| Due to various reasons such as global warming,in recent years,the occurrence of extreme climates such as downbursts has become more frequent.When the downburst occurs,the columnar high-speed sinking airflow generated by the convection of the hot and cold air at high altitude violently hits the ground,and then diffuses around each radial direction of the impact center,forming a near-earth airflow with a very high radial velocity,which causes damage to the building structure.The impact will cause great damage to the building structure.Therefore,research on the roof wind load characteristics of various types of buildings under the action of abnormal wind loads such as downbursts will become very necessary.Large-span roof structures are currently popular architectural choices,but because their height is usually low,they are in areas with large changes in wind speed and high turbulence in the atmospheric boundary layer,which makes the impact of downbursts more pronounced on their wind loads.It is easy to form obvious turbulences such as impact,separation,reattachment and vortex shedding.The double-sided spherical shell type long-span roof structure is a relatively new type of large-span structure.Compared with the traditional spherical shell type structure,the dynamic response of the double-sided spherical shell type structure under wind load is very different.In an extreme climate,the wind pressure on the lower surface may even exceed the wind pressure on the upper surface,causing serious damage to the structure.In order to clarify the wind pressure distribution rule of the double-sided spherical shell structure under the action of the downburst,and to enhance the understanding of the catastrophic weather phenomenon of the downburst,it provides a certain reference for the engineering design,and also takes into account The characteristics of the mountain area are more than flat ground in the occurrence area.In this paper,the wind load characteristics of the double-sided spherical shell long-span roof under the two terrain conditions are studied by using the downburst wind tunnel test and CFD numerical simulation.The main work is: And conclusions are as follows:(1)Using a double-sided spherical shell long-span roof as a research object,a rigid pressure measurement model was made,and a wind pressure test test was performed by hitting a storm wind tunnel to study its different radial positions(r=0.75 Djet ?1.00Djet?1.25Djet?1.50Djet?1.75Djet?2.00Djet;)changes in its upper and lower surface wind pressure distribution characteristics;and under the conditions of the slope,the radial distance position of the fixed slope bevel(slope Mouth position r=0.75Djet?1.00Djet?1.25Djet?1.50Djet),change the position of the model from the bevel(U=0mm?150mm?300mm?450mm),and study the upper and lower surface wind pressure of the model at various positions on the slope Distribution.(2)Using CFD numerical simulation technology method,using ICEM to divide the double-sided spherical shell model using a hexahedral structured mesh,and using Reynolds average method(RANS)to carry out numerical simulation of downburst,The working conditions are compared with the measured data of the test,and the same trends as those of the simulation results and the test results are studied,as well as the numerical differences in some working conditions.Analyze the difference of the wind field of the downburst in the two terrain conditions,and combine the flow field around the model to analyze the wind pressure distribution of the double-sided spherical shell long-span roof in each case.(3)The average wind pressures measured on the flat and sloping fields of the building model are compared and analyzed,and the influence of different terrains on the average wind pressure distribution of the upper and lower roofs is studied.The research results show that the radial distance has a significant effect on the average wind pressure of the model roof under flat conditions.The closer to the storm center,the greater the positive pressure on the roof;as the radial distance continues to increase,the roof wind The pressure began to decrease,the average wind pressure changed from positive pressure to negative pressure,and the maximum negative wind pressure appeared at r=1.25 Djet,after which the roof wind pressure no longer changed significantly with the increase of the radial distance.The windward side of the lower roof has positive wind pressure at all positions.The value of the wind pressure gradually decreases with the increase of the radial distance,but always maintains the normal wind pressure.The leeward side of the lower roof is basically affected by the location of the direct airflow.The influence of airflow wake,so its wind pressure distribution changes significantly with the change of radial distance,and the value basically fluctuates around zero.In slope terrain conditions,when the building is located at the bevel,the average wind pressure value of the roof on the building decreases with the increase of the radial distance at the bevel.When the radial distance at the bevel is greater than 1.25 Djett,the upper roof The average wind pressure value is stable,and the change of the radial distance will no longer have a significant effect on the average wind pressure value.The wind pressure on the windward side of the roof under the model changes greatly with the change of the radial distance at the groove.When the radial distance at the groove is less than 1.00 Djet,the wind pressure on the windward side is positive at this time.After the distance is greater than 1.25 Djet,the wind pressure on the windward side of the jet changes to a negative value,and the negative pressure value gradually increases with the increase of the radial distance of the groove.The effect of the position on the slope on the model wind pressure is mainly reflected in the case where the bevel position is r=0.75 Djet.When the bevel distance continues to increase,the model's wind pressure at each position on the slope no longer changes significantly.By comparing and analyzing the CFD numerical simulation results with the test results of the downburst wind tunnel test,it is found that the overall positive and negative wind pressure distribution area of the roof is relatively consistent.Taking the wind pressure value on the roof center line for further comparison and analysis,the two results The curve basically agrees with the overall trend.The wind pressure obtained by numerical simulation is slightly greater than that obtained by experiments.The area with strong air separation such as the front end of the upper windward side of the upper roof has relatively large errors. |
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