Prestressed CFRP Reinforced RC Columns Seismic Performance Study

Our country is prone to earthquakes.As bridges serve as the lifeline of transportation,it is of great significance to strengthen bridge piers for seismic resistance.Traditional reinforcement methods have some drawbacks,such as increasing the crosssectional area.After reinforcement,the dimensions of the components significantly increase,reducing the available space within the structure.Another method is external steel reinforcement,but steel is susceptible to corrosion and detachment.Fiber reinforcement is considered one of the most suitable materials for reinforcing reinforced concrete(RC)due to the lightweight and high strength of fiber-reinforced polymers(FRP).Currently,research on parameters such as axial compression ratio,fiber prestress level,number of layers,and wrapping methods in the seismic performance of FRP-strengthened RC columns is still not comprehensive.Therefore,this study combines experimental and finite element analysis to explore the influence of axial compression ratio,prestress level,number of carbon fiber-reinforced polymer(CFRP)layers,and wrapping methods on the seismic performance of prestressed CFRPstrengthened RC columns.The following work was conducted.(1)This article conducted quasi-static load tests on RC columns using anchors developed by our research team.It analyzed the bearing capacity,hysteresis curve,ductility,skeleton curve,and strain development of each specimen.The influence of axial compression ratio(0.3,0.5,0.7),prestress level(0.3,0.4),fiber layer number(2layers,4 layers),and wrapping method(full wrapping,intermittent wrapping)on the seismic performance of pre-stressed CFRP-strengthened RC columns was studied.However,due to the limitations of the experimental conditions,the data of the test columns are limited,and the applicability of the analysis results is low.Therefore,Opensees was used to simulate and supplement the experiments in order to improve the applicability of the results.(2)Finite element analysis of the experiments was conducted using Opensees,and the accuracy of the model was verified from three perspectives: hysteretic curve,skeleton curve,and characteristic points.The reinforced columns under axial compression ratios of 0.3 and 0.5,prestress level of 0.4,full wrapping with fiber fabric,and double-layer wrapping with fiber fabric were simulated and supplemented in the experiments.Combined with the simulation and experimental results,the seismic performance of different specimens with varying axial compression ratios,prestress level,fiber fabric layers,and wrapping methods was compared and analyzed.The results indicate that the axial compression ratio affects the initial stiffness,lateral bearing capacity,and deformation capacity of the specimens.Increasing the axial compression ratio reduces the ductility of the specimens,which is unfavorable for their seismic performance.The pre-stress force had limited improvement in the seismic performance of the reinforced specimen.The number of fiber cloth layers improved the seismic performance of the specimen more obviously than the pre-application force.Full wrapping reinforcement significantly enhances the ultimate displacement and energy dissipation capacity of the specimens,resulting in a better improvement in seismic performance.(3)A comparison was made on the seismic performance of specimens with the same axial compression ratio,and the optimal reinforcement method of prestressed carbon fiber fabric under axial compression ratios of 0.3,0.5,and 0.7 was discussed.It was found that under different axial compression ratios,the seismic performance of specimens reinforced with 0.4 prestress level and 4-layer full wrapping of fabric was optimal.Compared with the discontinuous wrapping method,under the full wrapping method,increasing the prestressing force had a greater impact on the improvement of the specimens’ lateral bearing capacity,and increasing the number of layers had a better effect on improving the specimens’ deformation capacity.In order to better apply the research results to practical engineering,considering the economic effects of engineering applications,recommended reinforcement methods were provided for axial compression ratios of 0.3,0.5,and 0.7.