坡地高层建筑非稳态雷暴冲击风荷载特性研究

目前结构风工程对于雷暴冲击风风荷载的研究多局限于稳态冲击射流模型，较少考虑风速随时间的变化以及坡地地形等因素的影响.基于冲击射流模型，引入衰减函数使得射流的入口风速更加接近真实的雷暴冲击风整个生命周期的衰变过程，并通过瞬态大涡模拟(LES)分析了坡地地形中坡顶位置处典型高层建筑的建筑风荷载特性及坡地地形雷暴冲击风场特性.结果表明，LES瞬态模拟具有较高的可靠性，非稳态冲击风场的风速波动较大，变化规律与实测的下击暴流风速曲线类似；建筑表面的风荷载具有强烈的非平稳特性，且随着风速迅速衰减；非稳态冲击风的风荷载波动大且潜在破坏能力更强；坡地地形下建筑迎风面风荷载普遍比平地小，且对建筑中上部的影响明显要大于底部，随着起坡角度的增大,建筑中上部风荷载逐渐减小.
The existing researches for wind load characteristics of the downburst mainly concentrated on stationary impinging jet model，but rare investigation was for time-varying characteristics and the impact of mountain terrain. In this paper，based on the impinging jet model，the decay function was brought in to make the inlet wind velocity more close to the decay process of the whole life cycle of the thunderstorm，and the wind load characteristics of typical high-rise buildings on the top of the slopes and the characteristics of the thunderstorms on the slope landforms were analyzed by transient large eddy simulation (LES). The results show that the transient simulation of LES is more reliable，the wind speed fluctuation of the unsteady shock wind field is larger，and the variation law is similar to the measured wind speed curve. The unsteady wind load shows strong unsteady characteristics，greater fluctuations and rapid attenuation with wind speed. The wind load fluctuation of unsteady shock wind is wide and has strong potential to damage，the wind load on the sloping terrain is generally smaller than that of the flat ground，and the influence of the slope terrain on the upper part of the building is obviously higher than that of the bottom. With the enlarging of slope angle，the upper wind load gradually decreases.