Investigation of concrete cracking phenomena by using cohesive fracture-based techniques: A comparison between an embedded crack model and a refined diffuse interface model

Cracking simulation in concrete-like structures is the subject of numerous investigations of computational kind, in which different modeling techniques based on either smeared or discrete fracture approaches have been proposed. In this work, two different finite element-based cohesive fracture models, proposed by some of the authors and belonging to the discrete approaches, have been compared: (i) a novel refined diffuse interface model and (ii) a well-established embedded crack model, which are based on an inter- and intra- element fracture approach, respectively. In particular, the first one is based on an intrinsic cohesive zone formulation, according to which nonlinear interface elements, equipped with a softening constitutive law, are inserted among all the finite elements of the computational domain. The second one, which has been successfully used to simulate concrete cracking along nonprescribed paths and is here used a reference model, combines the cohesive crack concept with the embedded strong discontinuity approach, allowing the cracks to be inserted across finite elements as discontinuities in the corresponding displacement field once a certain stress criterion is satisfied. These two models have been compared by analyzing the cracking behavior in concrete specimens subjected to general loading conditions. A critical discussion of the obtained computational outcomes, in terms of computational efficiency and numerical accuracy for both predicted loading curve and crack pattern, shows the strengths and limits of the investigated discrete fracture models.