Analysis Of Seismic Behaviors Of Story Isolated Muliti-tower Structures With Large Base

With the development of story isolated technology in recent years,more and more buildings adopt seismic isolation structures.Since the story isolated can effectively extend the natural vibration period of the structure and greatly reduce the response of the structure,it has Widely used in projects of subway superstructures.Regarding the subway superstructure,usually a large base is built above the subway,and then residential structure or shopping malls are built on the large base.By setting the story isolated above the large base,the fortification intensity of the superstructure can be reduced,and the rebar of the superstructure can be reduced,which has obvious advantages in reducing the cost of the structure.However,the center of mass of the superstructure and the center of stiffness of the story isolated can not be completely overlapped,which makes the torsional effect of the superstructure not to be ignored.As the embedded part of the superstructure and the subway garage,the lower structure has a higher story height and weaker stiffness.In order to satisfy the requirements of stiffness ratio and performance-based design,The walls and columns of the substructure have big section sizes and excessive reinforcement.Therefore,this paper conducts the dynamic elastoplastic analysis of story Isolated mulititower structures with large base under the action of rare earthquakes and super rare earthquakes,and carries out related research.This paper mainly studies the influence of the stiffness ratio of the lead-core rubber bearing,the eccentricity ratio of the story isolated,the embedded stiffness ratio of the story isolated and the stiffness ratio of the first and second storys of the substructure on the seismic behaviors of the structure.The specific work content is as follows:(1)The dynamic elastoplastic analysis of story Isolated muliti-tower structures with large base under the effects of rare earthquakes and ultra-rare earthquakes shows that the seismic performance of story Isolated muliti-tower structures with large base is good under the premise of performance-based design.Even under the effect of ultra-rare earthquakes,its safety reserves are relatively sufficient.(2)By changing the stiffness ratio of the lead-core rubber bearing and the eccentricity ratio of the story isolated,the influence of the changes of the above factors on the seismic performance and torsional performance of the single-tower isolated structures with large base is discussed.The results show that the changes of the above factors have almost no effect on the structure below the story isolated,while for the story isolated and above,the damping coefficient of the superstructure can be increased.As the stiffness ratio of the lead rubber bearing increases,the story drifts and torsion angle decrease first and then increase.The increase of the eccentricity ratio of the story isolated can reduce the drifts of the structure,but it has the effect of increasing the torsion angle.Therefore,this paper gives the recommended values for the stiffness ratio of the lead rubber bearing and the eccentricity ratio of the story isolated for this type of structure.The stiffness ratio of the lead rubber bearing is controlled between 65% and 80%,and the eccentricity ratio of the story isolated is controlled at 3%,and the seismic performance of the structure can achieve the optimal effect.(3)By changing the stiffness ratio of the story isolated and the stiffness ratio of the first and second storys of the substructure,the effect of the change of stiffness ratio on the seismic performance and torsion performance of the story isolated single-tower structures is discussed.The results show that the reduction of the stiffness ratio of the story isolated can only increase the torsion angle of the story above the story isolated.The reduction of the stiffness ratio of the first and second story of the substructure can not only increase the torsion angle of the story isolated and the above stories,but also increase the absolute acceleration,drifts and story displacement of the substructure,and reduce the story shear force.The shear force on the story has a decreasing trend,and the changes on the first story are more obvious.At the same time,this paper gives the recommended values for the stiffness ratio of the story isolated and the stiffness ratio of the first and second stories of the substructure for this type of structure.When the stiffness ratio of the lower floor to the upper floor of the story isolated is used to calculate the stiffness ratio of the story isolated,the recommended value of the stiffness ratio limit is 1.2,but measures must be taken to control the torsion effect of the superstructure.When calculating the stiffness ratio of the first and second stories of the substructure,in order to improve the safety reserve of the seismic isolation structure,it is recommended to increase the limit of the stiffness ratio from 1.1 to 1.2.