Wind Tunnel Test Research On The Influence Of Roof Pitches And Integral Length Scales On The Local Wind Pressure Characteristic Of Low-rise Buildings

Every year,a lot of low-rise buildings collapsed,casualties and economic losses because of typhoon in chain every year.The damage caused by low-rise building loss accounted for more than half of the total loss.and low-rise building damage mainly appears in the roof for the corner,gable,roof edge,and ridge regions.There are many factors that affect the wind pressure characteristics of the low-rise building,such as turbulence,turbulence integral scale,wind direction angle and roof pitches.At present,there are relatively few researches on the roof vulnerable area of low-rise building,Therefore,it is very important to study the wind pressure on the roof of low-rise building.Based on wind tunnel test of rigid model for gabled-roof low-rise buildings with a 1:20scale ratio,the distribution characteristics and variation regularities for mean,fluctuating pressure coefficients and statistic peak value of wind pressure on gable roofs of low-rise building with different roof pitches are investigated by considering roof pitches and wind directions as variables.On the basis of these,the suggestion for dividing the roof area into several regions is proposed according to the peak pressure on the roof,and the shape coefficients in these divided zones are compared with the value specified in codes.The results show that the most unfavorable peak pressure coefficients are located in the windward corner,the value of which will decrease with the increase of roof pitches.The gable roofs can be divided into corner,roof edge,gable,and middle regions when the roof pitches range from 0 to9.6 degrees.While ridge and connection between gable and ridge regions should be further divided when the roof pitches range from 9.6 to 45 degrees.The shape coefficients in divided zones are significantly influenced by roof pitches,the absolute value of shape coefficients in leeward roof are larger than the value specified in code,which indicates the value in code is unsafe.At last,best on integral length scales is 0.339 m 、0.446 m 、 0.605 m for homogeneous turbulence floe field.The paper studies the effect of wind pressure distribution and change regularities on the mean,fluctuating and extreme wind pressure on double slope roof low-rise building in local area under integral length scales,and further discusses wind pressure on the corner,gable,roof edge,and ridge regions.The study found that integral length scales change is not obvious influence on the mean wind pressure coefficient,but its has a great influence onthe fluctuating and extreme wind pressure coefficient.With the increase of turbulence integral length,the mean,fluctuating and extreme wind pressure coefficient will increase.When the wind perpendicular to the long side of the roof,on the windward roof,from the windward roof more far,the mean wind pressure coefficient is reduce,the fluctuating wind pressure coefficient is reduce on the gables and corner regions,and the fluctuating wind pressure coefficient is increase.In the leeward roof,from more far the ridge of the roof,the mean,fluctuating wind pressure coefficient is reduce.The wind pressure on windward roof edges and the gable regions of double slope roof low-rise building is lager,these local area are easy to be damaged under the strong wind.