Based On The Analysis Of Seismic Performance Of Full-life Offshore Bridges

With the completion of large bridge projects,the construction of bridge in our country is entering into a glorious period.Because of specialty of the offshore environment,the research of the reinforced concrete durablity attracts more attention.The reduction of the reinforced concrete durability makes the sensitive seismic issues become more important.The principal point of the thesis is the seismic performance of the offshore bridge structures before and after deterioration.The thesis is divided into three parts:research on the factors of offshore-structure's deterioration,the selection of indices of structural seismic performance,and the study on the offshore-bridge seismic performance through an example.Firstly,the factors leading structure deteriomtion of offshore bridge from inside and outside were analyzed in the thesis.Secondly,the offshore environment,as an outside environment factor,was analyzed enphatically.The relationship between deterioration degree of structure and service time,under the single factor or dual factors external effect,including offshore-wind,freeze-thaw,and corrosion by salt,as separately detailed in the study.At last,the variation of the performance parameters for deteriorated structure was summarized.According to the research results and existing references,the displacement response was proposed to evaluate the aseismic performance of deteriorated structure and the target displacements for different performance levels were proceed to set Based on the Pushover method,by changing the parameters of the finite element model for bridge pier via Midas a kind of FEM software,it could be concluded that as the material deteriorated,the displacement of pier crown caused by seismic increased,and compared with concrete,steel can make a more remarkable negative effect on the aseismic performance of deteriorated structure.The basic principle of Pushover analysis method is studied and the concrete implementation steps.Bridge calculation model is studied.The distribution characteristics of plastic deformation of the bridge and the position of plastic hinge,structural elastoplastic simulation,the performance of lateral force loading pattern,refinement and implementation of the capacity spectrum method and so on has carried on the thorough discussion.Last part of the thesis,an example of an offshore bridge was studied.In this part,a finite element model of the full-bridge was established aided by the FEM software Midas.By taking a time-history analysis under the seismic load considering the offshore wind and wave as external effects,the structure's seismic response according to the structure deterioration was conputed and analyzed.In conclusion,with the structure deterioration,its seismic performance was seriously deteriorated which should be received additional consideration during the seismic design.