An Overall Process Analysis Of Bonding Failure Load For Corroded Reinforced Concrete Beams

In the hundred years history of the development of concrete structure,the durability problem has long been recognized,but because of the complexity of the problem and the lack of testing of advanced technology and other reasons,since people know on the durability of reinforced concrete is far from fully and thoroughly.Therefore,the bonding performance of reinforced concrete corrosion under the environment of further research is very necessary.In this paper,shortcomings of previous studies on the mechanical properties of corroded reinforced concrete structure based on the method by combining experimental research and theoretical analysis,the research work carried out the following:(1)In this paper to examine the effects of corrosion on the bonding behavior of reinforced concrete beams,tests of 6 reinforced concrete beams in which there is no anchorage length of tensile longitudinal reinforcements at support were conducted.One of the beams was a contrast one without chloride immersion,and the other five beams were immersed in chloride solution and their corrosion tests were accelerated by imposing silicon controlled rectifier DC according to their respective scheduled prescribed corrosion time.The prescribed corrosion time was determined in terms of the corrosion volume of reinforcement and the Faraday law.Corrosive cracks at the bottom of corroded test beam were first examined to relate the corrosion volume to the crack width.Thereafter,four-point bending test for each corroded beam was conducted to study the effects of corrosion damage of reinforcement on the load deformation of test beams.The crack propagation paths at both sides of beam during bending test and final fracture pattern of the post-test beam were observed.The history relation curves between load and deflection,load and cross-sectional concrete /reinforcement strain at mid-span,as well as the bonding stress of reinforcement and its slippage were graphed.That how to affect the bonding properties of reinforcement by corrosion damage was discussed.It was shown by the experimental results that the corrosive cracks occurred around the tensioned reinforcements at the bottom of corroded test beams and the greater corrosion rate,the wider the cracks;during the initial stage of load,strains at mid-span of all test beams changed linearly along sectional height,and the section still kept plane,however,with increasing the load,strains at the mid-span presented nonlinearly along sectional height,but the section did not keep plane.With the increase of corrosion rate,the neutral axis kept rising;during the process of load,the load induced cracks spread from the mid-span to the beam supporters at its both sides or from the beam bottom to the beam top.As the load grew further,the bond was teared along the direction of longitudinalreinforcements and thus caused debonding failure of the beam and finally slippage;during the initial stage of corrosion,bearing capacity due to the debonding failure for the test beam went up but went down with the increase of corrosion rate.When the corrosion rate reached a certain value,the bearing capacity was less than that of the uncorroded test beam and then decreased further as the corrosion rate grew.(2)The methods and principles of FEM analysis of RC structures with ANSYS program were fully introdueed.With a numerieal simulation example of poll-out tests and RC beams,the methods and skills of establishing the FEM model,solving of the FEM model,solution results analysis and so on were fully introdueed.With analysis of the simulation results,it was proved that the ANSYS program could be expediently adopted to simulate RC strutcures,and had advantage esatestablishing FEM model,results analysis as well as good aceuracy.(3)In conjunction with the impacts of corrosion damage on the bonding strength and reinforcement performance by present tests,a correlative numerical model of commercial Ansys finite element software was established to analyze the corroded test beams,which gave numerical solutions that agreed well with the present test results.The model was used to simulate an overall process analysis of bonding failure load for corroded reinforced beams,presenting the slippage distribution,crack propagation,Von Mises stress nephogram,concrete strain and stress distribution and deformation variation of the corroded beams in the overall process.The present results provide a new frame of the durability analysis of corroded RC beams.