Flexural behavior of precast UHPC beam with prestressed bolted hybrid joint

Abstract

Ultra-high performance concrete (UHPC) is suitable for precast and assembled bridges due to its unique characteristics. Therefore, an efficient, safe, and durable joint connection that fits between the precast UHPC beam segments is of crucial importance. In existing conventional prestressed joints, a potential safety hazard exists because steel strands corrode under long-term detrimental environmental conditions. To address this issue, a prestressed bolted hybrid joint was proposed in this study. Eight precast UHPC beams with different types of joints were constructed. Experimental tests were conducted to examine the flexural behavior and load-bearing mechanism of the prestressed bolted hybrid joint, prestressed joint, and bolted joint. The flexural capacity, characteristic loading values, deformation characteristics, and the failure modes of the three types of joints were investigated and the influences of the bolts and epoxy resin adhesive on the flexural capacity of the joints were also discussed. The test results showed that the failure of the hybrid joint was characterized by the local crushing of the UHPC at the top compression zone together with shearing off of some of the bolts. The flexural capacity of the hybrid joint was significantly improved and was 46.8–60.3% higher than that of the conventional prestressed joint. The overall flexural capacity of the hybrid joint can be divided into two parts, the contributions of the prestressed UHPC joint and bolted connection. The epoxy resin adhesive had little effect on the slip resistance of the bolted joint; however, its bonding effect increased the cracking moment and flexural capacity of the joint by 16.5–29% and 11.5–21.8%, respectively. Besides, due to the strengthening effect of the bolted steel plates and the prestressing, the overall stiffness of the UHPC beam with the hybrid joint was significantly higher than that of the prestressed joint and the bolted joint after joint opening. Based on the test results, a computational method was proposed for calculating the slip moment, joint-opening moment, and ultimate flexural capacity of the prestressed bolted hybrid joint and the prestressed joint, and the feasibility of the hybrid joint was verified.