Study On Numerical Model Of Concrete Nonlinear Fracture Based On X-SBFEM

In engineering field,the problem of concrete structure fracture is always an important factor of the safety of engineering structure.Especially for the dam,the crack propagation is often fatal to the dam safety.The linear elastic fracture mechanics and nonlinear fracture mechanics are the two mature directions of fracture analysis.While,the linear elastic fracture analysis method ignores the influence of fracture process zone.This simplification is largely a loss of objectivity.From the perspective of discrete fracture,nonlinear analysis of crack to solve cohesive traction of the fracture process zone is of great significance to improve the accuracy of the fracture process and the practical engineering design.From the perspective of nonlinear fracture mechanics model,it is an effective scheme to insert the cohesive interpolation element and introduce the shadow domain.However,the recently developed linear asymptotic superposition method can reduce the computational complexity to the former.In this method,the nonlinear crack propagation problem is simplified to linear elastic problem.Simulation of the nonlinear behavior of the fracture process zone is by using the super element based on the scaled boundary finite element method to solving the non-homogeneous differential equation.X-SBFEM has the advantages of two methods of XFEM and SBFEM,and to a large extent abandoned the shortcomings of both.Simulating the crack tip domain uses the scaled boundary finite element method.By means of its semi-analytical solution,it has obvious advantages in solving the infinite domain problem and the singularity of crack tip.When the center of gravity is placed at the crack tip,the side-face force can be applied to the crack face at the crack tip.However,if it is used to simulate the crack tip,it is necessary to know the asymptotic solution of the analytical form in advance to construct the complex enrichment function.The special numerical integration technique is often needed to form the element stiffness matrix.The extended finite element method is used to simulate the middle crack,and the advantage of no remeshing of the extended finite element method is better than that of the scaled boundary finite element method.In addition,the two methods can be connected within the framework of the finite element method.In this paper,we propose a model based on X-SBFEM and linear incremental iteration method and level set model to simulate the process of quasi brittle material(concrete)crack.The cohesive traction is exerted in the form of SBFEM Side-face traction.Three points bending beam with single edge notch and four points notched shear beam is numerically used to simulate the influence of energy dissipation in FPZ.The accuracy and application results of the method are verified.Finally,the method is extended to the model of typical concrete gravity dam.Then,the necessity of considering the fracture process zone and the effectiveness of the method are discussed.