Research On Seismic Isolation Performance Of Frame-Core Tube Structure In Near-Field High Intensity Area

The frame-core tube structure has excellent mechanical performance and flexible spatial layout,and is widely used in high-rise buildings.With the complexity of the building site and the continuous increase of the construction height,its seismic performance is facing severe challenges.Therefore,this paper applies the seismic isolation technology to the high-rise frame-core tube structure in the high-intensity area,and uses multiple near-site vibrations as the excitation input.,the structural response parameters are obtained through finite element analysis,and the seismic isolation performance of the structure in the near-field high-intensity area is studied based on different isolation arrangements.The main work and conclusions are as follows:（1）Based on the existing near-field ground motion related research,according to the near-field ground motion selection criteria,the near-field ground motion required for this study is selected.The average PGA of the selected eight near-field ground motions is 0.615 g,which is about 3 times of the 8 degree seismic fortification earthquake acceleration,the peak range of the response spectrum is 0.5s ～ 1s,the peak duration is short,the Fourier spectrum value is concentrated in 0Hz ～ 2Hz,and the low frequency components are rich.（2）Based on the actual engineering,the finite element analysis software established the high-rise frame-core cylinder structure model in the high intensity zone,analyzed the vibration characteristics of the structure,analyzed its displacement and internal force changes,and the results showed that the response response trend of the structure was basically the same as that of the reaction spectrum analysis and the time course analysis,and the layer shear force and layer displacement mutation were obvious at the change of the beam and column section,and the displacement angle between the layer 2 was the largest.（3）Based on the analysis results of the original structure,three basic isolation and three floor isolation layout schemes were designed,and modal analysis and dynamic time history analysis were used to analyze the seismic response of structures with different isolation layouts under fortification earthquakes.The analysis results show that: After the seismic isolation layer,the first natural vibration period of the structure increased by 50.57% and 43.12% on average;the average reduction of story shear force was 47.29% and 44.78%;the average reduction of story displacement angle was 34.89% and 32.14%,and the average reduction of story displacement was 26.74% and 24.92%;therefore,the isolation arrangement can effectively reduce the seismic response of the structure,and the foundation isolation arrangement is better than the floor isolation arrangement.（4）Based on the optimal basic isolation and layer interval seismic arrangement under fortified earthquake,the near-site vibration was selected as the excitation input for seismic response analysis,and the analysis results showed that the average amplitude reduction of the layer shear force,layer displacement angle and layer displacement of the basic seismic isolation structure was 42.57%,21.63% and 45.73%,and the seismic isolation effect was good;the partial branch seat of the layered seismic isolation layer was shifted beyond the limit,and a viscous damper（VFD）was added to the seismic isolation layer to form a combined interlayer isolation system,and the structure was isolated and controlled,and the layer shear force was controlled.The average reduction of layer displacement angle and layer displacement was29.15%,21.53% and 31.64%,and the seismic isolation effect was better.Therefore,under the action of near-site vibration,the basic seismic isolation structure is better than the stratum seismic structure.（5）Through the analysis of energy consumption ratio,it can be seen that the average energy consumption of the foundation isolation structure is 45.92%,and the average energy consumption of the layer isolation structure with VFD effect is 34.22%.The foundation isolation structure can absorb the near-field vibration energy more effectively.Combined with the analysis of the isolation performance,the design scheme of the foundation isolation structure is the best isolation design scheme.