Study On Seismic Behavior Of Corroded Reinforced Concrete Piers Strengthened With ECC

In the long-term service process of bridge,due to the influence of environment and load,the material performance gradually deteriorates and the risk of seismic damage increases.Using the high ductility and strain hardening characteristics of Engineering cement-based composite(ECC)to strengthen the pier can effectively improve the seismic performance of the pier.Based on the seismic vulnerability assessment method,combined with the deterioration law of pier material properties,this paper studies the time-varying seismic vulnerability of RC piers and the vulnerability change trend after ECC reinforcement.The main research contents are as follows:(1)Based on ABAQUS software,the reasonable material constitutive relationship is selected,the buckling of longitudinal reinforcement is simulated by calling subroutine,the bond slip between reinforcement and concrete is simulated by adding nonlinear spring element,and then the refined finite element model is established.The rationality of the modeling method is verified according to the repeated load test of corroded RC column and ECC strengthened RC column.(2)The finite element models of corroded RC columns and ECC strengthened corroded RC columns are established to study the influence of different ECC strengthening measures on the seismic performance of corroded RC columns.With the increase of the height and thickness of ECC,the characteristic displacement and energy dissipation capacity of the specimens increase greatly,and the maximum increase of yield displacement,ultimate displacement and energy dissipation capacity is 23.93%,69.65% and 64.90%.(3)Based on an engineering example,the finite element models of corroded RC piers and ECC strengthened piers are established,and the nonlinear dynamic time history analysis is carried out.By comparing the seismic responses of the two kinds of piers under different seismic waves,the influence of ECC reinforcement on the seismic performance of corroded RC piers is studied.(4)Considering chloride ion erosion,according to Fick’s second law and Monte Carlo sampling,the corrosion time of reinforced concrete pier is calculated,and the deterioration law of reinforced concrete material performance is analyzed,and then the finite element model of durability damage RC pier with different service life is established.Based on the incremental dynamic analysis(IDA)method,the timevarying seismic vulnerability of RC piers is analyzed.The analysis results show that with the extension of service life,the seismic performance of piers degenerates,and the exceeding probability of piers under different damage states increases gradually.(5)After ECC reinforcement,the vulnerability of the bridge pier is reduced.The reduction range of the probability of exceedance is small when the bridge is slightly damaged or moderately damaged,and the reduction range of the probability of exceedance is significantly increased when the bridge is seriously damaged or completely damaged.When PGA is 0.4g,the exceedance probability of ECC strengthened pier under four damage states of slight damage,moderate damage,severe damage and complete damage is 0.08%,3.46%,30.91% and 40.06% lower than that of RC pier respectively.