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为解决跨海桥梁桥墩施工与防腐问题,提出了超高性能混凝土(UHPC)-钢筋混凝土(RC)组合桥墩新结构,简称U-RC组合桥墩,以UHPC外筒作为永久模柱,现浇内核钢筋混凝土;以平潭海峡大桥为工程背景,开展了U-RC组合桥墩的结构设计与计算,并与原设计方案的工程量和造价进行了比较;进行了3根内核RC柱、3根UHPC模柱、3根U-RC组合桥墩的极限承载力试验,测量了试件的混凝土纵向应变与横向应变,研究了试件的破坏形态与裂缝发展过程,得到了试件的极限承载力试验值,分析了U-RC组合桥墩的受力性能。研究结果表明:U-RC组合桥墩的承载力大于设计内力,满足现行规范要求;采用UHPC模柱取代钢模板的桥墩设计方案,可节约钢材约2 410t,工程造价节省约30%;3根UHPC圆筒的极限荷载均值为1 342kN,3根RC柱的极限荷载均值为1 370kN,二者之和小于3根U-RC组合桥墩极限荷载均值3 033kN,说明UHPC模柱对核心混凝土有一定的套箍作用,采用简单迭加方法计算U-RC组合桥墩的轴压极限承载力是可行且偏保守的;在轴压试验中,U-RC组合桥墩的破坏模式为核心混凝土的横向变形导致UHPC模柱出现竖向裂缝,并与核心混凝土在界面处分离;达到极限荷载破坏时,外包UHPC层出现纵向裂缝,荷载增大,裂缝增长,并有混凝土剥落现象,但U-RC组合桥墩破坏时其外包UHPC层纵向应变未达到极限压应变。
In order to solve the problems of construction and anticorrosion of bridge piers across the sea, a new UHPC-RC composite piers structure is proposed, which is called U-RC composite piers. The UHPC outer cylinder is used as a permanent mold, Reinforced concrete. Taking the Pingtan Strait Bridge as the engineering background, the structural design and calculation of the U-RC composite piers are carried out and compared with the engineering design and construction cost. Three inner RC columns, three UHPC Model columns and three U-RC composite piers. The longitudinal strain and transverse strain of the concrete specimens were measured. The failure morphology and crack development of the specimens were studied. The ultimate bearing capacity of the specimens was obtained , The force performance of U-RC composite piers is analyzed. The results show that the bearing capacity of U-RC composite piers is greater than the design internal force, which meets the current codes and requirements. The pier design with UHPC die instead of steel formwork can save about 2,410 tons of steel and save about 30% of the construction cost. Three UHPC The ultimate load of cylinder is 1 342kN, the average load of 3 RC columns is 1 370kN, and the sum of the two is less than 3 033kN of the ultimate load of 3 U-RC composite piers, which shows that UHPC mold column has certain core concrete In the axial compression test, the failure mode of the U-RC composite pier is that the transverse deformation of the core concrete leads to the UHPC When the U-RC composite bridge pier breaks down, the vertical cracks in the mold column appear and are separated from the core concrete at the interface. When the ultimate load failure is reached, the longitudinal cracks occur on the outer UHPC layer, the load increases, the cracks increase and the concrete spalls. Its outsourcing UHPC layer longitudinal strain does not reach the ultimate compressive strain.