| Combined base seismic isolation technology have made rapid development,which combines the different bearings in a certain way.Generally combines the laminated rubber bearings with the sliding bearings.Through the reasonable parameter design,the advantages of two kinds of bearings form a complementary,mean that they can consume the seismic energy by frictional slip and provide restoring force to avoid the residual displacements as well.As seismic isolation technology and research become gradually mature,combined base isolation has entered the field of high-rise buildings.But for the high-rise seismic isolation buildings,A slightly large aspect ratio might cause the larger overturning moment generated at the superstructures and lead to the lift-off of isolation layer.Further it could induce the combined isolation system to be ineffective.Therefore,in this paper,the combined base isolation was applied in the high-rise buildings to explore the damping mechanism and the key parameters.Finally the conclusions provides the reference on engineering practice.The main work is as follows.(1)Starting from the multi-particle inter-layer shear systems,the slip judgment criteria of the combined seismic isolation system was deduced.Meanwhile,elaborated the motion equations the seismic isolation layer prior to and after slip.In order to clarify the influence of different waves on the time history-analysis of seismic isolation structures,according to characteristics of prior to and after seismic isolation respectively,selected two groups of waves including five natural waves and two artificial waves.Finally the results showed that the structures after seismic isolation were generally safe.(2)According to the requirements of relative specification,built the models of the high-rise frame-shear structures based on the different friction pressure ratios by adopting the ETABS,in which,the parallel combination base isolation was adopted.Then the time-history analysis was used to analyze the seismic response under different intensity,which based on that selected three different waves to input in one direction according to the behavior of structures after seismic isolation.The analysis results showed that there was an optimal relationship between the friction pressure ratio and the seismic response of the structures.Compared with the laminated rubber isolation system,when the friction pressure ratio ranged from 0.2 to 0.4,the combined seismic isolation system could achieve better isolation effect.(3)Established a high-rise frame-shear structure with proper friction pressure ratios by adopting the ETABS,in which,the parallel combination base isolation was adopted.Then the time-history analysis was used to analyze,which based on that selected three different waves to input according to the behavior of structures after seismic isolation.In addition,considering the unequal characteristics in tension and compression stiffness of the rubber bearing,changed the value of the tension to compression stiffness ratio.Finally studied the influence of the tension to compression stiffness ratio on parallel combination base isolation.The analysis results showed that,when the ratio of tension to compression stiffness ratio ranged from 1;8 to 1:10,the effect on the superstructure design was small,and the calculation of the seismic isolation bearing was also consistent with the actual.(4)On the basis of the existing formula of the aspect ratio limit of parallel combination base isolation,the vertical earthquake action was additionally considered.Took that the isolation bearings at the edge of isolation layer did not generate tension and compression stress that exceed the limit of relative standard as the control condition.Meanwhile considering the most unfavorable combination of the vertical seismic action with others,the simplified formula of the aspect ratio was improved,and analyzed the influence of relevant factors on the aspect ratio limit. |
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