| The complex development of the cracks on the surface of concrete component is a great challenge of many researchers from engineering mechanics and materials science to devote them to it. So it is of great importance and significance to investigate the development of the cracks in order to estimate the safety of the concrete component.It is most intuition of the cracks development to take on the damage of the concrete. The development of the cracks will be influence the mechanical capability of the different structure directly, and determine the safety, durability, applicability of the structure. It is also to be one of the measurements of the structure's lifetime. The development of the cracks can be taken as the sign of the destruction of the material. It is of great value to estimate the structure's degree of the failure base on the development of the cracks.This article is aimed at the more profound mechanism, and then provides credible theory to estimate the damage condition of the reinforced concrete component with fractal theory based on the investigation of the former. The academic and experimental investigation following three question are to be investigated with the application of fractal theory: the relationship between the cracks' development on the reinforced concrete component, the numerical simulation of the four-point bending beam test which aimed at the fractal description of the cracks, and the influence of the reinforcing steel bar's corrosive degree developed with the development of the crakes on the surface of the reinforced concrete component. And the thesis has achieved certain results:(1)Through four-point reinforced concrete's bending beam experiment, the thesis adopts fractal theory to study the orderliness of the cracks' development. It makes clear that:①The cracks of damaged reinforced concrete is with self-similar in statistics until middle-late stage.②The characteristic values(P, f ,B) of the surface cracks have quantitativerelationships with fractal dimension. The fractal dimension of surface cracks can be taking as one evaluation index of the damage degree of reinforced concrete. The relationships of the above index are just as the following:(2) Use the numerical simulation RFPA-2D to simulate the four-point bending reinforced concrete beam experiment. The orderliness of the cracks' development and the self-similar in statistics corresponding the load displacement curve's descending shape is studied. It makes clear that:①When the component is in sight of destroy, the surface cracks is of distinct self-similar in statistics. The fractal dimension of cracks grows gradual rapidly. It is mainly because the accretion of the cracks' breath.(2) The stress of the component redistributed with load ,and the fractal dimension is also largen.(3) Through the experiment of the reinforced concrete with force cracks, use fractal theory, infection of the erode degree of the reinforcing steel bar by cracks o n the reinforced concrete's surface is studied. This thesis probe into the feasibility of fractal theory on estimate of reinforced concrete's damnification. It makes clear that:①With a experiment of reinforcing steel bar in the reinforced concrete, witch is be to loaded with cracks, the feasibility of the adoption with fractal theory on surface cracks is confirmed.(2) The characteristic values( B ) of the surface cracks have quantitative relationships with fractal dimension under textual condition:(3) The danger of corrosion is increasing with the increase of fractal dimension. The change rate of the danger of corrosion is increasing with the increase of fractal dimension in the late of the experiment.④As the fractal dimension increasing, the corrosion of reinforcing steel bar become more danger, so fractal dimension of surface cracks can be take as a evaluation index of the damage degree of reinforced concrete. |
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