Seismic Response And Vulnerability Analysis Of Structural System After Seismic Isolation Reconstruction Of Existing Frame Buildings

As an important part of achieving a resilient city,seismic resilience has been widely implemented in the field of engineering construction in recent years.Due to the increase of service time,the adjustment of seismic zoning map and the change of use function,the seismic performance of some existing buildings in the city is difficult to fully meet the new seismic demand.As one of the main methods to improve the seismic resilience of single structures,seismic isolation technology has excellent performance in the field of disaster prevention and shock absorption of engineering structures,and is often used for the reinforcement and reconstruction of existing buildings.For existing buildings with basements,due to the stability of the substructure in the process of isolation transformation and the interaction of various components in the new structural system after transformation,it is more complicated than the new isolation structure.A systematic study on the seismic response characteristics and seismic vulnerability of such existing buildings after isolation transformation will provide theoretical basis and technical reference for the engineering application of such structures.In this paper,the combination of theoretical analysis and numerical simulation is used to study the influence of the cross-section size of the lower pillar on the seismic response and collapse probability of the whole series after the isolation transformation.Taking the actual project under transformation as an example,its feasibility is analyzed.The main contents of this paper are as follows:(1)Based on the theory of compressive bar stability,the RC column is simplified as a bending vertical bar,and the laminated rubber bearing is simplified as a special hinge bearing with horizontal stiffness and bending stiffness.The seismic response of the top of the lower pillar column,the top of the isolation layer and the whole series isolation system was simulated by numerical simulation.The results show that the change of the section size of the lower pillar will affect the overall stability of the series system.With the increase of the section size of the lower pillar,the displacement response of the top of the lower pillar and the end of the series system decreases first and then tends to be stable.The displacement response of the isolation bearing and the maximum inter-story displacement angle response of the superstructure increase slightly.The results of numerical simulation are consistent with the variation of the critical bearing capacity expression.(2)The incremental dynamic analysis method is selected to simulate the elastic-plastic dynamic response of the whole structure of the series isolation system under the condition of the change of the section size of the lower pillar.The vulnerability curve of the whole series structure is obtained by using the quantitative standard limit given by the new isolation standard.The results show that due to the complex mechanism of the series isolation system,the overall seismic performance of the structure can be effectively improved by appropriately increasing the section size of the lower pillar.With the increase of ground motion intensity,the damage probability of the isolation bearing in the whole series with the increase of the lower pillar section is higher than that without the increase of the lower pillar section.(3)Taking the actual project as the background,through the finite element software modeling,the seismic response of the actual isolation structure,the design isolation structure,the original seismic structure and the feasibility of the actual isolation structure are compared and analyzed.The results show that after the seismic isolation transformation of the original seismic structure,the vertex acceleration and interlayer displacement are significantly reduced,and the seismic performance is improved.Compared with the design isolation structure,the actual isolation structure has the same seismic response as the upper structure.Because the actual increase in the cross-section size of the lower pillar is greater than the design increase,it shows good stability,but the safety redundancy is too abundant to achieve good economic results.After the seismic isolation transformation,the natural vibration period of the structure is expanded to 3.1 times of the original structure,and the ability to resist the corresponding intensity earthquake is significantly improved.The indicators of the isolation layer meet the relevant requirements of the ’Code for Seismic Design of Buildings’,and the expected results are achieved.