Seismic Behavior Of Reinforced Concrete Columns Corroded In Longitudinal Reinforcement

The corrosion of reinforcement is one of the main factors that cause the durability problem of RC structures.With the increase of service time,corrosion of steel reinforcement gradually degrade the seismic capacity of RC structures and increase their seismic vulnerability.For the actural RC structures,steel corrosion degrees varies in differnent location,and the influence mechanism of steel corrosion in different location on the mechanical propoties of RC components are also diffenent.It is necessary to evaluate the impact of corrosion location of steel reinforcement on the seismic performance of RC comonents.In this thesis,experimental study on the seismic performance of full-scale RC columns with corrosion in different longitudinal reinforcements was carried out.The main contents and results of this research are summarized as follows:1.11 full-scale reinforced concrete columns were designed and manufactured according to the current Chinese siesmi design code.The longitudinal reinforcement and stirrups in different locations of 9 specimens were corroded by electrochemical acceleration.All specimens were tested under low-cycle reversed loads.The influence of corrosion location,corrosion ratio and axial compressive ratio on the seismic performance of RC columns,i.e.,damage evolution,loading capacity,deformation capacity,strength degradation,stiffness degradation and energy dissipation capaciry,were compared and analyzed.2.According to the test results,it is found that for the spesicmens with longitudinal reinforcement corrosion in the sighe side perpendicular to the loading direction,the seismic behaviors such as failure mode,hysteretic curve,skeleton curve,strength degradation and ultimate deformation are asymmetric.With the increase of corrosion rate,all performance indexes are degraded,and the asymmetry is more obvious.At the beginning of loading,the negative strength degraded obviously,but with the increase of corrosion ratio,the corroded steel bars fractured at the end of loading,which made the positive strength degrade obviously.3.The influence of corrosion on the deformation capacity of the specimen is more significant than on the loading capacity.For the specimens reinforcement corroded in single side perpendicular to the loading direction and corrodion ratio of `15%,the reduction of the positive loading capacity is only 5% and the negative loading capacity is only 3%,while the positive ultimate displacement dropped up to 37% and negative ultimate displacement decreased up to 20%4.In the initial loading stage,there was little effect of steel corrosion on the hysteretic energy dessipation of specimens,while at the later loading state,the influence of steel corrosion on the energy dissipation capacity of the specimen was obvious,and the hysteretic energy dissipation decreased with the increase of corrosion at the same drift amplitude.5.The influence of stirrup corrosion on the seismic performanc of RC columns depends on the corrosion location.For the specimen with stirrup corrosion in the side perpendicular to the loading direction,corrosion of strrup induced the degradation of loading capacity,ultimate deformation and energy dissipation capacity.For the specimen with stirrup corrosion in the side parallel to the loading direction,the stirrup corrosion had little effect on the seismic performance of the specimen.6.The restoring force model of RC columns considering non-uniform corrosion ratio of longitudinal bars in different locations was proposed,which is in good agreement with the experimental results,and can be utilized in the nonlinear seismic response analysis of corroded RC columns.