Research On Dynamic Bond Behavior Between Corroded Steel Bar And Concrete

Steel corrosion in concrete due to action of surroundings is a phenomenon commonly observed in engineering. It is important to study dynamic bond behavior of corroded steel bar and concrete, and to establish bond stress and relative slip of corroded bars and concrete for the nonlinear finite element analysis of the structures which have been served for several years. As a subtopic of the project of National Natural Science Foundation deal "parameters identification and system simulation assessment of RC structural with damage due to corrosion and cracking" , the research work was supported by National Natural Science Foundation of China (50079002). The major contents are mainly summarized as follows:Based on the results of accelerated electrochemical corrosion experiments of tensile specimens, the effect of electrochemical environment on corrosion velocity of rebar was discussed. Based on available experimental data, the empirical relationship between the average corrosion penetration depth and the maximum pit depth was obtained, and the empirical relationship between the surface crack width and the average corrosion penetration depth was established.Based on the result of dynamic tensile test, the rule of distribution of bond stress along the anchorage length with time was discussed. The rule of distribution of bond stress, residual strain of re-bar, and residual bond stress with corrosion were discussed. Bond behavior under different loading frequencies was preliminary studied. As a result, the conclusion that bond behavior is sensitive to loading rate is derived.The bond-anchorage mechanism of corroded reinforced concrete under dynamic loads was discussed. According to the test data the constitutive relationship of the bond stress and relative slip of corroded bars and concrete has been established, which can be used in the nonlinear finite element analysis of the structures which have been served for several years. The Full Method on Transient Dynamics was applied to analyze nonlinear dynamic behavior of tensile specimens. Besides, a finite element model of corroded reinforced concrete structure and some relevant parameters were discussed. Based on the result of test and nonlinear finite element dynamic analysis, some factors influencing dynamic bond behavior of corroded steel bar and concrete were discussed.Some existing models of steel corrosion in concrete were discussed .Meanwhile, a new model , based on an existing model , was presented, in which the effects of electrochemical corrosion velocity , large c/d and large diameter re-bar were considered by revising the coefficients. The probable harm of non-uniform corrosion in axial direction to structures and some factors related with corroded cracking expansion force were discussed based on the result of test and nonlinear finite element analysis. Keywords: dynamic behavior tensile test bond-slip anchorage length corroded steel bar...