Research Of The Protection Effect Of The ICCP-SS System On Reinforced Concrete Hollow Columns

Reinforced concrete hollow columns have the advantages of large structural rigidity,good seismic performance,light weight,ability of reducing the seismic inertia force,saving materials,etc.,and are now widely used in reinforced concrete structures such as wire poles and bridge piers.However,in the coastal area,for reinforced concrete hollow columns,there are adverse effects such as seawater back-irrigation erosion and the use of sea sand(containing Cl~-)in some structures,which will cause serious damage to the structure.In this regard,traditional solutions include cathodic protection(Impressed Current Cathodic Protection,ICCP)and structural reinforcement(Structural Strengthening,SS),but these two methods have their own limitations.In recent years,some scholars have proposed a dual protection system called ICCP-SS,which combines the advantages of cathodic protection and structural reinforcement,and complements their respective limitations.Existing research has proved that the ICCP-SS system has a good protection effect on simple supported beams,continuous beams and reinforced concrete solid columns,but its protection effect on reinforced concrete hollow columns needs further research.Therefore,this article focuses on the dual protection of the ICCP-SS system for reinforced concrete hollow columns to investigate the protection effect of the system on hollow columns.The main contents of the research include:(1)Axial compression experiments of long/short hollow columns with different hollow ratios were conducted to study the confinement effect of FRCM(Fabric Reinforced Cementitious Matrix)which played a role of structure strengthening in the ICCP-SS system on long/short columns with different hollow ratios.The experimental results show that,compared with unconfined specimens,the FRCM confined specimens have a certain degree improvement in bearing capacity,ultimate strain and compressive stiffness;the improvement of hollow ratio and slenderness ratio will weaken the mechanical performance of unconfined specimens,and FRCM confinement has a good mitigating effect on this weakening.In this experiment,the basic design model of FRP confined specimens was revised according to the relevant characteristics of the specimens.The model was used for ultimate strength calculation and stress-strain curve simulation.The results show that this model can predict well the mechanical properties of hollow specimens.(2)Axial compression experiments on hollow columns with different corrosion rates were conducted to study the effect of FRCM,which plays a role of structural reinforcement in the ICCP-SS system on hollow columns with different corrosion rates.The experimental results show that FRCM confinement has a positive effect on the bearing capacity,ultimate strain and compressive stiffness of corroded specimens,but this effect will be relatively weakened with the increase of the corrosion ratio;the corrosion of rebars will weaken the mechanical properties of unconfined specimens,and FRCM confinement has a mitigating effect on this weakening.In this chapter,the model of Chapter 2 is modified by introducing the coefficient of corrosion ratio.This model predicts accurately the ultimate bearing capacity and the stress-strain curve of corroded specimens.(3)An experiment to measure the distribution of chloride ions in specimens under the influence of ICCP to study the effect of ICCP-SS system on the migration and distribution of chloride ions in concrete under the condition of internal erosion of hollow columns.The experimental results show that:the effect of ICCP has a significant protection effect on the outside of the rebar and a adverse effect on the inside of the rebar,but this effect is relatively small;for left and right sides of the rebar,ICCP also has a certain protection effect,which is relatively obvious near the rebar.In addition,through theoretical analysis,and comparing the experimental results of this paper with the experimental results of similar working conditions,the electric field distribution of this experiment is predicted.