Bending Behavior Of RC Beam Under The Action Of Steel Corrosion And Freeze-thaw Cycles

Steel corrosion and freeze-thaw cycle are the two most important factors affecting thedurability of reinforced concrete structures,which are the important content of the durabilitystudy in civil engineering field，has become worldwide issues and got common concern frommost of countries.Based on summarizing the achievements in scientific research home andabroad,this paper designed and completed RC beam bending behavior experiment research underthe action of steel corrosion and freeze-thaw cycles.The main contents of this paper is as follows：(1)Longitudinal reinforcement of the12beams were rapidly corroded throughelectrochemical rapid corrosion method,then bending behavior experiment has been carried outfor the corroded beams.We detailedly analized their bearing capacity,deflection,concretestrain,steel strain and crack development etc.The steel mechanical properties and bondperformance between steel and concrete,which affect the overall performance,are analyzed andsummarized.(2)Unsame freeze-thaw cycles test for12beams were carried out through laboratory rapidfreeze-thaw test.We detailedly compared the mass loss and test phenomenon between corrodedbeams and corroded beams， then analyzed mechanical property such as bearingcapacity,deflection.Concrete mechanical properties and bonding properties between steel andconcrete that affect the overall performance of the structure under the action of freeze-thaw cyclewere analyzed and summaried.(3)Combinating the results of steel corrosion test and rapid freeze-thaw test,we summarizedthe change rules in bearing capacity,concrete strain of mid-span section,deflection,steel strainand crack develop of the beams under the action of steel corrosion and rapid freeze-thawcycle.Based on existing flexural strength calculation formula under the action of steel corrosionor freeze-thaw cycle,through the comparison and analysis of the test data,we established theflexural strength calculation formula of the beams under the action of steel corrosion andfreeze-thaw cycle.We can reach the following conclusions based on the above work：(1)By theoretical derivation and test date comparison of the beam ultimate load analysisunder the action of steel corrosion test,freeze-thaw test,tests and two together,we found that thebearing capacity damage is not the simple sum of the steel corrosion effect and the freeze-thaweffect,but there exist coupling effect.(2)Through the test beam analysis of load-deflection curve,the deflection increased with thecorrosion rate increases significantly under the same load.And the deflection increasedsignificantly with the increasing number of freeze-thaw under the same load.The deflectionchange rule of the beams under the action of steel corrosion and freeze-thaw cycle is that,thedeflection of same corrosion rate reinforced concrete beams increased with the increase in thenumber of freeze-thaw cycles under the same loading conditions,and the deflection of the beamsunder the same freeze-thaw cycles increase with the corrosion rate increases. (3)By the analysis of the beam mid-span section concrete strain,we found that the beammid-span section maximal concrete strain of same corrosion rate reinforced concrete beamsincreased with the increase in the number of freeze-thaw cycles under the same loadingconditions,and that of the beams under the same freeze-thaw cycles first reduce and then increasewith the corrosion rate increases.(4)The mid-span steel strain of same corrosion rate reinforced concrete beams increase withthe increase in the number of freeze-thaw cycles under the same loading conditions,and that ofthe beams under the same freeze-thaw cycles increase with the corrosion rate increases.(5)Through the analysis of crack width in the loading process,it can be seen that the maincrack width of same corrosion rate reinforced concrete beams increase with the increase offreeze-thaw cycles under the same load,and that of the beams under the same freeze-thaw cycleschange slightly complex,the general trend is that the main crack width of corroded beams areslightly less than that of uncorroded beams.(6)In the freeze-thaw cycle process,the corrosive cracks number of the beam in90timesfreeze-thaw cycles is60%more than that of not corroded,and after freeze-thaw cycle90timesthe number of crack is stable.The corrosive crack width will develop with the increase offreeze-thaw cycles,and the crack width growth rate of the larger corroded beams is greater thanthat of the small corroded beams.