Study On The Influence Law And Mechanism Of Local Opening On Wind Load Of Long-span Cylindrical Reticulated Shell Structures

The long-span three-core cylindrical reticulated shell is sensitive to wind load due to its light weight and high flexibility.The wind load of cylindrical reticulated shells is greatly influenced by the local opening.While scholars have extensively studied the wind load characteristics of structures with a single local opening form,there are few studies on different combinations of local openings.Furthermore,the mechanism analysis of local openings on the wind load characteristics of structures is not very indepth.In view of this,this thesis takes an actual large-span cylindrical reticulated shell structure as the engineering background.Firstly,the surface wind pressure of the structure is tested by rigid model pressure measurement wind tunnel test when the top skylight,the bottom hole of the reticulated shell and the end gable hole are opened or closed.The influence of local opening on the overall force coefficient,shape coefficient and extreme wind pressure coefficient of large-span cylindrical reticulated shell structure is analyzed.Then,the wind load characteristics of large-span cylindrical reticulated shell structure under different local opening conditions are numerically calculated.The influence mechanism of local opening on the wind load of large-span cylindrical reticulated shell structure is analyzed,and the opening form of the structure is proposed.The main work and conclusions of this thesis are as follows:(1)The influence of local opening on the wind load of large-span cylindrical reticulated shell is clarified.Different local opening states have no obvious effect on the longitudinal overall force of the reticulated shell structure.The spanwise overall force has a certain influence at the wind direction angle of 0°～60°,and the vertical overall force is the most significant.Under the action of cross-flow wind,when the skylight at the top of the reticulated shell is closed,the structure bears a large upward vertical force.When the skylight on the top of the reticulated shell is opened,the upward vertical force is significantly reduced,and even becomes a downward vertical force.When only the skylight on the top of the reticulated shell is opened and other openings are closed,the downward vertical force is the largest.Under the action of longitudinal inflow wind,there is no obvious difference in structural wind load under different local opening conditions.When the skylight at the top of the reticulated shell and the end gable opening are closed,the absolute value of the negative extreme wind pressure coefficient is the largest.(2)The influence mechanism of local opening on wind load of long-span cylindrical reticulated shell structure is revealed.The change of wind load on the inner surface is the main reason for the change of the overall force and local wind load of the reticulated shell structure with the local opening.Under the action of cross-flow wind,only when the skylight at the top of the reticulated shell is opened,a high wind speed zone is formed at the top,which bears a large wind suction,and a strong vortex is generated inside the structure,resulting in a large wind suction on the inner surface,which is the main reason why the whole structure bears a large downward vertical force.When the hole at the bottom of the reticulated shell is opened,a large amount of air flows into the structure,and the air flow cannot flow out smoothly,resulting in a large wind pressure on the inner surface,which is the main reason why the whole structure bears a large upward vertical force.Under the action of longitudinal inflow wind,the air flow is separated at the top of the windward side gable,and the negative pressure of the reticulated shell is only large at the end position,and the rest positions are small.The opening and closing of the skylight at the top of the reticulated shell and the opening and closing of the bottom hole of the reticulated shell will not have a great impact on the internal air flow of the structure,so its impact on the wind load of the structure is not as significant as that of the spanwise inflow wind.