无缝桥Z形搭板的工作机理和计算方法研究

The jointless bridge has been widely applied in many developed countries to eliminate fundamentally the expansion joints which frequently have many diseases and need regular maintenance. Currently, the jointless bridge is paid more and more attention in China. The approach slab could be considered as the most critical and easily damaged component in jointless bridges, because it should not only be able to carry the vertical load and resolve the settlement of backfill, but also to transfer and absorb the longitudinal expansion and compression deformation produced by the main girder. In order to overcome the disadvantages of conventional approach slabs, an innovative type of approach slab with Z shaped is proposed in this research, which could be designed by modifying certain parameters to satisfy the requirement of different projects of jointless bridges. The main research contents are listed in the following. (1) The experimental and finite element analyses will be carried out in order to reveal the mechanism of longitudinal deformation absorption and transfer of Z shaped approach slab in jointless bridge under the longitudinal deformation of main girder, and determinate the ultimate longitudinal deformability of Z shaped approach slab. (2) The finite element model of the whole jointless bridge will be built, which can be used to analyze the evaluation method of the biaxial anisotropic stiffness of composite Z shaped approach slab and backfill system, and the influence of the stiffness of composite Z shaped approach slab-backfill system on the mechanical behaviors of the main girder in jointless bridges. (3) A large number of sensitive analyses will be conducted in order to find out the ultimate total length of the jointless bridges with Z shaped approach slab. (4) Based on the comparison between the working mechanism of Z shaped approach slab in the longitudinal direction and those of conventional approach slabs, the simplified calculation method of Z shaped approach slab will be proposed. The findings of this research can help to provide a new type of approach slab to jointless bridges and promote the further development of this typology of bridges in China, which are significant to the development of society and economy.

无缝桥取消了伸缩装置，能根除其多病害与常维护问题，已在发达国家大量使用，在我国的应用也越来越多。无缝桥中的搭板除了承担竖向荷载、缓减台后沉降作用外，还需要发挥吸纳与传递纵桥向伸缩变形的作用，成为无缝桥的关键构造和较易出现病害的构件。本项目创新地提出Z形搭板，以克服现有搭板存在的不足，并能通过参数的变化适应不同的需求。主要研究内容包括：（1）开展试验和有限元模拟研究，揭示Z形搭板对无缝桥主梁纵桥向变形的吸纳和传递机理，探明Z形搭板纵桥向极限变形能力；（2）建立无缝桥全桥有限元模型，研究Z形搭板和台后填土的纵桥向双向异性刚度取值方法及其对无缝桥主梁力学性能的影响；（3）开展参数分析，探明带Z形搭板的无缝桥极限长度值；（4）揭示Z形搭板与传统搭板纵桥向工作机理的异同性，提出Z形搭板的简化计算方法。本项目研究成果将为无缝桥搭板提供新的结构形式，推动无缝桥在我国的进一步发展，具有重要的社会经济意义。

无伸缩缝桥梁可从根本上解决有伸缩缝桥梁的伸缩缝易损性问题。既有无缝桥病害调查统计发现，搭板成为影响无缝桥使用性能的关键构件之一。在总结国内外搭板文献资料基础上，提出一种新型Z形搭板，开展模型试验、有限元模拟、参数分析和简化计算方法拟合等工作。研究结果可为完善我国无缝桥设计规范提供参考。本项目主要研究内容及结论如下：. （1）通过试验和有限元分析探明Z形搭板对无缝桥主梁纵桥向变形的吸纳和传递机理。Z形引板荷载-近台端纵桥向位移曲线呈现弹-塑性曲线的特点。随斜板倾角减小，斜板板厚、上板板长和远台端埋置深度增大，Z形搭板荷载-位移曲线的初始刚度和峰值荷载增大。与面板式搭板相比，Z形搭板荷载-位移曲线的初始刚度提高25.05%，峰值荷载增大42.29%；非线性段长度增大5倍以上，可减缓因刚度突变导致接线路面破坏。Z形引板各处转角均小于0.5°，基本上呈刚体移动。随着斜板倾角增大，Z形搭板远台端砂面变形减小，纵桥向变形吸纳能力增大。Z形搭板的上板和斜板交接处以及斜板和下板交接处均出现微裂缝。. （2）通过有限元模拟和参数分析研究Z形搭板和台后填土的纵桥向双向异性刚度取值方法。当斜板倾角介于25.56°~45°，上板板长介于4.51m~7.05m时，任意斜板板厚和远台端埋置深度的Z形搭板推拉刚度比大于1，有利于钢筋和预应力混凝土主梁受力。. （3）基于路面平整度限值，通过有限元模拟和参数分析探明带Z形搭板的无缝桥极限长度值。分析发现，对于总长不超过150m的无缝桥，Z形引板受推时，Z形搭板远台端路面平整度满足高速公路平整度限值要求；受拉时，斜板倾角小于44.6度、斜板板厚等于0.21m、上板板长大于7.00m及远台端埋置深度大于1.32m的Z形搭板远台端路面平整度满足普通公路平整度限值要求。. （4）对比Z形搭板与传统搭板纵桥向工作机理的异同性。采用双折线模型简化Z形搭板荷载-位移曲线。根据参数分析结果拟合Z形搭板-土组合刚度简化计算方法，并开展精度分析得到简化计算方法精度较高，满足工程使用要求。