Seismic Fragility Analysis Of Reinforced Concrete Continuous Girder Bridges Considering Near-fault Effects

A large number of earthquake damage show that near-fault pulse-like groundmotions are different from far field ground motions. The former leads to higherrequirements for structure. The near-fault pulse-like ground motions contain largevelocity pulse, thus it can produce great destructive power to structures. As animportant part of lifeline system, the bridges’ collapse will directly propose a threatto people’s life and property safety, and even severely hampers rescue efforts afterdisasters. The research on seismic response of the RC continuous girder bridgessubjected to near-fault pulse-like ground motions and the fragility degree of itscomponents and systems is of great importance to seismic design of the samebridges of near field region.Regarding a four-span RC continuous girder bridge, a series of simulation andanalysis are performed in this thesis. The main research contents are as follows:1) First, a number of near-fault pulse-like ground motion records and far fieldground motion records has been chosen. Then several basic characteristics ofnear-fault pulse-like ground motions are introduced. What’s more, comparisonbetween near-fault pulse-like ground motion records and far field ground motionrecords about response spectrum, fourier spectrum and power spectrumcharacteristics has also been performed. And the period and maximum velocity ofthe velocity pulse have been extracted.2) The finite element model of the RC continuous girder bridge is establishedby OpenSees. This paper then introduces the selection of materials and elementmodel. After the nonlinear time history analysis of the bridge, the seismicperformances of the bridge subjected to near-fault pulse-like ground motions and farfield ground motions are studied and compared.3) The traditional probabilistic seismic demand analysis of the RC continuousgirder bridge is performed. Through the comparison, Sa is the more proper groundmotion parameter.Then probabilistic seismic demand analysis with the considerationof individual earthquake ground motion parameters, two ground motion parameters,and grouping by PGV is performed to reflect the impact of the near-field pulse-likeeffects.4) Based on the traditional probabilistic seismic demand analysis results, Theseismic fragility analysis of reinforced concrete continuous girder bridges subjectedto near-fault pulse-like ground motions and far field ground motions is performedand compared. The seismic fragility of bridge components and systems subjected tonear-fault pulse-like ground motions is larger than that of far field ground motions. At last, the seismic fragility analysis of RC continuous girder bridges consideringnear-fault effects with two parameters, Sa and PGV, is performed.Thecorresponding seismic fragility surfaces are then achieved. Seismic fragility curveswith different Sa or PGV values are extracted respectively.