节段拼装预应力UHPC-RC组合箱梁受弯性能试验

为充分发挥超高性能混凝土（UHPC）和普通钢筋混凝土（RC）材料在箱梁桥应用中的力学性能，开展了节段拼装预应力UHPC-RC组合箱梁的静载试验，研究其受力过程、破坏形态和裂缝开展情况。结果表明：组合箱梁经历了弹性变形、裂缝开展和结构破坏三个不同受力阶段；裂缝首先由梁跨中节段接缝张开逐步发展至顶板翼缘，梁底板和腹板均未见明显裂缝，开裂的受拉区应力主要由预应力筋承担，最大裂缝宽度随荷载增加分阶段线性增大，试验梁最终以RC顶板混凝土压溃破坏而失效；受力过程中，UHPC U型梁和RC顶板能够保持良好的协同工作；组合箱梁存在一定的剪力滞效应。

Experiment on flexural behaviors of a segmental pre-stressed UHPC-RC composite box beam

To fully take advantage of the mechanical performance of ultra-high performance concrete (UHPC) and normal reinforced concrete (RC) in their applications to box girder bridges, static testing on a prefabricated segmental pre-stressed UHPC-RC composite box beam was carried out to investigate its mechanical behaviors, failure pattern and crack development. Experimental results show that the composite box beam undergoes three different stress stages, namely, elastic stage, crack development stage and failure stage. Cracking was initiated from the joint between mid-span segments of the beam, and there were no cracks visible on the bottom slab and web of the beam. After cracking, the tensile stress was mainly carried by the prestressed tendons. The maximum crack width increased piecewise with the increment of load. Finally, the test beam failed due to the crushing failure of concrete in the RC slab. During the entire loading process, the UHPC U-beam and the RC slab can work well together, and a certain shear lag effect was observed in the composite box beam.