| An understanding of bonding performance between steel bar and concrete is the prerequisite for research of concrete's ultimate bearing capacity under high temperature, residual bearing capacity after high temperature and the structural member's repair and strenthening. Based on Hunan province science and technology key item, the entire process analysis and simulation research about reinforced concrete frame structure under fire (06FJ2002)", the paper mainly studies damage mechanism and influencing factors on the bonding performance between steel bar and concrete under and after high temperature. The main contents are as follows:(1) Based on the grey correlation mathematics model of the grey system theory, the previous test data of bond-slip is analyzed quantitatively, and then the main influencing factors on bonding performance are researched. The results indicate that the subsequent key influencing factors are concrete strength grade, diameter size of steel bar, protective coating thickness of the concrete and anchorage length. Because the high temperature affects the concrete strength significantly, it also affects bonding performance between steel bar and concrete under and after high temperature. All these factors provide a basis for key influencing factors of bond-slip test under and after high temperature.(2) Damage mechanism is employed to analyze deterioration situation of the bond-slip performance between steel bar and concrete under and after high temperature, then damage model of the reinforced concrete's interface is established. Based on the previous analysis, damage evolution equations and damage constitutive equations are deduced. Interface damage mechanics and damage evolution mechanism are analyzed and interface damage development is compared under and after different temperature.(3) The finite element software (ANSYS) is applied to analyze and simulate the pull test model. The simulation data is compared with test data and validity of the analysis method is proven. Concrete strength and steel bar diameter are analyzed, these are two main influencing factors of bonding performance after high temperature. The analysis indicates that under the same temperature when bond-slip is small the concrete strength's influence on the bond performance is not significant. The concrete strength's influence on the bond performance becomes significant with slip increasing. However concrete strength's influence on ultimate bonding stress decreases and its influence on ultimate displacement increases as the temperature rises. Steel bar diameter's influence on bonding performance between steel bar and concrete under high temperature is similar to concrete strength's.The corresponding conclusions in the paper about the bonding performance under and after high temperature have significance for structural member's fire-resistance design and strengthening after fire. |
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