Research On Isolation Layer Design Of Multi And High Rise Isolation Structure

The isolation technology can prolong the natural vibration period of the structure and reduce the seismic response of superstructure,which has been widely used in the engineering field and has shown good isolation effect in the actual earthquake disaster.With the improvement of seismic isolation technology,the design of isolation layer of isolation structure still has no normative guidance.The optimum arrangement of isolation layer and the mixed use of isolation bearings remains the hot spot in the application of seismic isolation technology.In this paper,the design of seismic isolation layer of high-rise base-isolated structure is studied.Based on the design of frame structure,frame-shear wall structure and shear wall structure with base isolation,the height-width ratio of the isolation structure,the seismic performance of three kinds of base isolation structures under earthquake,the stress of the floor slab of the seismic isolation layer of the frame-shear wall structure and the optimal parameters of the seismic isolation layer with viscous dampers are studied and analyzed.The main results are as follows:(1)The research situation of optimization method of isolation layer design at home and abroad is summarized and equivalent analysis models commonly used in seismic isolation structure are introduced.On the basis of the existing formula for calculating the limit value of the height-width ratio of the isolation structure,to improve the formula,the different strength in tension and compression of the isolation rubber bearing is considered and the isolation rubber bearing is allowed to appear the tension stress not exceeding the limiting value in accordance with the specification.The common methods to control the tensile force of the isolation rubber bearing are summarized in view of the tensile force of the bearing is easily generated in the high-rise isolation structure with large height-width ratio.(2)The frame structure,frame-shear wall structure and shear wall structure with height-width ratio of 4 are designed as base isolation structures.Using the software SAP2000,the models are eatablished considering the different strength in tension and compression of the isolation rubber bearing.With the dynamic time-history analysis,the dynamic response of the superstructure,the isolation effect,the maximum displacement and the stress distribution of isolation bearings are compared The results show that only the tensile stress of the isolation bearings in the base-isolated frame structure supports exceeds the limit,and horizontal seismic action of the superstructure of three kinds of base-isolated structures can be designed according to the lower half degree.(3)Based on the frame-shear wall structure,the stress distribution of slab under horizontal earthquake between seismic isolation layer of seismic isolation structure and standard floor of non-isolated structure is analyzed and compared,the seismic performance of seismic isolation layer slab and the influence of openings on the slab stress of the isolated layer is studied.The results show that the stress distribution in the floor of the isolated layer is similar to that of the standard floor slab,and the peak stress of the seismic isolation layer is higher than that of the base isolated structure.The seismic isolation layer designed according to the standard requirements can meet the seismic performance requirements under different fortification intensities earthquake.Furthermore,the slab of the isolated layer should not open the hole,if the hole is required,it is suggested to choose the symmetrical openings instead of corner openings as possible.(4)The viscous damper is added to the isolation layer of three kinds of isolation structures,the influence of damping coefficient,velocity index and number of damper on the isolation effect is analyzed.And the effect of viscous damper is defined as additional damping ratio.The results show that when the additional damping ratio is 14%-25%,the combination isolation structure will achieve the optimal isolation effect.On the basis of the optimal parameters of viscous dampers,considering the influence of the viscous dampers,the influence of the diameter of the lead rubber bearing in the isolation layer is analyzed.The results show that the diameter of the lead rubber bearings in the periphery of the isolation layer is reduced by 100 mm,the structure can meet the requirements of the specification and has some economic benefits.