PSI - Issue 47

Caroline Bremm et al. / Procedia Structural Integrity 47 (2023) 261–267 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. LDEM: (a) Basic cubic module employed in the discretisation and (b) bilinear constitutive law attributed to the bars.

Successful applications of such a method are available in the literature (Colpo et al. (2016), Birck et al. (2019), Zanichelli et al. (2021), Vantadori et al. (2023)). 2.1. LDEM in the Abaqus/explicit environment The LDEM, explained in the previous section, is introduced in the Abaqus/Explicit environment to use the tools available in this software and reduce the degrees of freedom of the problem by combining the LDEM with FEM when needed. In this version, the lattice elements are represented by 3D truss elements available in Abaqus, by using the Brittle Cracking Constitutive Model provided by the library of the Abaqus software (Dassault Systèmes (2013)). The explanation of how the LDEM can be implemented in the Abaqus/Explicit system is exposed in detail in the work of Schumacher et al. (2020). Several successful applications of this version of LDEM have been published by Schumacher et al. (2020), Medeiros et al. (2022), Driely et al. (2020), and Kosteski et al. (2014, 2015), among others. 3. Models description The concrete axial compression testing is here numerically simulated in the LDEM implemented in the Abaqus/explicit environment. Two tri-dimensional numerical models are developed, and more precisely:  Model A, by using LDEs (Fig. 2a);  Model B, by using a hybrid model combining LDEs and FEs (Fig. 2b). In each model, two different boundary conditions are considered to represent two extreme contact conditions between the sample and the steel loading platen. More precisely, one represents a frictionless contact, named Frictionless condition in the following, and the other represents a perfect contact between the sample and the loading platen, named Fixed condition in the following. In Model A, the boundary conditions are applied directly to the nodes of the cubic module (see Fig. 2a). In the case of the Frictionless condition, only vertical prescribed displacements are applied to the lower and upper surfaces in order to compress the sample. In the Fixed condition, horizontal displacements are constrained, and vertical prescribed displacements are applied to the lower and upper surfaces in order to compress the sample. In Model B, the concrete is simulated by using LDEs, whereas the steel loading platens are simulated with FEs. The above conditions are considered through the contact laws available on Abaqus. More precisely, the ‘‘surface -to surface contact’ contact option is used, together with the hard contact and rough or frictionless contact law, to simulate the Fixed and Frictionless conditions, respectively. The outer surface of the lower steel plate is restricted in all directions, and prescribed displacements are applied to the upper surface of the upper plate.