The shear strength formulas of UHPC joints were developed and the calculated results from the proposed formulas agreed well with the test results with an average ratio of 1.05 and a coefficient of variation of 0.079. Moreover, four calculation models for the UHPC joint shear strength were proposed based on the forms of existing shear strength formulas of UHPC joints and 61 push-off test results available in the previous studies were used to evaluate the calculation models.