Experimental and Simulation Studies on the Shear Performance of Precast Ultra-High-Performance Concrete Keyed Joints

This study investigates the shear performance of precast ultra-high-performance concrete (UHPC) keyed joints through experimental and numerical simulation approaches. Double-sided direct shear tests were conducted on four UHPC joint specimens with variations in key configuration (large-keyed and double-keyed), key-tooth inclination angle (27° and 45°), and the presence of internal shear reinforcement. Key parameters included cracking load, ultimate shear capacity, load-displacement response, crack propagation, and failure modes. The results indicated that joint configuration significantly influenced the failure mode and ultimate capacity, with double-keyed joints exhibiting higher shear strength and more stable post-peak behavior compared to large-keyed joints. A smaller inclination angle enhanced cracking resistance and shear stiffness, while the addition of internal reinforcement improved ductility but slightly reduced the cracking and ultimate loads. Furthermore, a three-dimensional finite element model using the concrete damage plasticity constitutive law was developed and validated against the experimental results. The simulation accurately captured the crack development and failure mechanisms, demonstrating good agreement with the test data, though it tended to overestimate the post-peak residual strength. The findings provide valuable insights for the design and application of precast UHPC keyed joints in segmental structures.