低矮房屋风荷载特性及近地面台风风场应用研究

发布时间：2018-12-08 18:09

【摘要】：本文基于低矮房屋台风实测系统获得的实测数据,详细研究了台风登陆前后近地面风特性,在风洞试验中模拟了台风风场,分析了某实际工程在模拟台风风场中的风压分布。另一方面,运用现场实测和风洞试验相结合的方法研究了平坡屋面低矮房屋的风压特性和极值风压估计,探讨了现有的极值估计方法在台风实测中的应用,阐述了实测与风洞试验风压特性差异。通过进一步模拟低矮房屋屋盖角部突然破坏的风洞试验,分析了突然开孔的瞬时风压分布特征、内压频谱特性及其传播机理。本文的研究成果对台风多发地区的抗风设计具有重要的意义。本文的主要结论如下:(1)台风“海鸥”登陆过程中,脉动风向强度对顺风向和横风向湍流强度均有增强作用,横风向湍流强度随着脉动风向的增大呈近似线性增长。分析发现顺风向脉动风速谱在低频段与经验谱吻合较好。(2)根据某可开合大跨屋盖结构在台风风场和常规风场试验结果分析,结果表明相同开启状态时,台风风场下活动屋盖的平均风压分布规律和B类风场相似,屋盖的开启会减小屋盖表面的平均风压。在台风风场高湍流度作用下活动屋盖更容易遭受不利极值风荷载。此外,活动屋盖的完全开启对屋盖的脉动风压系数影响显著。(3)实测与试验结果分析表明屋面角部测点实测平均风压大于风洞试验结果.对于屋面边缘中部区域,垂直来流时,实测风压比试验风压大约40%。实测风压非高斯性程度强,处于负偏态和高峰态较多,相应测点的试验结果非高斯性程度弱,分析认为三参数Gamma分布可以很好地描述低矮房屋风压概率分布特性。(4)通过误差分析确定实测极值风压最佳观测短时距是30s。根据峰值风压系数估计结果,发现现有的极值估计方法难以稳定且精确地计算实测峰值风压,其中Sadek-Simiu法偏于保守,在无法准确获取峰值风压情况下,可采用该方法进行估算。基于Sadek-Simiu法的实测与试验峰值风压系数结果对比,发现实测峰值风压绝对值相对试验结果高20%~40%。(5)低矮房屋角部突然开孔时房屋内部出现瞬时负压,内压在开孔后0.05s趋于稳定。脉动内风压系数与来流湍流强度大小密切相关,内部区域风压相关程度高,可用一个测点代表内压时域特性。(6)湍流流场和均匀流场作用下内压相干函数曲线出现了不同数量的峰值,分析认为可能是建筑振动、来流湍流、特征湍流造成的。在斜风向下,屋盖表面出现锥形涡,极易产生Helmholtz共振。当不考虑阻尼作用,内压传播方程中惯性系数C_I=1.6时,Helmholtz共振频率理论值与试验值基本相等。与墙面存在主开孔的研究结果对比,发现屋盖角部存在一个开孔率约4.8%的方形孔时惯性系数值较大。
[Abstract]:Based on the measured data obtained from the low-rise house typhoon measurement system, the near-surface wind characteristics before and after the typhoon landing are studied in detail. The typhoon wind field is simulated in the wind tunnel test, and the wind pressure distribution of a practical project in the simulated typhoon wind field is analyzed. On the other hand, the wind pressure characteristics and extreme wind pressure estimation of low-rise roof with flat slope are studied by using the method of field measurement and wind tunnel test, and the application of existing extreme value estimation methods in typhoon measurement is discussed. The difference of wind pressure characteristics between measured and wind tunnel tests is expounded. Based on the wind tunnel test which simulates the sudden failure of the roof corner of the low housing, the instantaneous wind pressure distribution, the spectrum characteristics of the internal pressure and the propagation mechanism of the sudden opening are analyzed. The results of this paper are of great significance to the design of typhoon-prone areas. The main conclusions of this paper are as follows: (1) during the landing of Typhoon Seagull, the intensity of pulsating wind direction increases in both downwind and crosswind directions, and the intensity of crosswind turbulence increases approximately linearly with the increase of fluctuating wind direction. It is found that the spectrum of downwind pulsating wind velocity is in good agreement with the empirical spectrum at low frequency. (2) according to the experimental results of wind field and conventional wind field of a large span roof structure, the results show that the wind velocity spectrum is in the same open state. The average wind pressure distribution of moving roof under typhoon wind field is similar to that of B type wind field, and the opening of roof will reduce the average wind pressure on roof surface. The moving roof is more vulnerable to adverse extreme wind load under the action of high turbulence in typhoon wind field. In addition, the full opening of the moving roof has a significant effect on the fluctuating wind pressure coefficient of the roof. (3) the analysis of the measured and tested results shows that the measured mean wind pressure at the corner of the roof is greater than that of the wind tunnel test. For the middle part of roof edge, the measured wind pressure ratio is about 40. The non-Gao Si degree of measured wind pressure is strong, the negative skewness and peak state are more, and the test results of corresponding measuring points are weak. It is considered that the three-parameter Gamma distribution can well describe the probability distribution characteristics of wind pressure in low buildings. (4) through error analysis, the best observed short-time distance of measured extreme wind pressure is 30 s. According to the estimation results of the peak wind pressure coefficient, it is found that the existing extreme value estimation methods are difficult to calculate the measured peak wind pressure stably and accurately. The Sadek-Simiu method is conservative and can not accurately obtain the peak wind pressure. This method can be used to estimate. Based on the comparison of the measured and tested peak wind pressure coefficient by Sadek-Simiu method, it is found that the absolute value of the measured peak wind pressure is 20% 40% higher than the test result. (5) the instantaneous negative pressure appears in the house when the corner of the low building suddenly opens. The internal pressure tends to be stable at 0.05 s after opening. The wind pressure coefficient in the pulsating region is closely related to the turbulence intensity of the incoming flow, and the correlation degree of the wind pressure in the inner region is high. (6) there are different peaks in the coherent function curve of internal pressure under the action of turbulent flow field and uniform flow field, which may be caused by building vibration, flow turbulence and characteristic turbulence. Under the oblique wind direction, a cone vortex appears on the roof surface, which is easy to produce Helmholtz resonance. When damping is not considered and inertial coefficient C_I=1.6 in the equation of internal pressure propagation is not considered, the theoretical value of Helmholtz resonance frequency is basically equal to the experimental value. Compared with the research results of the main hole in the wall, it is found that there is a square hole with an opening ratio of about 4.8% at the corner of the roof.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU312.1

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