Study Of Wind Load On Claddings Of Flat Roof Warehouse With Large Aspect Ratios Or Large Height-width Ratios

Buildings with aspect ratios greater than 2 and height-width ratios greater than 0.5 are widely distributed in coastal and suburban areas where wind disasters occur frequently.Their claddings are most vulnerable to wind-induced damage,leading to structural damage and loss of indoor goods.The building dimensions included by codes are mainly for low-rise buildings,rarely involving buildings with larger aspect ratio and heigjit-width ratio.Compared with the distribution of wind pressure on low-rise buildings,the increase of aspect ratio and aspect ratio will lead to a larger negative pressure gradient in wind-sensitive areas such as the windward angle of roof and a smaller negative pressure extreme value in the middle of roof.If the wind resistance design of the above buildings is carried out according to the standard of low-rise buildings,the wind pressure in the wind sensitive area will be underestimated,and the wind pressure in the middle of the roof will be overestimated,resulting in the coexistence of danger and conservatism.Therefore,it is urgent to study the wind pressure value of claddings with large aspect ratio and high aspect ratio,so as to provide basis for wind load design of claddings.On the basis of reviewing the history of wind load development of claddings and sumrarizing the influence of geometric parameters on wind pressure,a flat roof model with aspect ratio greater than 2 and aspect ratio greater than 0.5 is selected for wind tunnel test to explore the influence of geometric parameters on wind pressure extremum,including the following aspects:1. Distribution of the most critical peak coefficients of roof and wall in all wind directions is studied.The results show that when the inflow acts vertically on the roof,the length-width ratio will change the length of cross-.ind direction,and the height-width ratio will change the turbulence of the roof height,thus affecting the size of the high negative pressure zone of the roof.In the oblique wind direction,the larger the length-width ratio or the high-width ratio,the larger the range of action of the conical vortices,the larger the negative pressure extremxmi in the conical vortices.2.Area average extreme pressure of the claddings with the increase of the subsidiary area is studied.The region with similar gradient variation in all wind direction wind pressiire extreme value is selected to calculate the surface extreme values of different subsidiary areas in the region,and the attenuation law is fitted by logarithmic linear function,and the surface extreme value reduction coefficient curves of each region are obtained.The results show that the maximum attenuation rate of negative pressure on the cormer of roof is the greatest,and the attenuation rates of roof edge,gable comer and longitudinal wall edge are all reduced.The aspect ratio only affects the attenuation speed of roof corners,and the extremum attenuation speed of other areas has nothing to do with aspect ratio and aspect ratio.3.For the convenience of design,this paper uses K-means clustering method with weak subjectivity and strong mathematical theory to partition the claddings,and classifies the measuring points with high similarity of negative pressure extreme value in all wind direction into the same partition;introduces the effective index in statistics,and chooses the best number of partitions.The results show that the roof is divided into three zones:comer,edge and middle.The gable is divided into two zones:corner and middle.The vertical wall is divided into two zones:edge and middle.The boundaries of each zone are mainly related to the aspect ratio of the building.4.Combining the results of the zoning with the reduction coefficient curve,the formula of the extreme value of wind pressure and the reduction coefficient of this area can be used to calculate the extreme value of wind pressure in any subsidiary area of the scoring area,which is convenient for designers to use.