Experimental Study On Wind Pressure Characteristics Of Square High-rise Buildings In Steady Downburst Wind Field

With the development of society,the number of high-rise buildings keep increasing,we should consider not only the safety and comfort of high-rise buildings in boundary layer wind field,but also the safety of main structure and enclosure structure under some extreme wind.As a near-ground strong wind,downburst will bring great harm to buildings' principal part and their enclosure structures.At present,there is a lack of systematic research on the surface wind pressure distribution of high-rise buildings in such wind fields.Based on the simulation of downburst wind field by impinging jet device,the pressure measurement wind tunnel tests of typical high-rise buildings under different terrain and landform conditions have been completed.The distribution of wind pressure and the characteristics of wind load on the surface of buildings have been analyzed and summarized.The non-Gaussian characteristics of fluctuating wind pressure on the surface of buildings have been discussed preliminarily.The main research contents are as follows:(1)The distribution of surface mean wind pressure of high-rise buildings in different topography,landforms and locations is systematically studied.Under flat terrain,the change of the lateral position of the building makes the extreme area of wind pressure on the windward side of the building move to the edge of the building.With the increase of surface roughness,the distribution of negative pressure on the cross-wind side near the storm center does not change much,and the maximum values of wind pressure coefficients on other sides decrease.Under sloping terrain,with the increase of slope angle,the maximum area of wind pressure coefficient on the windward side gradually enlarges,while the maximum value of negative pressure coefficient on the leeward side and the cross-wind side gradually decreases,and the distribution of wind pressure on the leeward side no longer presents symmetrical characteristics.With the slope away from the windward side of the building,the maximum wind pressure coefficient on the windward side and its occurrence height increase gradually,while the maximum negative pressure coefficient on the leeward side and the windward side decreases first and then increases.(2)The layer wind load characteristics of buildings in different landforms,landforms and locations are studied.In flat terrain,the layer resistance coefficient first decreases and then increases along the building height direction.With the increase of the radial distance,the mean value of the layer resistance coefficient of the building decreases gradually,and the attenuation amplitude of the top area of the building is larger than that of the bottom area of the building,in this process,the height at which the maximum layer resistance coefficient occurs decreases.When the transverse position of the building deviates,the resistance coefficient decreases and the lift coefficient increases.With the increase of radial distance,the mean value of layer resistance coefficient decreases gradually,and its maximum height remains at 0.45 H.In sloping terrain,when the building is located at the groove,the maximum resistance coefficient of the building floor appears at the lowest level.In sloping terrain,when the building is located at the groove,the maximum resistance coefficient of the building floor appears at the lowest level.In sloping terrain,when the building is located at the groove,the maximum resistance coefficient of the building floor appears at the lowest level.In sloping terrain,when the building is just at the top,the maximum layer resistance coefficient appears at the bottom.As the starting position of slope gradually away from the windward side of the building,the height at which the maximum layer resistance coefficient occurs increases.(3)According to the fluctuating wind pressure on the surface of high-rise buildings under flat terrain and based on Kolmogorov test,the non-Gauss characteristics of wind pressure on the surface of high-rise buildings under different working conditions are analyzed.The non-Gaussian region of the windward surface mainly appears in the middle and upper part of the surface,with the increase of the radial distance,the non-Gaussian area gradually extends to the top of the building and the edges on both sides,and gradually extends to the bottom,with the increase of surface roughness,the non-Gaussian region gradually expands downward.Most area of the cross-wind and leeward areas were non-gaussian,the radial distance and surface roughness have little influence on them.Therefore,when considering the extreme wind action of downburst,attention should be paid to the calculation of extreme wind pressure in the upper and middle parts of the building windward face and the edge areas.