Numerical evaluation of test setups for determining the shear strength of masonry

The bond shear strength between masonry units and mortar is the weakest link in a masonry wall. Different material tests have been developed in order to characterize this bond behaviour. The objective of this study is to evaluate three common test setups through non-linear finite element analysis. The simulation method is based on our recent development of cohesive elements, which allows for the first time to fully capture the force-deformation characteristic of shear tests in 3D from the onset of loading until the residual shear strength and to retrieve typical shear failure modes observed in experiments. This study provides new insights into our understanding and interpretation of such shear tests: (1) elastic analysis, which has been widely used in the past, does not yield a stress distribution that is representative of the stress distribution at maximum resistance; (2) while friction coefficient is well estimated (the error is less than 10%), the local cohesion is underestimated by all three test setups of which the error lies between 13 and 32%; (3) the randomness of the material properties leads to a further underestimation of the mean value of the local cohesion; (4) differences in the material properties of the two joints of the triplet test units do not jeopardize the applicability of this test setup and estimations of the mean properties are obtained with similar reliability as for couplet tests

A Steering Environment for Online Parallel Visualization of Legacy Parallel Simulations

International audienceIn the context of scientific computing, the computational steering consists in the coupling of numerical simulations with 3D visualization systems through the network. This allows scientists to monitor online the intermediate results of their computations in a more interactive way than the batch mode, and allows them to modify the simulation parameters on-the-fly. While most of existing computational steering environments support parallel simulations, they are often limited to sequential visualization systems. This may lead to an important bottleneck and increased rendering time. To achieve the required performance for online visualization, we have designed the EPSN framework, a computational steering environment that enables to interconnect legacy parallel simulations with parallel visualization systems. For this, we have introduced a redistribution algorithm for unstructured data, that is well adapted to the context of M × N computational steering. Then, we focus on the design of our parallel viewer and present some experimental results obtained with a particle-based simulation in astrophysics

An optimized finite-element library: Akantu

Akantu means a little element in Kinyarwanda, a Bantu language. From now on it is also an opensource object-oriented library which has the ambition to be generic and efficient

Specification of a micro-transgranular fracture parameter

The micro-transgranular fracture calibration with a help of an efficient parallel numerical tool is demonstrated in this poster

Akantu: scalability test for the JOSS publication

<p>Code and results for the scalability test presented in the JOSS paper for Akantu.</p> <p>The test case consist in a cube of size 2m x 2m x 2m meshed with 4'392'180 tetrahedra and 734'594 nodes. This cube is fixed on the bottom and a compressive force is applied on top and a shear load is applied on for sides. This load is only designed to induce a uniform fragmentation in the sample in order to trigger the insertion of lots of cohesive elements. At the end of the simulation we have ~ 460'000 cohesive element inserted.</p&gt

Conception et mise en oeuvre d'une plate-forme de pilotage de simltions numériques parallèles et distribuées

Le domaine de la simulation numérique évolue vers des simulations de phénomènes physiques toujours plus complexes. Cela se traduit typiquement par le couplage de plusieurs codes de simulation, où chaque code va gérer une physique (simulations multi-physiques) ou une échelle particulière (simulations multi-échelles). Dans ce cadre, l'analyse des résultats des simulations est un point clé, que ce soit en phase de développement pour valider les codes ou détecter des erreurs, ou en phase de production pour confronter les résultats à la réalité expérimentale. Dans tous les cas, le pilotage de simulations peut aider durant ce processus d'analyse des résultats. L'objectif de cette thèse est de concevoir et de réaliser une plate-forme logicielle permettant de piloter de telles simulations. Plus précisément, il s'agit à partir d'un client de pilotage distant d'accéder ou de modifier les données de la simulation de manière cohérente, afin par exemple de visualiser "en-ligne" les résultats intermédiaires. Pour ce faire, nous avons proposé un modèle de pilotage permettant de représenter des simulations couplées et d'interagir avec elles efficacement et de manière cohérente. Ces travaux ont été validés sur une simulation multi-échelles en physique des matériaux.The numerical simulations evolve more and more to simulations of complex physical phenomena through multi-scale or multi-physics codes. For these kind of simulations data analysis is a main issue for many reasons, as detecting bugs during the development phase or to understand the dynamic of the physical phenomena simulated during the production phase. The computational steering is a technique well suited to do all this kind of data analysis. The goal of this thesis is to design and develop a computational steering framework that take into account the complexity of coupled simulations. So, through a computational steering client we want to interact coherently with data generated in coupled simulations. This afford for example to visualize on-line the intermediate results of simulations. In order to make this possible we will introduce an abstract model that enables to represent coupled simulations and to know when we can interact coherently with them. These works have been validated on a legacy multi-scale simulation of material physics