【作者】 胡尚瑜；

【导师】 李秋胜；

【作者基本信息】 湖南大学 ， 结构工程， 2012， 博士

【摘要】 我国是世界上受台风影响最严重的国家之一,每年登陆我国东南沿海地区的台风平均次数为8-9个。台风所造成的人员伤亡和财产损失主要由台风风致灾害所造成的,风致灾害中绝大多数为居民房屋及低矮建筑风损破坏和倒塌。本文针对台风风致灾害中低矮建筑的风损和风毁问题,应用现场实测、风洞实验及理论分析相结合的方法,对台风作用下近地台风风场特性和低矮建筑风荷载进行了深入、系统的研究。本文主要研究内容及成果如下：(1)基于近海岸台风观测系统,获取了登陆台风10m高度三维风速数据,对在近海岸地貌强风条件下,l0m高度的风特性和湍流特性进行了统计分析。各向湍流强度Iu、Iv、Iw均值范围分别为0.11-0.14、0.06-0.11和0.03-0.05。阵风因子同湍流强度正相关,湍流积分尺度随湍流强度增加而相应减少。(2)基于平坡屋面实验房及台风观测系统,获取了近地台风风速实测数据,从来流不同地貌和台风不同区域影响的角度,对台风风场近地湍流特性进行了分析。台风外围大风区域l0m高度的各向湍流强度、积分尺度、阵风因子大于台风眼壁区域实测值。台风眼壁区域的顺风向和竖向脉动风速功率谱值与台风外围区域实测功率谱值差别不大,而台风眼壁区域的横风向脉动风速功率谱值大于台风外围区域实测谱值。(3)基于双坡屋面实验房及台风观测系统,获取了近地台风风速实测数据,对近地边界层台风风场特性进行了研究。近地边界层1OOm高度范围内的平均风速剖面符合对数律和指数律分布,平均湍流强度剖面符合指数律。与良态季风条件下相比,台风风剖面参数如摩擦速度值、地面粗糙度长度、风剖面幂指数值等相对变大；台风天气条件下实测的平均湍流度相对季风实测值增大20%以上。(4)基于平坡型实验房获取的近地风速和房屋表面风压同步实测数据,对平坡屋面角部区域的风压规律和风压影响因素进行了研究。在斜向强风作用下,屋檐角部区域实测最大峰值负压为-4240.0Pa,峰值负压系数最小值为-13.5。ASCE7-10规范规定值低估了屋檐角部区域的峰值负压。分析了角部区域峰值压力在时间和空间的平均效应。探讨了不同来流湍流强度和湍流积分尺度及竖向风攻角对角部区域风压的影响。(5)基于双坡屋面实验房获取的台风风速和双坡屋面表面风压同步实测数据,对双坡屋面风压分布规律进行了研究。在斜向风作用下,迎风屋面屋脊角部边缘测点、屋檐角部区域具有较高的局部峰值负压和脉动风压,风压系数的概率分布为非高斯分布。并运用非高斯峰值因子极值分析方法对屋檐和屋脊角部区域的风压进行了极值分析,最后将屋檐和屋脊角部区域的峰值负压系数的实测值及极值分析的结果与ASCE7-10规范规定值进行了比较,发现ASCE7-10规范低估了屋檐和屋脊角部边缘区域的峰值负压。(6)以平坡屋面和双坡屋面实验房现场实测结果为基准,开展了两实验房的模型测压风洞试验研究。在受气流分离和锥形旋涡影响下的屋面屋檐和屋脊区域的峰值负压及脉动风压的风洞实验值与现场实测值存在较大差异,风洞实验结果低估了屋面屋檐和屋脊区域的峰值负压和脉动风压。同时开展了不同流场条件、不同坡度屋盖形式和屋面建筑构造对屋面风荷载影响的相关风洞实验研究。(7)基于现场实测研究结果,应用准定常理论分析了屋面角部区域的等效静态风压系数、脉动风压系数和脉动风压谱。准定常法预测的等效静态风压系数与平均风压系数存在较大差异。准定常方法相对低估了平坡屋面角部区域脉动风压系数。屋脊和屋檐角部区域的脉动风压谱预测值与实测值在低频范围内相对吻合较好,在高频范围脉动风压预测谱低估其实测谱。根据香港天文台横澜岛观测站实测台风风速资料,考虑各年台风发生频次不同,运用复合极值Poisson-Gumbel模型分析了台风多发地区的极值风速。证明了采用复合极值Poisson-Gumbel模型统计分析极值风速结果相对合理。最后根据等效静态风压系数和极值风速分析结果,分析了台风多发地区的低矮建筑平坡屋面的极值风压。本文的研究成果,可为台风多发地区低矮建筑的覆盖物及构件的抗风设计及相关风荷载规范的修订提供参考依据。更多还原

【Abstract】 Typhoons are one of the most destructive natural disasters in the world. The southeast coastal regions of China are exposed to strong tropical cyclones with an average number of eight or nine making landfall each year. As a result, the wind-related disasters cause significant property losses and heavy causalities in this region almost every year. Based on post-storm evaluation of damage and losses, buildings and structures in the typhoon-prone region, in particular residential houses and light industrial structures might easily be damaged or destroyed in extreme wind storms. Hence, there is an urgent need to understand the extreme wind loads, which are the primary causes of damages of low-rise buildings subjected to typhoons or strong wind storms. In this study, the wind loads on low-rise buildings during typhoons were investigated through field measurements, wind tunnel tests and theoretical analysis. The major objective of the study is to further understand near ground typhoon-generated wind characteristics and wind loads on low-rise buildings under extreme wind conditions during typhoon landfalls. The major scope and achievements of this study are as follows:(1) Mean wind speed and wind turbulence characteristics of typhoon winds in surface boundary layer were studied based on three-dimensional wind data, which were recorded from ultrasonic anemometers at10m height at sites near seashore during landfalling of typhoons. The mean values of longitudinal turbulence intensity ranged from11%to14%for the coastal terrain under strong wind conditions. The mean values of lateral turbulence intensity ranged from6%to11%. The mean values of vertical turbulence intensity varied from3%to5%. The relations among turbulence parameters such as turbulence intensities and gust factor, turbulence intensities and turbulence integral scale length were analyzed. Gust factor increases with increasing turbulence intensities. The integral length scales decreased with increasing the longitudinal turbulence intensity. By fitting the results of the turbulence parameters, the relations among the parameters were proposed.(2) A full-scale instrumented flat roof low-rise building has been constructed and implemented to monitor wind velocity field and building surface pressures during typhoons. The near ground wind turbulence characteristics such as turbulence intensity and integral length scale, gust factor and wind velocity spectra were quantified in different terrain exposures and different portions of a typhoon based on the field measurement of wind data. The observed turbulence intensities (TI), turbulence integral length scale and gust factor values in the outer convective Rainband region of a typhoon were larger than those near the Eye-wall region of the typhoon. The normalized power spectral values of the longitudinal and vertical wind components for typhoon winds within different typhoon portions show similar energy distributions. However, the energy content of the lateral wind component in Eye-wall region was slight higher than that in the Rainbrand convective region.(3) The mean wind speed and wind turbulence characteristics of typhoons in surface boundary layer were studied base on the wind velocity data recorded from a full-scale instrumented gable roof low-rise building and100-m meteorological tower during landfalling of typhoons. The results revealed that in the near-surface range (<100m) vertical distribution of mean wind speed on seashore can be well described by a logarithmic law and a power law. The variation of the mean longitudinal turbulence intensity with height approximately followed a power law. Compared with those measured in monsoon wind climates, there are apparent increases in shear stress velocity, surface roughness length and exponent of power-law profile. The average values of turbulence intensity observed during typhoons were more than20%higher than those obtained during monsoons.(4) The results of extreme suction pressure coefficients and the mechanisms of the generation of the peak pressure coefficients on a corner of the flat roof instrumented low-rise building were studies based on the field measurements of wind data and associated building surface pressures during typhoons. Detailed analysis of the mean, standard deviation and negative peak pressures measured on the roof corner zone were conducted to investigate the pressure distribution characteristics in conical vortex region under oblique approaching wind directions. The measured maximum peak suction pressure was-4,240Pa and the associated minimum negative peak pressure coefficient was-13.5. The observed minimum negative peak pressure coefficient on the windward leading edge of the corner area exceeded that recommended by ASCE7-10Standard. Moreover, the effects of spatial and temporal average on the peak pressures on the corner zone were discussed. The effects of turbulence integral length scale and turbulence intensity on the roof pressures in conical vortex flow regime were evaluated. The effects of fluctuations of incident wind direction and vertical wind angle on the peak suction pressures generation on the corner zone were estimated using non-convection pressures coefficients.(5) Wind loads on the gable roof of a low rise building were studied based on the wind velocity data and pressure data recorded from the instrumented low-rise building. The results revealed that high local suctions on ridge corner and eave corner were observed under oblique flows. Probability distributions of fluctuating pressures on the ridge corner and eave corner were non-Gaussian. The extreme value analysis was performed using an automated procedure to determine the peak suction pressure coefficients. The estimated extreme peak pressures were compared to those stipulated by ASCE7-10Standard, the observed and estimated suction pressure coefficients on the windward leading edge of the ridge and eave corner zone exceeded that recommended by ASCE7-10Standard.(6) Wind tunnel tests were conducted to assess the wind loads on the two experimental buildings. The model test results were compared to the field measurements to evaluate the accuracy of the wind tunnel simulations. Further comparisons of the full-scale measurements and wind tunnel simulations of negative peak and fluctuating pressure coefficients near the roof corners, roof ridges and leading roof edges showed distinct discrepancies. Wind tunnel test results underestimated the field measured negative peak and fluctuating pressure coefficients in separated flow regions and conical vortex regions. Additional wind tunnel tests were also conducted to investigate the effects of different terrain conditions and varying gable roof angles on the wind pressures on the roofs of the low-rise buildings. Furthermore, wind tunnel tests were performed to evaluate the effectiveness of parapets mounted at the roof-edge on mitigating these high suctions.(7) Field measurements of wind velocity and pressure data have been used to evaluate the performance and the effectiveness of the Quasi-steady Theory, which was employed to predicted pseudo-steady pressure coefficients and pressure fluctuations on the roof corner zones. The measured mean pressure coefficients were compared with those predicted pseudo-steady pressure coefficients and distinct discrepancies were observed. The theory underpredicts the rms pressures on the corner zones for conical vortex region. The measured pressure spectra at several locations on the windward ridge and eave corner agreed with the predictions of the Quasi-steady theory in low frequency range quite well. However, the predicted spectra decayed significantly faster than the measured pressure spectra in high frequencies. Taking into account of the annual occurrence frequency of strong tropical cyclone, the Compound Poisson-Gumbel extreme value distribution was adopted to model the extreme wind speeds, which were obtained from anemometers at the Waglan Island meteorological station by Hong Kong observatory. The results indicated that the suggested model is reasonable, and is suitable to describe the probability distribution of extreme wind speeds in typhoon-prone regions. Finally, the extreme wind pressures on the roofs of the low rise buildings were evaluated with the application the pseudo-steady pressure coefficients and extreme design wind speeds.The outputs of the field measurements and wind tunnel test study on the wind loads on the two instrumented low-rise buildings during typhoons are expected to provide useful information and reference on revising the wind loads design standard for the wind-resistant design of low-rise buildings in typhoon-prone regions.更多还原