This paper presents a novel mesh reorientation algorithm that enhances the reliability of crack path prediction in cohesive zone cracking models by reducing the inherent mesh bias. The proposed method realigns interface elements to maximize their local tensile traction, facilitating cracking in energetically more favorable direction. Extensive testing shows that the algorithm consistently improves results in 2D and 3D applications, enabling more reliable predictions, including cracks originating within the domain, without requiring crack tracking or pre-specifying crack initiation points.

Cement-mortar is a type of particulate ceramic composite which is widely used as a binder in the construction industry. The complex fracture behavior of the structure depends mainly on the fracture characteristics of the cement in the mortar. Here, we have explored the microstructural characteristics of the cement-mortar using a novel X-ray computed tomography (XCT) technique. The cement mortar has been prepared using standard Madras sand and ordinary Portland cement. A specimen of size 20X20X20 mm³ has been reconstructed with a resolution of 21.2 μm. A reconstructed 2D image of the cement -mortar is used for the mesoscale finite element simulations of the crack propagation. In the proposed model, the material properties of the mortar have been distributed among the finite elements based on the greyscale histogram of the reconstructed image to represent the heterogeneity of the material. The correlation between the material properties and grey scale values covered by an element has been established using a grayscale marker. Here, the greyscale marker has been defined by averaging the grey levels of the image covered in the finite element grid/window using in-house MATLAB code. Later, the cohesive interface elements (CIEs) were inserted in the finite element mesh to simulate the complex nonlinear fracture behavior of mortar in tension. The mechanical and fracture properties of the CIEs have been used from the literature and are also mapped to the same distribution. The effect of the window size has been studied on the stress-strain response and fracture pattern of the specimen. Finally, an optimum size of grid/window is recommended for the cement mortar.

Cohesive fracture models are an established tool for the prediction of fracture in concrete. However, the reliable estimation of fracture parameters, specifically traction separation laws, is a necessary step towards their successful application. Currently, fracture parameter estimation is mainly performed by fitting simple analytical models to experimental results. This requires the design and execution of dedicated experiments, for which analytical models are available. Numerical models, along with optimisation and inverse problem solution techniques have the potential to lift the limitations inherent in the above process, allowing for instance the estimation of fracture parameters from more general experiments, involving complex geometries and loading conditions. However, fracture is computationally demanding process to simulate, while the solution of inverse problems requires multiple model evaluations, which can render whole process infeasible.This work explores the application of a simple technique for accelerating fracture simulations to the identification of fracture parameters of concrete. The technique relies on statically condensing parts of the model that are not affected by fracture, thus substantially reducing the model size, while preserving the accuracy and generality of the original model. Furthermore, it can be combined with different discretisation schemes such as standard or extended finite elements (FEM/XFEM), allowing for increased flexibility. The accelerated models are combined with Bayesian optimisation, allowing to solve the inverse problem in a highly efficient way. The effectiveness of the proposed approach is demonstrated through physical and numerical experiments.

Additive manufacturing is emerging as an appealing alternative to standard construction methods, providing capabilities for optimum designs while reducing material usage and construction waste. However, additively manufactured concrete members often come in several non-typical, e.g., tessellated and/or polytope geometries. In this study, a computational framework is developed for the analysis of concrete members reinforced with continuous steel fibres. To this end, a cohesive phase field model is used to simulate fracture in the concrete matrix within a Virtual Element Method (VEM) for the discretization of the resulting coupled system of governing equations. To accurately represent the reinforcement layout while retaining a relatively simple computational model, an embedded element technique is adopted. This combined framework aims at optimizing the discretization processes, overcoming limitations associated with finer mesh requirements while delivering accurate predictions. The effectiveness and robustness of the combined methodology is explored within the context of 2D deformable domains.