Analysis On Seismic Performance Of Reinforced Concrete Piers Under The Chloride Ion Corrosion Environment

Along the bridge's service life, material performance degradat ion happens. The deteriorat ion o f steels and concrete will be more serious for the structures under the chloride ion corrosion environment especially. As the foundation of bridge, if piers' injury happened, it will affect the durabilit y and safet y of the who le bridge, then the predetermined seismic performance will also reduce. So it is necessary to analysis the bridge seismic performance. This art icle is carried out according to the Natural Science Foundat ion o f China(51278183)-Research on Reasonable Earthquake Resist ing System o f Bridge in Mountain Zone Base on Time-dependent Fragilit y. By a t ypical mult i-span cont inuous girder bridge, meanwhile considered the materials' degradat ion of reinforced concrete piers under the chloride io n corrosion environment, this paper has done the fo llowing works about the bridge pier's seismic performance:(1) Firstly, the bridges' destruct ion forms in the earthquake are described as well as the durabilit y. Then this essay reviewed the status of research progress about the chloride ion erosion and the seismic fragilit y. And the necessit y to study the seismic performance for reinforced concrete piers is elucidated.(2) This essay describes the mechanism o f chloride io ns on steel corrosion in detail. At the same t ime, the chloride io n in concrete diffusio n model is summarized. Based on the Fick's second law, it analyzes the important factors affect ing the chloride ion diffusio n model, and the values of main parameters is given refer to the design standard.(3) A finite element model which taken as the example bridge is established by Open Sees. Co mbined with previous research results, this paper has summarized and selected the appropriate material degradat ion models. According to these models, then the init ial corrosio n time of longitudinal reinforcement s and st irrups, corrosio n rate and material degradat ion law are calculated.(4) According to select ing three commo nly used seismic waves, three t ypical analysis cases under the chloride corrosive environment, consist ing o f the lo ngitudinal reinforcement corrosio n, the stirrup corrosion a nd the combinat io n corrosio n o f the longitudinal reinforcement and stirrup, are invest igated to study the effects of material degradat ion on the seismic performance of concrete piers. Then this paper co mpares the seismic capacit y and seismic response results of each condit io n. And the impact o f t ime-dependent material degradat ion is considered.(5) Based on the principle o f bridge seismic fragilit y, 100 seismic waves which are suitable for the ground are selected to conduct non-linear time-historical analys is before and after considering material degradat ion. Meanwhile the t ime-dependent seismic fragilit y curves under the different three condit io ns are built by ut ilizing tradit ional reliabilit y. And this paper co mpares the piers' seismic fragilit y.Finally, this essay summarizes the conclusions of the study, and the shortco mings and the direct ions of future research are po inted out.