Study On Wind Load Characteristics Of Long-span Saddle-shaped Roof Under Downburst

In recent years,such extreme weather phenomena as the downbursts have become more frequent due to global warming.China has a vast territory and a complex climate,which occurs frequently in southwestern China,southern China,and eastern Tibet.The average wind speed of the downburst wind field will reach an extreme value in the near ground,which has a strong destructive force and will cause great damage to the building structure.It is necessary to carry out research on the wind load characteristics of the building structure for the wind load such as the downburst.Due to the large volume of the large-span roof structure and the prominent shape of the bluff body,when the wind field encounters its obstacle,it will form obvious turbulence such as impact,separation,re-adhesion and vortex shedding,and the height of the large-span roof structure is low.It is often in an area where the downwind wind speed is strong,which makes the impact of the downburst on its wind load more obvious.The wind load characteristics and the inflow characteristics of the structural surface are no longer consistent.The wind load mechanism will be more complicated,which will bring great difficulties to the wind load characteristics of the surface of the structure,and the current large-span space structure under the impact of the downburst There are relatively few studies on surface wind loads.To this end,the article combines the wind tunnel test device and CFD numerical simulation technology to carry out related research on the wind load characteristics of the saddle surface under the action of the downburst.The main work and conclusions are as follows:?1?Taking the diamond shape,ellipse shape and round saddle surface as the research object,the rigid pressure measurement model was made separately,and the rigid model wind pressure test was carried out by using the downwind wind tunnel device.The distribution of wind pressure under the three radial distance saddle model and the outflow port and the wind direction are studied.?2?Using CFD numerical simulation technology,using ICEM to divide the hexahedral structured grid,using the Reynolds average method,using the RNG k-?model to simulate the downburst wind field;the same research object and the same work are tested under the action In the case of simulation research,combined with the wind field flow around the model,the distribution of wind pressure on the surface of different modeling saddle surface models is analyzed.?3?Comparing the numerical simulation results with the experimental results,the results agree well with the overall trend,while the wind pressure coefficient values in the regions where the airflow separation is stronger than the leeward surface and the leeward roof are slightly larger.The results show that the wind direction angle is the most important factor affecting the distribution law of wind pressure.The roof under each wind direction angle is mainly affected by wind suction.The negative pressure extreme values of the three modeling models are all under the wind angle of 0°to 15°.Under the same working conditions,the surface of the oval model roof has the smallest negative pressure coefficient,followed by the diamond shape and the largest circle.The radial distance mainly affects the extreme value of the wind pressure coefficient.The closer to the center of the storm,the greater the positive pressure on the roof,while the negative pressure reaches the maximum at 1.00 D_jet to 1.25 D_jet.