山区大跨悬索桥非平稳高湍流风效应研究

Affected by the complex terrain, mountain winds showed the significantly non-stationary and high turbulence characteristics, the existing classical wind load models are established on the basic assumption of stationary wind velocity, and the impacts on the aerodynamic characteristics of fluctuating wind velocity are not considered. Thus it is difficult to accurately reflect wind-induced vibration characteristics of long-span bridge under mountain winds action. Based on the structural health monitoring system of long-span suspension bridge, the non-stationary wind effects on the suspension bridge are discussed based on the field measurement and theoretical analysis method. First of all, the natural wind and flow field around the bridge are obtained based on the wind-structure coupling results simulated by the CFD numerical method, and the optimal location and layout of anemometers and wind pressure sensors are determined. Based on the existing monitoring system of the bridge, the wind pressure sensors and a certain number of anemometers are supplemented for long-term observation, the natural wind field, flow field and wind pressure of cross section are obtained. Based on the numerical fitting of the measured results, the theoretical model of mountain winds’ non-stationary random process and spatial distribution can be derived and its’ key parameters can be identified. Also the wind pressure distributions can be studied and reveal the aerodynamic properties of the bridge’s cross section. Finally, the measured characteristics of non-stationary buffeting responses can be studied based on the vibration monitoring system of the bridge, and establish the non-stationary buffeting analysis method based on the measured strong wind data. The project can provide safety and good performance for long-span mountainous bridges under strong wind.

受复杂地形影响，山区强风呈现显著的非平稳及高湍流度特征，现有结构风振分析又是建立在风速平稳性、同时不考虑脉动风速对气动力参数影响的假定基础上，难以准确反映山区桥梁风振特点。基于山区大跨度悬索桥健康监测系统，采用现场实测与理论分析方法对桥梁的非平稳风效应展开研究。首先，采用CFD数值模拟结构的风致耦合效应，得到自然风场和绕流场区域，确定风速仪及风压传感器的选型及优化布设。在桥梁现有监测系统基础上，补充风压传感器及一定数量的风速仪，对其自然风场、绕流场及断面风压进行长期观测；对实测结果进行数值拟合，获得山区强风非平稳随机过程及其空间分布的理论模型并对其关键参数进行识别；研究断面风压分布特性，揭示桥梁的气动力特性。最后，基于桥梁的振动监测，研究其非平稳抖振响应实测特性，同时基于实测强风数据，建立大跨悬索桥非平稳抖振的理论分析方法。研究结果可为我国山区大跨悬索桥梁的抗风设计和安全运营提供理论依据。

受复杂地形影响，山区强风呈现显著的非平稳及高湍流度特征，现有结构风振分析又是建立在风速平稳性、同时不考虑脉动风速对气动力参数影响的假定基础上，难以准确反映山区桥梁风振特点。基于山区大跨度悬索桥健康监测系统，采用现场实测与理论分析方法对桥梁的非平稳风效应展开研究。首先，采用CFD数值模拟结构的风致耦合效应，得到自然风场和绕流场区域，确定风速仪及风压传感器的选型及优化布设。在桥梁现有监测系统基础上，补充风压传感器及一定数量的风速仪，对其自然风场、绕流场及断面风压进行长期观测；对实测结果进行数值拟合，获得山区强风非平稳随机过程及其空间分布的理论模型并对其关键参数进行识别；研究断面风压分布特性，揭示桥梁的气动力特性。最后，基于桥梁的振动监测，研究其非平稳抖振响应实测特性，同时基于实测强风数据，建立了大跨悬索桥非平稳抖振的理论分析方法。本项目依托某大跨悬索桥的健康监测系统，取得了山区强风以及桥梁动力效应的相关实测数据，并开展了通过小波变换、EMD分解以及HHT等时频域手段展开山区强风的非平稳特性研究。采用局部平稳小波过程，得到评估山区强风非平稳随机过程时变功率谱密度的方法，其分析理论能够对一般的非平稳随机过程具有更好的适应性。基于该方法建立基于小波分析的非平稳风速模型，并详细分析了山区强风的实测风速资料，得到其风场时频域特性及参数并探讨了其导致非平稳的原因。根据非平稳风速场描述方法，依托山区强风的实测数据，基于时变强风平均风速、平均风速剖面以及演变功率谱函数构成山区强风的非平稳风场模型。将山区强风的风致作用力表达为时变平均风力、与时变气动力系数相关的非平稳抖振力以及与时变颤振导数相关的气动自激力三部分。建立了山区强风作用下桥梁断面的非平稳气动力模型，同时结合虚拟激励法得到山区强风作用下大跨度桥梁时变平均风响应以及利用演变谱方式表达的非平稳抖振响应的时频解析方法。