Study On Seismic Performance And Fragility Of Reinforced Concrete Girder Bridge

The bridge is an important part of transportation systems. Due to the neglect of bridge earthquake-resistance and low design criteria in the past, the seismic capacity of many constructed bridges are weak, therefore it is necessary to carry out the research on seismic performance of bridge. According to bridge characteristics in China, this thesis proposed a method to analyze the seismic performance of the simply supported beam bridge piers with Incremental dynamic analysis method(IDA) and then do the research on the influence of the pier height, weight above the pier and reinforcement ratio. Then,125seismic records are used to analysis the continuous-beam bridge with the same piers height and the different piers height in nonlinear dynamic time-history analysis. The fragility curves are established to analysis piers, bearing and the bridge system. Above all, the main processes are as follows:(1) Based on the comprehensive reading and understanding of related study home and abroad, this thesis conducted a systematic review and comprehensive summary of the IDA analysis methods and the development of fragility analysis.(2) In this thesis, the seismic performance of the simply supported beam bridge piers is researched with IDA analysis method, and analyse the effect of the pier height, the weight on the top of pier and reinforcement ratio on the performance point. The results show that: pier height changes the pier seismic performance most, while the weight on the top of pier almost has no influence on it. The reinforcement ratio influences the performance point OP, IO, LS slightly and CP huge.(3) To analysis the fragility of the continuous girder bridge, PGA is selected as the ground motion intensity measure, while the displacement-ductility ratio, displacement are selected as the damage measures of the pier and the bearing refer to the related researches.(4) Taking a continuous girder bridge with the same pier height as example, the fragility curves of piers, bearings and the bridge are established after a serious of nonlinear dynamic-history analysis. Then the research on the curve rules and their differences is done. The research shows that the failure probability of different piers is indifferent. After suffering from a slightly earthquake, the laminated rubber bearing is easily slightly and moderately damaged than PTFE rubber bearing; but the PTFE rubber bearing is easily damaged at seriously damaged and collapsed. Bridge, as a whole, is easily damaged than any of the components.(5) Most of the bridges have different piers height actually, So it is necessary to do the research on the these bridge. The same seismic records can to do time-history analysis to establish the fragility curves, the comparison shows that the failure probability of the1#and2#piers are almost the same when they are slightly damaged, while it is different under moderately damaged, seriously damaged and collapsed, the lower pier is easily damaged. The laminated rubber bearing on the lower pier is easily damaged.(6) Compare the fragility curves of the two kinds of bridges, it can be saw that the fragility curves are almost the same while the whole bridge is slightly damaged, moderately damaged and seriously damaged, the asymmetrical bridge is higher that the symmetrical one, the curves are apparently different while the whole bridge is s collapsed.