Study On Simplified Fragility Analysis And Seismic Performance Of Rigional Bridges

With the requirement of the disaster mitigation of the urban city,establishing a disaster-mitigation plan has become a necessary work of the government.Fragility analysis is an important technology for the seismic assessment of the bridge structures.However,the traditional method of the fragility analysis of the bridge structure can not meet the special requirement of the seismic assessment of the regional bridges in urban city with huge amount of structures.Therefore,developing a simple method is an important basis for the fast seismic assessment of the bridges in an urban city.In this thesis,the Pushover analysis method,which has the advantage of simple and less calculation,is utilized in the seismic performance analysis of the regional bridges.Aiming at the effects of the bearing deformation on the seismic lateral force,a new type of lateral load distribution pattern is developed for the Pushover analysis.Based on the proposed pattern,a simple fragility analysis method and a fragility matrix establish method are developed and used for the seismic performance evaluation of an urban city.The main contents of this thesis include:(1)Based on the OpenSees software package,the refined finite element model of reinforced concrete bridge is established.The relationship between the moment and the curvature is obtained through the analyzing the bridge pier sections.The influence of different lateral loading distribution pattern on the accuracy of the static elasto-plastic analysis of the bridge is also investigated.(2)Based on the specific characteristics of bridge structures,a new type of lateral loading distribution pattern of bridge structure is proposed.Through the comparison of the analysis results with the conventional Pushover analysis methods and the dynamic time history analysis,it is demonstrated that the proposed lateral loading distribution pattern is more suitable for the structural analysis of bridges.(3)The seismic performance of multiple reinforced concrete bridge of an urban city is analyzed.The effects of the axial compression ratio,volume ratio of the stirrup,thickness of protective layer and transverse beam are also investigated,and the quantifiable results are also obtained.(4)A simple fragility analysis method and the established method of the fragility matrix are also proposed.The proposed methods are used to establish the fragility curves of multiple bridge under the longitudinal and transverse earthquake excitations.According to the seismic damage status,the common characteristics of the fragility curve and the fragility matrices are obtained.The analyzed results can be used for the basic data of the seismic performance assessment of the concerned urban city.