基于结构性能的双缆多塔悬索桥成桥状态确定及计算方法研究

Double-cable multi-span suspension bridges are a new type of cable bridges. As a type of long-span bridges, they have good prospects for application. Determination of the finished bridge state is the main problem when designing and building double-cable multi-span suspension bridges. This project deals with the determination and calculation of the finished state of double-cable multi-span suspension bridges. First, considering the “tower-cable-girder” synergistic effect, a simplified mechanical model of the double-cable multi-span suspension bridge is built. To provide a theoretical foundation for the analysis of finished bridge state, analytic formulas for the structural deformation and sliding-resistance coefficient of the main cable are deduced. Formulas are verified by finite element models and model test. Second, analytic calculation and numerical analysis are utilized to reveal the effect for structural deformation and cable sliding resistance made by finished bridge state. A determination method for the reasonably finished state of double-cable multi-span suspension bridges is developed using the method of multi-objective optimization and considering the overall structural property indices. Finally, by considering the established construction state as the target and combing the loading features of the double-cable system and the computing theory for the cable, a computing method are proposed for the parameters such as the main cable shape, unstressed main cable length, and sling force. The research result holds theoretical significance and is important for engineering applications.

双缆多塔悬索桥是一种新型缆索体系桥梁，力学性能优良，在大跨度桥梁中具有广阔应用前景。合理成桥状态的确定是设计、建造双缆多塔悬索桥的核心问题，本项目拟对双缆多塔悬索桥成桥状态的确定及其计算方法开展研究。首先，构建考虑“塔—缆—梁”协同作用的双缆多塔悬索桥简化力学模型，推导塔、梁变形以及主缆抗滑安全系数解析公式，并通过数值分析和模型试验进行验证，为成桥状态分析提供理论基础；其次，基于理论分析和数值分析，揭示成桥状态对结构变形、受力及主缆抗滑稳定性的影响规律；基于多目标优化方法，综合考虑各结构性能指标，提出双缆多塔悬索桥成桥状态优化目标的确定方法；最后，以既定成桥状态为目标，结合双缆体系受力特点和缆索计算理论，提出双缆多塔悬索桥主缆线形、主缆无应力长度及吊索力等参数的计算步骤和方法。研究成果具有重要的理论意义和工程应用价值。

多塔缆索体系桥梁在超大跨度桥梁建造中极具竞争力，双缆多塔悬索桥是一种新型多塔缆索体系桥梁结构，能够有效提升结构刚度，减小中塔受力，具有良好的应用前景。但是该桥型设计理论不完善，特别是桥塔刚度、主缆垂跨比、荷载在上下主缆分配比例等参数取值均缺乏理论依据，也无经验可循。项目通过研究双缆及传统悬索桥结构变形及主缆在中塔鞍座抗滑解析计算方法，以主缆抗滑安全系数和加劲梁挠跨比为控制指标，获得了传统及双缆多塔悬索桥中塔刚度上、下限值计算方法；分析了恒载集度、上下缆垂度、跨长等因素对中塔刚度取值的影响；以三塔两跨悬索桥为例，传统多塔悬索桥仅在恒活载比值大于6.5时，才存在合理的桥塔刚度；双缆多塔悬索桥结构刚度主要来自于缆索体系，其中塔可以采用柔性桥塔。首次设计实施了双缆多塔悬索桥模型试验，对三塔两跨双缆悬索桥模型进行典型工况下的加载，测试桥塔、加劲梁变形及桥塔受力；测试结果与有限元模型及理论计算结果进行对比，验证了双缆多塔悬索桥分析理论的准确性，同时也证明了双缆多塔悬索桥的结构性能。项目研究了双缆悬索桥“上缆变下缆”布置方式在空缆状态下的抗滑安全性，基于规范中抗滑安全系数计算公式提出了主缆在空缆状态抗滑安全系数计算方法，并验证了公式的准确性。分析了摩擦系数及跨长对于空缆状态主缆抗滑的影响，考虑空缆状态主缆抗滑，上下缆垂度差值不宜过大；需采取施工措施防止主缆在施工阶段发生滑移。研究为双缆多塔悬索桥设计提供了重要依据，建议了垂跨比、桥塔刚度等主要参数的取值范围，为双缆多塔悬索桥的工程应用奠定了基础。