Research On The Response Spectrum Of Base Isolation Structure

Response spectrum theory is one of the basic theories of anti-seismic structuredesign. Base-isolation structures, featuring long period, high damping degree andliability to yield, are different from traditional structures. They are often very likelyto enter the inelastic stage in earthquakes. Chinese current code defines an elasticdesign response spectrum to design a structure, and no provisions about inelasticspectrum in it.However, if we use an elastic response spectrum to design base-isolatedstructures, the accuracy of the calculation and the safety of the structure will bedoubted. Therefore, in order to promote the applications of the base-isolationstructures, this thesis studies inelastic response spectrum of the base-isolationstructures, with the hope of enriching the response spectrum theory.Based on the existing theories and previous researches, this thesis includes thefollowing studies:1) The author of the thesis made a brief introduction to the analytical model ofthe base isolated structure and its application. Introducing the restoring force modelof a base isolated structure, we make a detailed discussion on Bouc-Wen model whichis used in this thesis, and the control parameters of its hysteresis loop are also studied.Finally, the best parameters of Bouc-Wen model are obtained to simulate baseisolated structures.2) A Newmark-β time history analysis method is established on the base of theincrement of the dynamic differential equation of Bouc-Wen model, and the iterativeformula of Newton-Raphson is also established on the base of the differential controlequation of Bouc-Wen model.3) The iterative formula based on the Bouc-Wen model is derivated. TakingEL-Centro wave as an example, the inelastic acceleration response spectra, theinelastic displacement spectra, ductility spectra and the spectral displacement-spectralacceleration curve are calculated. The effect of the structural damping ratio, thesecond stiffness coefficient, the near-field and far-field earthquake are discussed, anda series of relevant conclusions are obtained.4) The inelastic spectrum which applies to the seismic code is presented in thethesis. According to site type of Code, seismic waves can be divided into three categories. Through a lot of time history analysis and statistical processing, theinelastic acceleration response spectra, inelastic displacement response spectra,ductility spectra and the spectral displacement-spectral acceleration curve of the threetypes of venues are established. Furthermore, the author of the thesis discusses theimpact of different site conditions, different seismic conditions and the strengthreduction factor for the inelastic response spectra.