| The structural dynamic nonlinear analysis has always been the core issue in seismic research. The focus of the dissertation is to apply modern mathematic means (i.e. wavelet transform & HHT theory and the main tools and methods of researching chaotic system) to structural dynamic simulation. In the process of seismic signal input, traditional Fourier Transform is replaced by Wavelet Transform and Hilbert-Huang Transform, the two most effective tools to handle non-stable signals, are fully exploited to achieve plentiful characteristic information. In the process of numerical calculation, the main tools and methods of researching chaotic system are used to figure out the maximum Lyapunov Index, Phase Trajectory. Poincare Section, Power Spectrum etc in nonlinear dynamics, so that structural complex dynamic behavior and the paths of getting into and out of chaos can be obtained. The research result provides "repairable under moderate earthquake, and not collapsed in big earthquake" with a new thinking and method of research. Therefore, in the dissertation, studies in the following areas are mainly carried out:(1) Studying earthquake transient response analysis of structure based on Wavelet Transform and HHT; differentiating displacement response characteristics between the long-periodic structure and short-periodic structure---in short periodic structure, the response being stable vibration controlled, and in long-periodic structure, response being transient vibration controlled; revealing the unique kinetics regularity & characteristics in long periodic structure under earthquake effect and especially finding the dynamic response patterns of different characteristics in two different cycles in the same towering structures;providing basic research data for the anti-seismic design of the especially high & long structure under wind load.(2) Analyzing non-stable characteristics of earthquake ground motion based on Wavelet Transform and HHT seismic instantaneous spectrum study; in order to reflect PAR index of different seismic waves, innovatively proposing that vibration peak energy maximum value and crest factor be a quantitative index to assess the destructive effect of seismic wave vibration strength; studying the effect of choosing restoring force models on nonlinear seismic response; and providing references for reasonable choice of structural seismic design ground motion input and the restoring force model.(3) Obtaining seismic elastoplastic system yield process and mechanism from earthquake response analysis of elastoplastic systems:structural system yield having a cumulative effect, "drift" phenomenon existing in recovery stress & deformation hysteresis loop and gap and collision is the source of the structure’s chaotic state; studying the hysteretic nonlinearity system of RC structures with clearance crack, finding that system stiffness softened and resonance point drifted.(4) Focused study on the complex stress state of the structure with cracks, collision and slip after the earthquake’s damage to concrete structure and reciprocating loading on the cracks in earthquake; study on chaos system differentiation and application of the above-mentioned structure; establishment of the calculation model for fracture gap and the collided structure; derivation of a formula to dynamic response; application of numerical recognition method in chaotic vibration to identify and depict chaotic vibration phenomenon and dynamic characteristics of chaos in engineering structure; providing scientific basis for the new-generation anti-seismic code and implementation of digitalization, visualization and rationalization of the structure simulation calculation.(5) Studies on damage mechanism and practical calculation method of the two kinds of structure under the impact of earthquake; studies on calculation solution to the first passage failure of the long periodic structure and calculation solution to the cumulative damage of the short periodic structure, providing necessary technological preparation for estimating the age of the structure after the impact of strong earthquake in advance. |
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