| In response to the development demands of intensive city and seismic resilience in China,interstory seismic isolation technology has gradually been applied to over-track buildings in highintensity regions.Most of these buildings are designed as the inter-story isolated multi-towers built on a large chassis.Investigating the impact of design parameters on seismic response and resilience level,identifying the critical design parameters that dominate seismic resilience,and proposing an efficient conceptual resilience design method has become the key challenges in seismic resilience design of such buildings.To address these challenges,an actual engineering project located in the 8 degrees region was selected as the prototype case.Two critical design parameters,yield ratio and embedded stiffness ratio,were selected as variable,and 15 study cases was designed.The influence of yield ratio and stiffness ratio on inter-story drift ratio and absolute floor acceleration of the upper towers and large chassis was analyzed based on the above-mentioned simulation method,the impact of yield ratio and stiffness ratio on seismic resilience level of the building was clarified,the selection method of critical design parameters was suggested,and a conceptual resilience design method based on critical design parameters was proposed.Finally,the reliability and efficiency of the method were verified through a designed case.The main research contents of this paper are as follows:(1)Based on statistical data,a typical inter-story isolated multi-towers built on a large chassis located in the 8 degrees region was selected as the prototype case.A total of 15 study cases were designed,through designed five yield ratios(4.0%,3.5%,3.0%,2.5%,2.0%)by adjust the layout of the isolation system,and three stiffness ratios(2.0,2.6,3.2)by changing the stiffness of the large chassis.The 15 study cases were verified to meet the relevant design requirements of the code through time history analysis,indicated that the prototype case can be used for subsequent investigation.The influence of yield ratio and stiffness ratio on isolation indices(horizontal seismic absorbing coefficient of tower,isolation system displacement,maximum compression and tensile stress of isolators)was revealed.(2)Based on the shaking table test of a 2-story isolated RC frame structure completed by the project team previously,a suitable refined elasto-plastic numerical simulation method for isolated buildings using the finite element software PERFORM-3D was investigated and validated.Firstly,the accuracy of isolator element in PERFORM-3D to simulate the mechanical behavior of the isolators was verified based on the compression-shear test of the isolator.Subsequently,the shaking table test was simulated using PERFORM-3D.The results showed that the relative difference between the simulated and experimental values of roof displacement and isolation system displacement was less than 1.8%,and the relative difference between the simulated and experimental values of inter-story drift ratio was the range from 1.9% to 7.6%,which indicated that the refined elasto-plastic numerical simulation method is reliable.(3)The refined elasto-plastic analysis models of 15 research cases were established using the above method,and nonlinear time-history analysis was performed for the design basis earthquake and maximum considered earthquake under 11 ground motions.The engineering demand parameters,inter-story drift ratio and absolute floor acceleration,required for resilience assessment were extracted,and the impact of yield ratio and stiffness ratio on the engineering demand parameters was analyzed.The results showed that absolute floor acceleration of the tower significantly decreased as the yield ratio decreased and the stiffness ratio increased.The inter-story drift ratio of the tower generally showed an increasing and then decreasing trend with the increase of stiffness ratio.The ignored affect of yield ratio on the seismic responses of the large chassis was found,while the increase of stiffness ratio reduces the inter-story drift ratio and slightly increase the absolute floor acceleration.(4)The seismic resilience level of the 15 research cases was evaluated,and the impact of the critical design parameters(yield ratio and stiffness ratio)on the seismic resilience level of the building was analyzed.The key seismic responses and components that affect the seismic resilience level of the building were identified.It was found that the seismic resilience level of the 15 study cases was determined by the resilience level of the repair time,and its resilience level was mainly controlled by the absolute floor acceleration and the acceleration-sensitive non-structural components of the tower.The seismic resilience level of the building increased with the increase of stiffness ratio and the decrease of yield ratio,and the upper limit of the yield ratio that can achieve Level 3 increased with the increase of stiffness ratio.For a building with a stiffness ratio of 2.0,2.6,and 3.2,the upper limit value of yield ratio is 2.5%,3.0%,and3.5%,respectively.Based on the above research,a conceptual resilience design method based on critical design parameters was proposed to achieve the resilience level of Level 3.The designed case indicated the proposed design method could achieve Level 3,and verified the reliability and efficiency of the proposed design method. |
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