Fracture Fractal And Bearing Capacity Evaluation Of Small And Medium Span Concrete Beam Bridge

With the rapid development of concrete materials,more and more engineering structures take concrete as the main material,but the damage cracks will inevitably appear in the use of concrete structures.At present,most of the research is based on the actual damage to the structure for fractal analysis,while the fractal analysis of finite element simulation damage cracks is almost No.Therefore,it is necessary to carry out damage simulation and fractal analysis for concrete structures with damage cracks.By using the finite element method to simulate the damage crack,the relationship between the fractal dimension of the simulated damage crack and the actual damage crack and the mechanical properties of the structure is studied.In this paper,a fractal analysis method based on the plastic damage theory is proposed to simulate the damage cracks.Taking three structures with different stress states as examples,the damage and fractal analysis is carried out to explore the relationship between the fractal dimension of the damage cracks simulated by finite element method and the mechanical properties of the structure.The accuracy of the research results is further verified by combining the analysis results with the engineering practice.The main work and achievements of this paper are as follows:(1)The research of damage theory and fractal theory at home and abroad is briefly described and summarized,which provides theoretical reference for the research of this paper.(2)It is proved that it is feasible to calculate fractal dimension with MATLAB and fraclab,and the maximum error is less than 10%.The relationship between the fracture fractal dimension and the mechanical properties of beams without web reinforcement is studied.This paper briefly analyzes the causes of common cracks in several concrete bridges,and makes fractal calculation for the cracks in bridges.(3)Taking the crack damage of bending beam,shear beam and tension column as an example,the calculation method of the fractal dimension of the damage crack simulated by finite element method is mainly introduced.It is found that the fractal dimension of the damage crack simulated by finite element method is larger than the fractal dimension of the actual damage crack under the same load.The fractal calculation of simulated damage cracks with different mesh sizes is carried out,and the influence of mesh sizes on the fractal dimension of simulated damage cracks is explored.(4)It is found that the fractal dimension of simulated damage crack is linear with the fractal dimension of actual damage crack and external load,and it is quadratic function with deflection,and the relationship between them is given.(5)Combined with the engineering example,the fractal analysis of the bridge crack damage is carried out,and then the relationship between the fractal dimension of the simulated damage crack and the mechanical properties of the bridge is further explored to verify the accuracy of the previous research results.