| The seismic isolation technology of roof isolation can reduce the dynamic response of foundation structure for the large-span space structure,but the influence on the isolation effect of the lower frame structure cannot be ignored.In this paper,a national theater is used as the research object,and the finite element models of seismic and roof isolation structures are established by SAP2000 and the dynamic time history analysis is carried out.Based on the basic principle of structural dynamics,a simplified three-particle model of roof isolation structure is established,and the parameters of the particle model are analyzed.The dynamic response of the roof isolation structure under different parameters is compared and analyzed,thus the optimal parameter range of the roof isolation structure is determined,and the isolation effect before and after parameter optimization is compared.The main contents and conclusions of this paper are as follows:(1)The rationality of the selected seismic waves for the model calculation and analysis is verified,and the dynamic characteristics,base shear force and interlayer displacement of the lower frame structure before and after the isolation of the large-span spatial structure are calculated and analyzed.The results show that the selected 9 seismic waves meet the requirements of the code.After the roof isolation design of the large-span spatial structure,the natural vibration period of the structure can be greatly extended and the base shear force of the structure can be reduced.The seismic reduction coefficients of the fourth and fifth interlayer displacement of the lower frame structure are 1.12 and 1.08,respectively.The isolation effect of the interlayer displacement between the two layers is poor.(2)The simplified particle calculation model of large-span spatial structure is established and the correctness of the model is verified.The program for solving the dynamic response of three-particle structure is written by MATLAB software.The simple harmonic wave and seismic wave are input to the particle model for parameter analysis.The effects of ground motion frequency,roof structure mass and isolation layer stiffness on the seismic response of the structure are studied.The analysis shows that the isolation effect is better when the frequency component of the local vibration only contains the fundamental frequency of the structure.When the mass of the roof structure is about the original mass 7,the base shear force of the structure is the smallest,and the response of the lower frame structure is also small.The natural frequency of the roof structure is close to the main frequency of the structure.(3)The finite element model of different roof structure mass and isolation layer stiffness was established by SAP2000,and the relationship between structural seismic response and roof structure mass and isolation layer stiffness was analyzed.The results show that when the mass of the roof structure is about 7 times the mass of the original roof structure,the natural vibration period of the structure is the largest,the base shear force of the structure and the interlayer displacement of the lower frame structure are the smallest.(4)The isolation effect of the original roof isolation structure and the roof isolation structure after parameter optimization is compared.The results show that the first-order period of the optimized roof isolation structure is 1.2 times of that before optimization.The damping coefficient of the base shear in the X direction of the roof isolation structure before and after optimization is 0.927 and 0.868,and the damping coefficient of the base shear in the Y direction of the roof isolation structure before and after optimization is 0.890 and 0.854;the damping coefficients of the fourth and fifth inter-story displacement of the lower frame structure before and after optimization are 1.12,1.101 and 1.082,0.993,respectively.The optimized roof isolation structure has better damping effect on the lower frame structure. |
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