Conference Agenda

Bonded anchors are widely used fastening elements in civil and structural engineering applications,
particularly where high-strength connections are required for structural safety and performance. These
anchors are essential in various construction scenarios, such as the retrofitting of existing structures or the installation of structural components. To further enhance the load-bearing capacity of these systems, post installed supplementary reinforcement (PISR) bars can be introduced. This reinforcement strategy is particularly effective in improving performance under tensile and shear loading conditions. In order to accurately assess and predict the load-bearing capacity of such reinforced bonded anchor systems, we investigate a novel numerical modeling approach based on a phase-field damage-plasticity framework. The method builds upon the Concrete Damage Plasticity (CDP) model originally developed by Grassl and Jir´asek (2006), incorporating a recent phase-field extension. This extension is crucial in addressing the issue of mesh sensitivity commonly encountered in conventional damage models. The phase-field approach allows for a smooth and continuous representation of crack initiation and propagation, thereby enabling the simulation of complex failure patterns. The proposed model is implemented within an explicit finite element (FE) framework, using the commercial software package Abaqus/Explicit. This platform allows for efficient simulation of nonlinear material behaviors under various loading scenarios. Our numerical implementation ensures stable and accurate results even for complex three-dimensional geometries and highly nonlinear problems involving contact and bonded interfaces. To evaluate the robustness and accuracy of the proposed modeling strategy, we conduct a comprehensive numerical
study that includes a wide range of test cases and reinforcing conditions. The simulation results are benchmarked against experimental data. The findings demonstrate that the proposed phase-field damage-plasticity approach exhibits excellent predictive capabilities. It accurately captures both the global structural response and the localized damage evolution of the bonded anchor systems with and without supplementary reinforcement. Overall, the study highlights the effectiveness and versatility of the proposed computational framework. The combination of the CDP model with the phase-field method offers a powerful tool for analyzing and designing reinforced fastening systems in complex and demanding engineering applications. Accordingly, this approach is well-suited for investigating structural elements subjected to various loading conditions.

This work presents an analytical micromechanical model for quasi-brittle materials featuring coupled, directiondependent friction and cohesion. Building on mean-field homogenization, the formulation addresses key limitations of existing models by introducing an implicit solution procedure and an energy-based damage law based on a total, rather than partial free energy derivative. Along with a newly proposed damage resistance function ensuring linear softening under tension, the model captures complex emergent behaviors from a simple set of parameters. Numerical examples show that hardening under compression, anisotropic crack evolution, and confinement strengthening effects are all qualitatively reproduced from the prescribed tensile behavior without any additional parameters. They also demonstrate the model’s ability to handle complex stress-states in a stable and physically meaningful way.

This article presents a recently developed mixed finite element method for modeling brittle and quasi-brittle fracture in large structures, involving contact and large deformations. The proposed formulation includes four independently approximated fields: stresses, logarithmic stretches, rotation vectors, and displacements. The first two are associated with conserving linear and angular momentum, respectively. While, the other two fields are associated with the constitutive and the consistency equation between displacements and deformation. The relationship between the rotation vectors and the rotation tensor is established by an exponential map. The stresses are approximated in the Hdivspace, and the remaining three fields are approximated in the L2 space. This formulation results in a very sparse system of equations that can be efficiently solved in parallel using hybridization with a block solver, thereby enabling highly scalable and robust solvers. The system hybridization involves ’breaking’ the Hdiv space, such that continuity of normal fluxes, i.e. tractions, is no longer enforced apriori. A hybridized field is also introduced on the mesh skeleton faces and contact surfaces. Such a field acts as a kinematic Lagrange multiplier enforcing continuity of normal tractions. Moreover, the hybridized Lagrange multiplier field is conveniently used to enforce contact conditions, and introduce displacements discontinuities. Furthermore, since the Hdivspace provides traces of fluxes on faces, the mixed element enables efficient calculation of face crack release energy. Since this methodology enables crack propagation on fixed mesh technology, along with being based on an energy-based crack propagation criterion, it inherits the robustness of the phase field while being as efficient as methods which resolves crack discreetly. In an algebraic sense, since all fields in the interior become fields in the L2 space, and fields on skeleton faces are in H1/2 space, the system of equations is extremely sparse and can be solved using a Schur complement, eliminating interior fields.

This paper proposes a new three-dimensional cyclic constitutive model for reinforced concrete structure based on the explicit finite volume method. These developments are based and largely inspired on Sellier’s model (Sellier et al., 2013a; Sellier & Millard, 2019) which is a plastic-damage model that already integrates several essential phenomena such as crack opening and reclosure, shear failures and the behavior of reinforcements. However, to ensure optimal efficiency under cyclic loading, improvements will be made to the compressive behavior of concrete as well as on the cyclic behavior of reinforcements. It was decided to implement this enhanced model on a program based on the explicit finite volume method because this method allows the efficient resolution of highly nonlinear systems. However, strict criteria must be defined to guarantee the stability and convergence of the calculations. To validate these developments, the model results will be compared with experimental tests carried out at the specimen and structure scales.

A gap test an experimental and numerical test, which is designed to show that the effective mode I fracture energy depends strongly on the crack-parallel normal stress. Talking about the fracture energy one should distinguish between the initial and the total fracture energy. According to Nguyen et al., the initial fracture energy is the area under the initial tangent of the traction–separation curve while the total fracture energy represents the area under the traction–separation curve. Alternatively one can estimate the total fracture energy as the area between the up-and-down curve and the horizontal yield line in the load-displacement diagram. Authors of this paper tried to recreate numerically the gap test with a concrete specimen and to calculate the total fracture energy. They used the concrete damaged plasticity model in Abaqus software. Results presented in this paper are continuation of the authors’ work, presented previously at the FraMCoS 2025 conference.

An extension of a recently proposed cohesive zone model that combines mixed-mode fracture with regularized friction for quasi-brittle materials is presented. This interface material model is characterized by mixed-mode fracture in tension-shear, and by cohesion and Coulomb friction in compression-shear. In previous work, the discontinuity arising in the traction-separation relation due to the introduction of friction has been smoothed through a time-independent function. In this contribution, to remove the step dependence resulting from the previous formulation, a time-dependent regularization is proposed. Similarities and discrepancies between the two procedures are discussed.