采用UHPC-RC阶梯桩的整体桥试设计

为了增大桥台基础柔度，适应整体桥纵桥向变形需要，提出了上部采用超高性能混凝土（UHPC）材料、下部采用普通混凝土（RC）材料的UHPC-RC阶梯桩，进行了这种新型桩基整体桥的试设计，在桩顶3 m范围内用截面尺寸为30 cm×30 cm的UHPC代替原来的70 cm×50（70） cm普通混凝土，并采用MIDAS软件建立了全桥空间有限元模型。研究结果表明:恒载作用下，试设计桥梁端负弯矩相比于原桥明显减小；在偏载和中载作用下，试设计桥主梁在桥台处的负弯矩分别减小14.2%和22.8%；整体降温作用下，主梁的轴力和弯矩均都有显著减小，桩身的最大剪力和最大弯矩出现在桩顶位置，分别减小52.2%，59.8%；在整体升温作用下，桥台的最大剪力和最大弯矩出现在桥台顶部位置，分别减小32.6%，45.8%；UHPC-RC阶梯桩是一种适合中国国情、有发展前景的无缝桥桩基新结构。

Trial-design Study on Integral Abutment Bridge by Using UHPC-RC Stagewise Piles

A UHPC-RC stagewise pile with ultra high performance concrete （UHPC） was proposed to increase the flexibility of the foundation and adapt to the longitudinal deformation of the integral bridge. The trial-design of integral abutment bridge employing such a new kind pile was performed. In the top 3 m of the pile, UHPC with 30 cm×30 cm section was used to instead of the original 70 cm×50(70) cm RC. The finite element model of the whole bridge was established by using MIDAS software. The study results show that negative bending moment at the end of the beam in the trial-design bridge is obviously reduced compared to the original bridge under dead load. The negative bending moments decrease about 14.2% and 22.8% respectively under offset load and central load. When the temperature drops, the axial force and bending moment of beam are significantly reduced. The maximum shear force and bending moment of the pile occur at the top of the pile, and they decrease about 52.2%, 59.8%, respectively. When the temperature rises up, the maximum shear force and bending moment of the abutment appear at the top of the abutment, and decrease by 32.6% and 45.8%, respectively.Trial-design study indicates that UHPC-RC stagewise pile is a new type pile which is suitable to be used in integral bridge in China.