Study On Corrosion Fatigue Performance Of Steel Bar Under Stray Current Of Rail Transit

In recent years,Chinese rail transportation has been developing rapidly and ranked first on operating mileage in the world.Rail transit infrastructure has higher requirements for safety and ride comfort than common facility structures.Modern electrified train widely uses rail as the power supply return line.With the insulation performance between rail and infrastructure degenerated,part of the power supply backflow in the form of stray current will leaks from the rail,flows into the reinforced concrete structure of rail bridges and accelerate the corrosion of steel bars.At the same time,long term train operation will cause fatigue damage to railway transportation infrastructure.The coupling action of corrosion fatigue and stray current causes damages and leads to serious reinforced concrete structure performance degradation and reduces service life significantly.In this paper,a experimental study on the steel bars' corrosion fatigue performance under stray current is presented,which provides basic theory and test method for the fatigue life prediction and performance evaluation of reinforced concrete structures.The damage law of static reinforcement in simulated concrete pore solution under single factor of stray current is studied.It is found that the corrosion of steel surface in the process of strong anodic polarization will change phase from "passive state” to “activated pitting".Within the strong anodic polarization range,the corrosion loss rate of rebar is closely related to the rebar potential.The stray current and fatigue load acting on steel bars are tested simultaneously.Therefore,the stray current corrosion fatigue standard sample is specially designed,which solves the problem that the steel bar is not easy to immerse in the electrolyte during the fatigue test,and the current on the sample can leak to the test machine.The damage law and fatigue life of reinforced concrete in simulated concrete pore solution are studied,and the "weakest section yield" phenomenon of high stray current level and high fatigue load has been found.Observe the cross-section of steel fatigue failure,evidence is found that fatigue and corrosion coupling lead to steel destruction.This paper gets the S-N curve under different stray current corrosion levels and E-N curve under different fatigue load levels.Furthermore,the E-S-N surface model which include two factor of stray current and fatigue load is presented.The theoretical and experimental basis for rebar's corrosion fatigue life prediction with stray current corrosion is established.