Seismic Performance Analysis And Seismic Vulnerability Assessment Of RC Bridge Piers With Material Performance Degredation In The Whole Life Cycle

As part of lifeline engineering,bridge plays an important role in the earthquake relief process.The seismic performance of existing bridges has been greatly degraded during the normal use due to the impact of environmental factors.Pier is as the main load-bearing component,the Stability of it directly related to the quality of disaster relief.Based on the effect of chloride ion erosion in marine environment,the seismic behavior of reinforced concrete bridge piers is explored in the whole life cycle and the seismic vulnerability is evaluated.The specific research contents are as follows:(1)On the basis of previous research results,the transmission process of chloride ion in concrete and erosion mechanism of steel bar under marine environment is summarized.The average initial corrosion time and corrosion rate of steel bar were determined by the method of one dimensional Fick second law and Carlo Monte sampling method.A model for the degradation of the diameter and the yield strength of the steel bar is established.(2)The nonlinear dynamic analysis model of a cylindrical reinforced concrete bridge pier in the whole life cycle was established by using ABAQUS software for 3 cases only considering the corrosion of longitudinal bars,only considering the stirrup corrosion and simultaneously considering the corrosion of the both.By means of low cycle to reset,the hysteretic energy dissipation capacity,the characteristic value of the displacement load skeleton curve and the stiffness degradation curve of the bridge piers under the three conditions are compared and analyzed.Effect of material deterioration on seismic behavior of reinforced concrete bridge piers is explored.(3)Reinforcement form as well as loading conditions is unchanged.Considered of longitudinal reinforcement and stirrup corrosion condition,the thickness of reinforced protective layer of the cylindrical bridge pier is changed.Using the same loading method and evaluation index,effect of thickness of reinforced protective layer on the seismic performance of reinforced concrete bridge piers of the marine environment is explored.(4)A method is proposed to define the damage index of reinforced concrete bridge piers under earthquake action,which is based on the top horizontal displacement of bridge piers.By pseudo static analysis,the limit values of the four kinds of conditions,which are minor damage,moderate damage,severe damage and completely destroyed of the bridge piers are quantified.ABAQUS software was used to build the nonlinear dynamic analysis model considering the longitudinal reinforcement and stirrup corrosion.Ida analysis was carried out by selecting 10 ground motion records.The probabilistic seismic demand model is obtained for the different time of the bridge piers.Based on this,the seismic fragility curve of bridge piers is established.Seismic vulnerability of reinforced concrete bridge piers under deterioration of materials is assessed.Finally,compared with the existing research results,the correctness of the method is proved.