Parameter Analysis And Optimization Of Three-Dimensional Isolated Megaframe Structure

The mega-sub aseismic structure(here in after referred to as the aseismic structure)is formed by separating the top and sides of sub structure from the main structure.Three-dimensional isolation bearing and ordinary isolation bearing are respectively set at the bottom of sub-structures of the aseismic structure to form the three-dimensional isolated megaframe structure,the horizontal isolated mega-sub structure(here in after referred to as the 3D isolated mega-sub structure and horizontal isolated mega-sub structure).The research objects of this paper are the 3D isolated meag-sub structure model and its simplified model,the main contents are shown as follows:(1)Modal analysis and dynamic analysis under multi-dimensional earthquake of the aseismic structure,horizontal isolated structure and 3D isolated structure are carried out by using ETABS software.The results indicated that the vertial vibration of 3D isolated structure appears in the seventh mode of vibration,which is earlier than the horizontal isolated and the aseismic structure;the vertical component of the coupled earthquake will magnify the horizontal dynamic response of the 3D isolated structure compared to the single-direction excitation;under the multi-dimensional seismic excitation,the horizontal seismic response of 3D isolated structure is greater than that of horizontal isolated structure and aseismic structure;In addition,the 3D isolated structure has good vertical vibration control effect,while the vertical vibration control effect of horizontal isolated structure can be ignored.(2)The influence of the number and layout of the vibration reduction substructure,damping coefficient ratio of horizontal and vertical isolated layer,the horizontal and vertical frequency ratios of the substructure and main structure,the mass ratio of the substructure to the main structure on the vibration reduction of mega-frame was analyzed by using the simplified model of 3D isolated structure and the equation of dynamic under the action of horizontal and vertical coupling earthquakes,the results of seismic calculation for simplified model and finite element model by Newmark-P method are compared,and a kind of damping optimization scheme is proposed.The results indicated that the dynamic response of the simplified model is slightly larger than that of the finite element model,but the time history curve of the two model is more consistent;for the mega-frame structures with more than one vibration isolated substructure,the controlled effects performance can be enhanced by adding the number of the substructure;under the above mentioned parameters,an optimal parameter is present,which minimizes the dynamic response of the main-structure and the substructure;the damping control effect of the main and substructure under the new optimization scheme is better than the original scheme.(3)The collision between main structure and sub structure in the 3D isolated structure is simulated.the influence of seismic peak,gap ratio,vertical seismic component and substructure height on collision response are analyzed.The results show that the acceleration of the mainstructure and the substructure during the collision compared with the non-collision,and the baseplate shear force of the mainstructure is obviously enlarged,and at the same time,a huge collision force will be generated instantaneously;the response law of the collision force and the acceleration peak under collision of the subframe is related to the type of ground vibration that is input.