Numerical Study On Cracking Behavior Of Concrete Beams Based On Extended Finite Element Method

Concrete is a kind of material which is widely used in civil engineering,due to its tensile strength is much smaller than the compressive strength,concrete under the action of small tensile stress will cause cracks,the development of cracks will seriously reduce the durability and safety of concrete structures,it is of great significance for the design and safety evaluation of concrete engineering to study the cracking characteristics of concrete.This article with ABAQUS software,the crack propagation of plain concrete and reinforced concrete three-point bending beam is analyzed based on the extended finite element method,The main contents of this paper are as follows:Firstly,the basic idea of the extended finite element method is introduced systematically,the basic idea of concrete cohesive fracture model is expounded and three kinds of commonly used softening constitutive relation of concrete is summarized,the basic principles of the XFEM module in ABAQUS software is summarized,three classic crack problems are calculated by using this module.The fracture energy Gf of concrete with size effect measured in the experiment is used as the basic data,the actual fracture energy GF of concrete is calculated by using bilinear model of local fracture energy,and GF as a parameter of concrete,the standard three point bending beam model of plain concrete is established,the fracture process of concrete beam with different seam height ratio,different beam width and different seam width ratio is analyzed numerically.Three-point bending beam model of concrete with different strength is established,the crack propagation process of three-point bending beam of high-strength concrete reinforced concrete and C35 and C70 grade concrete layered pouring is simulated and analyzed.Finally,the crack propagation of three point bending beam with double cracks is analyzed.The three-point bending beam model of reinforced concrete is established,the bond slip constitutive model the European standard CEB-FIP1990 is used,the bond slip relationship between steel bars and concrete is simulated by the double point spring element Spring2,a group of code that automatically adds spring units is written in Python,the feasibility of the model is verified by comparing with the experimental results.The crack propagation process of reinforced concrete with different beam width,different reinforcement ratio and different strength grades was simulated and analyzed,The main fracture parameters of all kinds of specimens are obtained,and the stress distribution of steel bars at critical moment.Finally,by reducing the mechanical properties of steel and bond slip performance,the cracking process of reinforced concrete beams with different degree of corrosion of steel bars was simulated and analyzed.Considering the influence of reinforced concrete beams strengthened with steel plate after two times of stress,the crack width is calculated in the following two stages,in the first stage,the calculation method of concrete structure design code is adopted.In the second stage,based on the theory of bond slip,the maximum crack width of reinforced concrete beams is deduced.