考虑地形影响的高层建筑雷暴冲击风风荷载特性研究

发布时间：2018-12-27 18:16

【摘要】：由于雷暴冲击风引起的近地面强风具有极强的破坏性,结构风工程领域较早就开始研究这种极端天气现象。目前,大多学者更关注于雷暴冲击风所引起的近地面强风场特征,而关于山地地区雷暴冲击风作用下高层建筑的风荷载特性的研究比较少见,针对地形参数对建筑风荷载特征的影响规律就更加少见。因此,本文考虑地形影响,以高层建筑为研究对象,基于风洞试验、雷诺平均法(RANS)和大涡模拟方法(LES)研究了平地和坡地地形高层建筑表面风压分布特性以及地形参数对建筑风荷载特性的影响规律。主要研究工作包括:(1)平地与坡地地形下,高层建筑层风荷载规律研究。平地地形建筑层阻力系数沿高度方向各工况变化规律类似:阻力系数最大值位于建筑的中下部约1/4高度处,此范围之上随着高度的增加,层阻力逐渐减小;最大层风荷载出现在1.0~1.25D位置处,而后随着径向距离的增加,各层的阻力逐渐减小。对应情况下,坡地地形各层阻力都要比平地小,最大层阻力所在的高度也有所降低。与层阻力系数相比,层升力系数相对较小。(2)坡地地形对高层建筑风荷载影响规律研究。基于RANS稳态模拟和LES瞬态模拟均研究发现坡地地形高层建筑迎风面的风压并没有加速效应,地形参数对风压系数的大小有较大影响,相比平地地形而言,坡地地形高层建筑迎风面的风压反而有所减小。分析迎风面风压减小的原因大概有两方面:一方面,由于地形的存在,垂直于建筑迎风面的来流风水平风速分量有所减小,进而受到来流风的撞击力减小;另一方面,平行于建筑迎风面大大增加的竖向风速导致速压增加,二者共同导致坡地地形下建筑迎风面的风压系数有所减小。(3)基于LES瞬态模拟研究非稳态雷暴风作用下建筑物表面风压情况。风洞试验、RANS稳态模拟和LES瞬态模拟得到的时均层阻力系数具有较高的吻合度,三种方法相互验证了此研究结果的可靠性。而基于LES瞬态模拟得到的非稳态雷暴风风荷载波动较大,与平均风荷载相比,顺风向的极值阻力为平均风荷载的2.2~2.5倍。因此,在进行工程结构设计时,若是要考虑雷暴风的影响,建议在雷暴风平均风荷载的基础上考虑适当的放大。
[Abstract]:Due to the strong wind near the ground caused by thunderstorm, the extreme weather phenomenon has been studied in the field of structural wind engineering. At present, most scholars pay more attention to the characteristics of strong wind field near the ground caused by thunderstorm, but the research on wind load characteristics of high-rise buildings under the impact of thunderstorm in mountainous area is rare. The influence of topographic parameters on the wind load characteristics of buildings is even less common. Therefore, considering the influence of terrain, this paper takes high-rise buildings as the research object, based on wind tunnel test, Reynolds average method (RANS) and large eddy simulation method (LES) are used to study the wind pressure distribution on the surface of high-rise buildings in flat and sloping terrain and the influence of topographic parameters on the wind load characteristics of buildings. The main research work includes: (1) the wind load law of high-rise building under flat and sloping terrain. The variation law of resistance coefficient along the height direction is similar: the maximum resistance coefficient is located at about 1 / 4 height of the middle and lower part of the building, and the layer resistance decreases gradually with the increase of height; The maximum wind load appears at 1.25D, and then decreases with the increase of radial distance. In the corresponding case, the resistance of each layer of slope terrain is smaller than that of flat land, and the height of maximum layer resistance is also reduced. Compared with the layer resistance coefficient, the layer lift coefficient is relatively small. (2) the influence of slope topography on the wind load of high-rise buildings is studied. Based on RANS steady state simulation and LES transient simulation, it is found that wind pressure on the upwind surface of high-rise building in slope terrain has no acceleration effect, and terrain parameters have great influence on wind pressure coefficient, compared with flat terrain. On the contrary, the windward wind pressure of high-rise buildings on slope terrain is reduced. There are two reasons for the reduction of windward wind pressure: on the one hand, due to the existence of topography, the horizontal wind speed component perpendicular to the building upwind surface decreases, and then the impact force of the incoming wind decreases; On the other hand, the vertical wind speed parallel to the increase in the upwind surface of the building results in an increase in the velocity of pressure, Both of them lead to the decrease of building upwind pressure coefficient in slope terrain. (3) based on the LES transient simulation, the wind pressure on the building surface under the unsteady thunderstorm is studied. The results of wind tunnel test, RANS steady state simulation and LES transient simulation show that the time-averaged resistance coefficient has a high consistency. The reliability of the results is verified by the three methods. The wind load fluctuation of unsteady thunderstorm based on LES transient simulation is larger than that of the average wind load, and the extreme resistance in the downwind direction is 2.2 ~ 2. 5 times of the average wind load. Therefore, if the influence of thunderstorm is to be taken into account in the design of engineering structure, it is suggested that appropriate magnification should be considered on the basis of the average wind load of thunderstorm.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU973.213

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