Bond Properties And Bearing Capacity Of Corroded Reinforced Concrete Member

The durability of concrete structure is one of the problems widely concerned incivil engineering. Rebar corrosion often appears during normal use due to various kindsof reasons. Rebar corrosion not only makes reinforced effective section area decreaseand reinforced performance alteration, but also leads to the bond properties degradationbetween steel and concrete, thereby affects gravely bearing capacity of structuralmembers. There is significant theoretical meaning and practical value for estimatingaccurately durability of existing structure member in analyzing bond properties betweencorroded rebar and concrete and in establishing calculation method of bearing capacityof flexural member.Combined with theoretic analysis and experimental research, bond propertiesbetween corroded rebar and concrete are analyzed intensively. On this basis calculationmethod of bearing capacity of flexural member is established considering crackingforms of covers in different situation (midside or corner). Following respects are mainlyincluded in the research:Through beam bond test methods and embedded strain gauge means in rebar36corroded beam test members are tested. Influence on bond properties induced bycorrosion rate, concrete strength, diameter and cover thickness are analyzed. Theformulas of ultimate bond strength and bond-slip constitutive relation between corrodedrebar and concrete are established. Experiments results are shown: the more corrosionratio is or the less concrete strength is, the less required load of free end initiate slip is,the less slip of free end and loading end, mid-span deflection are, and at the same timethe more rebar strain in free end is and the less rebar strain in loading end is, the fasterbond stress transmit and the milder bond stress distribution is.Bearing capacity tests of4corroded reinforced concrete flexural members areconducted. Influence on load-deflection curve, strain distribution of midspan concreteand load-free end slip curve induced by corrosion ratio of rebar are analyzed.Discrepancy of strain distribution between corner rebar and midside rebar areresearched. Comparation of concrete strain between pure bending segment andbending-shear segment are made. Differences of ultimate load of flexural member with different corrosion ratio are proposed. The results are shown that ultimate load andstiffness of flexural member will degrade along with amplify of corrosion ratio of rebar,and rebar strain of in identical location will lower under the same load, and that strain ofmidside rebar is more5%than the same of corner rebar, and that strain reduce extend ofcorner rebar is more than the same of midside rebar when corrosion ratio increases, andthat concrete strain of pure bending segment increase more faster than that ofbending-shear segment. The last result is that concrete strain distribution of midspanalong beam height meets plane section assumption.Analysis model of corroded reinforced concrete beam test and flexural membersadopting finite element software are established separately. Bearing capacity ofcorroded reinforced concrete flexural members, load-midspan deflection relation, andstrain distribution of midside and corner rebar are researched. Strain imcompatibilitycoefficients between rebar and concrete strain based on corrosion ratio are analyzed.Combined with the bearing capacity experiment and numerical analysis ofcorroded reinforced concrete member, calculation method of bearing capacity ofcorroded reinforced concrete flexural members considering cracking forms discrepancyof covers in different situation (midside or corner) is established. Bearing capacity ofcorroded reinforced concrete flexural members based on corrosion ratio is analyzed.