新老桥间超高性能混凝土拼接接缝性能试验

Experimental Study on the Performance of the UHPC Stitching Joint Between New and Original Bridges

摘要:

依托上海市济阳路高架新老桥拼接项目进行了基于高应变强化超高性能混凝土(UHPC)材料的拼接缝试验.试验采用非对称加载，目的是模拟新老桥的不均匀沉降.试验结果表明，UHPC拼缝整个受力破坏的过程大致可以分为3个阶段：弹性阶段、裂缝发展阶段、持荷至破坏阶段.在UHPC板下缘首先出现裂缝，之后UHPC板侧面出现大量微小裂缝，裂缝均以微裂缝簇的方式呈现，裂缝宽度发展缓慢，且沿着板高向上发展.UHPC转角为1.2%时裂缝宽度仅为0.16 mm，具有出色的裂缝控制能力.最终，UHPC板底出现主裂缝，横向钢筋和门筋屈服，钢筋布置方式满足试件破坏形态要求，说明试件的配筋合理.结合有限元模型对试验进行模拟，吻合度较高.利用有限元进行参数分析，发现增加接缝自由长度和减小接缝厚度可以有效增强接缝弯曲性能.由于UHPC材料进行接缝施工具有方便、快捷、性能优越等优点，提出基于上下部构造不连接类型的接缝形式，并给出具体配筋方案.

Abstract:

Based on the bridgestitching project of Jiyang viaduct, Shanghai, an experiment was conducted on highstrain hardening ultrahighperformance concrete (UHPC) stitching joints. Asymmetrical loading was used to simulate the bridge uneven settlement in the experiment. The experiment results show that the entire process can be divided into three stages: elastic stage, cracks developing stage and failure stage. First, cracks appear under the UHPC panels; then, many micro cracks appear on the side of the UHPC panels. The cracks appear in the form of microcrack clusters, and the crack width slowly increases. When the UHPC panel rotation is 1.2%, the crack width is 0.16 mm, so the UHPC has excellent crackcontrol ability. In the end, the main crack appears at the bottom of the UHPC panels, and the transverse reinforcements yield because the reinforcement layout satisfies the requirements of the failure mode of the specimen. Thus, the reinforcement arrangement of the specimen is reasonable. The experiment was simulated using the finiteelement model, and the results were coordinated with experiment results. The parameter analysis was carried out by the finite element method, and the results show that increasing joint free length and reducing joint thickness can effectively enhance the bending performance of joints. Because the advantages of the UHPC joint are convenience, rapidity, and excellent performance, a joint form based on the type of nonconnection of upper and lower structures is put forward. What’s more, a detailed reinforcement scheme is given, which will serve as a reference for similar projects in the future.