| With the increase of the height of the building,the horizontal load of the mega-frame structure will be increased rapidly(including wind load and seismic load).In order to meet the requirements of structural safety and comfort,the three-dimensional seismic isolation bearings are arranged at the bottom of the column of sub-frame,which make it having functions of tuned mass damper.Under the action of fluctuating wind,the wind-induced responses of the sub-frame are reduced due to the three-dimensional seismic isolation bearing and the wind-induced response of the main frame can be reduced by the reacting force the sub-frame transmits to the main frame.In this paper,the seismic structure and isolation structure of the mega-frame are studied,and the main contents of this paper are as follow:(1)The advantages and disadvantages of two different wind speed time history simulation methods are analyzed in this paper,namely harmony superposition method and linear filtering method.The linear filtering method and Davenport spectrum are selected and the wind speed time history at different heights of the structure is simulated by MATLAB software.The results show that the linear filtering method is simple and convenient to simulate the wind speed time history,and it is suitable for programming.The harmony superposition method has high simulation accuracy,but the simulation process is complex and inefficient.By comparing the power spectrum and the target power spectrum,it can be seen that the simulated power spectrum is basically consistent with the target power spectrum,which can prove that the simulation of the fluctuating wind has good accuracy.(2)Through the modeling of finite element software SAP2000,the simulated fluctuating wind load is applied to the mega-frame seismic structure and the mega-frame isolated structure model,and time history response analysis under wind load is carried out.From the analysis results,we can see that setting isolation bearing in the mega-frame structure can effectively prolong the natural vibration period and the ductility of the structure,and it play a very good protective effect on the mega-frame.Choosing an appropriate tuning ratio and damping ratio can make the vibration damping effect of the mega-frame structure best.Compared to the seismic structure.the control effects of the mega-frame displacement and acceleration of the three-dimensional isolated structure reached 22.11%and 32.32%respectively;The control effects of the sub-frame A and sub-frame B displacement of the three-dimensional isolated structure reached 28.24%and 27.39%respectively;The control effects of the sub-frame A and sub-frame B acceleration of the three-dimensional isolated structure reached 35.45%and 34.23%respectively,and vibration control effects are obvious.Therefore,the mega-frame 3D isolated structure can effectively reduce the wind-induced response of the structure under fluctuating wind load,and it is a kind of perfect wind resistant structure.(3)Based on the equivalent wind spectrum theory,the response spectra-stochastic vibration modal analysis method is used to solve the reliability of structure,and the failure probability of the structure under wind load is obtained.Comparing the simplified mode and random vibration mode of displacement control reliability calculation,we can see that the simplified mode does not consider the influence of fluctuating wind on the structure,the results are relatively rough,it is suitable for preliminary design.And the random vibration mode takes account of the influence of fluctuating wind on the structure,the calculation results are accurate,but the calculation process is very complex,it is suitable for further scheme design.The calculation results show that the difference between the failure probability of simplified mode and random vibration mode are not very large,and the results are acceptable. |
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