The Research On Random Vibration Of The Serially Connected Isolation System

The seismic isolation technique has been widely applied in our country since1990s. In the existing developed structure-control technology, basic seismic isolation is considered as a kind of structurally passive seismic control method, which has a simple concept, stable performance and cost effective. With the daily improvement of building function and elevation effects, the designing scheme of a seismic isolation structure with a rubber bearing serially connected with cantilever column is born. Its main advantage is to make full use of the space and make the maintenance of the seismic isolation bearing convenient. The incident key problems are how to confirm the size of the cantilever column and the safety and stability of the serially connected isolation system. Therefore, new challenges are posed to the design of seismic isolation structure. Currently, the2010-year version of regulation on national building anti-seismic design only defines that serially connected isolation system belongs to story isolation on the macro level, proposes the story elastoplasticity displacement angle restriction under the influence of rare earthquake below the isolation layer and above the ground. But, serially connected isolation system is a strongly nonlinear construction member with variable stiffness and complicated dynamics characteristics, which needs further research. Therefore, this paper takes serially connected isolation system with a rubber bearing and cantilever column as the research object. It establishes the geometric nonlinearity dynamic equation of this system, applies the differential quadrature element method, analyzes the natural vibration performance and seismic response behavior of the serially connected isolation system, discusses the random response of serially connected isolation system and conducts shaking table tests on several models. The main content is as follows:(1) Establish the partial differential equation of geometric nonlinearity dynamic response of the serially connected isolation system with a rubber bearing and cantilever column. Based on the assumption of homogeneous column, deduce the equation of motion of geometric nonlinearity dynamic response of the rubber bearing by considering the geometric nonlinearity of the serially connected isolation system and applying the Hamilton variational principle; combined with the finite element method, expand this dynamic model and get the geometric nonlinearity governing equation and boundary conditions of the serially connected isolation system with a rubber bearing and cantilever column.(2) Analyze the natural vibration performance of the serially connected isolation system. Apply the DQ principle to disperse the governing equation and boundary conditions of the serially connected isolation system, choose the interchange method to handle the boundary conditions, adopt the method of combining DQ and finite element——differential quadrature element method (DQEM), formulate the matlab program to solve and analyze the natural vibration performance of the serially connected isolation system, study on the influence of factors like the stiffness of the bearing, vertical load and the slenderness ratio of the cantilever post on the frequency of the series seismic isolation system and discuss the negative effects on the frequency of the system by the combined effects of three kinds of factors and two kinds of factors.(3) Make use of time-domain DQEM to analyze the geometric nonlinearity seismic response of the serially connected isolation system with a rubber bearing and cantilever column. Aiming at the geometric nonlinearity governing equation of the serially connected isolation system, disperse it by DQ in the spatial domain first, then disperse it in the time domain by time-domain DQ step by step, formulate the iterative program to solve and analyze the seismic response of the serially connected isolation system under the influence of rare pulse horizontal earthquake in near field, calculate the result comprehensively and discuss the influence of slenderness ratio of cantilever post on the stability of the serially connected isolation system.(4) Discuss the analysis on the random response of the serially connected isolation system on the basis of geometric nonlinearity. Adopt the model of vibration power spectrum of the dual filtered white noise, solve and analyze the random response of the series seismic isolation system of the different slenderness ratio of the cantilever subjected in the’major earthquake’and compare it with the response result of the far field earthquake in the relevant the serially connected isolation system.(5) Aiming at the seismic response of the series seismic isolation system, conduct the research of the simulative shaking table test. Combining the practical seismic isolation project, design and formulate nine kinds of scale model of the serially connected isolation system, among which three are isolator nine are cantilever column. Finally, conduct the shaking table tests of60working conditions and conclude the acceleration reacting value of four measuring points of the series seismic isolation system model (the measuring points are table facet, the1/2height of the cantilever column, the top of the cantilever column and the top of the rubber bearing respectively). Make compared analysis of the seismic response of the series seismic isolation systems with different bearings and different cantilever columns, converse the model into the original system according to the ratio of similitude and make contrastive research of the results to provide certain reference for the shaking table tests of the full size serially connected isolation system model.