Concrete Fracture and Stress Analysis Using the Combined Finite-Discrete Element Method in the Brazilian Tension Test

ABSTRACT: Numerical modeling techniques using the combined finite-discrete element method have been utilized to explore the relationship between stress, damage, and crack propagation in concrete. Obtaining post-peak behavior from the Brazilian tension test is difficult because failure occurs abruptly. An experimental test method is described which enables monitoring of the post-peak cracking behavior in the Brazilian tension test by slowing the crack propagation. Experimental testing with this technique proved its capabilities in slowing crack propagation. The combined finite-discrete element method is used to further examine the stress states during this test and to understand the damage evolution present in this test prior to the peak strength. The method also allows for interpretation into the type of damage present throughout the entire test and the zones in which that damage initiates. A comparison is also performed between the numerical results and experimental observations to determine how well the numerical method captures the experimental results. This work enables a good understanding of how fractures form in the Brazilian tension test as well as a comparison between experimental and numerical technique results. 1. INTRODUCTION 1.1. Combined Finite Discrete Element Method In an effort to model inelastic behavior and predict the deformation and failure of materials, the combined finite discrete element method has been employed. The finite-discrete element method (FDEM) is an innovative numerical computation method that combines the efficiency of the finite element method (FEM) with the discontinuity framework of the discrete element method (DEM) to create a highly powerful and efficient system (Munjiza et al., 1999; Rougier et al., 2014). The comparison of DEM and FEM with a schematic visualization of FDEM is shown in Fig. 1. At the contact interfaces of the FDEM framework, there is bonding. The bonding is numerically represented with cohesion points along the boundaries of the deformable particles (Rougier, Knight, Lei, et al., 2014). The cohesion of these bonds is a combination of normal cohesion and tangential cohesion. When the material is exposed to significant stress, these bonds become strained and can become unbonded (Rougier, Knight, Lei, et al., 2014).