Fractal Characterization of Flexural Performance and Crack Propagation of ECC-Concrete Composite Girder
This study focuses on the flexural performance and influential parameters of the ECC(Engineering Cementitious Composites)and concrete composite girder,as well as the way to qualitatively characterize the crack propagation conditions.11 ECC-concrete composite girder specimens(composite specimens for short)with different parameters of material strength grade,reinforcement ratio,ECC layer thickness,PVA fiber volume as well as 3 concrete girder specimens(concrete specimens for short)with different concrete strength grade,were prepared for four-point flexural test,to study the load bearing behaviors,ductility and crack propagation.Based on the fractal theory and image processing technology,the fractal dimension was employed to characterize the crack propagation under different values of parameters.It is shown that the composite specimens exhibit better ultimate load bearing capacity and cracking resistant ability than the concrete specimens with same material strength and amount of reinforcement.Higher material strength leads to higher load bearing capacity and ductility of the specimens.When the volume fraction of PVA fibers is 2.0%,the overall distribution of cracks is more uniform.The surface cracks in composite specimens calculated by fractal dimension reveal self-similarity.During the loading process,the fractal dimension of composite specimens is smaller than that of ordinary concrete specimens,which is consistent with the experimental results.The fractal dimension of surface cracks decreases within a certain range with the increase of material strength grade,reinforcement ratio,ECC layer thickness,and PVA fiber volume fraction.The fractal dimension of cracks obtained by combined utilization of fractal theory and digital image technology can serve as a qualitative characterization index for crack distribution and the degree of bending damage of composite specimens.
NETL
NSTL
万方数据
