Field Measurements And Wind Tunnel Tests Of Wind Effects On A Low-rise Building

Typhoon landfalling is frequent and strongly influenced by the windstroms in China.The majority of the damages occurred on low-rise buildings, Previous wind disaster surveys indicated that most destroyed buildings in the disasters were low-rise buildings. Hagupit, the 14th strong typhoon of the year 2008, made landfall in Dianbai of Guangdong province on September 24 with wind speed of more than 172.8 kilometers per hour in its eye. The disaster damaged or collapsed up to 27700 low-rise buildings,which caused a direct economic loss of 13.4 billion yuan in China. Hurricane statistics show that the loss mainly by hurricane damage or collapse of low-rise buildings were caused by low-rise building roof corner,edge and ridge areas. The large suction(peak negative pressure)on low-rise buildings are usually occurred on roofs close to leading edges where wind flow separates.Therefore, it is necessary to understand the distributions of negative peak pressure and pressure fluctuations.However,there are rare researches on the effects of wind loads on low-rise buildings until now in China. It is well known that the effects of wind on low-rise buildings are determined by turbulent wind characteristics and building shapes etc. Wind pressures on the building surface and surface layer wind field characteristics stipulated in the present codes of wind-resistance design for low-rise buildings were determined by observations of monsoons.However,there exist significant differences between the characteristics of typhoon and monsoon and therefore the wind resistant design for low-rise buildings relied on the present code is unreasonable. As global climate became warming, the number of wind disaster increase year by year.Therefore the research on how to improve the resistances of low-rise buildings against serve typhoon is very important to the south-east coast areas in China.Based on size ratio 1.5:1:1(length:width:height) wind tunnel test data,the characteristics of mean,fluctuating and peak pressures coefficients on the windward roof edges and roof corner of 9 different slope angle low-rise buildings for wind azimuths of 0°, 30°, 45°,60°,90°were investgated, and the characteristics of the area-averaged pressure coefficients were summed up in the thesis.A full-scale experimental building,with width(B)×length(L)×height(h) =4m×6m×4m, was constructed to study wind effects on the low-rise building at sea shore terrain.The building can be moved to the location where the typhoon will make land and capture the extreme events to obtain important datas during typhoon or tropical storm.Based on field monitoring datas, the thesis selected some presented field measured measurements during Severe typhoon 0814"Hagupit",typhoon 0801"Neoguri", Severe tropical storm 0809"Kammuri",Tropical Storm 0714"Franciso"and monsoon.The characteristics of wind speed,wind direction, gust factor, turbulence intensity,turbulence scale and spectra were discussed in detail.The measurement arrangements for the wind pressures on the low rise building were also introduced . The characteristics of mean,fluctuating and peak pressure coefficients on the leading edges of the roof and the roof-corner regions were investigated, and the corresponding area-averaged wind pressure coeficients were summarized.Contours plots of the mean, minimum, maximum and RMS(root-mean-square) pressure coefficients on the roof surface were also presented. The wind velocity spectra and corresponding wind pressure spectral of representative points on the low-rise building were also investgated.The low-rise building model was made for the study of wind loads on the low-rise building at a geometric scale of 1:10.The model configuration and pressure tap loations were located at the same positions as those in the full-scale low-rise building.Mean,minimum,maximum and RMS values of pressure coefficients were obtained,and these values were discussed in detail.Comparisons with the field experimental results for wind loads on the low rise building were made to improve modelling techniques in wind tunnel tests.The outputs of this study are expected to be useful for further understanding of the characteristics of wind field during severe typhoon,it is also expected that the results presented in this paper should be valuable for wind-resistant design of low-rise buildings.