| The large volume and complex construction of a large-span space structure determine its susceptibility to vibration due to wind,and strong winds can seriously affect the safety and service life of a large-span building.In this paper,the damage to a large-span spatial doublecylinder mesh structure in a dry coal shed in Henan Province was destroyed by super strong winds.Due to the lack of detailed data on strong winds at the time and the complex flow field around the double-cylinder mesh building,it was not possible to conduct an in-depth study of the damage to the structure.In this paper,we obtained the flow field around the double-cylinder shell building under unsteady strong winds and reproduced the damage of the structure by wind,and analysed the damage of the structure through the wind pressure time course,wind load time course and wind vibration response of the key nodes in the key area of the structure.Based on the flow of the wind field around the building,we propose to change the flow of the flow field around the building by setting up local opening and closing aerodynamic measures,thus improving the wind resistance of the structure and increasing the ultimate wind load capacity of the structure.The five main works are as follows:(1)Based on the basic wind pressure information and site category in Henan,this paper refers to the simulation method of natural wind combined with the non-smooth characteristics of super strong wind,and uses MATLAB software combined with harmonic superposition method and fast Fourier transform method to accelerate the simulation to obtain non-smooth pulsating wind,and uses the short time averaging method to obtain time-varying mean wind,and sums the non-smooth pulsating wind and time-varying mean wind to obtain non-smooth strong wind.The accuracy and feasibility of the non-smooth strong wind simulation were verified by comparing the spatial four-point non-smooth wind velocity time course,the nonsmooth pulsating wind velocity time course,the power spectrum and the target power spectrum coincide,and the correlation function.(2)The wind tunnel test model and its flow field are modelled and calculated by ANSYS ICEM CFD and FLUENT software,and the LES-Large Eddy simulation method combined with the sublattice model is chosen to correct the simulated turbulence effects;the wall adaptive local vortex adhesion(WALE)model is chosen to deal with the wall effects;the prismatic mesh is chosen to divide the boundary layer and three meshing methods(structured mesh,unstructured mesh,mixed mesh)are used to divide the boundary layer.The pressure equation was calculated using the second-order accuracy discrete format method to obtain the wind pressure information on the building surface,and the wind pressure coefficients on the building surface were plotted by Tecplot 360 software with Li Yuanqi.The wind tunnel test data and simulation data cloud map were compared and analyzed to verify the accuracy and feasibility of the flow field simulation method and numerical calculation method in this paper.(3)Firstly,according to the method which has been verified for accuracy and feasibility in this paper,the information of wind velocity time,power spectrum and correlation function of102.4s non-stationary strong wind is obtained.By using ANSYS ICEM CFD and ANSYS FLUENT software,combined with the proven accurate and feasible wind simulation method and calculation method,the structural model and its flow field are constructed and the effect of the unsteady strong wind on the structure under the most unfavourable wind angle is calculated,and the wind pressure time course information of the building surface is obtained.Secondly,the non-linear static analysis(Pushover method)is used to analyse the plastic hinges in the bars using SAP2000 software and to determine the critical areas of the structure by combining the information on the average wind pressure,wind pressure extremes and pulsating wind pressure on the building surface of the double-cylinder mesh structure.A detailed analysis of the wind pressure time histories at each monitoring point in the critical areas is carried out and the wind load time histories at each node of the structure are obtained by combining the wind pressure time histories with the STADS software which has been verified to be correct.Finally,the structural damping coefficients are obtained by combining the frequencies of the key vibration modes of the structure under the structural modal analysis,and the wind vibration response of the mesh shell structure is calculated by SAP2000 using the Newmark method.By analysing the displacement timescales of the key nodes in the critical areas combined with the development of the plastic hinge of the structure at different instantaneous wind speeds,the structural damage by strong winds is reproduced.(4)The flow field around the large-span double-cylinder shell building is more complex than that of the single-cylinder shell building,and a detailed analysis of the flow field around the building is required to provide a basis for the air flow around other similar buildings.The comparative analysis concludes that the building can be generalised and the results obtained from this building simulation are also applicable to the same type of large-span double-cylinder mesh building.In this paper,with reference to the design of pneumatic measures for large-span roof structures and towering buildings and related research,we propose to improve the wind resistance of this large-span double-cylinder mesh shell structure by installing partial opening and closing pneumatic measures without increasing the number of bars or changing the material type.A comprehensive analysis was carried out based on the flow field around the idealised building and the real building model,the wind pressure on the building surface,the plastic hinge region,the wind load times at the nodes,and the displacement times at the nodes.(5)Firstly,the flow field around the building with pneumatic measures and the original building are compared and analysed;secondly,the wind pressure time data,wind load time data and displacement time data of the key areas and key nodes of the building with pneumatic measures before and after the installation of pneumatic measures are calculated by the same method as in(3),and these data are compared and analysed to prove the influence of pneumatic measures on the building;finally,by comparing and analysing the structure Finally,by comparing the types and distribution of plastic hinges between the pneumatic measures building and the original building under the ultimate wind load,it is obtained that the pneumatic measures method by setting up a local open and closed structure can improve the wind resistance of the structure by changing the flow field around the building and increase the ultimate wind load capacity of the structure.This paper proposes a method of pneumatic measures based on the partial opening and closing of the building surface,which is different from the traditional wind strengthening method of increasing the stiffness of the structure,and which improves the wind resistance and ultimate wind load capacity of the structure by changing the flow field around the building.The new ideas are presented in this paper. |
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