A PARAMETRIC STUDY OF MIXED-MODE FRACTURE PROPAGATION IN CONCRETE USING XFEM
Renan Marks de Oliveira Pereira1; Eleazar Cristian Mejia Sanchez2; Deane Roehl1
1 Tecgraf Institute and Department of Civil Engineering, PUC-Rio; 2 Tecgraf Institute, PUC-Rio
doi:10.20906/CPS/CILAMCE2017-0345
Resumo
Cracking is a fundamental characteristic of the behavior of quasi-brittle materials such as ceramic, rock and concrete. Certainly, cracking should be taken in consideration while predicting ultimate-load capacity for concrete-structures. In many studies, it has been proven that fracture mechanics is a good alternative for predicting concrete failure. However, the numerical modelling of crack propagation in finite element simulations is a cumbersome task due to mesh dependency to conform with the geometry of the fracture. The Extended Finite Element Method (XFEM) is a technique which combines the FEM with enrichment functions to represent discontinuities in the displacement field. Therefore, the XFEM allied to cohesive crack growth is an efficient choice for modelling fractures with a non-predefined path. In this work, a parametric study is presented for modelling a four-point bending test by using XFEM under mixed-mode fracture. There is a complexity for numerical models to represent mixed-mode fracture due to tensile-softening behavior normal to the fracture (mode I) and the shear retention parallel to the fracture (mode II). Different parameters were taken into account such as analysis type, solution control techniques, mesh refinement, damage model, fracture initiation and propagation criteria. The study was carried out using the XFEM formulation based on the Phantom Node Method in conjunction with a cohesive fracture law. The main purpose of this research was to elucidate about the strengths and weaknesses of using the XFEM in a mixed-mode situation. The numerical results and crack trajectories were compared to the experimental data with good agreement. Finally, the present work emphasizes the importance of using adequate parameters to perform numerical simulations that reproduce the experimental results.
Palavras-chave: Extended finite element method (XFEM); mixed-mode; concrete fracture; numerical analysis