【作者】 孙向东；

【导师】 刘沐宇；

【作者基本信息】 武汉理工大学 ， 桥梁与隧道工程， 2010， 博士

【摘要】 矮塔斜拉桥由于优越的结构性能、良好的经济指标及优美的桥梁造型,在200m左右跨径领域,具有极强的竞争能力。近年来,我国矮塔斜拉桥虽发展迅速,但日益发展的工程实践和相对较少的基础研究之间存在矛盾。现有研究多集中于中小跨径的窄幅结构,以工程归纳形成的构造共识和分析理论难以有效解决大跨、宽幅和长联矮塔斜拉桥工程中的实际问题。本文以江肇西江大桥为依托,围绕多塔宽幅单索面矮塔斜拉桥设计关键技术展开研究。通过理论归纳和仿真分析验证,本文主要研究成果和创新点如下：(1)针对大跨、长联工况,创新性提出墩、塔、梁固结体系多塔单索面矮塔斜拉桥桥型方案,有效解决多塔结构塔顶位移和结构刚度等核心技术问题。(2)为弱化超宽截面自重效应,创新性提出宽幅脊梁断面,通过采用长翼板加劲肋桥面体系和后浇段工序措施,有效改善主梁剪轴力滞效应；通过边中腹板差异设计,以适应边中腹板受力的不均匀性。(3)系统研究矮塔斜拉桥整体参数变化敏感性,为塔高、边中跨无索区长度和边中跨比等关键参数拟定提供理据,由研究结论可知,高塔型矮塔斜拉桥是发展方向,跨中无索区长度趋于减少,边中跨比取0.6时结构整体受力较优。(4)创新性提出预应力配合比概念,系统研究斜拉索和体内预应力敏感度比值,综合考虑二者造价因素、抵抗竖向荷载效应和平抑主梁应力效率的不同,提出斜拉索和体内预应力的最优配置比例。(5)为使墩、塔、梁固结体系多塔矮塔斜拉桥成桥后期处于合理受力状态,对混凝土徐变、基础模拟刚度和混凝土自重荷载效应进行敏感性分析可知,徐变对墩身影响最为显著,其值可达30%,其他两项同样不可忽略。(6)针对宽幅脊梁纵、横向空间受力特征和后浇加劲桥面系复杂的受力机理,原有以纵向分析为主的桥梁设计方法存在局限,本文创新性提出能兼顾纵横的空间设计方法。在此基础上,通过桥梁仿真分析,系统研究不同阶段、不同梁段剪轴力滞效应,为合理配束和设置后浇带提供理据；系统研究边中腹板受力不均匀性,提出不均性系数为1.3左右,据此精当拟定脊梁断面腹板厚度；明晰加劲肋桥面系受力机理,明确横向剪力滞系数和后浇带滞后浇筑可行时域。(7)通过动力特性分析可知,矮塔斜拉桥动力特性较接近于连续梁桥,振型主要由主梁刚度控制,主塔刚度只对主塔自身振动有影响。抗风和抗震对结构设计制约较少。(8)系统研究矮塔斜拉桥景观设计和斜拉索耐久性设计,在设计之初即采取有效措施,确保超大吨位拉索的可养护性和可更换性。换索研究表明,在不中断交通的条件下,考虑到荷载的不确定性,建议每次只能更换一对斜拉索。在无成熟工程经验可资借鉴的情况下,因无相关规范提供技术指导,江肇西江大桥实现了多项技术上创新,本文的研究成果对大桥的设计提供了可靠依据,也为类似工程的设计提供了有价值的参考。更多还原

【Abstract】 Low-pylon cable bridge has strong competitiveness in the field of 200m span because of its excellent structural performance, good economic indicators and beautiful bridge shape. In recent years, our country’s low-pylon cable bridge has developed rapidly, but there is conflict between growing engineering practice and relatively few basic research. At present, most researches are focus on narrow structures of middle-small span. The consensus and analysis theory based on construction can not effectively solve practical problems of large-span, wide-range and continuous girder low-pylon cable bridge. This paper takes Xijiang Bridge of Jiangmen to Zhaoqing Highway as example, and does research on key techniques of multi-pylon wide ridge single plane low-pylon cable bridge design. By summarizing theories and vivificating simulation analysis, the paper generalizes research findings and innovations as follow:(1) Innovatively proposes bridge plans of pier, tower and beam consolidation system multi-tower single plane low-pylon cable-stayed bridge in light of large span and long continuous bridge. It effectively solves core techniques problems of tower top displacement of multi-tower structure and structural stiffness.(2) In order to weaken the dead weight effect of overwide section, innovatively proposes the section of wide ridge section, it effectively improves the shear lag effect by measures of post-cast operation and bridge deck system of long wing panel stiffener. Diversity design is used for mid-web plate to fit non-uniformity of stressed mid-web plate.(3) Innovatively studies the sensitivity of low-pylon cable-stayed bridge’s parameters and provides theory for formulating key parameters of tower height, the length of side span and mid span without cable, and ratio optimization between side span and mid span. According to researches, we can see that high-pylon cable-stayed bridge is the trend of cable-stayed bridge’s development. When the ratio optimization between side span and mid span is 0.6, the stress state is optimum.(4) Innovatively propses the concept of prestress allocation. Systematically studies sensitivity ratio of stayed cables and internal prestress. And it proposes the optimal allocation of stayed cables and internal prestress on the basis of cost, resistance to vertical load and stabilize the prestress efficiency of main beam.(5) In order to keep pier, tower, and beam consolidation system multi-tower cable-stayed bridge at reasonable stress state, analyzes concrete creep, basical simulated stiffness and sensitivity of concrete dead weight load. The analysis shown that creep has most significant effect on the pier, and its value is 30%. But the other two aslo can not be ignored.(6) According to stress characteristics of wide ridge’s tovertical and transverse space, and mechanics of post-cast stiffener bridge deck, the paper innovatively proposes design with due consideration tovertical and transverse space, because there are some limits on original bridge design which is based on tovertical analysis. On the base of it, the paper systematically studies shear lag effect of different stages and different box girders by means of bridge simulation analysis. It provides evidence for reasonable tendon layout and post-cast band. It systematically studies non-uniformity of stressed mid-web plate and points out that the coefficient of non-uniformity is aroud 1.3. According to these, we can determine web plate’s thickness of ridge section, mechanics of stiffener bridge deck, coefficient of shear lag and lagging-cast practicability of post-cast band.(7) Through the dynamic characteristics analysis, the dynamic characteristics of low-pylon cable-stayed bridge is closer to continuous bridge’s. The stiffness of main mainly controls vibration mode. The stiffness of main tower only affects the vibration of main tower itself. Wind and seismic resistance have less constraints on structural design.(8) Study landscape design of low-pylon cable-stayed bridge and durability design of cables systematically. Effective measures should be taken in the early stage of design to ensure the conservation and raplacement of large tonnage cables. Researches of cable replacement have shown that without interrupting traffic, we can only change a pair of cables each time because of the uncertainty of load.Xiangjiang bridge of Jianmen to Zhaoqing highway makes a number of technique innovations, though there is no mature engineering experience and relevent specification for guidance. The research results of this paper provide reliable guidance for bridge’s design and also provide valuable reference for similar projects.更多还原