Optimal Selection On Ground Motion Intensity Measures For Performance-based Seismic Design Of Bridges

With the frequent occurrence of earthquake world widely, the damage associated with earthquake has increased gradually. During the earthquake, many uncertainties that associated with the structural performance and seismic demand determine that the deterministic method does not apply to seismic analysis of structures. Therefore, performance-based earthquake engineering (PBEE) based on total probability theorem has been recognized as the future development direction of structural seismic design theory. It has become a performance-based seismic design theory of bridge (PBSD) and successfully applied to seismic design of bridges. In PBEE and PBSD, we must quantify ground motion with intensity measure parameter, to describe the seismic activity of engineering site, and use it in bridge seismic design. Moreover, the relationship between seismology and seismic bridge has been considered as important part to in PBEE and PBSD theory. Its first analysis phase is probabilistic seismic hazard analysis (PSHA), which selects a reasonable ground motion intensity measure, to describe the seismic risk of engineering sit, and selects high-quality seismic wave compliance with real seismic environmental and seismic risk level of engineering site for structural dynamic analysis. Because the randomness of key characteristics of ground motion will be passed to next analysis phase and significantly affect the probability of seismic demand, seismic hazard curve of EDP and seismic fragility and so on, selecting reasonable IM and seismic waves has become a basic and critical step in PBEE and PBSD theory.Based on performance-based seismic design theory, peak ground acceleration (PGA) and spectral acceleration (Sa) are utilized as IM to analyze the bridge in this paper. On this basis, to develop the probabilistic seismic demand analysis method, a multi-parameter ground motion intensity measure -which based on the key modal spectral acceleration of ground motion intensity measure is proposed. The main work of this paper includes:(1)Researches related to probabilistic seismic hazard analysis, bridge seismic design theory, performance based earthquake engineering and seismic fragility analysis at home and abroad are reviewed comprehensively by reading a large number of literature;(2) Comparison of the effectiveness of peak ground acceleration PGA and spectral acceleration Sa are carried out for the PSDA of typical irregular continuous girder bridge. Sa is identified as an effective and conservative parameter than PGA;(3)To account for the effect of critical high modal of bridge structure, a simplified parameterization is proposed in order to improve the seismic demand and the accurate of seismic fragility;(4).To improve the practicality and maneuverability of the new multi-parameter IM, the appropriate probabilistic seismic risk analysis method is developed, which based on the critical modal for the period spectral acceleration of multi-parameter IM.