Fractal Research On Cracks Evolution Rule Of Reinforced Concrete Beams With Different Aggregate Sizes

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.The article made three reinforced concrete beams with the different aggregate sizes experimental study, analyzed that the aggregate sizes have effects to the crack with the developing process and the dehiscence pattern of reinforced concrete beam under the centralism load, mainly discussed that different aggregate sizes have effect to cracking moment,yield moment and ultimate bending moment of reinforced concrete beam,the conlusion gave that different aggregate sizes have effect to load—midspan deflection relationship and load—steel strain relationship of reinforced concrete beam.At the same time, the fractal geometry theory is used to analyse the sample in the crack appearance, the growth as well as the evolved distribution characteristic with the fractal geometry theory. The result indicated that:1.Under load of reinforced concrete beams with the different aggregate sizes the self-similarity in the crack appearance,the growth as well as the evolved distribution characteristic is appeared. Fractal geometry theroy can be used to describe the state of cracking damage under the influence of various stresses.2.The crack distribution is non-uniform under the destruction condition of reinforced concrete beam with the small particle aggregate size, then its extent of damage is the biggest.3.The surface cracking expansion way forms with fractal dimension distributes are between 1.10~1.40 of reinforced concrete beam with the different aggregate sizes, So the crack shape belongs to the striation distribution.4 . The same quantitative relationships have been established between the characteristic values( f , B ,ω) and the fractal dimension of surface cracks . The study shows that the fractal dimension of cracks grows gradual rapidly with that the accretion of the cracks breath.The fractal dimension of surface cracks can be taken as one evaluation index of the damage degree of reinforced concrete. Fractal geometry theory provide a new thought and method for study of the cracking and breakage of concrete structures. 5.A relationship has been established between reinforced concrete structural mechanics performance and the fractal dimension of surface cracks. The corresponding relations among the study show that with the increase of the concrete intensity , the fractal dimension of surface cracks reduces gradually.