Research On Seismic Performance Of Offshore Bridges Based On Material Deterioration

Bridges play a vital role in the transportation system,and offshore and cross-sea bridges play a key role in the rapid development of China’s politics,economy and culture.After the offshore bridge structure is put into use,it is affected by the harmful elements in the nearby water sources and the large changes of air humidity and temperature near the sea water,and it is repeatedly used by human beings,so that the material properties and appearance of the structure itself deteriorate.In this case,if an earthquake disaster occurs,offshore bridges are easily damaged.Therefore,it is of great significance to analyze the influence of material deterioration on the seismic performance of offshore bridges.In view of this,this paper takes a offshore bridge section as an example,using the ABAQUS finite element software to create a numerical model of the bridge structure,and analyze the seismic performance of the bridge structure for the degradation of material performance deterioration.This paper mainly carries out the following aspects:(1)Aiming at the research of material deterioration of bridge structure,this paper analyzes the factors that influence the material deterioration of offshore bridge structure,and then summarizes the relationship between the material performance deterioration of bridge structure and the service time of bridge under the single,double and multi-factor actions of concrete carbonation,freeze-thaw damage and steel corrosion.According to the actual situation of the bridge,the appropriate deterioration models of concrete and steel are selected to calculate the mechanical parameters of offshore bridge structure after material deterioration in different years.The results show that the performance parameters of steel bar and concrete change in different degrees under the influence of deterioration factors,which leads to the decline of bridge mechanical properties.(2)The numerical model of offshore bridge structure is established based on ABAQUS finite element software,and the dynamic time history analysis is carried out.Considering only steel corrosion,only concrete carbonization,only concrete freeze-thaw damage,concrete freeze-thaw damage and carbonization,concrete carbonization and steel corrosion,concrete freeze-thaw damage and steel corrosion,and all three,the seismic responses of offshore bridge structures in different service times are calculated respectively,and the pier top displacement,pier bottom bending moment and shear force of offshore bridges under different working conditions are compared and analyzed to explore the influence of material deterioration on the seismic performance of offshore reinforced concrete bridges.The results show that the deterioration of materials degrades the mechanical properties of steel bars and concrete,thus reducing the seismic performance of offshore bridge structures.Ignoring the material deterioration of bridge structure or considering only one kind of deterioration will seriously overestimate its seismic performance.(3)Using the data recorded by sea and land stations in Japan’s K-NET strong earthquake network to sort out the comparative samples of sea and land earthquakes.Based on the influence of various factors of material deterioration in the previous chapters,the dynamic time history analysis of bridge structures under offshore and onshore ground motions is carried out respectively.The seismic responses of bridge structures in different service times are calculated,so as to explore the influence of offshore ground motion on the seismic performance of offshore reinforced concrete bridges.The results show that the dynamic response of offshore bridge structure is amplified by submarine seismic action,and the seismic performance of bridge structure will be overestimated by land seismic input.