Experimental and analytical studies on direct shear performance of UHPC keyed joints

Abstract

The keyed joint in the precast ultra-high-performance concrete (UHPC) segmental bridge (PUSB) plays a critical part in the structural behavior of the entire bridge, which requires in-depth investigations to clarify its shear performance. To this end, experimental and analytical studies on 15 UHPC keyed joints were conducted to explore the effects of the joint type, number of teeth, size of teeth, angle of teeth, and reinforcement method on the shear behavior of UHPC keyed joints. Test results presented that the failure modes were significantly affected by the teeth number and the reinforcement method, which can be classified into three primary categories (direct shear, segmental shear, and stepwise shear). The epoxied joints exhibited better shear capacity and ductility than those of dry joints, and the large-keyed joints owned higher shear capacity than the small-keyed joints under the same shear area. Moreover, the mechanisms of the two reinforcement methods were analyzed: the teeth rebars effectively improved the brittleness of the specimen, and the internal tendons significantly enhanced the shear efficiency of the specimen. Finally, considering the bridging effect of steel fiber, a calculation model was proposed for the shear capacity of the UHPC epoxied-keyed joints. The test results were in good agreement with the analysis results, indicating that the proposed model can be used to predict the shear capacity of UHPC epoxied-keyed joints.