Analysis Of Time-varying Seismic Vulnerability Of ECC-RC Composite Bridge Piers Considering Service Life

During long-term service,the bridge is affected by the erosion environment and unfavorable loads,and its service performance will gradually degrade.The pier,as an important component of the bridge's resistance to earthquakes,has a great impact on the entire bridge.Compared with ordinary reinforced concrete bridge piers,the seismic performance of bridge piers can be improved through the improvement or selection of high-performance materials,but the degree of improvement and the evolution of seismic performance over the entire life cycle need to be further studied.This paper considers the durability damage of the pier during its service life.To analyze the influence of ECC and high-strength steel bars on the seismic vulnerability of the pier,the time-varying seismic vulnerability of the composite pier is analyzed.The main research contents are as follows:(1)Based on the Open Sees platform,ECC model ECC01,concrete model Concrete02,steel constitutive model Steel02,and corroded steel constitutive relations were selected.The rationality of the model parameters was verified based on repeated loading tests of ECC columns and corroded reinforced concrete columns.(2)Nonlinear finite element analysis models of RC columns,ECC-RC composite columns and high-strength reinforced ECC-RC composite columns were established to study the influence of high-strength reinforcement strength and replacement rate on the seismic performance of ECC-RC composite columns.The analysis shows that compared with the ECC-RC composite column,the characteristic load and displacement of the high-strength reinforced ECC-RC composite column increase with the increase of the reinforcement strength and replacement rate.The maximum increase in yield load,ultimate load,yield displacement,and yield displacement was 63.15%,60.88%,64.01%,and 43.09%;compared with RC columns,the ECC-RC composite columns' characteristic loads and characteristic displacements increased by 13.58%,13.33%,15.23%,25.02%.(3)According to the seismic performance analysis of RC pier,ECC-RC composite pier and high-strength reinforced ECC-RC composite pier,when the earthquake action is small and the PGA is 0.15 g,the use of ECC material and high-strength steel has a small impact on the seismic performance of the structure;when the earthquake action is large and the PGA is 0.6g and 1.0g,the seismic performance of the structure is significantly improved by using ECC material and high-strength steel bars.Compared with the RC pier,the displacement of the pier top of the ECC-RC composite bridge decreases by 7.08% and 9.53%;the curvature of the pier bottom decreases by 68.46 %,87.1%.The displacement of the pier top of the high-strength reinforced ECC-RC composite bridge decreased by 16.62% and19.84%;the curvature of the pier bottom decreased by 85.47% and 93.55%.(4)Based on X-TRACT software,select three types of bridge pier damage indicators,consider material durability damage during service life,use Open Sees to perform non-linear time history analysis on bridge pier,and use IDA method to analyze the time-varying seismic vulnerability of three types of bridge pier.The research results show that with the extension of the earthquake intensity and the service period of the bridge,the seismic vulnerability of the pier under different damage conditions gradually increases.After using ECC and high-strength steel bars,the time-varying seismic vulnerability of the pier is significantly reduced.As the damage increases,the reduction probability of the bridge pier increases.With the increase of service life,the impact of high-performance materials on the surpassing probability of bridge piers is slightly reduced.