Experimental Investigation Of Blockage Effects On Surface Wind Pressure Of Rectangular Tall Buildings In Wind Tunnel

The structure of modern high-rise buildings to the direction of higher and more gentle,wind load becomes one of the main controlling factors of structural safety and comfort.Scholars need to fully understand the wind effect of structure and ensure that the functions of high-rise buildings can run normally in service period.Wind tunnel pressure test of rigid model is the main technical to establish the wind load model of high-rise building,and the blockage effect is the problem that wind tunnel test often faced.Due to the existence of the wall of the wind tunnel,The blockage effect will have a serious impact on the flow field and the construction wind load,resulting in a large error in the wind tunnel test data.Therefore,it is necessary to study the blockage effect of wind tunnel experiment.Based on six groups of rectangular high-rise building wind tunnel test model,the effects of blocking effect on the average wind pressure coefficient,pulsating wind pressure coefficient,spatial correlation,power spectrum,coherence and peak wind pressure of the building model were studied under two different turbulence wind fields.The main conclusions are as follows:(1)With the increase of the model blocking ratio,the blocking effect leads to:The average wind pressure coefficient of the windward surface of the model is less affected,the decrease of the average wind pressure coefficient of the side and the leeward surface;The horizontal correlation is reduced and the vertical correlation is increased;The increase of the lateral flow velocity increases the horizontal correlation of the lateral measurement points;the increase of the flow rate leads to the increase of the energy of the vortex shedding and the acceleration of the frequency,and the peak of the lateral wind pressure power spectrum of the corresponding model And the frequency of the peak is reduced;The energy loss of the cone vortex in the wake region of the model decreases the spatial correlation of the leeward surface.(2)Under the two kinds of turbulence wind fields,the horizontal and vertical coherence of the wind pressure point at the leeward surface are decayed most rapidly,followed by the side surface and the slowest is windward surface.With the increase of the blockage ratio,the decay rate of fluctuating wind pressure level and vertical coherence slowed down on the model surfaces.Compared with the low turbulence wind field,the vertical and horizontal coherence decay rate decreases under high turbulence wind field.(3)The model with the blocking ratio bigger than 4.5%,the difference of the wind pressure coefficient of the windward surface is not obvious,but the difference between the side and the leeward surface is obvious,and the influence of the blocking effect on the extreme wind pressure coefficient should be considered.(4)The increase of turbulence increases the effect of blocking effect on the average wind pressure coefficient,pulsating wind pressure level and vertical coherence,but it will lead to the reattachment of the separated airflow,So that the corresponding measurement point spatial correlation enhanced.