山区峡谷非定常风场特性及对悬索桥气动稳定性能的影响

When bridge spans wide valley in mountainous terrain, wind field at the bridge site exhibit remarkable non-stationary spatio-temporal characteristics. Researches about the wind field characteristic and the aerodynamic stability of bridge at such valley terrain are relatively weak. The regulations about wind resistant design of bridge at mountainous valley terrain in the codes of every countries are far to meet the requirements. With the promotion of west development, more and more long-span suspension bridges will be built to span the valleys in mountainous terrain. This put forward urgently requirements on the clear understand of wind field characteristics in valley terrain and its effect on the aerodynamic stability of suspension bridge. Based on the wind field and deck response monitoring system of Lishui super span suspension bridge with main span of 856m, quantitative descriptions of wind field characteristics at valley site will be given by the analysis of data from field measurement, and the reasonable values for the power spectrum and spatial correlation of wind field will be studied, then take those analysis results as targets, the wind field at valley site can be simulated by wind tunnel test and CFD simulation; wind tunnel test of taut strip model of part of the main beam will be carried out to study the effect of turbulence on the spanwise of buffeting forces and self-excited forces in the simulated wind field at valley site; time domain analysis of finite element model will be used to investigate the aerodynamic stability of long span suspension bridge under strong wind in valley terrain, furthermore, the results of the finite element model will be validated by the field measurement of response, and the time domain analysis method will be improved, as result, it can provide reference for the wind resistant design of similar bridges.

当桥梁跨越深山峡谷地形时，桥址处风场具有显著的非定常时空特性，而此类地形条件下的风场特性及其引起的桥梁气动稳定性研究还较为薄弱，各国规范中关于山区峡谷地形桥梁抗风设计的条文远不能满足实际需要。随着西部大开发战略的深入实施，越来越多的跨越深山峡谷的大跨度悬索桥将被修建，这对明确峡谷风场特性及其作用下的大跨悬索桥气动稳定性提出了迫切要求。本项目拟以主跨856m的澧水特大悬索桥桥址峡谷风场与主梁风致响应同步监测系统为依托，由实测风场数据给出桥址峡谷风场特性的定量描述，研究紊流谱及空间相关性的合理取值，并以此为目标，实现峡谷风场特性的风洞及数值模拟；在风洞模拟风场中，借助主梁节段的气弹拉条模型测压测振试验分析紊流风场对抖振力及自激力展向相关性的影响形式；采用时域有限元法进行峡谷风作用下大跨悬索桥气动稳定性分析，由实测的主梁响应检验时域分析结果，并对其进行精细化改进，为类似桥梁的抗风设计提供参考。

随着西部大开发战略的深入实施，越来越多的跨越深山峡谷的大跨度悬索桥将被修建，然而区峡谷地形桥址处风场具有显著的非定常时空特性，而此类地形条件下的风场特性及其引起的桥梁气动稳定性研究还较为薄弱，各国规范相关条文远不能满足实际需要。围绕这一问题，本课题拟进行了以下几个方面的研究工作：.1、依托澧水大桥进行了峡谷风场及主梁风致振动响应的同步现场实测开展了山区非定常风场精细化分析，提出了峡谷桥址风场特性参数及风谱模型的合理取值。. 编制了专用的海量实测数据处理程序，直接获得风场特性参数的基本资料。结果显示澧水大桥峡谷风场三维特性显著，实测风剖面指数 在0.1515—0.4109之间波动，其平均值等于0.2609；峡谷内风场加速效应随高度增高显著减小，跨中谷顶处加速系数小于0.1，而靠近山体处四分点加速系数超过0.2。桥址处风攻角将明显不同于规范规定的各向同性地形，风攻角主要在分布在-9°和+7°之间，这对于山区大跨度桥梁的抗风设计安全将产生重要影响。.2、以实测风场数据为基础，结合国家地理高程数据库，利用Autodesk Civil 3D生成高程数据点云，通过逆向工程软件Imageware拟合成三维曲面，实现了大范围复杂地形数值模型的快速建立方法，改进了风场的CFD数值模拟精度。.3、进行了紊流风场对气动力展向相关性影响的研究.3.1采用强迫振动法研究了主动格栅紊流对理想薄平板，矩形钝体断面以及流线型箱梁断面颤振导数的影响。结果表明紊流风场对流线型断面颤振导数影响较小，而对矩形钝体断面影响显著。3.2通过强迫振动中的节段模型表面压力分布规律变化，揭示了紊流对颤振导数影响的内在机理为来流紊流引起断面迎风面分离与再附着流动的变化。定量的研究了紊流强度及积分尺度对颤振导数以及气动力跨向相关性的影响。3.3设计了反映结构风致振动三维特性的拉条模型测压测振试验。结果表明紊流引起了结构整体气动力相关性的明显衰减，但是气动自激力相关性衰减微弱。紊流场中箱型断面自激力相关性与矩形断面一样均具有相当高的相关性。.4、考虑几何非线性、气动力相关性、瞬时攻角等各影响因素，建立了山区峡谷强风作用下大跨悬索桥颤抖振响应非线性时域精细化分析方法，为准确预测类似山区峡谷处大跨度悬索桥风致响应提供了参考。