| Corroded reinforcement is one of the important factors affecting the durability of reinforcement concrete structures, the effects of corroded steel bars on bond slip behavior between steel bar and concrete are very significant. Bond between steel bar and concrete is a complex interaction and stress between steel bar and concrete is transferred by bonding. The performance of concrete structures will be reduced with the degradation of bond. Therefore, the study of bond slip behavior between corroded steel bars and concrete and different stage damage detection of corroded reinforced concrete for assessing the performance of corroded reinforced concrete structures that has important theoretical and practical significance. The suitability and sensitivity of nonlinear ultrasonic technical in the detection of corroded reinforced concrete were analyzed, and influence of stirrup spacing s, the protective layer thickness c and steel corrosion level ω on the bond slip behavior and nonlinear ultrasonic characteristic parameters throught corroded reinforced concrete pull-out test and nonlinear ultrasonic nondestructive testinginvestigated. Based on test result, corroded reinforced concrete bond-slip constitutive model was established, The experimental results and numerical simulation were compared and verified by the ANSYS finite element model. The main reseach contents are as follows:(1) The effects of the steel corrosion level, the protective layer thickness and spacing of stirrups on the ultimate bond strength were investigated and empirical formulas of the ultimate bond strength were established by pull tests. Based on the Standardized and the experimental data of this paper, bond-slip constitutive relationgship model of cnsidering different corrosion rates, the protective layer thick Ness and spacing of stirrups was established. Through the strain gauges were attached to the inside, the relationships of reinforced strain and bond strength with the changes of steel anchor position were studied and the functions of anchoring position were established.(2) Based on bond-slip constitutive relationgship model of this paper, Threedimensional solid model of pull tests were established by Beam188 steel element,Solid65 concrete element and Combin39 nonlinear spring element, and finite Element, Analysis was carried out by ANSYS to reinforced concrete whole process of bond failure. Corrosion rates, the protective layer thickness and spacing of stirrups were set as the parameter to study their effects on the bond behavior. Compasion were also made with the experimental results and the calculated results.(3) Applicability and sensitivity of nonlinear ultrasonic technology on concrete damage detection were analyzed and verified, through damage detection of samples before corrosion,after corrosion and the whole process of loading different by nonlinear ultrasonic technology. The variation of the steel corrosion level, the protective layer thickness and spacing of stirrups on nonlinear ultrasonic characteristic parameters were investigated and empirical formulas between ultimate bond strength and corrosion damage variation were established. |
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