Research On The Mechanism Of Seismic Isolation Of High-rise Composite Structure With Multilayer Seismic Isolation

The high-rise structure of the urban complex is a public transportation-oriented(TOD)development model,a multifunctional building integrating transportation,living,office and commerce.It is an important infrastructure project of a modern city.Due to its special stress characteristics and functional requirements,the high-rise structure of the complex is likely to cause greater casualties once earthquake damage occurs.And blindly increasing the load-bearing capacity and deformation capacity of structures or components not only increases the construction cost,but the results obtained are not satisfactory.The deformation-based seismic isolation design theory reduces seismic damage by installing energy-consuming devices in the structure,while the general seismic isolation design theory is difficult to achieve the best effect when directly applied to the composite structure.Therefore,this article propose a multi-layer layered seismic isolation form based on the high-rise structure of the complex,combined with the research status of related fields,calculate the parameters affecting the working mechanism of the multi-layer layered isolation structure through theoretical models,and use finite element software to explore different structures mass ratio(the ratio of the mass of the upper and lower structure of the isolation layer),frequency ratio(the ratio of the frequency of the upper and lower structure of the isolation layer)and the damping ratio(the equivalent damping ratio of the isolation layer)on the working mechanism of the multi-layered seismic isolation structure the law of influence.The study found:(1)As the mass ratio of the structure changes,the seismic isolation mechanism of the structure also changes.Within the parameters of this article:(a)Single-story seismic isolation structure: When the structure mass ratio is 2,the seismic isolation layer is located at the top of the podium.Due to the large chassis effect of the complex high-rise structure,the seismic isolation mechanism of the structure at this time it is the base isolation;with the reduction of the structural mass ratio,the isolation mechanism changes from base isolation to top-level isolation.(b)Double-layer seismic isolation structure: when the structural mass ratio(the mass of the upper and lower structures of the second seismic isolation layer)is 3,The structure between the two seismic isolation layers is equivalent to a new seismic isolation layer,and the seismic isolation mechanism of the structure is basic isolation;as the mass ratio of the structure decreases,the seismic isolation mechanism changes from basic isolation to basic isolation and the synergistic mechanism of top-level isolation.(2)The larger the equivalent damping ratio of the seismic isolation layer,the better the damping effect of the structure.Within the parameters of this paper: when the equivalent damping ratio of the seismic isolation layer is 0.4,the seismic isolation effect of the structure is better than the working conditions when the damping ratio is 0.3 and 0.2,and this law is not affected by the structure mass ratio.(3)When the structural mass ratio and damping ratio are constant,the structural frequency ratio is only related to stiffness.Therefore,as the frequency ratio of the structure changes,the dynamic characteristics of the structure will also change,thereby affecting the damping effect of each isolation mechanism.Within the parameters of this article:(a)Single-story seismic isolation structure: when the mass ratio of the structure is 0.2,the corresponding optimal structural frequency ratio interval is [0.7-0.9];when the mass ratio of the structure is 0.5,the corresponding the optimal structural frequency ratio interval is [0.6-0.8];when the structural quality ratio is 1,the corresponding optimal structural frequency ratio interval is [0.4-0.6];when the structural quality ratio is 2,the corresponding optimal The structural frequency ratio range is[0.15-0.25].(b)Single-story seismic isolation structure: when the mass ratio of the structure is0.3,the corresponding optimal structure frequency ratio interval is [0.8-0.9];when the structure mass ratio is 1,the corresponding optimal structure frequency ratio interval is[0.6-0.8];when the mass ratio of the structure is 3,the corresponding optimal structure frequency ratio interval is [0.2-0.4].