Study Of Wind Loads And Wind-driven Rain Effects On A Low-rise Building With Roof Overhang During Tropical Cyclones

Tropical cyclones(TCs)are the most serious natural disasters in the southeastern coastal areas of China,which cause huge economic losses and serious casualties every year.The destruction and collapse of low-rise buildings and secondary damages of building interior components are major wind-induced and rain-induced disasters by TCs.Therefore,there is an urgent need to study the activity characteristics of TCs,wind-induced damage mechanisms,and wind-driven rain(WDR)effects on low-rise buildings during TCs.In the present thesis,the activity characteristics of TCs in the past 68 years were statistically analyzed.And wind-driven rain effects and wind loads on a gable-roofed low-rise building with overhang in a TC-prone region of China were investigated by using a combination of full-scale measurements,wind tunnel tests and numerical simulations.The research content and main results of this study are as follows:(1)Based on the historical data of tropical cyclones in the Northwest Pacific ocean,the activity characteristics of TCs(including intensity,minimum central air pressure,life cycle,and generation position)landing in China and generating in the Northwest Pacific ocean in the years from 1949 to 2018 were investigated by using the method of quantile regression,respectively.(2)The characteristics of typhoon-generated near-surface wind at heights of 10 m,7m and 4m were analyzed based on field measured three-dimensional wind data.The relationships among turbulence intensity,ground roughness length,and height could be expressed as a logarithmic function,and fitting results of function parameters during typhoons deviated from the results under monsoons.The relationships between the longitudinal gust factor and the longitudinal turbulence intensity could be expressed as a non-linear function,and the relationships between the longitudinal turbulence integral scale and ground roughness length could be represented by an exponential function,which were fitted well by measured results during typhoons.(3)A field measurement facility for the wind loads and WDR effects on a gable-roofed low-rise building with overhang was established and implemented in a typhoon-prone region of China.Detailed analysis of the mean,standard deviation and negative peak pressures measured on the roof eave,ridge and overhang were conducted to investigate the pressure distribution characteristics under different approaching wind directions.And the probability density function,kurtosis coefficient,and skewness coefficient of the measured pres sures were discussed.The measured negative peak pressure coefficients on the roof eave,ridge and overhang of the low-rise building during typhoons are-10.19,-7 and-9.1,respectively.In addition,the WDR effects on the facades of the full-scale building during a typhoon were presented and discussed,which were compared with the semi-empirical formulas for estimating the WDR intensity on the facades.(4)A framework of extracting the time-varying average component and separating the time-varying fluctuation component of non-stationary data during typhoons was established,which was applied to s tudy measured non-stationary wind speeds and wind pressures.Compared with the results calculated by the conventional stationary analytical approach,the wind char acteristic parameters and wind pressure results calculated by the non-stationary analytical approach were more robust and reasonable.In addition,the evolutionary power spectral density(EPSD)was used to examine time-frequency turbulence spectra of fluctuating wind speeds and pressures.The effectiveness of the Quasi-steady Theory considering non-stationary feature to predict the wind pressures on the roof of the low-rise building was discussed.(5)Detailed wind tunnel tests for the instrumented low-rise building with geometric scale of 1:100 and 1:50 were performed under different upstream exposure conditions based on the field measured results.The pressure distributions on the roof,upper and lower surfaces of the roof overhang were presented.The effe cts of different terrain conditions and geometric scale ratios on wind loads on the roof were investigate.Furthermore,an improved peak pressure estimate approach suitable for small volume samples was proposed and its effectiveness was verified against the field measurements.The improved method yielded the closest predictions to the observed peak values than the other methods.(6)Cross-comparisons among the wind tunnel testing results,full-scale measurements,aerodynamic database,and design provisions were made for validation purposes.As compared with the field measurements during typhoons,the aerodynamic databases could provide valid predictions for mean and standard deviation pressure coefficients,but peak pressure coefficients were underestimated to some extent.And the wind tunnel modelling methodology could reproduce the variations of the mean,standard deviation and minimum pressure coefficients with changing wind direction on the roof eave,overhang and ridge,but would underestimate the extreme suctions on the roof ridge and overhang under the influence of airflow separation and conical vortex.In addition,it was observe d that the suctions on the roof overhang,roof eave and ridge determined from the wind tunnel tests were lower than those stipulated in ASCE 7-16.However,extreme wind pressures on the roof in the full-scale measurements during typhoons were greater than those stipulated in Chinese structural load standards(GB50009-2012)and ASCE7-16.(7)Numerical simulations of the WDR on the instrumented building were performed using the Eulerian Multiphase model and validated based on the field measured WDR results.The numerical simulations successfully estimated the cumulative WDR amounts and catch ratio values at different locations on the building facades,although the predicted values were slightly larger than the field measured results.Meanwhile,a detailed parametric study of numerical simulation was carried out to examine the influences of roof overhang,wind speed,wind direction,and horizontal rainfall intensity on the WDR amounts on the building facades.Then,the WDR effects on the low-rise building during a super typhoon were numerically reproduced and investigated.The field measurement techniques and records,wind tunnel test results,numerical simulation methodologies,and conclusions presented in this thesis should be useful to design enclosure structures of low-rise buildings and revise or improve the wind loads design standard in the typhoon-prone regions of China.