Quasi-static Test And Seismic Resilience Analysis Of Double Thin-walled Rocking Bridge Pier With Energy Dissipation Beams

Double thin-walled piers are often used in continuous rigid frame bridges with high piers,which have good bearing capacity and construction convenience.However,double thin-walled piers are easy to form plastic hinges under earthquake action,and the damage is difficult to be effectively repaired.Therefore,the seismic performance of the structure,especially the post-earthquake repairability,needs to be further improved.Previous studies have shown that prestressed rocking piers can effectively reduce the damage and residual deformation of piers under earthquake.However,the conventional self-centering structure still has the problems of insufficient energy dissipation capacity and poor repairability,which need to be further studied.Based on the self-centering mechanism of rocking piers,this thesis studies a more resilient rocking double-column pier structure through quasi-static test and numerical simulation analysis,and provides a basis for practical engineering applications.The main research work contents of this thesis are as follows:(1)This thesis summarizes the research work and achievements of domestic and foreign scholars on the design improvement method,related test,finite element analysis and practical application of self-centering rocking pier,understands the working mechanism and stress characteristics of self-centering rocking pier,and puts forward a new structure form of rocking pier with more seismic resilience.(2)Based on a typical double-column pier in a highway bridge,a double thinwalled rocking pier and a double thin-walled consolidated pier with energy dissipation beams were designed and manufactured.The two piers were of the same size and reinforcement for comparison.The failure phenomenon and damage evolution process of pier specimens were compared by quasi-static test.According to the performance indexes such as hysteresis curve,energy dissipation capacity and residual deformation obtained from the data collected in the test,the seismic performance of the two specimens was evaluated.When loading to failure,the concrete in the plastic hinge area of the double thin-walled consolidated pier falls off and the longitudinal reinforcement breaks,while the damage of the double thin-walled rocking pier is concentrated on the energy dissipation beam.The hysteresis curve of the double thinwalled consolidated pier is full,while the curve of the double thin-walled rocking pier is flag-shaped.The total energy consumption reaches 77.2 % of the double thin-walled consolidated pier,and the maximum residual displacement is 44.2 % of the double thinwalled consolidated pier,which reflects good self-centering characteristics.The quasistatic test results show that the double thin-walled rocking pier has good energy dissipation capacity and self-centering ability.(3)The post-earthquake repairability of double thin-walled rocking piers is studied.In the quasi-static test,the energy dissipation beam of the rocking pier was replaced to achieve rapid repair.The replacement time was within 2 hours and the maximum residual rotation angle of the pier column was controlled at 0.004 rad.The quasi-static loading was carried out again to evaluate the functional recovery after repair.The results showed that the energy dissipation capacity of the repaired specimen was 94.4%,and the maximum residual displacement increased by 10.1%,which proved that the structure had good repairability.(4)Based on the principle of structural mechanics,the balance formula of selfcentering mechanism of double thin-walled rocking pier in elastic stage and rocking stage during horizontal loading is deduced,and the correctness of the balance formula is verified by experimental results.According to the composition relationship of the flag-shaped hysteresis model,the hysteresis characteristic model of the double thinwalled rocking pier based on the superposition relationship of the stiffness contribution of the self-centering member and the energy-consuming member is solved with an example.The mechanical law obtained from the model shows that increasing the yield shear force and stiffness of the beam and reducing the prestressed stiffness will lead to an increase in the residual displacement of the structure.The energy dissipation capacity of the structure will increase with the increase of the shear capacity of the beam.This law provides a reference for the seismic toughness design of the selfcentering structure in terms of theoretical formulas.(5)The numerical modeling method of double thin-walled rocking pier specimens through Open Sees software is proposed.The correctness of the numerical model is proved by comparing with the experimental hysteresis results and the theoretical formula calculation results.The parameter analysis of the self-centering member and the energy dissipation member of the model is carried out.The results show that increasing the initial pretension of the pier can improve the bearing capacity of the structure,reduce the residual deformation,and have no effect on the energy dissipation.Increasing the shear yield capacity of the beam can enhance the energy dissipation capacity and lateral bearing capacity of the structure,and the residual displacement will also increase.The self-centering coefficient is introduced to evaluate the influence of the combined action of prestress and yield shear capacity of beams on the seismic performance of piers.The results show that the value of 1-1.5 is the optimal coefficient range for coordinating self-centering and residual deformation.