《结构防灾技术》课程教学课件（讲稿）第三篇 结构抗风 Wind-resistant structure 第九章 平均风的概率计算 Probabilistic Calculation of mean wind

第九章平均风的概率计算Chapter9ProbabilisticCalculationofmeanwind9.1基本风速和基本风压9.1 Basicwindspeedandbasicwindpressure1161612(smn121(su)5o12050100150100150200020000501o0150200t(min)t(min)t(min)（b）平均风速（a）厨时风速（e）规格化脉动风速统计特征空间特征、时间特征、Spatialcharacteristics,temporalcharacteristics,statisticalcharacteristics

第九章 平均风的概率计算 Chapter 9 Probabilistic Calculation of mean wind 9.1 基本风速和基本风压 9.1 Basic wind speed and basic wind pressure 空间特征、时间特征、统计特征 Spatial characteristics, temporal characteristics, statistical characteristics

9.1基本风速和基本风压9.1 Basicwind speed and basicwind pressure一、基本风速Basicwindspeed■平均风速的统计特性主要指重现期和极值风速概率模型一般把年最大风速作为概率统计的样本，由重现期和风速的概率分布获得该地区的设计最大风速，或称为基本风速The statistical characteristics of mean wind speed mainly denotesby the return period and the probabilistic model of the extremewind speed.Usuallythe annual maximum windspeed as the sampleofprobabilistic statistics, the design maximum wind speed iscalculated by the return period and probabilistic model, also calledbasicwindspeed

一、基本风速 Basic wind speed The statistical characteristics of mean wind speed mainly denotes by the return period and the probabilistic model of the extreme wind speed. Usually the annual maximum wind speed as the sample of probabilistic statistics, the design maximum wind speed is calculated by the return period and probabilistic model, also called basic wind speed. 9.1 基本风速和基本风压 9.1 Basic wind speed and basic wind pressure

9.1基本风速和基本风压9.1 Basicwind speedand basicwindpressure二、确定基本风速的标准Standard to determine basic wind speed1、标准高度的规定referenceheightThe height1Omis specified as referenceheight inChina2、地貌的规定TerrainOpen flat ground(空旷平坦地面)is regarded as the standardterrain3、平均风速的时距Averagingperiodoftheaverageisspecifiedas 10minutes4、最大风速的样本Sampleofmaximumwindspeed一年中仅出现一次Occursonceayear5、最大风速的重现期Returnperiodofmaximumwindspeed

二、确定基本风速的标准 Standard to determine basic wind speed 1、标准高度的规定 reference height The height 10m is specified as reference height in China 2、地貌的规定 Terrain Open flat ground(空旷平坦地面) is regarded as the standard terrain 3、平均风速的时距 Averaging period of the average is specified as 10 minutes 4、最大风速的样本 Sample of maximum wind speed 一年中仅出现一次 Occurs once a year 5、最大风速的重现期 Return period of maximum wind speed 9.1 基本风速和基本风压 9.1 Basic wind speed and basic wind pressure

9.1基本风速和基本风压9.1 Basicwind speed and basicwindpressure二、确定基本风速的标准Standard to determine basic wind speed重现期Returnperiod从保证安全的角度出发，基本风速不可能取极值风速样本的均值，而应取大于该均值很多的某个值作为设计依据。From the point view of safety, the basic wind speed should not bethe mean value of the sample ofextreme wind speed, and shouldbemuchlargerthanthe value,whichisthereference windspeedfor design该设计值选取的标准是大于该值的风速并不是经常出现的，而要间断一定的时间后再出现，此间隔即为重现期The wind speed larger than the design value does not occurfrequently, but occurs after a period of time. The time interval is thereturnperiod

重现期 Return period 从保证安全的角度出发，基本风速不可能取极值风速样本的均值， 而应取大于该均值很多的某个值作为设计依据。 From the point view of safety, the basic wind speed should not be the mean value of the sample of extreme wind speed, and should be much larger than the value, which is the reference wind speed for design. 该设计值选取的标准是大于该值的风速幵不是经常出现的，而要间 断一定的时间后再出现，此间隔即为重现期 The wind speed larger than the design value does not occur frequently, but occurs after a period of time. The time interval is the return period. 二、确定基本风速的标准 Standard to determine basic wind speed 9.1 基本风速和基本风压 9.1 Basic wind speed and basic wind pressure

9.1基本风速和基本风压9.1 Basicwind speedand basic windpressure确定基本风速的标准?Standardtodeterminebasicwindspeed重现期Returnperiod重现期为T.的基本风速，则表明在任一年中超越该风速一次的概率为1/T。，不超过设计最大风速的概率或保证率应为：Forabasic wind speed with a return period of To,theprobability of the wind speed exceeding the basic windspeed is 1/To-Andthe guaranteed probability,that is,theprobability of wind speed not exceeding maximum designspeedis:P = 1T

重现期 Return period 重现期为T0的基本风速，则表明在任一年中超越该风速一次的概 率为1/ T0 ，丌超过设计最大风速的概率或保证率应为： For a basic wind speed with a return period of T0 , the probability of the wind speed exceeding the basic wind speed is 1/ T0 . And the guaranteed probability, that is, the probability of wind speed not exceeding maximum design speed is: 0 1 P 1 T   二、确定基本风速的标准 Standard to determine basic wind speed 9.1 基本风速和基本风压 9.1 Basic wind speed and basic wind pressure

9.2最大风速的数理统计9.2 Mathematical statisticsof Maximumwindspeed极值风速概率模型：极值I型（Gumble）、极值II型（Frechet）和极值III型（Weibull）分布mp）的书数凡厨鞋生选丽国的池.极值I型（Gumble）分布-11F,(x) =expB-expu和分别称为位置参数和尺度参数，可由如下两式获得元D(x)=0,E(x)=x=μ+0.5772oCV6对应极值I型分布的设计最大风速可以表示为/6F =[0.5772+ In(-In F,)]x, =μ-oln(-ln F,)=x+yo,WTT

9.2 最大风速的数理统计 9.2 Mathematical statistics of Maximum wind speed

9.3结构上的平均风压9.3 The maximum average wind pressure on structure基本风压Basicwindpressure由于实测记录一般为风速，在工程设计时采用的风压（风力）需由风速进行转换计算Dueto the wind measurementis recordedas wind speedgenerally,the wind pressure (force)exerting on theengineering needto be calculatedfrom wind speed在不可压的低速气流下，假定无粘，不考虑体力，则可由伯努利方程得：2PV2

9.3 结构上的平均风压 9.3 The maximum average wind pressure on structure 一 基本风压 Basic wind pressure 由于实测记录一般为风速，在工程设计时采用的风压（风力） 需由风速进行转换计算。 Due to the wind measurement is recorded as wind speed generally, the wind pressure (force) exerting on the engineering need to be calculated from wind speed. 在丌可压的低速气流下，假定无粘，丌考虑体力，则可由伯努利方 程得： w   v  c 2 1 2 1 

流向高压气幕建筑物小股气流(Wi+dw)dAWdAd1压力线风压的形成当V=O时，W1=Wm（气流冲击结构物后其截面中心点产生的最大气流压强当V时，Wi=Wb（气流原先压力强度）O+WmWhpVW=Wb-Wm2222g=0.012018kN/m3（空气单位体积的重力），g=9.8m/s22风压:(kN/m2)W :1630

建筑物 小股气流 流向 高压气幕 压力线 dl w1dA (w1+dw1 )dA 风压的形成 g v w w wm v b 2 2 1 2 2        风压： 1630 2 v w  (kN/m2) 当v  0时，w1  wm（气流冲击结构物后其截面中心点产生的最大气流压强） 当v时，w1  wb（气流原先压力强度） wb   v  wm 2 2 1   =0.012018kN/m3（空气单位体积的重力），g=9.8m/s2

我国规范规定以当地比较空旷平坦地面（B类）、离地10米高度、50年重现期、10分钟平均最大风速v.为基本风速，并按wo=160%确定基本风压值China code takes the average maximum wind speed in10 minutes with a return period of 50 years and 10meters above the flat ground as the basic wind speedand the basic wind pressure is is determined by wo =11600非基本条件时，可根据上述三方面特性（空间特性、时间特性、统计特性）予以换算。Undernon-basicconditions,itcanbe convertedaccording to the three characteristic above (spatial,temporal and statistical characteristics)

二、风载体型系数windloadshapecoefficientμs根据基本风速计算的基本风压，并未考虑建筑体型的影响。Thebasicwindpressurebasedonbasicwindspeeddoesn'ttakethe shape of the building into consideration气流未被房屋干扰前的流速Airflow speed before disrupted by the buildings is denoted asVo, pressure is as po→房屋表面某点的流速theflowspeedofacertainpointonthesurfaceofthebuildingv，压力pressurep根据伯努里方程Based onBernoulli's equation，theequivalent formula is as follows:Po+pV.2/2= p+pv2/2W= p - po= (1-v2/vo2) pVo2/2 = μsWoμs=1-v2/v2—风载体型系数(shapecoefficient）

根据基本风速计算的基本风压，幵未考虑建筑体型的影响。 The basic wind pressure based on basic wind speed doesn’t take the shape of the building into consideration. 气流未被房屋干扰前的流速 Airflow speed before disrupted by the buildings is denoted as v0， pressure is as p0  房屋表面某点的流速 the flow speed of a certain point on the surface of the building v，压力 pressure p 根 据 伯 努 里 方 程 Based on Bernoulli‘s equation, the equivalent formula is as follows: p0+v0 2 /2= p+v 2 /2  w = p - p0 = (1-v 2 /v0 2 ) v0 2 /2 = sw0 s = 1-v 2 /v0 2 —风载体型系数( shape coefficient ) 二、风载体型系数 wind load shape coefficient s