The Seismic Responses Analysis On Story Isolation Structure Of Multi-story Frame And Three Particle Model

This article elaborated the development of isolated structure,the current research of story isolation structure,the mechanical model of LRB and the simplified calculation model of story isolation structure.On the base of current research,this article simplified story isolation structure as three particle model and multi-story frame structure,figured out the main influence parameters which can reduce the seismic action,for example,the location of isolation layer,the stiffness of isolation layer,the damping ratio of isolation layer,the yield-weight ratio of isolation layer,and changed the values of the main parameters to study the difference of evaluating indicator which can represent the seismic responses of story isolation structure.Through the comparison of the two analytical models,this paper summarized the seismic responses with the change of influence parameters of story isolation structure.Conclusions are summarized as follows:(1)When the isolation layer was set in the lower story,the period of story isolation structure is larger;the principle of vibration control is similar to base isolation.The first mode participating mass ratio is larger,and it indicate the vibration property of story isolation structure is controlled by the first mode;as the isolator set higher,the period of the inter-story isolation structure will decrease,but it is also larger than the period of seismic structure,and the principle of seismic control is like TMD.The first mode participating mass ratio decreases gradually,the vibration property of story isolation structure are mainly controlled by the first few mode.(2)With the increase of isolation layer horizontal stiffness,the period of story isolation structure increases gradually.For substructure of isolation layer,the existence of an optimal horizontal stiffness of isolation layer makes the seismic response of story isolation structure minimum.Therefore,when designing a project,the engineers should choose an optimal horizontal stiffness of isolation layer.For isolation layer,with the increase of horizontal stiffness,the story relative displacement decreases gradually,and finally increases gently.The absolute acceleration increases rapidly,and finally change gently.For superstructure,with the increase of horizontal stiffness,story shear force and story relative displacement increase rapidly,and finally increase gently;when the isolation layer was set in the lower story,absolute acceleration increases rapidly at first,and then increases gently,when the isolation layer was set in the higher story,absolute acceleration increases rapidly at first,and then decreases gently.(3)With the increase of isolation layer damping ratio:For substructure of isolation layer,seismic responses decrease gradually,and damping ratio is of great help to control seismic responses,for superstructure of isolation layer,seismic responses have a certain degree of decrease,but the decrease of the amplitude is small,damping ratio of the isolation layer is effective to control seismic responses,but the effect is not significant.When designing engineering,the damping ratio of isolation layer should be increased to reduce the seismic responses of substructure.(4)With the increase of isolation layer shear to weight ratio:story shear of isolation layer and substructure decreases firstly,and then increases,so there is an optimal ratio of shear to weight ratio,which can make the sheer force of substructure minimum;story relative displacement of superstructure increases gradually;story relative displacement of isolation layer decreases gradually;story relative displacement decrease firstly,and then increases;story absolute acceleration of isolation layer and superstructure increases gradually,story absolute acceleration of substructure decreases gradually.(5)Simplified multi story framework model into three particle equivalent model,the index error of the seismic responses calculated are within the allowable range of engineering,so the story isolation structure can simply as three particle equivalent model.