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Commend Stéphane

Professeur HES associé

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Professeur HES associé

Phone: +41 26 429 66 71

Desktop: HEIA_D40.13

Haute école d'ingénierie et d'architecture de Fribourg
Boulevard de Pérolles 80, 1700 Fribourg, CH

Chargé de cours

Haute école d'Ingénierie et de Gestion du Canton de Vaud
Route de Cheseaux 1, 1400 Yverdon-les-Bains, CH

HES-SO Master
Av. de Provence 6, 1007 Lausanne, CH

Faculty
Technique et IT

Main Degree Programme
Master of Science in Engineering

MSc HES-SO en Engineering - HES-SO Master

Modélisations numériques et physiques en géomécanique
Interaction Sol-Structure en terrain meuble

BSc HES-SO en Génie civil - Haute école d'ingénierie et d'architecture de Fribourg

Géotechnique et Mécanique des sols I
Ateliers interdisciplinaires

Ongoing

Optimization of support system for urban deep excavations with machine learning techniques

AGP

Role: Co-applicant

Financement: Hasler; FR - EIA - Institut iTEC; EPFL ENAC LMS

Description du projet : Productivity in the construction sector, particularly in soil excavation, has stagnated for decades. The main advances were made 30 years ago with the development of finite element simulation tools. Today, planning an excavation for a building is still based on a long human process of trial and error. At the same time, important steps are being taken to unify data models for different construction professions. Important progresses are also being made in the field of soil cartography in Switzerland, such as SwissTopo. The development of these models will provide large amounts of numerical data describing the different parameters and stages of building construction and in particular excavation in a given soil environment. The underlying scientific question is about the usability of such data to improve methods and knowledge about geotechnical structure design. More specifically, the objective of the OptiSoil project is to use this data to apply artificial intelligence algorithms using machine learning techniques to develop innovative excavation design techniques that optimize stability, risk and cost constraints.

Research team within HES-SO: Gisler Christophe , Montet Frédéric , Hennebert Jean , Rial Jonathan , Kuonen Pierre , Commend Stéphane , Donzallaz Jonathan , Menoud Ludivine , Minini Jocelyn , Buchs Colette

Partenaires académiques: FR - EIA - Institut iCoSys

Durée du projet: 03.02.2019 - 31.01.2024

Montant global du projet: 87'745 CHF

Statut: Ongoing

Completed

Evaluation des dommages sur les structures causés par les coulées de laves torrentielles : mise en place d'un prototype d'outil permettant de les quantifier, au-delà d'approches qualitatives

AGP

Role: Main Applicant

Financement: HES-SO Rectorat; GEOMOD

Description du projet : Les glissements de terrain et laves torrentielles sont parmi les dangers naturels les plus courants sur le territoire suisse, mais aussi parmi les plus compliqués à prévoir et modéliser. Selon un communiqué de presse datant d'avril 2018, le gouvernement suisse a d'ailleurs autorisé les mesures nécessaires pour l'alerte en cas de glissements de terrain dans le cadre du projet «Optimisation de l'alerte et de la transmission de l'alarme». Selon les experts [CH-2018 - scénarios climatiques pour la Suisse], les précipitations seront plus fréquentes et plus intenses à l'avenir, et le danger de glissements de terrain ou de coulées de boue augmentera. La plupart des cantons viennent de terminer d'établir leurs cartes des dangers, et se posent des questions concernant l'interaction de ces dernières avec l'environnement bâti. Le but de ce projet est ainsi d'initier une réflexion et de construire un prototype permettant d'évaluer l'interaction entre les laves torrentielles et le bâti existant de manière la plus exacte possible : dommages réels survenant sur un bâtiment réel, suite à un événement réel. Le produit découlant de ce projet sera un logiciel capable d'évaluer le dommage d'une structure réelle (en béton armé ou en bois par exemple) tenant compte de son état limite de rupture, suite à un écoulement de lave torrentielle donné. Les étapes pour parvenir à ce résultat seront les suivantes : - choix de plusieurs situations dangereuses sur la base de la documentation historique et/ou de cartes de dangers naturels existantes. Définition de la topographie, de la stratigraphie, et de l'action motrice ayant conduit au déclenchement de la lave torrentielle - construction d'un modèle aux éléments finis 2D reproduisant la topographie, la stratigraphie et les conditions hydrogéologiques associées à chacune des situations. Introduction d'une action motrice, par exemple de fortes pluies, induisant une montée du niveau de la nappe souterraine, et identification du mécanisme de ruine de la pente suite à cette action, et donc du volume de lave torrentielle potentiellement destructeur - propagation de la lave torrentielle le long de la pente, grâce à un second modèle tenant compte du couplage hydromécanique et détermination fine de la force d'impact sur le bâtiment menacé - construction d'un troisième modèle représentant la structure réelle du bâtiment menacé (béton armé, armatures, bois, lois de comportement non linéaires pour les différents matériaux), application de la force d'impact et prédiction sur la vulnérabilité du bâtiment suite à cet impact, en fonction du déplacement calculé - validation de l'approche en comparant les dommages estimés par le modèle aux dommages causés par les laves torrentielles sur plusieurs cas réels L'avantage et l'originalité de cette approche résident dans son caractère quantitatif, physique. Basée sur la représentation des différents phénomènes en jeu par une suite de modèles numériques, elle va au-delà de l'état de l'art actuel puisqu'elle n'introduit aucune autre approximation que celle des modèles qui la composent.

Research team within HES-SO: Torche Jérémy , Prina Howald Erika , Commend Stéphane , Boquete Ricardo , Buchs Colette

Partenaires académiques: INSIT; FR - EIA - Institut iTEC; Commend Stéphane, FR - EIA - Institut iTEC

Durée du projet: 01.09.2019 - 31.12.2021

Montant global du projet: 183'000 CHF

Statut: Completed

QUantification de l'ALéa (ou de l`incertitude) dans les calculs effectués à l`iTEC -SLL

AGP

Role: Main Applicant

Financement: SLL-2020

Description du projet : Les performances du bâti font l'objet de mesures quantitatives, du dimensionnement à l'exploitation. Elles vont servir au calcul de paramètres permettant de faire des choix constructifs ou opérationnels. Or, la plupart de ces mesures et paramètres sont entachés d'imprécisions, et celles-ci se propagent dans nos modèles de calcul. Les méthodes de dimensionnement basées sur les approches probabilistes sont relativement bien établies dans le domaine de l'ingénierie des structures, mais beaucoup moins dans les domaines de la géotechnique et du génie environnemental. Au niveau mondial, elles sont présentes dans les pays anglo-saxons et asiatiques, beaucoup moins en Europe. La complexité de ces approches fait que les outils de calculs existants sont peu pratiques à prendre en main, et donc peu appliqués. Le caractère innovant de ce projet réside donc dans l'établissement d'un transfert de technologie, permettant aux ingénieurs du domaine du GC de s'emparer de ces techniques. D'autres domaines de recherche et instituts rattachés au SLL pourraient potentiellement bénéficier de cette approche novatrice. Les objectifs de ce projet sont d'améliorer les compétences de mesure in situ de paramètres déterminants pour la performance et le confort du bâti, de tester des outils de calcul de propagation d'erreur ' ils nécessitent une prise en main non triviale, et enfin de définir le domaine d'utilisation de ces outils pour différentes applications du GC et de l'environnement. Objectifs: développer et s'approprier les méthodologies suivantes : 1. Maîtrise des techniques de mesures des débits et des flux de chaleur dans des gammes et des géométries très variables et très contraintes (à l'échelle du bâtiment ou de la parcelle) 2. Quantification de l'aléa associé aux données d'entrée de problèmes types du GC : ' Mesures de débits, de qualité de l'eau, de flux de chaleur ' Incertitudes sur les paramètres des matériaux (résistance et déformabilité) et les sollicitations associées au dimensionnement des bâtiments ' Incertitudes sur les propriétés des sols lors du la vérification de la capacité portante des fondations dans le domaine de la géotechnique 3. Calcul de propagation des incertitudes, calcul de sensibilité et de fiabilité (innovation : méthode permettant de quantifier la probabilité de défaillance)

Research team within HES-SO: Bullinger Géraldine , Spahni Bruno , Favre Boivin Fabienne , Froidevaux Manuel , Pfister Michael , Commend Stéphane , Bénet Loïc , Buchs Colette

Partenaires académiques: FR - EIA - Institut iTEC

Durée du projet: 01.03.2020 - 31.08.2021

Montant global du projet: 77'300 CHF

Statut: Completed

2023

Reliability-based decision-making with FE models for real-life case studies

Book chapter ArODES

Stéphane Commend, Jocelyn Minini, Marc Groslambert, Gil Jacot-Descombes

Dans Ching, Jianye, Phoon, Kok-Kwang, Shuku, Takayuki, Uncertainty, modeling, and decision making in geotechnics (pp. 401-424). 2023, Boca Raton : CRC Press

Link to the publication

Summary:

In this chapter, probabilistic analyses are applied to non-linear 3D FE models for two real-life case studies: (1) a deep excavation retained by a braced slurry wall and (2) the construction of a tunnel under a sensitive building. The use of accurate meta-models allows sensitivity and reliability analy ses to be performed in a reasonable time frame, in parallel with construction works if needed. It is shown that these FE computations have helped design engineers to make the following decisions: (1) eliminating a fourth level of struts for the braced excavation thanks to a live Bayesian analysis; (2) defining the optimal excavation steps for a tunnel excavation beneath a sensitive building, with the help of a reliability analysis considering two different excavation procedures.

Finite element-based probabilistic framework including Bayesian inference for predicting displacements due to tunnel excavation

Scientific paper ArODES

Jocelyn Minini, Yi Zhang, Marc Groslambert, Stéphane Commend

Computers and Geotechnics, 2023, vol. 162, article no. 105604

Link to the publication

Summary:

Excessive settlements due to tunnel excavation in urban sites may affect the stability of sensitive buildings, and additional design costs are needed to prevent these effects. In this article, a finite element-based probabilistic framework is presented and applied to a real-world case study to estimate tunnel-induced settlements. This probabilistic analysis framework consists of the following four fundamental elements: a sensitivity analysis to identify key parameters, an a priori reliability analysis using metamodels to calculate reliability indices and probabilities of failure, field monitoring results (e.g., settlements) and a Bayesian inverse analysis using the field measurements to update the probabilities of failure a posteriori. This framework is materialized through the linking of ZSOIL, a non-linear finite element soil–structure interaction software, and UQLab, a MATLAB®-based uncertainty quantification toolbox. With the application of this framework to a real-world case study in the Grand Paris Express project, key geotechnical parameters can be identified, reliability indices and probabilities of failure can be computed using metamodelling-powered Monte Carlo (MCS) and adaptive kriging Monte Carlo simulations (AKMCS). Finally, using Bayesian inverse analyses to update prior knowledge and refine posterior prediction, the probability that the settlements exceed acceptable values can be reduced, potentially leading to design cost savings.

Application of random fields and polynomial chaos expansions to slope reliability analysis

Scientific paper

Joana-Sophia Levkov, Gil Jacot-Descombes, Commend Stéphane

Proceedings of the 14th International Conference on Applications of Statistics and Probability in Civil Engineering (ICASP14), 9-13 July 2023, Dublin Ireland, 2023

Link to the publication

Summary:

This paper aims to find the difference between two types of probabilistic slope stability analysis under a rainfall event. The first admits a uniform soil and takes into account uncertainty of the soil properties. The second includes spatial variability of the soil properties. Both analyses are performed using a Monte Carlo framework with the help of a meta-model, in particular a Polynomial Chaos Expansion (PCE). The PCE is built based on 2D finite element realisations and allows a quick evaluation of new ones. This provides an efficient reliability analysis when performing the Monte Carlo Simulation method. A comparison between the probabilities of failure between the two approaches is shown. Furthermore, the effect of the correlation lengths of the random field on the probabilities of failure is evaluated.

Sensitivity and relability analyses applied to day-to-day geotechnical engineering using meta-models coupled with 3D finite elements

Scientific paper

Marc Groslambert, Gil Jacot-Descombes, Commend Stéphane, Bruno Sudret

Proceedings of the 14th International Conference on Applications of Statistics and Probability in Civil Engineering (ICASP2014), 9-13 July 2023, Dublin, Ireland, 2023

Link to the publication

Summary:

On one hand, finite element analyses have nowadays become a standard in order to design complex soil-structure interaction works, especially when dealing with sensitive structures in the vicinity of the project. On the other hand, reliability design and full probabilistic analysis are more and more used in practice. In this contribution we aim to show that day-to-day 3D finite element probabilistic analyses can now be performed in a reasonable amount of time, using adequate meta-models like Polynomial Chaos Expansions (PCE) or Polynomial Chaos Kriging (PCK). We illustrate this on a study for a tunnel which will be constructed in Lausanne, Switzerland, for a new underground line, still under development. A 3D finite element mesh is constructed, including real stratigraphy, excavation steps, support and bolting. Probability density functions are defined for soil parameters, loads... A sensitivity analysis is conducted first in order to select the relevant input parameters, and then a reliability analysis is performed, the quantity of interest being the settlement of a sensitive building due to the tunnel excavation. Special attention is put in this paper on the selection of the most adequate meta-model, on the error measurement (generalization of the leave-one out error) and on the size of the experimental design needed to construct a reliable surrogate model.

Refining 3D nonlinear finite element settlement predictions around a deep urban excavation with the help of a Bayesian approach

Scientific paper

Minini Jocelyn, Commend Stéphane

Proceedings of the 14th International Conferene on Applications of Statistics and Probability in Civil Engineering, ICASP14, 9-13 July 2023, Dublin, Ireland, 2023

Link to the publication

Summary:

This contribution presents a probabilistic and Bayesian approach for the finite element modelling of a deep excavation in a lacustrine environment in Geneva, Switzerland. Coupling non-linear 3D finite element modeling with highly accurate meta-modelling techniques was shown to be necessary in order to run time requiring analyses like Sobol’ sensitivity and Monte-Carlo reliability analyses. A priori input parameters’ probability density functions were based on geotechnical site tests, literature and our expertise. Displacement measurements from on-site monitoring were subsequently used during the first excavation phases in order to conduct an inverse Bayesian analysis. This helped us to refine our prior knowledge for final settlements’ probability density functions and associated failure probabilities. In particular, the need to install the fourth level of bracing has been evaluated in the light of this risk analysis.

2022

Analyses et modélisations sur les argiles plastiques du Sparnacien du Bassin parisien

Scientific paper ArODES

Yi Zhang, Stéphane Commend, Marc Groslambert

Revue Française de Géotechnique, 2022, vol. 171, article no. 3

Link to the publication

Summary:

Paris plastic clays are impermeable, normally consolidated or overconsolidated, and exhibit a swelling potential. The swelling (mechanical and hydric) of plastic clays is one of the major geotechnical challenges in the Grand Paris Express project, because its mechanism is complex depending on its physical and chemical characteristics, as well as its mechanical and hydric states. In this article, we first present the analyses of several experiences of the projects constructed in the plastic clays, as well as the geotechnical parameters and the constitutive laws used in these projects. Then, we present the different analysing methods of plastic clays, namely: analytical and empirical solution, semi-probabilistic finite element model and probabilistic approach. In addition, their numerical applications to the different kinds of underground structures were also carried out, namely: shafts, diaphragm walls and tunnels. The results of these calculations have been compared with monitoring measurements, which allow verifying the results of numerical simulations. At the end, an analysis using the Bayesian inference was performed in order to gain accuracy in the prediction of the swelling of plastic clays.

SLIDE-PM: a 2D-FEM prototype to quantify the vulnerability of buildings with respect to mudflows

Scientific paper

Colette Jost, Commend Stéphane, Jacopo Abbruzzese, Tanja Miteva, Erika Prina Howald

Proceedings of 20th International Conference on Soil Mechanics and Geotechnical Engineering, Sydney 2022 ISBN 978-0-9946261-4-1, 2022 , pp. 729-735

Link to the publication

Summary:

The design of protection measures against mud flows is usually justified by the vulnerability of a given building due to a possible event. Empirical approaches, hard to quantify, are often used. A new tool prototype is therefore developed, which allows quantifying the vulnerability based on three consecutive 2D finite element models. A first model, taking into account the topology, stratigraphy and hydrogeological conditions is first used to identify the rupture mechanism and therefore the size and shape of the resulting mudflow. Afterwards, the triggered volume is propagated along the slope using a second model and the impact force is quantified. Finally, this force is applied on a third nonlinear structural model. The vulnerability of the building is then estimated based on the resulting force-displacement curve. The propagation of the triggered volume and the calculation of the impact force is validated on a granular flow laboratory experiment. Then areal-life case study, namely the 2010 Wenjia Gully mudflow is simulated. The identification of the failure mechanism, the propagation and the impact force are compared to existing models of this event. Finally, the vulnerability of different fictitious buildings to this event is evaluated.

Experimental study and numerical simulation of Paris plastic clay

Scientific paper

Yi Zhang, Commend Stéphane

Proceedings of World Tunnel Congress, Underground solutions for a world in change, Copenhagen, Denmark, 2022

Link to the publication

Summary:

This paper presents the experimental study and numerical simulation of Paris plastic clay in a case study of Grand Paris Express project. Paris plastic clay is a highly plastic clay from the Sparnacian age (Lower Eocene) and forms the first tertiary deposits of Paris sedimentary basin, it has a very low permeability, is normally consolidated or overconsolidated, and is swollen in outcrops. To analyse and model Paris plastic clay, in-situ and laboratory tests, geotechnical analyses of test results, calibration of geomechanical parameters based on these analyses, 2D and 3D finite element modelling with the appropriate constitutive laws by semi-probabilistic and probabilistic methods were carried out. The monitoring allowed the comparison of measurements with the results of the numerical simulation to validate this approach.

2021

Calculs probabilistes des déplacements dus à la réalisation de tunnels à l’aide d’un modèle aux éléments finis

Scientific paper ArODES

Yi Zhang, Stéphane Commend

Revue Française de Géotechnique, 2021, vol. 167, no. 5

Link to the publication

Summary:

Finite element-based probabilistic analyses of displacements due to tunnel construction. The estimation of movements due to the construction of tunnels is an important subject for underground works projects in urban sites. These displacements, particularly settlements and swellings, may bring detrimental consequences to neighbouring buildings and structures under construction. This article presents the framework of a probabilistic approach using a finite elements model to estimate these displacements. It takes into account the uncertainties related to geotechnical problems (lack of input data, spatial variability of soils, etc.). Using the probability of failure Pf (or a reliability index β) as a function of the selected safety or performance levels, a method for the probabilistic evaluation of displacements is firstly defined. It is then applied to a tunnel constructed using the conventional method thanks to the coupling of the ZSOIL and UQLab tools. The reliability assessment (probability of failure and reliability index) of the safety function based on the results of finite elements model has been carried out successfully with FORM, AK-MCS and MCS methods. This probabilistic approach illustrates the reliability assessment for SLS (Serviceability Limit State) cases according to the Eurocodes.

2020

The White House Station of the Grand Paris Express Project

Scientific paper

Yi Zhang, Commend Stéphane, Quentin Martin-Lavigne, Jérôme Lacoste

Structural Engineering International, 2020 , vol. 30, no 4, pp. 460-467

Link to the publication

Summary:

The White House Station of the Paris metro Line 14 is part of Grand Paris Express, the largest metro project underway in Europe. It includes an underground station, a tunnel built by conventional tunnelling methods and a connection to the existing Paris metro Line 7. This paper describes its structural design, risk and structural analyses, construction and monitoring. The project is located in a dense urban environment with high risks relating to geology (fractured limestone, swelling clay) and sensitive neighbouring structures (high-rise buildings and an existing metro line). Based on past experience and geotechnical analysis of the site investigations results, the design of the station included overcut diaphragm walls (1.5 m wide, 47 m deep), cross-walls (0.63 m wide, 6 m high) and slabs (20 m wide, 120 m long and 1.5 m thick). To understand the soil-structure interaction for the existing and new structures, a three-dimensional finite element model was developed and parametric studies were performed. Owing to planning restrictions, construction works were phased concurrently with a significant amount of demolition. To observe the real-time behaviour of soils and structures, a substantial monitoring system was utilised and continuous geotechnical observations were carried out.

Using CNNs to optimize numerical simulations in geotechnical engineering

Scientific paper

Wolf Beat, Donzallaz Jonathan, Buchs Colette, Hayoz Amanda, Commend Stéphane, Hennebert Jean

Proceedings of IAPR Workshop on Artificial Neural Networks in Pattern Recognition, ANNPR 2020 : Artificial Neural Networks in Pattern Recognition, 2-4 September 2020, Winterthur, Switzerland, 2020

Link to the publication

Summary:

Deep excavations are today mainly designed by manually optimising the wall’s geometry, stiffness and strut or anchor layout. In order to better automate this process for sustained excavations, we are exploring the possibility of approximating key values using a machine learning (ML) model instead of calculating them with time-consuming numerical simulations. After demonstrating in our previous work that this approach works for simple use cases, we show in this paper that this method can be enhanced to adapt to complex real-world supported excavations. We have improved our ML model compared to our previous work by using a convolutional neural network (CNN) model, coding the excavation configuration as a set of layers of fixed height containing the soil parameters as well as the geometry of the walls and struts. The system is trained and evaluated on a set of synthetically generated situations using numerical simulation software. To validate this approach, we also compare our results to a set of 15 real-world situations in a t-SNE. Using our improved CNN model we could show that applying machine learning to predict the output of numerical simulation in the domain of geotechnical engineering not only works in simple cases but also in more complex, real-world situations.

2019

Prediction of unsupported excavations behaviour with machine learning techniques

Scientific paper

Commend Stéphane, Sacha Wattel, Hennebert Jean, Kuonen Pierre, Laurent Vulliet

Proceedings of XIV International Conference on Computational Plasticity, Fundamentals and Application (COMPLAS 2019), 2019 , pp. 529-535

Link to the publication

2012

Modelling the efficiency of a drainage gallery work for a large landslide with respect to hydrogeological heterogeneity

Scientific paper

Boris Matti, Laurent Tacher, Commend Stéphane

Canadian Geotechnical Journal, 2012 , vol. 49, no 8

Link to the publication

Summary:

This study describes transient hydrogeological and geomechanical models realized jointly in 2006 by the Geolep office (Géologie de l’Ecole Polytechnique) of the Polytechnical School of Lausanne (EPFL) and GeoMod SA within the framework of the stabilization work of the La Frasse landslide (Vaud, Switzerland). These models evaluate the impact of a deep drainage gallery with subvertical drainage boreholes towards the surface in terms of reduction of the deformation velocities and increase of the landslide’s factor of safety. The paper presents the effect of different pipe spacing of the drainage system. Considering the local heterogeneities, the results show that a mean spacing between the drainage boreholes of the order of 10 m is sufficient to control the temporal head fluctuations between the wells within a range of a few metres. Moreover, this solution induces a strong diminution of the predicted displacements during a specific crisis, from 101 cm for the model without drainage to around 14 cm for the drained model, and a significant gain of stability (from a factor of safety (FoS) of 1.05 to 1.30).

2004

Numerical simulation of earthworks and retaining system for a large excavation

Scientific paper

Commend Stéphane, Françoise Geiser, Jérémie Crisinel

Advances in Engineering Software, 2004 , vol. 35, no 10-11, pp. 669-678

Link to the publication

Summary:

The numerical simulation of a large excavation (145 m×165 m) for the construction of a watch production centre is described in this paper. A coupled 2 phase three dimensional non-linear finite element analysis was conducted with Z_Soil 3D v5 [Z_Soil 2002 User manual, 1985–2002] in order to verify and optimise the designed retaining system as well as to carefully predict the settlements, as many existing manufactures stand in the surroundings. A comparison of the predicted behaviour with in situ measurements is shown.

Stabilized finite elements applied to elastoplasticity: I. Mixed displacement–pressure formulation

Scientific paper

Commend Stéphane, Andrzej Truty, Thomas Zimmermann

Computer Methods in Applied Mechanics and Engineering, 2004 , vol. 193, no 33-35, pp. 3559-3586

Link to the publication

Summary:

A stabilized, mixed, displacement–pressure (u–p), finite element formulation for elasto-plastic solid media is developed in this paper. In particular it applies to low order finite elements with equal interpolation order for both displacement and pressure fields. The approach successfully eliminates the effect of volumetric locking for elastic nearly incompressible media and the elasto-plastic media exhibiting incompressible or dilatant plastic flow. The performance of the proposed formulation is compared with the stabilized formulation based on pressure Laplacian. It is shown that the proposed stabilized formulation also supports mixing different elements.

2001

Object-oriented nonlinear finite element programming: a primer

Scientific paper

Commend Stéphane, Thomas Zimmermann

Advances in Engineering Software, 2001 , vol. 32, no 8, pp. 611-628

Link to the publication

Summary:

This article describes an introductory object-oriented finite element program for static and dynamic nonlinear applications. This work can be considered as an extension of the original FEM_Object environment dealing with linear elasticity [Elmepress Int (1993)] and nonlinearity [Comput Struct 49 (1993) 767]. Mainly the static aspects are discussed in this paper. Interested readers will find a detailed discussion of the object-oriented approach applied to finite element programming in [Proceedings IABSE Colloquium on Expert Systems in Civil Engineering, Bergamo, Italy, 1989; Object-oriented Finite Elem Anal Comput Struct 34 (1990) 355; Comput Struct 40 (1991) 75; Int J Numer Meth Engng 35 (1992) 425] and also in [Computer Methods in Appl Mech Engng 98 (1992); The finite element method, 1987] and references therein. Our ambition, in this paper, is limited to a presentation of an introductory object-oriented finite element package for nonlinear analysis. Our goal is to make a starting package available to newcomers to the object-oriented approach and to provide an answer to the large number of demands for such a program received in recent time.

In the first part of the paper, a brief recall of the basics of finite element modeling applied to continuum mechanics is given. Von Misès plasticity including isotropic and kinematic hardening, which is used as model problem, is described. This first part also presents an overview of the main features of the object-oriented approach. In the second part of this paper, classes and associated tasks forming the kernel of the code are described in detail. A hierarchy of classes is proposed and discussed; it provides an immediate overview of the program's capabilities. Finally interactions between classes are explained and numerical examples illustrate the approach.

2023

Approche probabiliste et méthode observationnelle :

Conference ArODES

application à l’interaction entre tunnelier et pieux dans le cas du projet L16-1

Yi Zhang, Stéphane Commend, Gil Jacot-Descombes, Pascal Hamet

Actes du XVIIE Congrès International AFTES 2023 "Le souterrain au cœur des transitions", 2-4 Octobre 2023, Paris, France

Link to the conference

Summary:

Pressurized face Tunnel Boring Machines (TBM) are generally used to build tunnels in urban areas. The prediction of displacements induced by the pressurized digging of tunnels near piles is a complex technical subject, which depends on many factors such as the 3D effect of tunnel/ground/piles interaction, the geotechnical characteristics of the ground, the multiple sources of displacement around the tunnel boring machines, etc. In the Grand Paris Express project, limit of the impacts of tunnel boring machines on piles is an important topic in order to reduce the damage risk to neighboring existing structures. A full-scale experiment was carried out on line 16 lot 1 in Aulnay-sous-Bois as part of the TULIP research project (TUnnelling and Limitation of Impacts on Piles), set up by Société du Grand Paris, CETU, ENTPE and Université Gustave Eiffel. Eiffage Génie Civil and its Swiss partners HEIA-FR and GeoMod have developed a probabilistic approach coupled with the observational method. This article presents the application of this probabilistic approach to better understand the mechanism of tunnel/ground/piles interaction, based on comparaison with the results of experimental tests. A 3D finite element model is first realized to simulate the tunnel/terrain/piles interaction, then a sensitivity analysis is carried out to determine the most influential input probabilistic variables on the results. By combining the observational method with monitoring measurements, the use of Bayesian inference makes it possible to update the analysis hypotheses, so as to refine predictions (from a priori knowledge to a posteriori knowledge), then optimize the design if the value of the probability of failure decreases a posteriori.

Application of random fields and polynomial chaos expansions to slope reliability analysis

Conference ArODES

Joana-Sophia Levkov, Gil Jacot-Descombes, Stéphane Commend

Proceedings of the 14th International Conference on Applications of Statistics and Probability in Civil Engineering (ICASP14), 9-13 July 2023, Dublin Ireland

Link to the conference

Summary:

Sensitivity and relability analyses applied to day-to-day geotechnical engineering using meta-models coupled with 3D finite elements

Conference ArODES

Marc Groslambert, Gil Jacot-Descombes, Stéphane Commend, Bruno Sudret

Proceedings of the 14th International Conference on Applications of Statistics and Probability in Civil Engineering (ICASP2014), 9-13 July 2023, Dublin, Ireland

Link to the conference

Summary:

Prediction of diaphragm wall displacements using Bayesian model calibration

Conference ArODES

Jocelyn Minini, Stéphane Commend

Proceedings of the 14th International Conferene on Applications of Statistics and Probability in Civil Engineering, ICASP14, 9-13 July 2023, Dublin, Ireland

Link to the conference

Summary:

This contribution presents a probabilistic and Bayesian approach for the finite element modelling of a deep excavation in a lacustrine environment in Geneva, Switzerland. Coupling non-linear 3D finite element modeling with highly accurate meta-modelling techniques was shown to be necessary in order to run time requiring analyses like Sobol’ sensitivity and Monte-Carlo reliability analyses. A priori input parameters’ probability density functions were based on geotechnical site tests, literature and our expertise. Displacement measurements from on-site monitoring were subsequently used during the first excavation phases in order to conduct an inverse Bayesian analysis. This helped us to refine our prior knowledge for final settlements’ probability density functions and associated failure probabilities. In particular, the need to install the fourth level of bracing has been evaluated in the light of this risk analysis.

Calibration of highly computationally intensive propagation models of flow-like natural hazards

Conference ArODES

Colette Buchs, Jocelyn Minini, Stéphane Commend

Proceedings of Geo-Risk 2023, 23-26 July 2023, Arlington, Virginia, USA

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Summary:

Risk assessment of structures subjected to flow-like natural hazards, such as mud/debris flows, lahars, or avalanches, are commonly based on propagation models. Numerical models require significant computational effort to predict output quantities, such as run-off lengths, velocities, or impact forces. In this study, Bayesian inversion is applied to a well-documented case in order to calibrate the governing parameters of the propagation model on kinematic measurements. As this technique is heavy in terms of model evaluations, it is performed with the help of a surrogate model. To ensure the accuracy of this surrogate model, various meta-modeling techniques are compared in the case of a small experimental design. Finally, a propagation model is built on the best point estimate resulting from the calibration. The results of this model are compared to the actual measurements of the studied case in order to demonstrate the applicability of the presented approach.

2022

Experimental study and numerical simulation of Paris plastic clay

Conference ArODES

Yi Zhang, Stéphane Commend

Proceedings of World Tunnel Congress, Underground solutions for a world in change, 2-8 September 2022, Copenhagen, Denmark

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Summary:

SLIDE-PM :

Conference ArODES

a 2D-FEM prototype to quantify the vulnerability of buildings with respect to mud flows

Colette Jost, Stéphane Commend, Jacopo Abbruzzese, Tanja Miteva, Erika Prina Howald

Proceedings of the 20th International Conference on Soil Mechanics and Geotechnical Engineering, 1-5 May 2022, Sydney, Australia

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Summary:

The design of protection measures against mud flows is usually justified by the vulnerability of a given building due to a possible event. Empirical approaches, hard to quantify, are often used. A new tool prototype is therefore developed, which allows quantifying the vulnerability based on three consecutive 2D finite element models. A first mode!, taking into account the topology, stratigraphy and hydrogeological conditions is used to identify the rupture mechanism and therefore the size and shape of the resulting mudflow. Afterwards, the triggered volume is propagated along the slope using a second mode! and the impact force is quantified. Finally, this force is applied on a third nonlinear structural mode!. The vulnerability of the building is then estimated based on the resulting force-displacement curve. The propagation of the triggered volume and the calculation of the impact force is validated on a granular flow laboratory experiment. Then a real-life case study, an event in Wenjia Gully (China) is simulated. The identification of the failure mechanism compared to existing models of this event. Finally, vulnerability to this event of different fictitious buildings is evaluated.

2021

Méthodes probabilistes et analyses de fiabilité appliquées à la géotechnique

Conference

Commend Stéphane

Géotechnique Suisse. Cycle de conférences en ligne 2021, 17.03.2021 - 08.12.2021, Online (CoVid)

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2020

Using CNNs to optimize numerical simulations in geotechnical engineering

Conference ArODES

Beat Wolf, Jonathan Donzallaz, Colette Jost, Amanda Hayoz, Stéphane Commend, Jean Hennebert

Lecture Notes in Computer Science ; Proceedings of IAPR Workshop on Artificial Neural Networks in Pattern Recognition, ANNPR 2020 : Artificial Neural Networks in Pattern Recognition, 2-4 September 2020, Winterthur, Switzerland

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Summary:

2019

Prediction of unsupported excavations behaviour with machine learning techniques

Conference

Commend Stéphane, Sacha Wattel, Hennebert Jean, Kuonen Pierre, Laurent Vulliet

XIV International Conference on Computational Plasticity, Fundamentals and Application (COMPLAS 2019), 03.09.2019 - 05.09.2019, Barcelona

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2013

Etat de l’art – évolution, possibilités et limites des éléments finis en géotechnique

Conference

Commend Stéphane

FEM in der Geotechnik - Eléments finis et géotechnique, 07.11.2013 - 07.11.2013, Biel - Bienne

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Summary:

Il y a 50 ans, en 1963, l’ingénieur civil, muni de sa règle à calcul, calculait ses problèmes de capacité portante de fondation ou de stabilité de pente à l’aide des ouvrages de Terzaghi et dimensionnait ses structures avec ceux de Timoshenko. En 2013, un ordinateur personnel (PC) coûtant quelques milliers de francs permet le calcul des champs de contraintes et des déformations d’un problème d’interaction sol-structure par la méthode des éléments finis (EF) formulé sans approximation significative, bi- ou tridimensionnel, statique ou dynamique, mono- ou biphasé, non-linéaire (matériel et/ou géométrique), à plusieurs centaines de milliers de degrés de liberté, voire un million et demi, (Figure 1). Dans cet article, nous explicitons le contexte qui a permis cette évolution spectaculaire : le chapitre 2 aborde les progrès du matériel informatique et des méthodes numériques, le chapitre 3 se concentrant sur les aspects constitutifs et algorithmiques associés à la géotechnique. La pratique actuelle des éléments finis en géomécanique est illustrée au chapitre 4 par des exemples, une réflexion sur l’assurance qualité de cette méthode, ainsi que par des considérations sur la possibilité de l’utiliser de concert avec les normes actuelles. En guise de conclusion, le chapitre 5 aborde quelques points nous paraissant essentiels pour le développement futur des éléments finis en géotechnique.

Achievements

2020

Délégué de la commission SIA 267 au groupe TG C3 "reliability-based methods" pour la nouvelle mouture des Eurocodes SC7

2020 ; Comité scientifique

Collaborateurs: Commend Stéphane

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Task Group C3 – “Reliability based methods” Aims of the Task Group: 1a. In the Eurocode Reliability based design is introduced, however, the main verification of Limit States is by Partial factors. In recent years Reliability design and full Probabilistic Analysis are used in practice. Guidance for the verification of Limit States using these methods should be provided by TG C3. 1b. Check, that the same level of reliability is achieved as required by EC7 1c. The results of the group on Reliability of SC10 (Vrouwenvelder) should be incorporated. 1d. The derivation of partial factors for different service life durations should assessed (procedures only) 1e. Both soil and rock should be considered. 2. Provide answers to comments from Working Group review and the Formal Enquiry. The answer shall include recommendation for how to handle the comment, motivation for the recommendation and proposed revised text to include in EN 1997.

2016

Membre du Comité de la Société des Ingénieurs et Architectes (SIA) section Vaud, présidence 2022-2024

2016 ; Activité associative

Collaborateurs: Commend Stéphane

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La SIA Vaud est administrée par un comité exécutif de 12 membres composé d’architectes et d’ingénieur·es. Son / sa président·e est élu·e pour deux ans. Ses membres sont élus pour deux ans et rééligibles trois fois au maximum.

2002

Directeur-administrateur de GeoMod SA

2002 ; Activité professionnelle

Collaborateurs: Commend Stéphane

Link to the achievement

GeoMod ingénieurs conseils SA, société indépendante consacrée à la modélisation numérique de pointe de problèmes géomécaniques, a vu le jour en septembre 2002.

Les domaines d’activités touchés par GeoMod sont assez divers. A côté de mandats classiques de dimensionnement de géo-structures telles que tunnels, tranchées couvertes, fouilles ancrées ou étayées, fondations superficielles et profondes (pieux), stabilité de pentes, barrages et digues, ouvrages portuaires, sont venus se greffer d’autres domaines connexes, à savoir : l’assainissement de glissements de terrain, la géothermie et l’hydrogéologie en collaboration avec la société Terre+, ou la vérification au séisme de structures complexes (viaducs et échangeurs autoroutiers, barrages en remblai ou en béton armé).

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Géotechnique

Simulations numériques

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