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PEOPLE@HES-SO – Annuaire et Répertoire des compétences
PEOPLE@HES-SO – Annuaire et Répertoire des compétences

PEOPLE@HES-SO
Annuaire et Répertoire des compétences

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Zwicky Daia

Zwicky Daia

Ordentlicher Professor FH

Compétences principales

Structures du génie civil

Construction écologique

Matériaux multifonctionnels

Analyse structurale

Eléments mixtes & hybrides

Modélisation matérielle

Structures existantes

  • Contact

  • Enseignement

  • Recherche

  • Publications

  • Conférences

  • Portfolio

Contrat principal

Ordentlicher Professor FH

Téléphone: +41 26 429 69 50

Bureau: HEIA_D40.03

Haute école d'ingénierie et d'architecture de Fribourg
Boulevard de Pérolles 80, 1700 Fribourg, CH
HEIA-FR
Institut
iTEC - Institut des technologies de l'environnement construit

CV complet et autres informations potentiellement utiles à trouver sur https://www.researchgate.net/profile/Daia_Zwicky/experience

MSc HES-SO en Engineering - HES-SO Master
  • Maintenance de structures porteuses (en béton)
  • Encadrement des thèses de Master
BSc HES-SO en Génie civil - Haute école d'ingénierie et d'architecture de Fribourg
  • Calcul de structures I à III
  • Encadrement des travaux de Bachelor

En cours

Connexion innovante pour des planchers en bois-béton mixte encore plus compétitifs
AGP

Rôle: Requérant(e) principal(e)

Financement: HES-SO Rectorat; Vial SA

Description du projet : La construction en bois apporte une solution pour diminuer l'empreinte carbone dans ce domaine. L'association du béton et du bois permet de diminuer les désavantages du bois seul dans la construction de planchers de grandes ampleurs, en créant des planchers en bois-béton mixte (BBM). Les systèmes de liaison entre le bois et le béton actuellement utilisés dans les planchers BBM sont souvent réalisés au moyen de connecteurs métalliques. Ces derniers ont un impact important sur le temps de fabrication, la sécurité au travail lors du montage (embûches par connecteurs protubérants), et encore sur l'empreinte carbone et le tri lors d'un recyclage à la fin de vie. Le système exploré ici, travaillant avec des encoches remplies de béton, diminue déjà fortement le nombre de connecteurs métalliques, mais en utilise quand-même dans l'état actuel. L'objectif principal du projet est de pouvoir éliminer ces connecteurs métalliques, en développant une forme d'encoche optimisée qui permet de garantir la transmission des efforts entre le bois et le béton et qui demandera un temps de fabrication minimale. Une telle liaison pour les planchers BBM permettrait de répondre à la demande de clients de diminuer l'impact carbone, d'accélérer la fabrication (et supprimerait également un fournisseur péjorant les circuits courts), d'augmenter la sécurité des ouvriers lors du montage, et de faciliter le recyclage à la fin de vie. Ce projet vise à optimiser la connexion par encoche dans des planchers en bois-béton mixtes (BBM), en répondant aux exigences de rigidité, de résistance et de ductilité élevées, tout en ciblant l'augmentation de la rentabilité, de la sécurité des ouvriers et la réduction de l'impact carbone. Par la réduction du volume de l'encoche et l'élimination des connecteurs métalliques, le projet aspire à améliorer la production et le recyclage. Cette démarche s'appuie sur des simulations numériques sophistiquées et des essais expérimentaux ciblés, plutôt que sur de simples tentatives expérimentales itératives.

Equipe de recherche au sein de la HES-SO: Zwicky Daia , Chira Alexandru , Maillard Philippe

Partenaires académiques: FR - EIA - Institut iTEC

Durée du projet: 01.05.2024 - 31.05.2025

Montant global du projet: 55'000 CHF

Statut: En cours

Potentiel d'utilisation des bois feuillus dans la construction et leur apport à la stratégie énergétique Suisse 2050
AGP

Rôle: Requérant(e) principal(e)

Financement: FR - EIA - Institut ENERGY; FR - EIA - Institut iTEC; SLL-PR

Description du projet : On constate depuis une vingtaine d'année une forte tendance d'utiliser du bois dans la construction des bâtiments, aussi promu par des autorités publiques (qui ont un rôle de précurseurs) dans le cadre des stratégies net-zéro. On peut presque dire qu'il y a actuellement une prédisposition de chercher la réponse aux défis de la réduction des émissions grises de la construction (carbone) uniquement dans l'application fortement promue du bois (« Holz ist hui, Beton ist pfui »). Mais, il faut s'attendre que les ressources suisses en bois résineux ' actuellement utilisés quasi exclusivement ' ne suffisent pas pour satisfaire la demande pour les décennies à venir, en se rendant compte qu'il y a déjà aujourd'hui des importations en quantités assez élevées. Ainsi, il faut se poser la question s'il sera mieux de poursuivre cette démarche (i.e. augmenter encore les imports de bois résineux) et quels seront les effets y associés, ou si on aura meilleur temps d'intensifier l'exploitation des ressources suisses. Pour cette dernière, on n'évitera pas de se tourner de plus en plus vers les bois feuillus, en considérant les tendances dans la gestion des forêts (qui cible des forêts de plus en plus mixtes à la place des forêts presque monoculture, comme on l'a poursuivi dans les décennies passées) et dans la croissance naturelle à venir induite par le réchauffement climatique, i.e. la résilience plus importante des essences feuillues par rapport aux résineux (qui poussent mieux en altitude qu'au plateau suisse). Cependant, l'utilisation des bois feuillus pour la construction montrent des défis bien différents des résineux, aux niveaux de leur transformation et fabrication. En effet, la fabrication d'éléments en bois feuillus demande plus de transformations et de colle que pour les résineux. En revanche, ils offrent aussi des opportunités pour la construction par leurs caractéristiques mécaniques plus élevées que celles des résineux, affectant ainsi le dimensionnement d'éléments porteurs resp. les volumes de matériaux consommés, la performance des connexions structurales (y.c. celles pour les combiner avec d'autres matériaux dans des éléments mixtes) et encore les détails constructifs pour le montage ou le démontage pour un réemploi potentiel. Ainsi, les quantités mises en 'uvre, évidemment à performance équivalente, devraient diminuer. En combinaison avec des transports réduits (car la ressource peut être locale), la construction en bois feuillus pourrait être plus favorable en termes de bilan carbone que l'import des bois résineux (transformés ou non). Sous l'hypothèse d'une utilisation plus importante des bois feuillus, actuellement sous-exploités, le projet veut explorer les contributions potentielles d'une exploitation meilleure, voire maximale des bois feuillus suisses dans la construction des bâtiments aux objectifs de la stratégie énergétique SE 2050 ' ou alors, quantifier la réponse à la question si la construction en bois peut résoudre le défi de la réduction des émissions carbone à net-zéro. Cependant, il faut considérer qu'il y a aussi d'autres utilisations de bois feuillus (d'une certaine valeur, p.ex. mobilier, chaudière, papier etc.). Ainsi, il faudrait aussi prendre en compte ces demandes, y compris des transferts éventuels de volumes consommés, dans la comparaison à l'offre potentielle de bois feuillus. Tout cela dans l'objectif de pouvoir comparer offre et demande sur l'échelle temporelle (et, si les données sont disponibles dans cette résolution, aussi territoriale), en admettant différents scénarios d'évolution, et ainsi pouvoir évaluer si les bois feuillus suisses peuvent contribuer d'une façon significative à la décarbonation du domaine de la construction.

Equipe de recherche au sein de la HES-SO: Buri Hani , Zwicky Daia , Trevisani Sandro , Jusselme Thomas , Civatti Mattia , Priore Yasmine , Schulthess Lucile

Durée du projet: 01.09.2023 - 31.08.2025

Montant global du projet: 167'000 CHF

Statut: En cours

For more projects, please visit iTEC website

Rôle: Requérant(e) principal(e)

Description du projet :

https://www.heia-fr.ch/fr/recherche-appliquee/instituts/itec/recherche/ > structures

Equipe de recherche au sein de la HES-SO: Zwicky Daia

Statut: En cours

Terminés

Outil adaptif, basé sur les techniques du machine learning, pour la prédiction des performances des bétons à base d'agrégats recyclés issus des déchets minéraux de démolition
AGP

Rôle: Requérant(e) principal(e)

Financement: HES-SO Rectorat

Description du projet : Les agrégats naturels (graviers et sables) pour la production de béton sont de moins en moins accessibles en Suisse, car les dépôts deviennent occupés par l'habitat et l'excavation des rivières est fortement régulée. Parallèlement, les déchets de construction et de démolition (DCD) ' qui comprennent de grandes quantités de déchets minéraux granulaires (béton, briques, et autres matériaux céramiques concassés) ' constituent le flux de déchets le plus important. Même lorsque les DCD sont bien triés (pour le recyclage), la réutilisation de la fraction minérale reste un défi majeur. De grandes quantités sont stockées à un coût d'opportunité élevé ou utilisées dans des applications de faible valeur. L'utilisation des DCD minéraux comme agrégats recyclés pour le béton (recycled aggregate concrete, RC) a un grand potentiel écologique et économique. Mais, les approches actuelles de définition et d'optimisation des recettes RC sont empiriques par défaut et nécessitent des travaux coûteux et fastidieux. L'impact des agrégats recyclés sur les performances physique, écologique et économique du RC est un phénomène multifactoriel complexe, influencé par plus de dix propriétés des agrégats. Toutes ces propriétés sont affectées négativement par des résidus de pâte de ciment adhérant aux agrégats, dont la concentration et les caractéristiques varient significativement entre les différentes sources de DCD. Ainsi, les résultats d'un développement empirique traditionnel sont spécifiques au stock de DCD utilisé et ne peuvent à priori pas être transposés à d'autres sources. Dans le cas des agrégats fins (fine recycled aggregates, FRA), où la concentration en résidus de ciment est notoirement plus élevée, ces approches sont inadaptées aux reformulations récurrentes nécessaires pour répondre aux fortes variations des sources de DCD et, donc, pour permettre leur utilisation à grande échelle en remplacement des agrégats naturels. Pour ceci, Il faut se réorienter : du développement de formulations spécifiques, à celui de méthodes et d'outils pour les trouver plus efficacement. A savoir aussi qu'actuellement, les agrégats fins (< 16 mm) issus des DCD sont fortement sous-exploités, pour les raisons exposées ci-dessus, mais ils représentent entre 70% et 80% du volume de béton. L'objectif principal de ce projet est de contribuer au développement de nouveaux outils adaptatifs de formulation de recettes RC capables de traiter efficacement la grande variabilité des agrégats recyclés fins. Pour ce faire, nous appliquons des techniques d'apprentissage automatique (Machine Learning, ML) à des images de FRA variées associées à certaines de leurs données physiques, ainsi qu'à des bases de données étendues de performances mécaniques de RC. En parallèle à ces outils spécifiques, un calculateur d'écobilan contenant les marqueurs environnementaux les plus pertinents au RC est développé. Ce projet complète de manière significative l'exploration méthodologique initiée dans le projet ORCADEMO (Optimised Recycled Concrete mix design by Artificial intelligence image processing of DEMOlition waste) avec le financement du Smart Living Lab Fribourg, sur trois fronts, en permettant : 1. d'établir la base méthodologique pour la prédiction holistique de l'impact environnemental des recettes RC. 2. d'explorer davantage le potentiel de techniques d'imagerie appliquées à des photos de granulats pour développer des outils facilitant la formulation de bétons recyclés. 3. d'élargir considérablement la base de données utilisée pour entraîner les outils prédictifs, grâce à l'extension de la campagne d'évaluation empirique à des sources supplémentaires d'agrégats recyclés mixtes et des bases de données provenant de la littérature ou de producteurs de béton.

Equipe de recherche au sein de la HES-SO: Périsset Blaise , Citherlet Stéphane , Favre Didier , Zwicky Daia , Eicher Sara , Chabbi Houda , Ruffieux Killian , Fringeli Samuel , Guinchard Basile , Maillard Philippe , Pauletta Stefano , Frossard Mija , Cau Sonia Anselmina , Ston Julien

Partenaires académiques: FR - EIA - Institut iCoSys; FR - EIA - Institut iTEC; iE; Zwicky Daia, FR - EIA - Institut iTEC

Durée du projet: 16.03.2023 - 14.03.2025

Montant global du projet: 220'000 CHF

Statut: Terminé

Optimized Recycled Concrete mix design by Artificial intelligence image processing of DEMOlition waste
AGP

Rôle: Requérant(e) principal(e)

Financement: FR - EIA - Général école Ra&D; FR - EIA - Institut iCoSys; FR - EIA - Institut iTEC; FR - EIA - Institut iTEC

Description du projet : The project aims to further the use of recycled aggregate in conventional concrete, developing the methodological basis for an image-based machine learning approach to overcome concrete performance uncertainty when fine natural aggregates are replaced by recycled materials. Efficient anticipation of cost- and environmentally-effective mix design adjustments would be enabled by training image processing networks to predict concrete performance from standardized images of fine recycled aggregates.

Equipe de recherche au sein de la HES-SO: Zwicky Daia , Chabbi Houda , Donzallaz Jonathan , Ruffieux Killian , Fringeli Samuel , Pasquier Benjamin , Guinchard Basile , Serpell Ricardo , Cau Sonia Anselmina , Ston Julien

Durée du projet: 01.06.2022 - 31.12.2024

Montant global du projet: 174'134 CHF

Statut: Terminé

Net-zero GHG Emissions in the Building Area ' Bottom-up Approach (F2); Netto-Null Treibhausgasemissionen im Gebäudebereich ' NN-THGG_F2
AGP

Rôle: Collaborateur/trice

Requérant(e)s: FR - EIA - Institut ENERGY, Jusselme Thomas, FR - EIA - Institut ENERGY

Financement: OFEN

Description du projet : The Federal Government promotes basic and applied research, and the research-oriented development of novel energy technologies, especially in the areas of energy savings, efficient energy use, transmission and storage of energy and the use of renewable sources of energy. On 23 December 2022 (revised on 2 June 2023) the HEIA-FR / Energy and iTEC submitted an application at the Swiss Federal Office of Energy (SFOE) for financial support of the project «Net-zero GHG Emissions in the Building Area ' Bottom-up Approach (F2); Netto-Null Treibhausgasemissionen im Gebäudebereich ' NN-THGG_F2». This project has the following content: Net Zero is the answer, but what was the question? How can we build and renovate Swiss buildings so that they sustain life and well-being of future generations? In this project, we want to assess current practices to build and renovate buildings, in order to highlight solutions which are technically and economically feasible. We will model existing buildings with different greenhouse gas accounting methodologies and consider various future scenarios in order to reach a robust comparison between buildings. In particular, we will look at built buildings using biobased and reused/recycled materials or building components as well as new advanced and alternative construction materials. The components of the different studied buildings will then be integrated in the building stock model done by F1.

Equipe de recherche au sein de la HES-SO: Périsset Blaise , Favre Didier , Zwicky Daia , Lasvaux Sébastien , Jusselme Thomas , Priore Yasmine , Schulthess Lucile , Maillard Philippe , Frossard Mija , Cau Sonia Anselmina

Partenaires académiques: PSI; FR - EIA - Institut ENERGY; ETH Zürich - Chair of Sustainable Construction ; iE; Jusselme Thomas, FR - EIA - Institut ENERGY

Durée du projet: 01.07.2023 - 30.11.2024

Montant global du projet: 90'780 CHF

Statut: Terminé

Demountable two-way timber-concrete composite slab system
AGP

Rôle: Requérant(e) principal(e)

Financement: SLL-PR

Description du projet : In view of more sustainable building construction, timber is gaining a lot of popularity lately. However, due to its quite soft structural performance and to potential fire issues, it is frequently combined with concrete in floor slabs, being major contributors to the carbon footprint of buildings. Today's timber-concrete composite (TCC) slab systems majorly bear loads in one direction only, limiting architectural flexibility in floor layout. While few studies explore bidirectional TCC systems, they often consider high-performance materials and permanent coupling joints. A modular, detachable two-way TCC slab system could considerably advance sustainable construction, merging quality with cost-effectiveness. The proposal to be developed aims at: 1) conceiving and optimizing a prefabricated, precast two-way TCC slab system with reduced consumption (compared to unidirectional TCC slabs) of average-performance materials, thanks to the use of advanced numerical and analytical approaches; 2) developing a demountable system with a high degree of reusability using a minimum of wet joints; 3) validating the proposed ideas for conceptual design, connections, coupling joints, and structural design approaches through experimental testing, and 4) identifying the benefits stemming from the new slab system reg. carbon footprint in constructed examples of buildings from practice.

Equipe de recherche au sein de la HES-SO: Zwicky Daia , Chira Alexandru

Partenaires académiques: FR - EIA - Institut iTEC

Durée du projet: 01.09.2023 - 31.12.2023

Montant global du projet: 15'000 CHF

Statut: Terminé

New Ecological CONcretes based on low-energy BIO-based artificial Lightweight Aggregates with multifunctional properties
AGP

Rôle: Requérant(e) principal(e)

Financement: FR - EIA - Général école Ra&D; FR - EIA - Institut iTEC

Description du projet : Building on novel low-energy lightweight aggregates recently developed at iTEC by cold-bonding of local by-products, the proposed project aims to develop new ecological lightweight concretes optimized for the multifunctional requirements of lightweight timber-based construction, as defined within a holistic environmental performance research and development framework.

Equipe de recherche au sein de la HES-SO: Pathé Julien , Zwicky Daia , Robadey Jacques , Gomez-Von Allmen Sophie , Trevisani Sandro , Pignone Danilo , Marti Roger , Jusselme Thomas , Niederhäuser Elena-Lavinia , Serpell Ricardo , Priore Yasmine , Schulthess Lucile , Cau Sonia Anselmina , Ston Julien

Partenaires académiques: FR - EIA - Institut ChemTech; FR - EIA - Institut ENERGY

Durée du projet: 01.05.2021 - 31.08.2023

Montant global du projet: 182'600 CHF

Statut: Terminé

Initiation to pelletizing lightweight aggregates from biomass and cement (initiation to BIO-based Light Aggregate Pelletizing)
AGP

Rôle: Requérant(e) principal(e)

Financement: FR - EIA - Général école Ra&D; FR - EIA - Institut iTEC; FR - EIA - Institut iTEC

Description du projet : Lightweight concrete (LWC) reaches its lower density and improved thermal performances ' compared to normal-weight concrete ' thanks to aggregates made of expanded clay or glass (LWA, e.g. LECA®, MISAPOR®), being unfortunately environment-unfriendly (high production energy, inorganic waste). Their replacement with bio-sourced aggregates (e.g. cherry pits & grape seeds instead of sand & gravel) was proved to be more ecological at the trade-off of mechanical and economic performances, strongly limiting the replacement rates. This project wants to experimentally evaluate the feasibility of pelletizing LWA at room temperature from forestry and other biomass by-products (sawdust, combustion ashes) with cement as a binder, serving as a basis for follow-up research and potential commercialization.

Equipe de recherche au sein de la HES-SO: Zwicky Daia , Serpell Ricardo , Macchi Niccolò

Durée du projet: 01.09.2020 - 31.12.2021

Montant global du projet: 31'200 CHF

Statut: Terminé

Construire la densification des surfaces habitables urbaines en équilibre avec la nature
AGP

Rôle: Requérant(e) principal(e)

Financement: HES-SO Rectorat; INSIT

Description du projet : Tous pronostics démographiques prévoient un développement de plus en plus important des centres urbains. Pour lutter contre l'étalement des villes, ces dernières doivent être densifiées vers l'intérieur comme l'exige aussi la dernière LAT ' et ceci sur la base d'un stock de bâtiments urbains bien âgé. Un des moyens le plus prometteur pour densifier les villes existantes est l'augmentation de la capacité de logement des bâtiments existants par l'élargissement vers le haut, i.e. la surélévation des bâtiments. Déjà d'un point de vue des capacités de la structure du bâtiment existant, les éléments de surélévation doivent être les plus légers possibles afin de ne pas sur-solliciter la construction existante d'une façon excessive respectivement de rendre possible l'ajout d'un nombre maximal d'étages sans interventions disproportionnées sur la structure existante. Ces éléments de construction légers peuvent être réalisés en utilisant, soit des matériaux légers en dimensions usuelles, soit des matériaux de haute performance d'une densité (beaucoup) plus élevée mais permettant des dimensions très minces. Sur la base de bâtiments existants utilisés comme études de cas, des matérialisations génériques pour les éléments de surélévation sont proposées en tenant compte des exigences structurelles, thermiques, phoniques et de protection incendie en fonction de différents aménagements de surélévation. Les solutions développées sont évaluées par rapport aux impacts écologiques et économiques, à l'aide d'une bibliothèque de composants en considérant différentes combinaisons de matériaux de structure, d'isolation et de revêtements. A la multitude de combinaisons possibles de matériaux, s'en ajoutent plusieurs pour l'évaluation de l'impact du type d'aménagement intérieur et du nombre d'étages ajoutés. Ces évaluations écologique et économique permettaient d'identifier, quelles sont les solutions plus adaptées à la construction de surélévation et celles qui ne le sont pas, en considérant le type d'aménagement intérieur et le nombre d'étages ajoutés. De plus, elles permettent d'identifier les éléments prépondérants (et ainsi, à optimiser) pour l'impact écologique, en premier lieu. Les résultats montrent qu'il n'y a pas une réponse simple à la question, quelle est la matérialisation générale (« béton », « bois » etc.) la plus appropriée pour construire des surélévations. Faire des surélévations les plus hautes possibles est à priori bénéfique pour les impacts économique et écologique, mais plus elle est haute, plus il faudrait faire des compromis sur l'aménagement d'étage. Une surélévation plus haute sera aussi favorable à l'amortissement d'une rénovation énergétique de l'existant (i.e. les loyers supplémentaires grâce à la surélévation contribuent à « payer » la rénovation de l'existant). L'impact écologique se trouvent principalement dans les éléments de plancher y.c. la toiture tandis que sa distribution sur les différentes couches de l'élément varient fortement en fonction du matériau appliqué. Les couches non porteuses (i.e. second 'uvre : finitions, revêtements et parois de séparation) peuvent contribuer d'une façon très importante à l'impact écologique. Des résultats plus détaillés se trouvent dans le rapport technique final. Les résultats montrent encore qu'il n'y a pas de corrélation évidente entre le poids constructif de la surélévation et l'impact écologique. Par contre, cibler une réduction de l'impact économique est normalement au détriment de l'impact écologique, tandis qu'une augmentation des dépenses financières ne résultent normalement pas dans une réduction de l'impact écologique (au contraire). In fine, les résultats du projet permettaient de recommander des matérialisations préférentielles et de déconseiller d'autres.

Equipe de recherche au sein de la HES-SO: Radu Florinel , Périsset Blaise , Rudaz Joëlle , Citherlet Stéphane , Favre Didier , Zwicky Daia , Meszes Adam Attila , Schaller Marc , Torche Jérémy , Giorgi Morgane , Lasvaux Sébastien , Runser Julie , Bernasconi Andrea , Uboldi Paride , Bourrier Hervé , Jaquerod Grégory , Goulouti Kyriaki , Schwab Stefanie

Partenaires académiques: IGT; FR - EIA - Institut iTEC; FR - EIA - Institut TRANSFORM; Zwicky Daia, FR - EIA - Institut iTEC

Durée du projet: 15.11.2018 - 31.10.2021

Montant global du projet: 200'800 CHF

Statut: Terminé

Verstärken von Fahrbahnplatten mit Textilbeton
AGP

Rôle: Requérant(e) principal(e)

Financement: OFROU; FR - EIA - Institut iTEC; FR - EIA - Institut iTEC

Description du projet : Das Projekt arbeitet den Kenntnisstand zu Verstärkungen von Betonbauteilen mit Textilbeton gezielt für Kunstbauten auf - gegliedert nach Bauteil und hauptsächlicher Beanspruchungsart - und stellt den Projektverantwortlichen damit Bemessungsgrundlagen zur Verfügung. Die Einpassung dieser relativ neuen Verstärkungsmethode in Schweizer Gepflogenheiten und Regelwerke bei der Tragwerksanalyse und Bemessung werden aufgezeigt. Kenntnislücken für die spezifische Anwendung von Textilbetonverstärkungen auf Betonbauteile von Kunstbauten werden indentifiziert und allenfällige weitere Forschungsbedürfnisse formuliert.

Equipe de recherche au sein de la HES-SO: Maeder Marco , Zwicky Daia , Muresan Alex-Manuel , Chira Alexandru

Durée du projet: 01.01.2017 - 31.08.2021

Montant global du projet: 139'212 CHF

Statut: Terminé

Wood-based concrete: building construction with composite elements of wood-concrete compounds and timber
AGP

Rôle: Requérant(e) principal(e)

Financement: HES-SO Rectorat; Vial SA; FR - EIA - Général école Ra&D; JPF Construction SA; Erne Holzbau AG; TU Wien - ITI; FR - EIA - Institut iTEC; FNS; FR - EIA - Institut iTEC

Description du projet : This project focuses on the development of new principles for load-bearing elements made of wood or wood-based concrete. Alongside the improved static load-bearing capacity, these innovative building elements also offer economic and ecological ad-vantages (weight reduction, thermal and acoustic insulation, fire protection, heat storage, reusability as source of heat and electricity). Background Cement-bonded wood products are today mainly used for non-load-bearing purposes, e.g. as noise or fire protection panels. However, wood-based concrete in a new mixture could also be used in ceilings and wall elements and could thus make a contribution also to load-bearing. That said, knowledge about load-bearing elements involving wood-based concrete is still too limited for practical application to go ahead. In particular, data is lacking on the composition of wood-based concrete for specific uses, on the nature of the joints to be used, on how whole ceilings and wall elements can be planned economically and on the dimensioning methods to be applied to these elements. Aim The project aims to develop mixtures of lightweight concrete with different pre-treated wood components and to assess their suitability as load-bearing materials. The results will flow into a conceptual structural design of ceilings and wall elements and will be complemented by experiments with joints for the individual components. Applying dimensioning methods that have rarely been used before in wood construction, the researchers will predict the bearing capacity of entire building elements through to fracture and study it in load tests at a large scale. Practice-oriented dimensioning approaches will be derived from the results. Based on further pre-experiments and case studies, the researchers will assess other expected ad-vantages, e.g. for thermal insulation and storage, for fire and noise protection, and with regard to economic competitiveness. Significance Load-bearing elements containing wood-based concrete are lighter in weight and offer integrated noise and fire protection. Thanks to the high share of wood, these innovative building elements are largely based on renewable resources and provide thermal insulation and storage. They can moreover be used as source of heat and electricity after their dismantling. The dimensioning methods to be developed'so far limited to the traditional building materials steel and reinforced concrete'could make construction with wood and wood-based products more efficient and thus contribute to the appropriate use of Swiss forests and Swiss wood.

Equipe de recherche au sein de la HES-SO: Moix Jonathan , Andrey Jean-Paul , Monney Isabelle , Maeder Marco , Delaquis Dominique , Zwicky Daia , Meszes Adam Attila , Uboldi Paride , Herren Christoph , Corpataux Dominique , Raetzo Raphaël , Macchi Niccolò , Ropp Julien

Partenaires académiques: IGT

Durée du projet: 01.11.2010 - 31.12.2020

Montant global du projet: 1'170'216 CHF

Statut: Terminé

Développement de compétences de l'iTEC au service ultérieur du SLL
AGP

Rôle: Requérant(e) principal(e)

Financement: FR - EIA - Général école Ra&D

Description du projet : Cette famille de projet sert à l'acquisition et à l'approfondissement des compétences disponibles à l'iTEC, dans les domaines suivantes: - la caractérisation mécanique des matériaux de construction et sa modélisation numérique, grâce à des essais de laboratoire et des techniques de mesure fiables et exhaustives, de l'échelle du matériau (éprouvettes) à l'échelle des structures; - les villes "éponges" qui sont capables de gérer la qualité et la quantité d'eau, grâce à différentes techniques (notamment celles liées à la végétalisation), ainsi que la température environnant les bâtiments et les espaces de vie, à l'échelle de la parcelle; - l'exploration des applications structurales des semi-produits à la base de fibres de basalte, principalement en éléments hybrides avec d'autres matériaux, de la conception constructive à l'analyse structurale et le dimensionnement jusqu'aux détails constructifs. Ses activités s'inscrivent ainsi et seront utiles pour une gamme d'activités ultérieures de recherche appliquée et de développement du Smart Living Lab.

Equipe de recherche au sein de la HES-SO: Moix Jonathan , Bullinger Géraldine , Redaelli Dario , Spahni Bruno , Zwicky Daia , Favre Boivin Fabienne , Froidevaux Manuel , Uboldi Paride , Labiouse Vincent , Pfister Michael , Albertoni Loran , Bénet Loïc , Muresan Alex-Manuel , Frei Benjamin , Chamoun Sabine , Macchi Niccolò

Partenaires professionnels: FR - EIA - Institut iTEC; FR - EIA - Institut iTEC

Durée du projet: 01.04.2019 - 31.12.2019

Montant global du projet: 221'450 CHF

Statut: Terminé

2024

Constitutive modelling of deformation rate dependent response of steel timber shear connections
Article scientifique ArODES

Dan V. Bompa, Alexandru Chira, Daia Zwicky

Journal of Building Engineering,  To be published, 111159

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Résumé:

This paper presents experimental and numerical investigations into the deformation rate-dependent constitutive response of steel-timber shear connections with screws. After describing the test specimens and experimental arrangement, a detailed account of the complete deformation response and main mechanical parameters of the tested shear connections under three applied displacement rate levels are given. Specimens with small screw diameters had a relatively brittle response, failing shortly after yielding, whilst those with higher diameters showed ductile failure modes, with plastic hinges forming in the screws and concurrent extensive timber crushing. It was observed that the stiffness increases with the deformation rate due to the viscoelastic response of wood materials, whilst the peak load is largely constant. Nonlinear finite element simulations were carried out to validate the main numerical parameters for steel, timber, and interaction characteristics. After gaining confidence in the ability of the numerical models to predict closely the stiffness and peak load, numerical investigations were carried out to examine the influence of key material and geometric parameters on the stiffness, load resistance and deformation response. The studies showed that higher timber strength increases the initial stiffness and the peak load, while higher screw grades improved both stiffness and strength. Based on the results and observations, code-modified expressions for evaluating the stiffness and load resistance, as a function of the deformation rate, are proposed within the ranges considered, and validated against a collated database. Comparative assessments with existing literature indicate that the proposed equations provide improved estimates. Suggested closed-form relationships enable the characterisation of the full constitutive response of steel-timber shear connections, that can be adopted for discrete nonlinear modelling of connectors.

Properties of materials in existing structures
Chapitre de livre ArODES

Carmen Andrade, Dario Coronelli, Gerrie Dieteren, Davide Lavorato, Alberto Meda, Camillo Nuti, Joost Walraven, Kamyab Zandi, Daia Zwicky

Dans Walraven, Joost, Modelling structural performance of existing concrete structures (fib Bulletin)  (pp. 16-52). 2024

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Assessing the bearing capacity of existing structures
Chapitre de livre ArODES

Carmen Andrade, Beatrice Belletti, Dario Coronelli, Ane de Boer, Marta del Zoppo, Max Hendriks, Mehdi Kashani, Eva Lantsoght, Miguel Prieto, Zila Rinaldi, Joost Walraven, Yuguang Yang, Kamyah Zandi, Daia Zwicky

Dans Walraven, Joost, Modelling structural performance of existing concrete structures (fib Bulletins)  (pp. 76-167). 2024

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2022

Low-energy lightweight aggregates by cold bonding of biomass wastes :
Article scientifique ArODES
effects of raw material proportion adjustments on product properties

Ricardo Serpell, Daia Zwicky

Construction and Building Materials,  2022, vol. 346, article no. 128392

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Résumé:

The reported research explored the feasibility of cold bonding as a method to produce low-embodied-energy lightweight aggregates from locally available biomass wastes (wood sawdust and ashes) and cement, using response surface methodology to model the effect of raw material proportions on the properties of the product. The empirical exploration comprised the particle size distribution, saturated surface dry and oven dry density, water absorption capacity, drying shrinkage, short- (7 days) and long-term (70-days) particle crushing strength, and strength variability of the pellets. Aggregates with particle densities below 1.850 g/cm3 and crushing strengths above 1.5 MPa (comparable to expanded clay aggregates) were obtained. In the experimental region explored, increasing sawdust contents to decrease aggregate density negatively affected all the other aggregate properties tested. However, the negative impact was strongly reduced by increasing the ratio of coarse particles in the sawdust. Intermixing cement in the raw material mixture – as opposed to adding it as a coating to the already formed pellets – resulted in better formed, smaller, and stronger pellets, and reduced strength variability. The response model obtained was validated and used to optimize aggregate properties with the specific set of raw materials and production methods studied.

2021

The times they are a-changin’
Article professionnel ArODES

Daia Zwicky

Structural Engineering International,  2021, editorial, p. 325

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Strengthening of bridge deck slabs with textile reinforced concrete = Verstärken von Fahrbahnplatten mit Textilbeton = Renforcement de dalles de roulement avec le béton armé aux textiles
Livre ArODES

Daia Zwicky, Alex-Manuel Muresan, Marco Maeder

2021,  Ittigen : Office Fédéral des Routes (OFROU),  63 p.

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Résumé:

Ce rapport présente les résultats de l’évaluation de l’aptitude de différentes approches analytique pour le dimensionnement à l’état-limite ultime (ELU) d’un renforcement à la flexion des dalles de roulement des ponts-routiers avec du béton armé aux textiles (béton textile, BT). Le BT est un matériau composite qui combine la résistance à la traction élevée des fibres des textiles avec l’adhérence et les protections mécaniques et thermiques fournies par des bétons à petits granulats, c.à.d. des mortiers à base de ciment. En plus d'être utilisé dans la fabrication de nouveaux éléments en BT, ce matériau peut également être utilisé en tant que couches de renforcement d’éléments en béton armé (BA) existants. Les textiles les plus populaires utilisées dans ce type d'application se composent de fibres de carbone, de basalte, de verre et de PBO (polyphénylène-2,6-benzobisoxazole, alias « Zylon »). Après leur production, ces fibres sont regroupées en fils très résistants à l'aide de résine. Ces fils sont ensuite tissés en textiles, normalement en forme de grilles. Pour le renforcement à la flexion d’éléments BA existants, la préparation du support joue un rôle crucial. Afin d'assurer un comportement monolithique à l'interface, il doit être rendu rugueux par l’hydrodémolition avant d'appliquer le système de renforcement. Une fois ce processus terminé, la première couche de mortier peut être appliquée, normalement par giclement à voie sèche ou humide, suivie par des couches successives de textile-mortier jusqu'à ce que le niveau de renforcement souhaité soit atteint. En plus d'offrir un enrobage supplémentaire à l’armature en acier dans un élément BA existant, le mortier joue un rôle structural important pour l’ancrage des textiles au bord de la zone fonctionnelle. L'ancrage par adhérence a été étudié à travers d’une campagne expérimentale qui a permis de compléter des données expérimentales de la littérature et de calibrer une série de paramètres d’un modèle théorique précédemment développé. L’étude s'est conclue par la proposition d’une approche analytique pour le calcul de la résistance d'ancrage des fils des textiles noyés dans le mortier. Des détails concernant cette proposition et l’étude expérimentale figurent aussi dans le présent rapport. Afin d’identifier une approche théorique appropriée pour le dimensionnement du BT en tant que renforcement à la flexion des dalles unidirectionnelles, une base de données de résultats expérimentaux a été créée en rassemblant des données de la littérature existante. Elle contient les résultats d’environ 150 expériences sur des éléments renforcés et non renforcés de référence. Chaque entrée couvre 58 paramètres relatifs à la configuration de test, la géométrie des sections, les propriétés des matériaux et les résultats expérimentaux. Dans un premier temps, ces données ont été évaluées empiriquement pour déterminer statistiquement le type de matériel de textile utilisé, les types de défaillances observés et l'augmentation de la résistance à la flexion. Cette dernière est augmentée, à la moyenne et indépendamment du matériau de textile, de 20-25% par couche de textile. Différentes approches analytiques ont été ensuite appliquées afin de tester leur adéquation, en comparant la résistance à la flexion théorique avec les résultats expérimentaux. Une première approche considère l’adhérence du textile à la matrice comme rigide et a pour résultat une forte surestimation de la résistance réelle à la flexion avec un grand coefficient de variation (COV) encore. Ce que justifie l’introduction des coefficients de réduction de la rigidité axiale des textiles, comme aussi postulé dans la littérature, qui résident dans les particularités du comportement à l’adhérence à l’interne des textiles mais aussi avec le mortier qui les enrobe. La seconde approche appliquée va donc vers l'autre extrême, en considérant qu'il n'y a pas d’adhérence entre le textile et la matrice mais que le textile est ancré à l'extrémité de l’élément par le mortier. Cette approche donne des résultats conservateurs de la résistance théorique à la flexion mais n’est pas non plus considérée comme satisfaisante, en raison du COV élevé. Les troisième et quatrième approches appliquées cherchent à identifier des coefficients de frottement respectivement des coefficients d’adhérence entre le textile et la matrice mais, en raison de leur inapplicabilité pour les configurations de flexion 3 points et des COV élevés, ces approches ont aussi été abandonnées. Enfin, une méthode analytique est retenue, qui introduit des déformations-limites à la traction par flexion pour les textiles pendant que l’armature en acier existante est en écoulement, en s’orientant ainsi à des approches provenant des lamelles en polymère renforcées par fibres collées. Grâce à la calibration raffinée de ces limites, une moyenne de 1 du rapport entre les résultats expérimentaux et théoriques et le COV le plus bas de toutes les approches évaluées sont obtenus. Cette approche a l’avantage d’être bien orienté vers la pratique. Le désavantage est que le mode de rupture prépondérant ainsi n’est pas explicitement décrit par cette vérification. Dans les essais, on observe normalement des ruptures de l’ancrage ou de délamination des textiles qui sont plutôt liés, les deux, à une sollicitation à l’effort tranchant qu’à la flexion. Ainsi, il est recommandé de compléter le dimensionnement à la flexion par déformations-limites avec la vérification de l’ancrage des textiles dans la zone théoriquement non-fissurée (en analogie avec la SIA 166). Ce rapport présente aussi un modèle de dimensionnement pour la vérification de l’ancrage des textiles qui montre une bonne concordance avec des résultats expérimentaux et des COV satisfaisants. En plus, il démontre que la résistance de l’ancrage est limitée et que la résistance à la traction des textiles ne peut normalement pas être exploitée. Pour le dimensionnement pratique avec les déformations-limites, il y a besoin d’identifier des valeurs de dimensionnement qui se basent, à leur tour, sur des valeurs caractéristiques. Des déformations-limites pour ces derniers ne peuvent pratiquement être recommandées qu’uniquement pour les textiles en fibre de carbone ou de PBO car trop peu de données étaient disponibles pour les textiles en fibre de verre et de basalte. Le béton armé aux textiles ou le béton textile représente une méthode viable pour renforcer les éléments structuraux existants en béton armé à la flexion. Les avantages principaux de cette méthode de renforcement sont la facilité d'application sur le chantier, qui implique des outils déjà utilisés, ainsi qu’une meilleure résistance au feu en comparaison avec des solutions utilisant des armatures collées. L'incidence potentielle du renforcement à la flexion avec du béton textile sur la résistance au cisaillement ou à la fatigue ainsi que sur le comportement à l’état de service des dalles de roulement n'a pas pu être évalué en raison de l’indisponibilité de données dans la littérature. Des recherches sur cet effet sont clairement souhaitable, portant, en particulier, sur des essais en grandeur réaliste avec des renforcements aux textiles en basalte et en PBO et sur des situations plus générales (taux d’armature en acier plus élevés, autres élancements des dalles etc.). Ainsi, des déformations-limites pour ces matériaux peuvent être établies et des sections de contrôle peuvent être identifiées plus précisément. Les effets des renforcement textile seront bien probablement affectés par l’influence de l’adhérence entre textile et mortier sur le comportement de l’élément renforcé où des recherches supplémentaires devraient aussi être effectuées. Une attention particulière devrait être prêtée à l’évaluation de l’efficience de trois couches de textiles et plus, à identifier par des essais d’ancrage à longueur variable et par des essais à la flexion en grandeur réaliste. Ces résultats, en combinaison avec des réflexions théoriques ultérieures devraient permettre de décrire le comportement des textiles et leur adhérence. Une perte potentielle de la capacité du renforcement en béton textile due à la sollicitation par des charges de fatigue serait un autre sujet important à étudier. Pour ces deux sujets, le modèle d’adhérence décrit dans ce rapport peut servir comme base. Enfin, les résultats de toutes ces évaluations devraient de refléter dans des directives normatives (p.ex. par une révision de la SIA 166). Ceci nécessitera, en plus, la dérivation et l’identification des valeurs caractéristiques, des coefficients de conversion et des facteurs des sécurité des matériaux.

2020

Suitability evaluation of structural analysis approaches for determining the flexural capacity of reinforced concrete elements strengthened with textile-reinforced mortar
Article scientifique ArODES

Alex Muresan, Daia Zwicky

Structural Engineering International,

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Résumé:

This study presents the evaluation of various structural analysis approaches to theoretically determine the bending resistance of flexural reinforced concrete elements strengthened with textile-reinforced mortar (TRM), which are gaining more and more attention as external strengthening layers. To assess the increase in capacity due to strengthening, multiple experimental studies from the literature were evaluated. Different structural analysis approaches for determining the flexural strength increase were tested against the experimental data. Finally, the consideration of strain limits for the textile layers, as also applied in the dimensioning of externally bonded fiber-reinforced polymers, proved to be the most reliable analytical approach.

Mechanical properties of organic-based lightweight concretes and their impact on economic and ecological performances
Article scientifique ArODES

Daia Zwicky

Construction and Building Materials,  2020, vol. 245, article no. 118413

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Résumé:

This study aimed at improving mechanical properties of wood-cement compounds, basically consisting of Portland cement and of up to 60% of untreated sawdust, through an aggregate skeleton made of organic aggregates (fruit pits, crushed nut shells) and lightweight aggregates (expanded clay and glass). Experimental results show that workability and strength development can be notably improved. Compressive strength can be doubled, and elastic modulus can be tripled. All properties exhibited a marked influence of organic aggregate content. Contextualized comparisons show that the developed alternative lightweight concretes (LC) can be economically competitive with regular LC while the eco-balance is reduced by 70–80%.

2018

Construction with wood-cement compounds and timber
Chapitre de livre ArODES

Daia Zwicky, N. Macchi, A. Fridez, V. Sciboz, M. Maeder, M. Medziti

Dans The fifth fib-Congress, Betonbau in der Schweiz = Construction en béton en Suisse = Structural Concrete in Switzerland  (1 p.). 2018,  Lausanne : fib-CH, p/a EPFL ENAC IBETON

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Résumé:

Pourable lightweight wood-based concretes (or wood-cement compounds, WCCs, respectively) were developed and assessed with respect to struc tural properties, targeting their structural combination with timber. Composite slab and wall elements were conceived and evaluated experimentally and analytically in full-scale tests up to rupture and for long-term behaviour. Practical structural design approaches were also derived. Further assessments targeted properties of thermal and fire protection, recyclability, eco-balance and economic competitiveness. Possible use in residential, office and school buildings was proven.

A solid foundation for a new flexible structure in IABSE’s technical activities
Article professionnel ArODES

Daia Zwicky

Structural Engineering International,  2018, vol. 28, no. 2, p. 109

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2017

HEIA-FR/HES-SO, activities at iTEC
Chapitre de livre ArODES

Daia Zwicky

Dans Guadagnini, Maurizio, COST Action TU1207 Next Generation Design Guidelines for Composites in Construction: State-of-the-Art Report  (pp. 374-384). 2017,  Sheffield : The University of Sheffield

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Publications antérieures
Article scientifique

Zwicky Daia

Multiples, 2017

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Résumé:

A trouver sur ResearchGate !

2015

Chillon Viaduct deck slab strengthening using reinforced UHPFRC :
Chapitre de livre ArODES
full-scale tests

Daia Zwicky, Eugen Brühwiler

Dans Alexander, M. G., Beushausen, H.-D., Dehn, F., Moyo, P., Concrete Repair, Rehabilitation and Retrofitting IV : Proceedings of the 4th International Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR-4), 5-7 October 2015, Leipzig, Germany  (2 p.). 2015,  London : Taylor & Francis

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Résumé:

The twin Chillon Viaduct, situated next to world-famous Chillon Castle on the A9/E27, was conceived by Jean Muller, designed by Jean-Claude Piguet, and built in the late 1960s. This chapter focuses on full-scale failure tests on specimens representing zones between and above the webs of the box girder. The primary goal was to verify the expected increase in ultimate resistance due to the R-UHPFRC layer, as expected through analytical models. The full-scale tests confirmed that also an unstrengthened slab undergoing strength reduction due to Alkali-Silica Reaction would not fail by punching of a wheel load. Casting of the R-UHPFRC strengthening on the 2.1 km long Chillon Viaduct was performed during five weeks, ending in September 2014. Structural design of the strengthening layer was performed using analytical resistance models which were validated by non-linear finite element modelling, calibrated to the present test results.

Chillon Viaduct deck slab strengthening using reinforced UHPFRC :
Chapitre de livre ArODES
numerical simulation of full-scale tests

Hamid Sadouki, Eugen Brühwiler, Daia Zwicky

Dans Alexander, M. G., Beushausen, H.-D., Dehn, F., Moyo, P., Concrete Repair, Rehabilitation and Retrofitting IV : Proceedings of the 4th International Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR-4), 5-7 October 2015, Leipzig, Germany  (2 p.). 2015,  London : Taylor & Francis

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Résumé:

The strengthening method of bridge deck slabs by means of an Ultra High Performance Fiber Reinforced cement-based Composite material (UHPFRC) overlay has been validated by a specific experimental program which is presented in a companion contribution. This chapter presents results of a non-linear finite element analysis of the structural and cracking behavior of composite UHPFRC/concrete slabs subjected to loading similar to loading of real bridge decks. The deck slab of the Chillon Viaduct located on the Swiss National Highway on the East end of the Lake of Geneva, was strengthened by adding, on the previously hydro-jetted top surfaces of deck slabs, a 40 to 50 mm thick layer of UHPFRC which is additionally reinforced by steel rebars. Finite volume elements with 20 nodes were employed to represent the geometry of the structure, consisting of Reinforced Concrete (RC) monolithic slab elements and composite R-UHPFRC—RC slab elements, steel loading platesand supporting beams.

2013

Theoretical influence of stirrup ductility on shear assessment of concrete girders
Article scientifique ArODES

Daia Zwicky

Structural Engineering International,  2014, vol. 24, no. 2, pp. 236-245

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Résumé:

Applying simplified design code provisions for the shear assessment of existing concrete girders may result in unnecessary strengthening, justifying the effort to apply more refined approaches. Based on the cross-sectional analysis for continuous girder zones (B-regions), this paper discusses the theoretical influences of transverse reinforcement ductility and effective web concrete-compressive strength on shear resistance. It is shown that the plastic deformation capacity is fundamentally influenced by the hardening behavior of the transverse reinforcement and by the bond properties between reinforcement and concrete. For typical examples of stirrup configurations, allowable compression field inclinations are derived and are also compared to the provisions of the fib Model Code 2010 and the Generalized Stress Field Approach. This paper concludes with an outlook on practical considerations and how the findings have been integrated in the recently published Swiss code SIA 269/221 on existing concrete structures.

Bond and ductility :
Article scientifique ArODES
a theoretical study on the impact of construction details - part 2: structure-specific features

Daia Zwicky

Advances in concrete construction,  2013, 1, 2, 137-149

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Résumé:

The first part of this two-part paper discussed some basic considerations on bond strength and its effect on strain localization and plastic deformation capacity of cracked structural concrete, and analytically evaluated the impacts of the hardening behavior of reinforcing steel and concrete quality on the basis of the Tension Chord Model. This second part assesses the impacts of the most frequently encountered construction details of existing concrete structures which may not satisfy current design code requirements: bar ribbing, bar spacing, and concrete cover thickness. It further evaluates the impacts of the additional structure-specific features bar diameter and crack spacing. It concludes with some considerations on the application of the findings in practice and an outlook on future research needs.

Bond and ductility :
Article scientifique ArODES
a theoretical study on the impact of construction details - part 1: basic considerations

Daia Zwicky

Advances in concrete construction,  2013, 1, 1, 103-119

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Résumé:

The applicability of limit analysis methods in design and assessment of concrete structures generally requires a certain plastic deformation capacity. The latter is primarily provided by the ductility of the reinforcement, being additionally affected by the bond properties between reinforcing steel and concrete since they provoke strain localization in the reinforcement at cracks. The bond strength of reinforcing bars is not only governed by concrete quality, but also by construction details such as bar ribbing, bar spacing or concrete cover thickness. For new concrete structures, a potentially unfavorable impact on bond strength can easily be anticipated through appropriate code rules on construction details. In existing structures, these requirements may not be necessarily satisfied, consequently requiring additional considerations. This two-part paper investigates in a theoretical study the impacts of the most frequently encountered construction details which may not satisfy design code requirements on bond strength, steel strain localization and plastic deformation capacity of cracked structural concrete. The first part introduces basic considerations on bond, strain localization and plastic deformation capacity as well as the fundamentals of the Tension Chord Model underlying the further investigations. It also analyzes the impacts of the hardening behavior of reinforcing steel and concrete quality. The second part discusses the impacts of construction details (bar ribbing, bar spacing, and concrete cover thickness) and of additional structure-specific features such as bar diameter and crack spacing.

2025

Leveraging Embedding Vectors of Aggregate Images for Particle Size Distribution Estimation and Concrete Compressive Strength Prediction
Conférence

Fringeli Samuel, Chabbi Houda, Ruffieux Killian, Ston Julien, Zwicky Daia

17th International Conference on Agents and Artificial Intelligence, 22.02.2025 - 24.02.2025, Porto, Portugal

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Résumé:

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Leveraging embedding vectors of aggregate images for particle size distribution estimation and concrete compressive strength prediction
Conférence ArODES

Samuel Fringeli, Houda Chabbi Drissi, Killian Ruffieux, Julien Ston, Daia Zwicky

Proceedings of the 17th International Conference on Agents and Artificial Intelligence (ICAART 2025)

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Résumé:

Accurate prediction of concrete properties, such as compressive strength, is essential for ensuring structural performance. Particle size distribution (PSD) and nature of aggregates are key components of concrete mix tures, significantly influencing their final compressive strength. This paper presents a novel approach that leverages embedding vectors extracted from images of aggregates using the DinoV2 model to efficiently pre dict compressive strength. DinoV2 is a state-of-the-art vision transformer that excels at generating high-quality embeddings for various visual tasks. In this study, the effectiveness of these embeddings is evaluated by using them to classify and estimate the PSD of aggregates on public datasets. Small neural models trained on these vectors achieved comparable accuracy to the best found fine-tuned ViT-16 model, demonstrating the poten tial of using embedding vectors for accurate PSD prediction. Building on these results, a new approach for predicting concrete compressive strength by combining embedding vectors with data on concrete mix com ponents is explored. A small dataset of concrete mixtures was created. To mitigate the challenges of limited data, augmentation techniques were proposed to generate additional, realistic mix designs. An ablation study was performed, indicating promising results and highlighting the potential of this new approach for predicting other concrete properties.

2024

Exploration of lightweight binders and aggregates made from biomass waste
Conférence ArODES

Julien Ston, Daia Zwicky

Proceedings of the International Conference on Concrete Sustainability (FIB ICCS), 11-13 September 2024, Guimarães, Portugal

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Résumé:

This study explored the potential of using high-calcium grate ash and fly ash from wood combustion in combination with metakaolin and limestone as a replacement material for cement in low-clinker binders. Three products were investigated: sand mortars and lightweight mortars, as well as pellets in order to obtain lightweight, low-clinker, and waste-embedding aggregates. In mortars, the sulphur- and potassiumrich fly ash was found to be detrimental to the strength, even at low amounts (5%), whereas the grate ash could replace up to 15% of cement in a binder. This addition improved early age strength but rather acts as a filler at later age. Slaking the ash before blending was found not to be necessary, although it slightly improved mechanical performance. Lightweight mortars were explored by replacing sand with sawdust, another byproduct from the timber transformation chain. Low densities (of 900-1500 kg/m3) could be obtained, but it was also shown that these lightweight materials would be better suited for non-structural applications, such as thermal insulation. A batch of lightweight aggregates based on these mortars was produced through pelletizing, obtaining a material with properties close to that of low-grade expanded clay aggregates.

Development of cold-bonded lightweight concrete aggregates using biowaste
Conférence ArODES

Daia Zwicky, Julien Ston

Proceedings of the IABSE Symposium Manchester 2024, Construction's role for a world in emergency, 10-12 April 2024, Manchester, UK

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Résumé:

The use of lightweight concrete could overcome some of the disadvantages of normal-weight concrete. However, the fabrication of lightweight aggregates is energy intensive and considerably draws on non-renewable resources. The positive consequences from lighter weight on supporting structural components’ dimensions are frequently outrun by the increase in carbon footprint of up to 65% stemming from the lightweight aggregates. On this background, fabrication of lightweight aggregates in a low-energy cold-bonding pelletizing process, using bio-based waste and byproducts, and alternative binders in combination with or instead of cement was explored. Presented results cover reflections for recipe mix design, observations made in the pelletizing and hardening process, results obtained for density, strength, thermal properties, and carbon footprint of this alternative way to produce lightweight aggregates for concrete.

2023

Generic materialization for heightening of buildings and their effects on embodied carbon and costs
Conférence ArODES

Daia Zwicky

Proceedings of cisbat 2023, the built environment in transititon, Hybrid International Scientific Conference, 13-15 September 2023, Lausanne, Switzerland

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Résumé:

Targeting urban and sub-urban building archetypes, generic but practice-oriented materializations of basic construction elements (slabs and walls) and their combinations were conceived for heightening of existing buildings by two to four floors. The developed concepts considered numerous construction materials and requirements from architecture, structural engineering, building physics, and fire protection. Evaluations explored the effects on embodied carbon, weight and estimated cost per surface unit of market-oriented element combinations, to identify suitable (and inappropriate) materializations and to detect governing elements and materials. Globally, a heightening by four floors is better than by two, in terms of relative carbon and cost impacts, but some trade-offs in architectural floor plan layout may be required. Seeking cost reductions is generally disadvantageous for embodied carbon while an investment increase does not necessarily provide a reduced carbon footprint. Overall, timber construction results in the lowest embodied carbon (around 5 kg CO2,eq/m2·a) while being up to 10% more expensive than the cheapest and up to 15% heavier than the lightest materializations (which depend on the floor plan layout). Lightweight concrete construction can be the most economic materialization but is also up to 200% heavier than the lightest (which can possibly not be supported by the existing building), and results in up to 45% more embodied carbon than constructing with timber.

2019

Anchorages of stirrups under transverse tension in concrete :
Conférence ArODES
development of a design model

Mirhat Medziti, Daia Zwicky

Proceedings of 2019 IABSE Congress - The Evolving Metropolis, 4-6 September 2019, New York City, USA

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Résumé:

According to Swiss code SIA 262 "Concrete structures", stirrups of reinforced concrete beams must "surround the tensile longitudinal reinforcement" and must "be anchored to mobilize the static height of internal forces". For existing concrete structures, Swiss code SIA 269/2 provides stirrup detailing requirements while limiting these directives for stirrup anchorage to the compression zone. In zones of negative bending, these requirements are often not satisfied for execution reasons. This question is addressed in a largely experimental Ra&D project. Anchorage tests were performed and analyzed, with a total of 144 tests on 9 concrete beams. These underwent a longitudinal tensile force up to 1’000 kN to simulate transverse cracking at stirrup anchorages in negative flexure zones. The study parameters are crack width (0, 0.4 and 0.9 mm), stirrup diameter (10 and 14 mm), bar ribbing (smooth and ribbed) and hook angle (90°, 135°, 180° and straight bars). A design model based on the "tension chord model" (TCM) developed at ETH Zurich is proposed. This simple and practical design model has proved its effectiveness to consider bond effects. Reduction factors for bar diameter (kØ), relative bar ribbing (kfR), hook effect (kθ) and crack width (kw) were taken into account for calibration. Results of analytical calculations are coherent with experimental tests.

Experimental development of alternative lightweight concretes
Conférence ArODES

Daia Zwicky

Proceedings of 2nd International Conference of Sustainable Building Materials (ICSBM 2019), 12-15 August 2019, Eindhoven, The Netherlands

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Résumé:

It is difficult to compete with normalweight concrete: it is pourable, usually self-compacting, hardening reasonably fast, cheap and locally available in large quantities. Its excellent fire protection and good acoustic insulation for airborne sound are further advantages in construction. But, regular concrete is very heavy, being disadvantageous for transportation and hoisting and results in the fact that a concrete structure predominantly supports its self-weight. Also, concrete qualities applied in building construction usually provide a far too high strength, as geometry is often dictated by constructability (minimum dimensions for concreting). Concrete further provides poor thermal insulation and unpleasant user experience (it “feels” cold), and is rather challenging to recycle. Last but not least, concrete manufacture is largely based on non-renewable resources and has a high environmental impact. Thus, alternative lightweight concretes should be further developed. Starting from earlier developments on “wood-based concrete” (or wood-cement compounds WCCs), essentially consisting of Portland cement (PC) and other mineral binders and of up to 60% of untreated sawdust, this study aimed at improving their mechanical properties by integrating an aggregate skeleton from organic aggregates (fruit pits, crushed nut shells) and lightweight aggregates from largely available or renewable resources (expanded clay and glass). 15 different recipes for “WooCon” (from wood-concrete) were designed and evaluated, in a first phase, for possible self-compaction as a basic fresh-state requirement for their targeted application in prefabrication. In a second phase, basic mechanical properties of 5 retained WooCon recipes were evaluated, by testing elastic modulus, compressive strength, and their development over 28 days as a further important prefabrication requirement. These results were also used to modify predictive expressions for correlating compressive strength and elastic modulus. In a third phase, estimates of economic and ecological performances were established, in order to assess the competitiveness of the newly developed WooCon recipes. The fourth evaluation phase of long-term properties (shrinkage and creep) of the 3 most promising WooCon recipes is currently ongoing. The study results show that adding an aggregate skeleton to WCCs, i.e. converting them into WooCon, can notably improve workability properties, up to self-compaction. Compressive strength can be doubled and elastic modulus can be tripled. Strength development can be predicted by generally accepted expressions and can even reach very rapid early hardening. Elastic modulus can be correlated quite accurately to compressive strength. In all evaluated mechanical properties, a marked influence of the applied percentage of organic aggregates could be observed. Economic impacts of WooCon majorly reside in costs for organic aggregates and cement, and result in unit prices up to 2.5 times higher than regular lightweight concrete (LC); however, if contextualised for mechanical elements, WooCon can perform better than regular LC. Lime filler and cement are the major contributors to ecological impact (global warming potential, GWP) but the overall result shows 75-80% reductions in comparison to regular LC.

2018

Reducing semi-probabilistic methods to acceptable structural safety deficits in deterministic assessments of existing concrete structures
Conférence ArODES

Daia Zwicky

Proceedings of 6th International Symposium on Life-Cycle Civil Engineering (IALCCE), 28-31 October 2018, Ghent, Belgium

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Résumé:

Probabilistic assessment of existing structures can be a powerful tool for efficiently prioritizing the necessity of maintenance interventions within usually limited budgets available for this activity of ever increasing importance – spend the limited money where it is the most effective. However, structural engineers in practice usually have neither sufficient know-how nor enough time at hand to apply full- or semi-probabilistic procedures in their daily structural assessment work. They need an easily applicable deterministic evaluation tool to judge what level of structural safety deficit is still acceptable if recommending disproportionate (structural) interventions shall be avoided. Based on semi-probabilistic updating methods, further considering generally accepted reliability indexes and proportionality of maintenance interventions, a simplified proposal for acceptable structural safety deficits in deterministic assessments of existing concrete structural elements is derived and discussed. Varying material qualities, as possibly encountered in existing structures, and different types of potentially governing failure modes are considered, in order to link deterministic degrees of compliance (that is, inverse of “unity checks” as applied elsewhere) to reliability indexes which, in turn, are related to efficiency of maintenance interventions and the need for urgent safety measures. These reflections are applied, on the one hand, in combination with directives for new structures and, on the other, with prescriptions for the assessment of existing structures, considering information provided in Swiss codes.

Dimensioning the flexural strenghtening of concrete slabs with textile reinforced mortar :
Conférence ArODES
literature data evaluation

Alex-Manuel Muresan, Daia Zwicky

Proceedings of IABSE Conference 2018 "Engineering the past, to meet the needs of the future", Copenhagen, Denmark, 25-27 June 2018

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Résumé:

When strengthening reinforced concrete slabs with textile reinforced mortars (TRM), the “correct” consideration of the global bond behaviour between textile and cementitious matrix is identified as the main challenge in determining the most appropriate global analytical model. The first model evaluated here is based on classical assumptions for structural concrete design. The second model, as another extreme assumption, is completely neglecting textile bond in the cracked zone, thus assuming it as unbonded, end-anchored, external reinforcement. The third model is based on the simplifying assumption of the textile reinforcement being only significantly activated when the internal steel reinforcement is yielding. Analytical results from these approaches are compared to a database containing more than 130 test results reported in literature, and are statistically evaluated.

2017

Bracing of large GFRP frames with very slender GFRP panels
Conférence ArODES

Niccolò Macchi, Daia Zwicky

Proceedings of 39th IABSE Symposium, Engineering the Future, 21-23 September 2017, Vancouver, Canada

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Résumé:

Glass fibre reinforced polymers (GFRP) were developed in the first half of the 20th century. They have high strength (especially for tensile stresses), low density, high resistance in corrosive environments, and free formability. Despite these advantages, GFRP materials are not widely used in construction yet. The main reasons are low stiffness of GFRP (relative to its strength) and the absence of codified and generally accepted design standards. Structural engineers typically have limited knowledge and experience with these materials. In this study, an approach to design slender GRFP bracing panels with methods similar to those used for plated steel girders is developed and compared to results of full-size shear tests.

Bond behavior of steel and timber reinforcement in wood-cement compounds
Conférence ArODES

Marco Maeder, Daia Zwicky

Proceedings of 2nd Concrete Innovation Conference, 6-8 March 2017, Tromsø, Norway

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Résumé:

For the advancement of sustainable, cement-based construction of buildings, composite elements made of timber and wood-cement compound (WCCs) are developed at iTEC since 2012. Earlier research on recipe development, workability, mechanical properties and recyclability trough combustion of WCCs shows that this material is usable as construction material and not just as material for finishing layers. After studies on structural behavior and eco-balance of single-span timber-WCC composite (TWCCC) slab elements, as well as tests to determine the building-physical performance of WCCs and the structural behavior and design of story-high TWCCC wall elements, one wants to know if it is possible to reinforce WCC to apply it in continuous slab elements. To further extend the application domain of TWCCC-based construction, different concepts for continuous TWCCC slab elements are currently developed and evaluated, in collaboration with an industrial partner. As certain zones of the WCC section in these structural systems will be loaded in flexural tension, provision of reinforcement is principally required. As WCCs provide rather little strength and stiffness, existing concrete design rules for anchorage, crack width calculation etc. may not necessarily be applicable. Furthermore, applicability of alternative reinforcement material should also be considered, as required by the industrial partner. With this background, pull-out tests were performed on specimens with long bond length of traditional steel reinforcing mesh as well as timber battens, untreated and planed, as reinforcement. The paper shows and discusses test setup and results of these pull-out tests. It further shows first parts of a bond stress-slip law. The paper concludes by identifying remaining research challenges in view of a practical application of reinforced WCC.

2016

Development of extremely thin prefabricated concrete façade elements
Conférence ArODES

Daia Zwicky, Hans-Rudolf Bärtschi

Proceedings of 19th IABSE Congress Stockholm, 21-23 September 2016

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Résumé:

Story-high, prefabricated concrete façade elements with 6-8 cm thick outer layers were frequently used in building construction in the 1960/70s. In current construction and rehabilitation, they are much thicker (12-15 cm) or economically non-competitive, due to significantly increased concrete cover or the required use of stainless steel reinforcement, respectively, for durability. Additionally, these elements are placed further away from the support structure, owing to significantly increased requirement in thermal insulation. The outer shell of a façade element of the late 1960s was 4-8 cm away from the support structure while today, it is placed at a distance of 16-32 cm. The potential of replacing steel bars in prefabricated concrete façade elements by non-metallic glass-fiber reinforced polymer (GFRP) reinforcement was explored experimentally in a collaborative research project, targeting 5 cm thin elements and also requiring to test an associated new anchor system.

Multi-functional features of pourable wood-cement compounds :
Conférence ArODES
mechanical, building-physical, economic and ecological performance

Marco Maeder, Daia Zwicky

Proceedings of WCTE 2016, World conference on timber engineering, 22-25 August 2016, Vienna, Austria

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Résumé:

Cement-bonded wood products are used in construction since the beginning of the 20th century. Until today, however, they are essentially applied as non-structural finishing layers, e.g. as support for stucco, as fire protection or acoustic insulation panels, providing good fire resistance, thermal and acoustic insulation properties with a relatively low and thus, structurally advantageous material density. If to be applied structurally, these materials should not be regarded as substitution material for regular structural concrete but rather be used in composite elements. They also exhibit rather low stiffness and strength properties. Structural wood-cement compounds (WCCs) may also provide further functional features e.g. contributing to thermal and acoustic insulation or fire protection, thereby compensating for their reduced mechanical properties. The contribution presents results from different tests performed with the objective to determine short- and long-term mechanical properties, thermal insulation, specific heat capacity, acoustic insulation, and combustibility features of WCC-based constructions. It further examines and assesses the economic and ecological potential of WCC-based structural elements and discusses potential challenges in the structural use of WCCs.

Slab elements made of timber and wood-cement compounds :
Conférence ArODES
structural and other performances

M. Eymard, Daia Zwicky

Proceedings of Structures and Architecture: Beyond their Limits, 3rd International Conference on Structures and Architecture (ICSA2016), 27-29 July 2016, Guimarães, Portugal

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Résumé:

Cement-bonded wood-based materials (Wood-Cement Compound: WCC) are used in construction since the beginning of the 20th century already. Until today, however, they are chiefly used as non-structural finishing layers where their good fire resistance, thermal and acoustic insulation properties are combined with a relatively low and thus, structurally benefi-cial density. WCCs should not be seen as an alternative to regular structural concrete – as stiff-ness and strength of WCCs usually are rather low – but should rather be applied in structural el-ements with composite action, e.g. together with timber or other light-weight structural elements (to not unnecessarily increase the overall weight). This article reports on results from full-scale tests up to failure on timber-WCC composite slab elements and compares their structural per-formance to more traditional timber-concrete composite slabs. Test results for determining acoustic insulation properties of timber-WCC slab elements are also presented as well as an eco-balance analysis.

Wall elements made of timber and wood-cement compounds :
Conférence ArODES
building-physical properties and structural performance

Daia Zwicky, Niccolò Macchi

Proceedings of Structures and Architecture: Beyond their Limits, 3rd International Conference on Structures and Architecture (ICSA2016), 27-29 July 2016, Guimarães, Portugal

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Résumé:

Cement-bonded wood-based materials (wood-cement compounds, WCCs) are used in construction since more than 100 years. Until today, they are chiefly used non-structurally where their good fire resistance, thermal and acoustic insulation and thermal mass are combined with a relatively low density. Main application forms of WCCs are prefabricated panels but pour-able mixes are also available. WCCs allow creating light-weight structural elements if applied, for example, in composite timber-WCC elements. Such multi-functional elements cannot only fulfill a structural task but provide also building-physical performances. This paper reports on test results for thermal insulation and specific heat capacity of WCCs and timber-WCC walls, also comparing them to performance features of other construction materials and code requirements. The paper also presents results from full-scale buckling tests, and evaluates the suitability of structural design approaches. This contribution is complemented by companion papers on me-chanical properties of WCCs and performance features of timber-WCC slab elements.

Pourable wood-cement compounds :
Conférence ArODES
properties, potential and challenges of a new structural material

Niccolò Macchi, Daia Zwicky

Proceedings of Structures and Architecture: Beyond their Limits, 3rd International Conference on Structures and Architecture (ICSA2016), 27-29 July 2016, Guimarães, Portugal

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Résumé:

Wood-cement compounds (WCCs) are composite materials made of wooden aggregates and mineral (cement) binders. These materials are widely used as prefabricated panels in the construction industry. A main obstacle for using casted WCC in construction elements is high shrinkage of the young product and frequently difficult workability of the mixes. This pro-ject addresses both of these problems by developing self-compacting low-shrinkage WCCs. An-other objective of the study is to reduce cement content, which is typically very high in WCCs (500 to 700 kg/m3 of Portland cement). By replacing Portland cement with inert fillers or poz-zolanic waste materials, the environmental impact of the WCCs can be lowered and a “greener” cement-based material is created. To assess the effectiveness of the developed recipes, WCC specimens are evaluated with regard to shrinkage, workability and mechanical performance.

Ecological performance of timber / Wood-cement compound composiste slabs
Conférence ArODES

Marco Maeder, Daia Zwicky

Proceedings of Sustainable Built Environment (SBE) Regional Conference, 15-17 June 2016, Zurich, Switzerland

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Résumé:

Wood-cement compounds (WCCs) have been being used in construction since the beginning of the 20th century, mostly as a secondary structure or finishing layers such as sound or thermal insulation elements. However, WCCs’ stiffness and strength are rather low, therefore WCCs should be combined with timber or a similar light-weight structural material used as a load-bearing element. The use of WCC for composite elements allows to take advantage of both materials, particularly of the strength of timber and the insulation properties of WCC. Furthermore, WCC slab elements do only require a minimal secondary structure due to their beneficial sound and thermal insulation properties. This paper reports on a life-cycle assessment (LCA) where those new and promising composite slab elements have been compared to traditional concrete, wood and timber-concrete composite (TCC) slabs regarding greenhouse gas emissions (EGG), non-renewable primary energy (NRPE) and environmental impact points (UBP).

2015

Combustibility of wood-cement compounds
Conférence ArODES

Daia Zwicky

Proceedings of the 10th Conference on Advanced Building Skins, 3-4 November 2015, Berne, Switzerland

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Résumé:

Wood-cement compounds (WCCs) contain 30% to 40% combustible matter. Consequently, it is essential to determine if this kind of material is able to burn and produce energy as a way of recycling. Therefore, explorative combustibility tests were performed on three different WCCs. The ignition temperature is around 210°C, independently of the WCC recipe. Combustion stops at removal from the furnace. WCCs can thus be considered difficultly inflammable and may therefore serve as a fire protection layer. Available calorific values between 3 and 6 MJ/kg are significant, and also clearly show a beneficial effect of activated charcoal. The energy required for grinding as a preparation for combustion is almost negligible. The time for complete combustion is a function of furnace temperature, density and calorific value of WCC. Ash content, i.e. inorganic residue, is rather important with 55% or higher. Optimal combustion conditions primarily depend on material density and furnace temperature. Combustion fumes do not show particular pollutants. CO2 and NOx emissions are more than proportional at temperatures beyond 800°C or if the WCC contains activated charcoal, respectively. NOx emission during combustion may be a potential problem and should be considered in the design of the combustion process.

WCC-based load-bearing wall elements
Conférence ArODES

Niccolo Macchi, Daia Zwicky

Proceedings of the 10th Conference on Advanced Building Skins, 3-4 November 2015, Berne, Switzerland

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Résumé:

Timber construction has become more and more competitive by adapting efficient prefabricated construction methods and by recent changes in fire protection norms. Until recently, multy-story buildings had to contain an escape route built in non-combustible materials. Nowadays, the fire protection rules veer towards performance-oriented criteria, as seen recently with the changes of Swiss fire protection specifications. However, cladding of the structure is still necessary in most cases and it is usually necessary to fill voids of the structure with non-structural materials, such as mineral wools etc. Massive structures that incorporate the fire cladding functions and add to thermal inertia while still retaining some degree of insulation and can, due to their low weight, be easily integrated into the prefabricated timber-construction process could have a big potential in timber construction.

Mechanical properties of wood-cement compounds
Conférence ArODES

Daia Zwicky

Proceedings of the 10th Conference on Advanced Building Skins, Berne, Switzerland, 3-4 November 2015, Bern, Switzerland

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Résumé:

The most widely used construction material is reinforced concrete which is heavy, has rather high embedded carbon, strongly draws upon non-renewable resources, is challenging to re-use, and exhibits rather poor building-physical properties. A high potential for a more sustainable development of building construction is located in timber-based composite structures. These should be, however, not be produced with regular concrete, as this still introduces the mentioned disadvantages. Mixes of cement with wood components, so-called wood-cement compounds (WCC), may be one of the answers for an even more sustainable evolution of timber-concrete composite construction. Some of the non-renewable parts (gravel, sand) of concrete are substituted with renewable ones in WCCs, with the objective to create a light-weight, pourable, self-compacting, cheap, easily recyclable, and thus, “greener” cement-based construction material that has further benefits with regard to building-physical properties to be exploited in so-called hybrid structural elements. This paper reports on results of laboratory testing for determining short- and long-term mechanical properties of newly developed WCC recipes, i.e. density, elastic moduli, compressive and tensile strength, shrinkage, and creep properties. Furthermore, their economic feasibility is assessed as well and potential challenges in structural applications of WCCs are pointed out.

Mechanical properties of wood-cement compounds
Conférence ArODES

Daia Zwicky

Proceedings of 10th Conference on Advanced Building Skins, 3-4 November 2015, Berne, Switzerland

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Résumé:

The most widely used construction material is reinforced concrete which is heavy, has rather high embedded carbon, strongly draws upon non-renewable resources, is challenging to re-use, and exhibits rather poor building-physical properties. A high potential for a more sustainable development of building construction is located in timber-based composite structures. These should be, however, not be produced with regular concrete, as this still introduces the mentioned disadvantages. Mixes of cement with wood components, so called wood-cement compounds (WCC), may be one of the answers for an even more sustainable evolution of timber-concrete composite construction. Some of the non-renewable parts (gravel, sand) of concrete are substituted with renewable ones in WCCs, with the objective to create a light-weight, pourable, selfcompacting, cheap, easily recyclable, and thus, “greener” cement-based construction material that has further benefits with regard to building-physical properties to be exploited in so-called hybrid structural elements. This paper reports on results of laboratory testing for determining short- and long-term mechanical properties of newly developed WCC recipes, i.e. density, elastic moduli, compressive and tensile strength, shrinkage, and creep properties. Furthermore, their economic feasibility is assessed as well and potential challenges in structural applications of WCCs are pointed out.

Forensics of a partially collapsed timber roof
Conférence ArODES

Daia Zwicky

Proceedings of the IABSE Conference, 23-25 September 2015, Geneva, Switzerland: Structural Engineering: Providing Solutions to Global Challenges

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Résumé:

The roofing of an office building partially collapsed after being in use for almost twelve years. The author was appointed as an independent structural expert to investigate the damage event, by approval of all involved parties, i.e. owner, building insurer and roof constructor. The expert report should give answers to several questions related to forensic engineering, e.g. reasons for the partial failure of the roof elements; influence of the snow load present at the moment of partial collapse; faults or deficits in the structural concept, in element production or execution etc. The paper reports on the course of events and actions, the structural and architectural conception of the roofing, its structural behavior, determination of updated failure loads, associated structural safety assessment and degrees of compliance. The paper gives no conclusion on legal or insurance issues.

2014

Use of wood waste as a resource for structural wood-concrete compounds
Conférence ArODES

Niccolo Macchi, Daia Zwicky

Proceedings of the 1st Conference on Performance and maintenance of bio-based building materials influencing the life cycle and LCA, 23-24 October 2014, Kranjska Cora, Slovenia

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Bending behavior of glulam beams reinforced with flax fiber sheets
Conférence ArODES

Loïc Chopard, Daia Zwicky

Proceedings of the 7th International Conference on FRP Composites in Civil Engineering (CICE 2014), 20-22 August 2014, Vancouver, Canada

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Résumé:

The structural performance of timber beams in bending could be considerably improved if the behavior of the flexural tension face were enhanced. This paper reports on an experimental and analytical study on the structural behavior of full-scale beams made of glued laminated timber, reinforced with natural fiber sheets. Two 5m-span beams were strengthened with flax fiber sheets and tested to rupture, along with a non-reinforced reference specimen. Comparisons between analytical predictions and experimental results proved very satisfactory, although the latter were rather disappointing. The paper further discusses improvement options for the applied reinforcement concept, as well as other reinforcement applications for flax fiber sheets.

Post-buckling shear resistance of composite panels
Conférence ArODES

Daia Zwicky, Joël Mabboux

Proceedings of the 7th International Conference on FRP Composites in Civil Engineering, CICE 2014, 20-22 August 2014, Vancouver, Canada

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Résumé:

The structural potential of applying glass fiber reinforced polymers (GFRP) as shear panels, i.e. slender structural elements loaded primarily in in-plane shear, is far from being exploited. Current design proposals only consider the resistance up to elastic buckling, leading to a relatively low economic competitiveness of such structural elements. The paper reports on a research project on the structural behavior of Vierendeel frames made of GFRP U-profiles, braced with riveted or bolted GFRP panels of variable thickness, particularly targeting their post-critical shear resistance. The paper discusses the results of full-scale tests, and evaluates the influence of the different connector types on ultimate loads and general bearing behavior of the test specimens. It reports on findings from non-linear FE analysis and compares them to the full-scale test results as well as to analytical predictions according to existing proposals for steel panels, i.e. tension field approaches. It further draws conclusions on the appropriate design method for determining the post-critical resistance of slender GFRP panels loaded in in-plane shear, and identifies future research needs.

Shear design of composite panels :
Conférence ArODES
post-buckling tension field action

Daia Zwicky, Joel Mabboux

Proceedings of Footbridge 2014, 5th International Conference, Footbridge: past, present & future, 16-18 July 2014, London, UK

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Résumé:

The potential of glass fibre reinforced polymers (GFRP) as structural shear panels, i.e. slender elements loaded primarily in in-plane shear, is far from being exploited. Current design proposals only consider the resistance up to elastic panel buckling, leading to a relatively low economic competitiveness of such structural elements. This paper reports on a comprehensive research project on the structural behaviour of Vierendeel frames made of GFRP U-profiles, braced with riveted or bolted GFRP panels of variable thickness, particularly targeting their post-buckling (i.e. post-critical) shear resistance. The contribution discusses the results of full-scale tests and evaluates the influence of the different types of connections on ultimate loads and general bearing behaviour of the test specimens. It reports on findings from extensive non-linear FE analysis and compares them to the full-scale test results as well as to predictions based on existing proposals for the post-critical shear resistance of slender steel panels, i.e. tension field approaches. It further draws conclusions on the appropriate structural design method for determining the post-critical resistance of slender GFRP panels loaded in in-plane shear and identifies future research needs.

Hybrid structural elements made of timber and wood-based concrete
Conférence ArODES

Daia Zwicky, Niccolò Macchi

Proceedings of the hybrid2014 :IABSE Workshop Exploring the Potential of Hybrid Structures for Sustainable Construction, 22-24 June 2014, Fribourg, Suisse

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Bending behavior of glulam beams reinforced with flax fiber sheets
Conférence ArODES

Loïc Chopard, Daia Zwicky

Proceedings of the hybrid2014 :IABSE Workshop Exploring the Potential of Hybrid Structures for Sustainable Construction, 22-24 June 2014, Fribourg, Suisse

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Eco-balance of different construction methods in timber and concrete for floor slabs :
Conférence ArODES
a case study

Yannick Plüss, Daia Zwicky

Proceedings of the hybrid2014 : IABSE Workshop Exploring the Potential of Hybrid Structures for Sustainable Construction, 22-24 June 2014, Fribourg, Suisse

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Structural behavior of an all-GFRP vierendeel frame braced with slender shear panels
Conférence ArODES

Joel Mabboux, Daia Zwicky

Proceedings of the hybrid2014 : IABSE Workshop Exploring the Potential of Hybrid Structures for Sustainable Construction, 22-24 June 2014, Fribourg, Suisse

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A case study on the eco-balance of a timber-concrete composite structure in comparison to other construction methods
Conférence ArODES

Yannick Plüss, Daia Zwicky

Proceedings of the CIC 2014, Concrete Innovation Conference, 11-13 June 2014, Oslo, Norway

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Résumé:

In today’s building construction tenderings, ecological aspects are often taken into consideration. Therefore, it is of vital importance that all stakeholders – architects, structural engineers, owners, constructors etc. –, have an idea on the eco-balance of different construction methods, in order to choose the one being the most appropriate for the tendered project, also in view of building labels. Nowadays, the most widely used construction material for mid-size buildings, such as multi-storey office buildings or schools, is reinforced concrete. Regrettably, concrete requires much energy for production and transportation, strongly draws upon non-renewable resources, and is rather challenging to recycle. Therefore, alternative construction methods are required and to be assessed with regard to their eco-balance. Construction with timber-concrete composite (TCC) elements allows significant reduction of concrete quantities while providing comparable serviceability performance. To provide first insight on the ecological performance of different construction methods, this paper shows case study results of a Life Cycle Assessment for a typical building floor slab. It compares several construction methods, i.e. a traditional reinforced concrete slab, TCC structures as well as a pure timber structure. Traditionally, composite action in TCC elements is provided by mechanical interface connectors (screws, dowels etc.), the latter being habitually designed with elasticity-based approaches. Recently, a new type of shear connection has been developed at the University of Applied Sciences Fribourg omitting the use of mechanical connectors. The new connector shows very stiff and extremely ductile behaviour, principally allowing the application of plasticity-based structural design methods. Based on this observation, the paper further analyses the impact of the applied structural design approach – traditional elasticity-based or more sophisticated plasticity-based approaches – on the eco-balance of the floor slab. It concludes by giving an outlook on the most important elements and concerned stakeholders for improving the eco-balance of typical mid-size buildings.

Structural behavior of thermally insulating cellular glass concrete beams
Conférence ArODES

Philip Messerli, Loïc Chopard, Daia Zwicky

Proceedings of the hybrid2014 :IABSE Workshop Exploring the Potential of Hybrid Structures for Sustainable Construction, 22-24 June 2014, Fribourg, Suisse

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Wood-based concrete :
Conférence ArODES
a promising material for hybrid construction of buildings

Daia Zwicky, Niccolò Macchi

Proceedings of the hybrid2014 :IABSE Workshop Exploring the Potential of Hybrid Structures for Sustainable Construction, 22-24 June 2014, Fribourg, Suisse

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Wood-based concrete for composite building construction with timber
Conférence ArODES

Niccolò Macchi, Daia Zwicky

Proceedings of the CIC 2014, Concrete Innovation Conference, 11-13 June 2014, Oslo, Norway

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Résumé:

Construction and operation of buildings has an important environmental impact. The most widely used construction material is concrete; which is heavy, has rather high embedded energy, strongly draws upon non-renewable resources, is challenging to re-use, and exhibits rather poor building-physical properties with regard to thermal insulation and storage capacity, acoustic insulation. Last but not least, the concrete types used today in mid-size building construction are essentially far too good from a structural point of view. Mixes of concrete with wood components, so-called wood-concrete compounds (WCC), may be one of the answers to the challenge of a more sustainable evolution of concrete-based construction. They substitute some of the non-renewable parts (gravel, sand) of the concrete composition with renewable ones. From an environmental and economic point of view, by-products of the wood utilization chain shall be used with the objective to create a light-weight, pourable, self-compacting, cheap and “greener” construction material that has further benefits with regard to building-physical properties and might even be partially recyclable. From a sustainability point of view, WCC should rather be used in composite action with timber than be reinforced with reinforcing steel. Developing such “greener” types of concrete may thus considerably contribute to a sustainable development of mid-size building construction. The challenge, however, is finding appropriate WCC composition that solves the problem of delayed hardening of concrete due to the natural sugar embedded in wood.

2013

Concrete slab strengthening with CFRP textile reinforced shotcrete
Conférence ArODES

Daia Zwicky

IABSE Conference, Rotterdam 2013: Assessment, Upgrading and Refurbishment of Infrastructures, 6-8 May 2013, Rotterdam, The Netherlands

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Résumé:

This paper reports on a new strengthening system for concrete elements, being composed of carbon- fiber reinforced polymer fabrics (CFRP fabrics) embedded in shotcrete. The strengthening system was evaluated in a test series on full-scale single span slab strips of 6 m length, on a non-strengthened reference specimen and two slab strips with different strengthening ratios. The paper discusses the test results with regard to serviceability limit state (flexural stiffness, crack widths, and admissible loads for given deflection limits), and to ultimate limit state (strengthening ratio, behavior at rupture, post-peak bearing capacity, and ductility). It concludes with some analytical considerations on the structural behavior and bearing capacity of the new strengthening system.

Réalisations

2024

Nichtlineare Analyse des Tragverhaltens von Holz-Beton-Verbunddecken

 2024 ; Thèse de Master

Collaborateurs: Zwicky Daia

Méthodes et approches d'analyse structurelle (élastique, plastique et non linéaire) pour le dimensionnement des poutres fléchies en bois-béton mixte à portée simple, en focalisant sur l'influence du comportement structurel non linéaire des connecteurs, ainsi que la prise en compte des effets différés (fluage & retrait) et de la fissuration du béton

2022

Détermination des contraintes d'adhérence des barres d'armatures dans des structures existantes en béton armé

 2022 ; Thèse de Master

Collaborateurs: Zwicky Daia

Développement analytique des propositions pratiques pour la considération des différents impacts sur l'adhérence des barres d'armature pour les structures en béton existantes, en se focalisant sur la nuance d'acier et les propriétés géométriques des barres d'armature et l'épaisseur d'enrobage

2021

Calcul plastique des poutres mixtes en bois-béton avec connexion complète ou partielle

 2021 ; Thèse de Master

Collaborateurs: Zwicky Daia

Analyse de l'applicabilité des méthodes de dimensionnement selon la théorie de plasticité sur les poutres fléchies en bois-béton mixte avec appuis isostatiques, en focalisant sur l'influence du comportement structural des connecteurs et le degré de connectivité

2020

Conception et comportement structural des poutres mixtes en bois-dallettes

 2020 ; Thèse de Master

Collaborateurs: Zwicky Daia

Ce travail s’occupe du comportement structural des poutres mixtes, composées des éléments longitudinaux en bois en combinaison avec des tables de compression en « wood-cement compound » (WCC) et composites en fibres de lin ou de basalte (composites alternatifs), appelées « dallettes » . L’objectif ultime est de vérifier la faisabilité et l’aptitude pratique de ces éléments porteurs novateurs et innovants pour la construction des planchers de bâtiment (habitation, école, bureau).

2018

Ancrage sous traction transversale d’étriers dans le béton armé – développement d’un modèle de dimensionnement

 2018 ; Thèse de Master

Collaborateurs: Zwicky Daia

Ce travail s’occupe des développements analytiques ciblant la proposition d’un modèle de dimensionnement orienté vers la pratique pour l’ancrage d’étriers dans des zones tendues par la flexion (ainsi, en subissant une traction transversale) et la détermination des résistances à l’effort tranchant des poutres en béton armé y associées.

Grid anchorage in textile reinforced concrete – experimental and analytical development of a structural design model

 2018 ; Thèse de Master

Collaborateurs: Zwicky Daia

Développement analytique et expérimental d'un modèle de dimensionnement pour les ancrages par adhérence des treillis de renforcement en fibre de carbone dans le béton textile

2016

Structural behavior and design of shear panels made of glass fiber reinforced polymers (GFRP shear panels)

 2016 ; Thèse de Master

Collaborateurs: Zwicky Daia

Développement d'un modèlede calcul et validation expérimentale du dimensionnement des panneaux élancés en polymère renforcé par fibres de verre sous effort tranchant

2015

Ancrage des treillis en fibres de carbone dans le béton projeté

 2015 ; Thèse de Master

Collaborateurs: Zwicky Daia

Ce travail s'occupe du développement d'un modèle de dimensionnement pour les ancrages des treillis de renforcement en fibre de carbone aux bouts des zones renforcés. Cet ancrage peut se faire par adhérence, par des moyens mécaniques (rail d'ancrage) ou par une combinaison des deux. Au niveau des essais en laboratoire et des analyses théoriques, l'étude proposée focalise sur l'ancrage par adhérence.

2014

Einfluss von Konstruktionsdetails auf das Verformungsverhalten von bewehrtem Beton

 2014 ; Thèse de Master

Collaborateurs: Zwicky Daia

L'étude analyse et évalue analytiquement et expérimentalement les impacts des détails constructifs « insuffisants » sur le comportement à l'adhérence et la capacité de déformation plastique, en focalisant sur les modèles formant la base des directives de la norme SIA 269/2 (2011) et en se concentrant sur l'enrobage en béton et la surface relative des nervures.

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