Study On Structural Behavior Of Corroded Steel Fiber Reinforced Concrete Bridges

Steel fiber reinforced concrete(SFRC)is a new type of composite material,which is widely used in various projects because of its excellent mechanical properties.However,in recent years,the problem of steel fiber corrosion has gradually emerged,which has seriously affected the structural safety and service life.In order to understand the mechanical properties and time-varying law of steel fiber reinforced concrete(SFRC)after corrosion,and to solve the problem of the influence of SFRC corrosion on the bearing capacity of steel fiber reinforced concrete bridges,this paper carries out theoretical and experimental studies on the strength changes of SFRC with different corrosion degrees.The main research contents and results are as follows.(1)The mechanical properties of steel fiber reinforced concrete(SFRC)with different corrosion modes were tested,and the variation rules of compressive strength,tensile strength and elastic modulus of SFRC with different corrosion degrees were obtained.The results of the first test,that is,first corrosion and then pouring,show that the compressive strength and tensile strength of steel fiber reinforced concrete decrease with the increase of steel fiber corrosion rate,and the second test,that is,first pouring and then rusting,shows that the compressive strength and tensile strength of steel fiber reinforced concrete increase with the increase of dry-wet cycle days,and the overall trend is first rising and then decreasing.(2)In order to realize the random distribution of steel fibers,the command stream of MATLAB is compiled.Then the finite element model of steel fiber reinforced concrete with different corrosion degree is established by using finite element analysis software ADINA.The bond strength between steel fibers and concrete with different corrosion rate is simulated by spring element method.The compressive strength and tensile strength of steel fiber reinforced concrete are tested and simulated.The simulation results are in good agreement with the experimental results,which verifies the reliability of the simulation method.Through the simulation analysis of steel fiber reinforced concrete flexural toughness test,it is found that when the steel fiber corrosion rate is 3.418%,the flexural tensile strength and flexural toughness of notched beams decrease by 10.1%.When the steel fiber corrosion rate is 6.61%,the flexural tensile strength and flexural toughness of notched beams decrease by 10.1%.It is 15.4% lower.(3)Fitting the test results,the influence equations of steel fiber corrosion rate and dry-wet cycle days on the strength of steel fiber reinforced concrete are obtained respectively;the finite element simulation results are analyzed,considering the influence of two parameters of concrete matrix strength and steel fiber corrosion rate,the compressive strength,tensile strength,flexural strength and flexural toughness of the corroded steel fiber reinforced concrete are established.Prediction equation;Considering the chloride ion erosion,the chloride ion concentration distribution in concrete at different time was predicted,and the influence of steel fiber corrosion on the evaluation of bearing capacity was determined as the change of material strength.(4)Based on the project of No.3 Bridge in Luohuangcheng District and assuming the concentration of chloride ion in its environment,the bearing capacity of the bridge after 25 years is predicted and analyzed.According to the forecasting analysis and comparison,the bearing capacity of the relying project after 25 years is 33.2% lower than that of the ordinary concrete beam and 42.4% lower than that of the steel fiber reinforced concrete beam.Therefore,the bearing capacity of the corroded steel fiber reinforced concrete bridge can be evaluated by referring to the strength prediction formula in this paper.