Experimental study on the performance of the UHPC longitudinal joint between existing bridge decks and lateral extensions

Abstract An experiment on high‐strain hardening ultra‐high‐performance concrete (UHPC) stitching joints was conducted based on the bridge‐stitching project of Jiyang viaduct, Shanghai. In this experiment, asymmetrical loading was used to simulate the bridge differential settlement caused by soil settlement. The experimental results showed that the entire process could be divided into three stages: elastic stage, cracks developing stage, and failure stage. During these stages, cracks appeared at the bottom of the UHPC slab. Then, many microcracks appeared at the side of the UHPC slab. These microcracks appeared in the form of microcrack clusters, and the width of these cracks increased slowly. It indicated that UHPC had good crack‐control ability. Finally, the main crack appeared at the bottom of the UHPC slab, and the transverse reinforcements yielded. It indicated that the reinforcement layout met the requirements of the failure mode of the specimen. For further analysis, the finite‐element model (FEM) was established. And the results showed that the bending resistance of the joints could be effectively enhanced by increasing the free length of the joint or reducing the thickness of the joint. Based on this experiment and analysis, a nonconnected joint form between slabs and girders was put forward. And the detailed reinforcement scheme of this nonconnected joint form was given. This reinforcement scheme could serve as a reference for similar projects.