强风区缆索体系桥梁桥塔风振响应及可靠性研究

With the development of cable system bridge tower to being higher, lighter and more flexible, performance of dynamic response during strong wind by passing through all wind speed ranges is more complicated. There are questions on unsteady wind-induced responses and corresponding reliability for bridge tower considering wind effects of cable, girder and tower and their nonlinear influences. This work will be carried out through wind tunnel tests, numerical simulation and theoretical analysis. It is necessary to explore the signature turbulence effect of long-span cable-stayed bridge tower wind field and conduct research on numerical model of unsteady aerodynamic forces on bridge tower in time domain passing through all wind speed ranges considering wind effects of cable, girder and tower. Then the influence rules of inflow characteristics and structure parameters of the tower-cable-deck system on aerodynamic parameters and wind-induced responses for bridge tower are summarized, for identifying distribution pattern and numerical characters of aerodynamic parameters and wind-induced responses. Finally, reliability of bridge tower subjected to strong wind load based on maximum entropy principle is analyzed and the dynamic relation between section morphology and reliability for bridge tower is established, and the results can provide a certain support for reliability-based wind resistant desigh of bridge tower in strong wind region.

随着缆索体系桥梁桥塔向更高、更轻、更柔的方向发展，强风经历全过程的动力响应情况更复杂，针对桥塔考虑缆索、主梁和桥塔风效应影响及构件非线性影响的非定常风振响应及相应的可靠性等方面均存在不少疑问。拟采用风洞试验、数值模拟和理论分析相结合的方法，探究强风区大跨度斜拉桥桥塔局部风场的特征紊流效应，开展考虑缆索、主梁和桥塔本身风效应影响的基于风速全过程的桥塔非定常气动力时域模型的研究，总结来流特征和桥塔-索-面体系结构参数对桥塔气动力参数和风振响应的影响规律，确定气动力参数（如三分力系数、自激力、气动导数、气动导纳等）和风振响应的分布类型和数字特征，基于最大熵原理进行桥塔风振可靠性分析，建立桥塔断面形态与桥塔风振可靠度之间的动态关系，为强风区桥塔基于可靠度的抗风设计提供一定的支撑。

随着缆索体系桥梁桥塔向更高、更轻、更柔的方向发展，强风下的动力响应更为复杂，且缆索体系桥梁中的缆索、主梁和桥塔之间也具有强耦合性，双重耦合下的桥塔风振响应及其可靠性还没有展开系统研究。本课题综合考虑桥塔局部风场的特征紊流效应和索-塔-面耦合非线性振动影响，对缆索体系桥梁桥塔的风振响应和可靠性展开了较为全面的研究。首先通过小波分解和可变时距划分得到了时变风速来表达场地的平均风特性，选用极值I型作为极值风速概型，采用最小绝对偏差法进行参数估计，得到了年最大风速概率分布拟合曲线。建立了塔-索-面耦合非线性振动模型和桥梁有限元分析模型，通过四个独立的一维多变量随机风场模拟缆索体系桥梁的随机脉动风场，采用节段模型测振测力、气弹模型风洞试验获取了主梁、桥塔的静力三分力系数、气动导数和风振响应，然后基于考虑来流紊流和特征紊流的抖振力谱线性叠加的桥塔抖振力自功率谱，建立了缆索体系桥梁抖振频域分析模型。通过分析发现，桥塔、拉索和桥面的频率比为2：2：1时，三者发生强烈的耦合作用，桥塔尾流涡脱频率与桥塔周边小尺寸细长结构的脉动气动力卓越频率接近时，小尺寸细长结构可能发生涡振；抖振频域分析结果与传统Sears气动导纳抖振分析和气弹模型试验结果吻合较好，前者结果介于后两种方法的计算结果之间。另外，缆索垂度效应、雷诺数效应对桥塔气动力和振动特性有一定影响，但其规律需进行深入研究。基于Monte Carlo试验和统计学方法确定了气动力参数和风振响应分布满足对数正态分布类型。建立了桥梁涡振可靠度分析的功能函数并进行了计算，其计算精度较好，计算效率高于Monte Carlo法；桥梁涡振失效概率对 和 的敏感性最大，参数数字特征中，变异系数对失效概率的影响最大。综上所述，本研究为进一步精细化强风区缆索体系桥梁桥塔风振分析以及基于可靠度的抗风设计提供了一定的支撑。