Study On Wind Load Characteristics On The Rectangular Flat Roof Under The Physical Simulated Downburst

The downburst is an extreme weather system with high frequency,large range of influence and strong destructive power.The downburst can produce a strong downdraft,and when the downdraft strikes the ground,it will generate radiation outflow in the near ground area.Both the downdraft and the outflow have a strong destructive effect on buildings and cause very serious disasters all over the world.Therefore,it is important to study the wind field characteristics of the downburst and the wind load characteristics of the building structure under the action of the downburst.It is of great theoretical and practical significance to understand the catastrophic effect of the building structure under the impact of the downburst.Based on the method of laboratory physical simulation,this paper studies downburst and the wind load characteristics of rectangular flat roof under the action of downburst.The main research work is as follows:1?Based on the theory of wall jet flow,the downburst wind field was simulated by downburst simulator.And then the horizontal and vertical wind velocities in downburst wind field were measured.Furthermore,the characteristics of the wind profile are analyzed.Finally,the test results were compared with theoretical models,measured results and atmospheric boundary layer.The results show that the wind profile of horizontal wind is greatly affected by the radial position,and the position where the maximum value appears is the same as the diameter of the outlet port from the center of the downburst impact test platform;Besides,the horizontal wind speed wind profile obtained by the physical simulation is in good agreement with the theoretical model,which can be used to study the wind load characteristics of the subsequent building structures;2?The rectangular flat roof model pressure test under the action of static downburst was carried on to study the wind load characteristics.By changing the radial position and setting angles of the model in the wind field,the variation of wind load of static downburst is analyzed when the location and direction angle of downburst are different.The results show that when the building model is in the core area of the downburst,the high pressure in the exit zone of the simulator causes the entire surface of the building model to be compressed;Besides,as the radial distance increases,the influence of wind speed on the wind load increases,and the wind load is similar to the monsoon.3?The rectangular flat roof model pressure test under the action of moving downburst was carried on to study the wind load characteristics.Compared with the static downburst,the results show that the average is consistent in both cases.Then,the moving speed of the downburst and the offset position and setting angle of the model in the wind field were changed to analyze the changes of wind load.The results show that the wind load caused by the high pressure in the exit zone of the downburst simulator is basically unchanged under different working conditions,and the wind load caused by the wind speed changes greatly.