Response Analysis For Deformation Sensitive Large Span Structure Under Spatial Variation Seismic Ground Motion

Large span structure being a part of modern civilization undertakes importantsocial functions. Safety of large span structure is given special consideration. Seismicground motion is a complicated time-space process. Previous seismic design and-research are always concerned with seismic time variation characteristics instead ofits spatial variation. Wave-passage effect, incoherence effect and local site effect aremain factors of spatial variation of seismic ground motion. Considering spatialvariation is a more feasible input method to structures with large planar dimension.The dissertation is mainly concerned in response analysis for deformationsensitive large span structure under spatial variation seismic ground motion.Based on the systematical summarization on the past research work in the field(Chapter 1), random process model of seismic ground motion is discussed and itsparameters are specified in Chapter 2. Firstly, common random models of seismicground motion are reviewed in this chapter. Then modified models based on filteredwhite noise model are summed up. Analysis and contrast of wave filtering lowfrequency and high frequency characteristics are carded out. With maximum responseestimate theory of random vibration, response spectrum of single degree of freedom(SDF) system under stationary seismic ground motion is calculated. Throughequivalent stationary method, response spectrum under non-stationary seismic groundmotion is calculated. By adopting random vibration theory, conversion between powerspectrum and response spectrum is realized by iteration method By adopting seismiceffect factor curve of Chinese current structure seismic design code (GB50011-2001)as object response spectrum, conversion program between power spectrum andresponse spectrum (RSTOPS) is compiled by iteration method, thus power spectrumarchive compatible with response spectrum of seismic code is built. By adoptingnonlinear fitting method, parameters of Hong feng-Jiang jin ten model are fitted withcalculated power spectrum and its two parameters:ω_h,G₀ are given in this Chapter.Chapter 3 mainly discusses generation method of seismic ground motion. Firstly,three main factors of seismic ground motion and physical descriptive variables arereviewed in this chapter. Generation principle of uniform excitation artificial seismicground motion compatible with response spectrum of Chinese seismic code isintroduced. The method of power spectrum with amplitude spectrum modification isproposed in this chapter. Program of generation of artificial seismic ground motion compatible with response spectrum of Chinese code is complied. Based on randomprocess theory, a method of simulation of spatial correlated multi-point ground motionhas been proposed by simplification of cross power spectral density matrix. Onlydecomposition of lagged coherent density matrix is required instead of Choleskydecomposition of cross power spectral density matrix. Thus complex matrixcomputation is avoided and simulation efficiency is improved. A correspondingprogram has been compiled using the method.Chapter 4 mainly discusses time history analysis method and its application.Firstly, structural motion equilibrium under multi-point seismic ground motionexcitation is built. An unconditioned convergence solving method (wilson-θmethod) is introduced in this chapter. The emphasis of this chapter is applying timehistory analysis method to calculate seismic response of a steel large span arch of astadium. The main contents conclude: build of finite element model, seismic wavegeneration under uniform and multi-point excitation, apply big mass method to timehistory method. Calculation results are analyzed and some conclusions are given.Chapter 5 mainly discusses response spectrum method of multi-point excitationand its application. Firstly, basic principles of response spectrum method underuniform and multi-point excitation are introduced. Contrast and analysis of responsespectrum methods under uniform and multi-point excitation which include: B-Kmethod, H-V method, MSRS method and Y-T method. MSRS (Multiple-SupportResponse Spectrum Method)method is deduced by strict random vibration theory andregarded as an application of CQC method. Responses of two types of continuousbeams with two span: flexible beam and stiff beam are calculated by MSRS method.Responses characteristics of two types of beam under spatial variation seismic groundmotion are analyzed and some conclusions are given.