| With the continuous development of China’s economy,the increasing urban population makes the demand for housing increase sharply,urban construction land is becoming increasingly tense.In order to increase the use area,it is a better way to add storeys to old houses.The light steel storey-adding renovation has the advantages of increasing the use area without increasing the occupied area,short construction period and saving resources.However,after the steel structure is revamped,there is a sudden change in stiffness between the storey-adding structure and the original reinforced concrete structure,under the action of earthquakes,a remarkable whiplash response can be produced,the dynamic characteristics of the whole structure will also change greatly,therefore,it is necessary to study the seismic performance of the structure after adding storeys.In this paper,the isolation technology is applied to the retrofitting of old buildings with additional stories,and the seismic response of the structure with additional stories under earthquake action is studied.This paper mainly studies the following contents:(1)Three kinds of analysis models for different layered systems are established by SAP2000 finite element software,which are traditional aseismic structure,direct storey-adding structure and isolation storey-adding structure and the modal analysis is also carried out.The results show that the natural vibration period of the structures with different story-adding systems increases,compared with the direct storey-adding system,the increase of the isolation storey-adding system is larger.(2)The time history analysis of three models under frequent earthquakes and rare earthquakes is carried out.Three kinds of seismic waves are applied to obtain the interlayer shear force,interlayer displacement angle and acceleration and bearing hysteresis curve of three structural models.Through the analysis,the response variation law and the seismic effect of three structural models under different earthquake actions can be obtained.The results show that,because the isolation layer can absorb part of the seismic energy transmitted to the upper part,the seismic response of the upper part of the isolation layer structure decreases in varying degrees compared with that of the direct layer structure,and the effect of reducing the seismic response is obvious,but the seismic response of the lower part of the isolation layer structure increases and decreases.(3)The time history analysis of the two-way ground motion input to the model of storey-added isolation structure is carried out,by comparing the inter-story shear force,displacement angle,acceleration and bearing hysteresis curves of isolated storey-adding structure under unidirectional and bidirectional ground motions,the influence of bidirectional ground motions on the seismic performance of storey-adding structure is analyzed.The results show that the inter-story shear force,inter-story displacement angle and acceleration of the structure increase to a certain extent under two-way seismic excitation,and the variation law is similar to that of one-way seismic excitation.In addition,the hysteretic area of isolation bearings is also increased compared with unidirectional earthquakes,which indicates that isolation bearings play a more full role under the action of two-way earthquakes,and the effect of shock absorption is better.(4)The time history analysis is used to analyze the seismic performance of the original structure with different storeys.The seismic response of the structure is observed through the change of the number of storeys added to the structure,and the effect of storey isolation on the seismic reduction of the structure is compared and analyzed.The results show that different layers have great influence on the internal force of the structure,and the weak position of the structure may change with the change of layers.Compared with the frequent earthquakes,the structure under rare earthquakes has better seismic mitigation effect. |
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