Study On The Index Of Seismic Design Of Offshore Continuous Girder Bridges Based On The Performance

A thorough research on designing index of seismic resistance about offshore bridge is made in this thesis, including the following contents:The earthquake hazard and the development of offshore bridge in recent years are introduced in detailed, and a review of the research status domestic and abroad based on the seismic performance of bridge structure aspects is given.The earthquake recurrence period is adopted on the description of earthquake risk. In view of the characteristics of offshore bridge, the seismic fortification category has been improved by using the four grade earthquake fortification level, based on the existing design code. Referring to the project examples and the related standards, the method of determining the earthquake return period according to the seismic fortification category and seismic fortification level is analysed detailed. On the basis of the relevant literature, the qualitative description of the seismic performance standard of offshore bridge is given and the quantitative index of all levels of fortification level is suggested.The basic theory and the implementing process of static elastoplastic analysis, the existing lateral distribution pattern and the transformation of equivalent single degree of freedom system are introduced detailed. Associated with adopting the earthquake recurrence period on earthquake risk description, improvement is made on the calculation, basing on the existing involved standards. And the way how to get the elastic design spectra curve by utilizing the earthquake recurrence period is analysed.In this thesis finite element models of different height of pier structures are established using OpenSees software. The Moment-Curvature analysis and characteristics analysis is made about different structures on transverse direction. Four different loading patterns including uniform distribution, triangular distribution, distribution of power series, the first mode of vibration distribution, are selected to do Pushover analysis about different pier structures. And incremental dynamic analysis is also done, using seven earthquake waves randomly selected. Employing the result of the incremental elastoplastic dynamic analysis as the datum, the results of the Pushover analysis of several different distribution patterns are evaluated by means of studying on the coordinate index of performance point D. Finally the mass participation ratio of the first modal is adopted to indicate the applicable range of the Pushover analysis of several different distribution patterns.