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Bader, T. K. & Ormarsson, S. (2023). Modeling the Mechanical Behavior of Wood Materials and Timber Structures. In: Niemz, P., Teischinger, A., Sandberg, D. (Ed.), Springer Handbook of Wood Science and Technology: (pp. 507-568). Springer
Open this publication in new window or tab >>Modeling the Mechanical Behavior of Wood Materials and Timber Structures
2023 (English)In: Springer Handbook of Wood Science and Technology / [ed] Niemz, P., Teischinger, A., Sandberg, D., Springer, 2023, p. 507-568Chapter in book (Refereed)
Abstract [en]

This chapter aims at highlighting the benefit of numerical methods and their broad application in the field of wood, engineered wood-based products (EWPs), structural elements including glued-laminated and cross-laminated timber, and engineered timber structures. It focuses on the hygrothermo- viscoelastic material behavior of these elements and structures as a consequence of the behavior of wood materials. After motivating the need for models of wood, different types of numerical models and their application for determination of mechanical properties and dimensional stability of wooden boards, strand- and veneer-based engineered woodbased products, including glued-laminated and crosslaminated timber, as well as of connections in EWPs are reviewed and application examples are given. Methods and application examples are furthermore provided for moisturerelated stresses and deformations in timber structures, the influence of connections on the structural response, instability of structural systems, and modeling of prefabricated frame structures, before modeling of historical structures of wood is discussed. The chapter ends with discussing bottlenecks in modeling of wood materials and timber structures, which might be a starting point for further improvements and novel modeling strategies. © Springer Nature Switzerland AG 2023.

Place, publisher, year, edition, pages
Springer, 2023
Series
Springer Handbooks, ISSN 2522-8692, E-ISSN 2522-8706
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology; Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-123753 (URN)10.1007/978-3-030-81315-4_10 (DOI)2-s2.0-85152929646 (Scopus ID)9783030813147 (ISBN)9783030813154 (ISBN)
Available from: 2023-08-16 Created: 2023-08-16 Last updated: 2023-09-07Bibliographically approved
Kuai, L., Ormarsson, S. & Vessby, J. (2023). Nonlinear FE-analysis and testing of light-frame timber shear walls subjected to cyclic loading. Construction and Building Materials, 362, Article ID 129646.
Open this publication in new window or tab >>Nonlinear FE-analysis and testing of light-frame timber shear walls subjected to cyclic loading
2023 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 362, article id 129646Article in journal (Refereed) Published
Abstract [en]

Light-frame timber shear walls have been used as load-bearing elements in buildings for several decades. To predict the performance of such structural elements under loading, numerous analytical and numerical models have been developed. However, little focus has been on the prediction of the plastic damage behaviour and unloading of the walls. In this paper, a parametric Finite Element (FE) model is further developed by introducing elasto-plastic connectors to simulate the mechanical behaviour of the sheathing-to-framing connections. To verify the accuracy of the elasto-plastic model, full-size walls were tested and compared with results from simulations. The numerical results, from a few loading cycles, indicate that the model achieves reasonable accuracy in predicting both the nonlinear elastic and plastic deformations. Both experimental and simulation results demonstrate the importance of opening locations relating to the external racking force. The results also indicate that for a double-layer wall, its racking strength can be achieved by summation of the separate contribution from each layer. Furthermore, the internal layer was observed to contribute significantly less than the external layer since its nail pattern was based on the sheathing pattern of the external layer.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Timber structures, FE-modelling, Light-frame shear walls, Numerical model, Elasto-plastic connectors
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-118156 (URN)10.1016/j.conbuildmat.2022.129646 (DOI)000897057100003 ()2-s2.0-85141920114 (Scopus ID)
Available from: 2023-01-05 Created: 2023-01-05 Last updated: 2023-03-06Bibliographically approved
Ormarsson, S., Kuai, L., Mahjoub, M. A. & Aicher, S. (2023). Numerical and experimental study of glulam beams jointed with slotted-in steel plate connection. In: Nyrud A.Q., Malo K.A., Nore K., Alsen K.W.L., Tulebekova S., Staehr E.R., Bergh G., Wuyts W. (Ed.), 13th World Conference on Timber Engineering, WCTE 2023, Vol 2: . Paper presented at World Conference on Timber Engineering: Timber for a Livable Future, WCTE 2023, Oslo 19-22 June 2023 (pp. 1261-1268). World Conference on Timber Engineering (WCTE)
Open this publication in new window or tab >>Numerical and experimental study of glulam beams jointed with slotted-in steel plate connection
2023 (English)In: 13th World Conference on Timber Engineering, WCTE 2023, Vol 2 / [ed] Nyrud A.Q., Malo K.A., Nore K., Alsen K.W.L., Tulebekova S., Staehr E.R., Bergh G., Wuyts W., World Conference on Timber Engineering (WCTE) , 2023, p. 1261-1268Conference paper, Published paper (Refereed)
Abstract [en]

The present work focuses on analysis of deformation and strength behaviour of slotted-in steel plateconnections in glued laminated timber (GLT). In Eurocode 5 (EC5), the design of metal dowel-type timber joints is basedon the yield theory presented by Johansen [1]. It consists of analytical expressions to calculate the lateral load-carryingcapacity of single fastener joints that exhibit different (plastic) failure modes. When designing optimised multiple fastenerconnections that are exposed to dominating moment action, the calculation of fastener forces and their directions duringprogressive plasticization of the dowel group is difficult to perform manually. Therefore, a simple numerical model tosimulate progressive elasto-plastic force development for every individual dowel is needed. This study presents new andsimple models to analyse the bending deformations of glulam beams jointed with mechanical slotted-in steel plateconnections. The proposed models were experimentally verified using results obtained from a joint project with theMaterial Testing Institute (MPA) at University of Stuttgart.

Place, publisher, year, edition, pages
World Conference on Timber Engineering (WCTE), 2023
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-126785 (URN)10.52202/069179-0172 (DOI)2-s2.0-85171621042 (Scopus ID)9781713873297 (ISBN)
Conference
World Conference on Timber Engineering: Timber for a Livable Future, WCTE 2023, Oslo 19-22 June 2023
Available from: 2024-01-16 Created: 2024-01-16 Last updated: 2024-02-01Bibliographically approved
Blomqvist, L., Ormarsson, S. & Ziethen, R. (2023). Stress distribution in veneers under lamination and simultaneously bending: an experimental and numerical investigation. Wood Material Science & Engineering, 18(3), 995-1002
Open this publication in new window or tab >>Stress distribution in veneers under lamination and simultaneously bending: an experimental and numerical investigation
2023 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 18, no 3, p. 995-1002Article in journal (Refereed) Published
Abstract [en]

Laminated veneer products (LVPs) are veneers glued together into a predetermined shape. Experimental and numerical investigations were performed under lamination and simultaneously bending of veneer laminate to study the stress distribution in the laminate. Laminates of different thicknesses were made of peeled veneers of European beech. The veneers were coated with adhesive, inserted in a mould which had the shape of a semicircle, and finally pressed at 20 degrees C to a laminate. Two Teflon-polymer films including sensors for measurement of the contact pressure were placed on both sides of the laminate to measure the local contact pressure (contact stress) between the laminate and the mould. At the beginning of the bending process, the contact stresses were locally distributed over the laminate in a similar pattern as in a three-point bending; after the laminate was further bent, the stress distribution rearranged to be as in four-point bending. In the end of the moulding, the local contact stresses increased over the entire laminate and reached a 'peak-value' over bent area in the middle part of the mould. A finite-element model was created to study the bending process. Regarding the overall development of the contact stress variations, the experimental and the numerical results agreed.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2023
Keywords
Wood, European beech, veneer-sheet moulding, FE-modelling, contact pressure
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-116333 (URN)10.1080/17480272.2022.2099762 (DOI)000837148500001 ()2-s2.0-85135440583 (Scopus ID)
Available from: 2022-09-19 Created: 2022-09-19 Last updated: 2023-06-20Bibliographically approved
Kuai, L., Ormarsson, S., Vessby, J. & Maharjan, R. (2022). A numerical and experimental investigation of non-linear deformation behaviours in light-frame timber walls. Engineering structures, 252, Article ID 113599.
Open this publication in new window or tab >>A numerical and experimental investigation of non-linear deformation behaviours in light-frame timber walls
2022 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 252, article id 113599Article in journal (Refereed) Published
Abstract [en]

In recent decades, there is a trend in Scandinavian countries to build multi-storey residential houses using prefabricated timber modules. It is a highly efficient construction process with less environmental impact and less material waste. A significant building element in the timber modules is the light-frame timber wall, which has to be carefully analysed and optimized in this process. This paper presents a new parametric Finite Element (FE) model that can simulate both in-plane and out-of-plane deformations in the light-frame walls. A new and flexible (Eurocode based) approach to define the properties of the mechanical connections is introduced. A numerical model is presented through simulations of several walls that were verified with full-scale experiments. The results indicate that the numerical model could achieve fairly reasonable accuracy with the new approach. Furthermore, several parametric studies are presented and discussed from global and local points of view, to investigate the effects of certain parameters that are not considered in the design method according to Eurocode 5.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Timber structures, Internal force distribution, Light-frame shear walls, Parametric studies, Openings
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-111229 (URN)10.1016/j.engstruct.2021.113599 (DOI)000772614300002 ()2-s2.0-85120753014 (Scopus ID)2021 (Local ID)2021 (Archive number)2021 (OAI)
Available from: 2022-04-08 Created: 2022-04-08 Last updated: 2022-04-12Bibliographically approved
Florisson, S., Vessby, J. & Ormarsson, S. (2021). A three-dimensional numerical analysis of moisture flow in wood and of the wood's hygro-mechanical and visco-elastic behaviour. Wood Science and Technology, 55, 1269-1304
Open this publication in new window or tab >>A three-dimensional numerical analysis of moisture flow in wood and of the wood's hygro-mechanical and visco-elastic behaviour
2021 (English)In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 55, p. 1269-1304Article in journal (Refereed) Published
Abstract [en]

A three-dimensional numerical model was employed in simulating nonlinear transient moisture flow in wood and the wood's hygro-mechanical and visco-elastic behaviour under such conditions. The model was developed using the finite element software Abaqus FEA, while taking account of the fibre orientation of the wood. The purpose of the study was to assess the ability of the model to simulate the response of wood beams to bending and to the climate of northern Europe. Four-point bending tests of small and clear wood specimens exposed to a constant temperature and to systematic changes in relative humidity were conducted to calibrate the numerical model. A validation of the model was then performed on the basis of a four-point bending test of solid timber beams subjected to natural climatic conditions but sheltered from the direct effects of rain, wind and sunlight. The three-dimensional character of the model enabled a full analysis of the effects of changes in moisture content and in fibre orientation on stress developments in the wood. The results obtained showed a clear distinction between the effects of moisture on the stress developments caused by mechanical loads and the stress developments caused solely by changes in climate. The changes in moisture that occurred were found to have the strongest effect on the stress state that developed in areas in which the tangential direction of the material was aligned with the exchange surface of the beams. Such areas were found to be exposed to high-tension stress during drying and to stress reversal brought about by the uneven drying and shrinkage differences that developed between the outer surface and the inner sections of the beams.

Place, publisher, year, edition, pages
Springer, 2021
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-105945 (URN)10.1007/s00226-021-01291-9 (DOI)000669804600003 ()2-s2.0-85109351782 (Scopus ID)2021 (Local ID)2021 (Archive number)2021 (OAI)
Available from: 2021-07-15 Created: 2021-07-15 Last updated: 2021-09-03Bibliographically approved
Ormarsson, S., Vessby, J. & Johansson, M. (2021). Design of innovative modular-based timber structure based on advanced modeling and full-scale tests. In: World Conference on Timber Engineering 2021, WCTE 2021: . Paper presented at World Conference on Timber Engineering 2021, WCTE 2021, 9 - 12 August 2021. World Conference on Timber Engineering (WCTE)
Open this publication in new window or tab >>Design of innovative modular-based timber structure based on advanced modeling and full-scale tests
2021 (English)In: World Conference on Timber Engineering 2021, WCTE 2021, World Conference on Timber Engineering (WCTE) , 2021Conference paper, Published paper (Refereed)
Abstract [en]

The building of low and mid-rise modular-based timber buildings is a growing industry sector worldwide. Today, the use of prefabricated light-frame volume modules (sometimes with CLT walls) is a prevalent and innovative construction method. This building method has many advantages, though some of the technical solutions and design methods are quite challenging and should be optimised without risking structural safety. The paper presents results from an ongoing research project that deals with testing and numerical analysis of light-frame timber test modules. It focuses on the testing and simulation of global racking stiffness of different types of test modules and the testing of a friction-based joint between two test modules. The modules showed larger shear load carrying capacity than expected. They also showed a ductile failure behaviour and large variation in racking stiffness between different types of test modules.

Place, publisher, year, edition, pages
World Conference on Timber Engineering (WCTE), 2021
Keywords
FE-simulations, Light-frame timber modules, Modular-based timber buildings, Racking tests of modules, Architectural design, Stiffness, Testing, Wooden buildings, Fe simulation, Light frames, Light-frame timber module, Modular-based timber building, Modulars, Racking test of module, Racking tests, Test modules, Timber buildings, Timber structures, Timber
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-112573 (URN)2-s2.0-85120751254 (Scopus ID)
Conference
World Conference on Timber Engineering 2021, WCTE 2021, 9 - 12 August 2021
Available from: 2022-05-08 Created: 2022-05-08 Last updated: 2022-05-09Bibliographically approved
Sejkot, P., Iqbal, A. & Ormarsson, S. (2021). Finite-element modelling of connectors to achieve ductile connections in wood structures. In: World Conference on Timber Engineering 2021, WCTE 2021: . Paper presented at World Conference on Timber Engineering 2021, WCTE 2021, 9 - 12 August 2021. World Conference on Timber Engineering (WCTE)
Open this publication in new window or tab >>Finite-element modelling of connectors to achieve ductile connections in wood structures
2021 (English)In: World Conference on Timber Engineering 2021, WCTE 2021, World Conference on Timber Engineering (WCTE) , 2021Conference paper, Published paper (Refereed)
Abstract [en]

Mechanical connections in wood structures typically consist of structural members connected with combination of thin-walled steel angle brackets and fasteners in forms of nails or screws. Design of these steel connectors is typically based on short-term load bearing capacities. Observations from experimental testing indicate that both the angle bracket and the fasteners possess properties such the connections can be designed to behave in a ductile manner. This paper presents numerical simulations of ductile angle bracket connections calibrated against experimental results and subsequently validated. Special focus is on single nail behaviour when the jointed timber members are subjected to cyclic loading. Simulations of global behaviour of connections show that acceptable match between the simulation and the experimental results can be achieved despite relatively simple nail model is used for both loading and unloading behaviour.

Place, publisher, year, edition, pages
World Conference on Timber Engineering (WCTE), 2021
Keywords
Angle brackets, Full-scale tests, Numerical simulation, Python scripting, Ring nails, Timber connections, Computer software, Fasteners, Finite element method, Numerical models, Thin walled structures, Timber, Unloading, Wooden buildings, Angle bracket, Ductile connection, Full scale tests, Mechanical connections, Ring nail, Steel angle, Thin-walled steels, Wood structure, Python
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-112581 (URN)2-s2.0-85120725539 (Scopus ID)
Conference
World Conference on Timber Engineering 2021, WCTE 2021, 9 - 12 August 2021
Available from: 2022-05-08 Created: 2022-05-08 Last updated: 2022-05-09Bibliographically approved
Vessby, J., Ormarsson, S. & Sejkot, P. (2021). Impact of eccentricity in bracing supports on lateral instability of long-span timber trusses. In: World Conference on Timber Engineering 2021, WCTE 2021: . Paper presented at World Conference on Timber Engineering 2021, WCTE 2021, 9 - 12 August 2021. World Conference on Timber Engineering (WCTE)
Open this publication in new window or tab >>Impact of eccentricity in bracing supports on lateral instability of long-span timber trusses
2021 (English)In: World Conference on Timber Engineering 2021, WCTE 2021, World Conference on Timber Engineering (WCTE) , 2021Conference paper, Published paper (Refereed)
Abstract [en]

Timber roof structures built up by several trusses designed with structural timber members and jointed together by punched metal plate fasteners are considerably effective structures for long spans. They are considered cost-effective and can serve their purpose well during the lifespan of a roof. Lately, the limits of how long spans they can withstand for a normal loading situation have been pushed. Failures that often relate to lateral instability in the top chord or in other compressed members of the truss have been reported. The effect of various parameters on the load carrying capacity of the top chord is studied. Analytical solutions based on the method available in Eurocode 5 and a method based on the assumption of an elastic foundation is used in combination with finite element simulations. Results show that, in a Nordic context, the approach suggested in Eurocode is problematic due to the suggested bay length which is supposed to develop between lateral supports. Simulation results also suggests that load-displacement curves based on experiments performed on the connections involved should be used in simulations of the top chord rather than an elastic spring.

Place, publisher, year, edition, pages
World Conference on Timber Engineering (WCTE), 2021
Keywords
FE simulations, Lateral instability, Lateral support, Timber roof truss, Top chord, Codes (standards), Cost effectiveness, Finite element method, Plate metal, Roofs, Timber, Fe simulation, Long span, Roof structures, Roof truss, Structure build-ups, Timber roofs, Trusses
National Category
Building Technologies Construction Management
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-112580 (URN)2-s2.0-85120726709 (Scopus ID)
Conference
World Conference on Timber Engineering 2021, WCTE 2021, 9 - 12 August 2021
Available from: 2022-05-08 Created: 2022-05-08 Last updated: 2022-05-09Bibliographically approved
Kuai, L., Ormarsson, S. & Vessby, J. (2021). Modelling and experimental verification of light-frame timber modules loaded in shear. In: World Conference on Timber Engineering 2021, WCTE 2021: . Paper presented at World Conference on Timber Engineering 2021, WCTE 2021, 9-12 August 2021. World Conference on Timber Engineering (WCTE)
Open this publication in new window or tab >>Modelling and experimental verification of light-frame timber modules loaded in shear
2021 (English)In: World Conference on Timber Engineering 2021, WCTE 2021, World Conference on Timber Engineering (WCTE) , 2021Conference paper, Published paper (Refereed)
Abstract [en]

Building with prefabricated light-frame modules is an innovative construction method whose market share is increasing in Sweden. It is often used to build low and mid-rise residential buildings where the modules are premanufactured in factories with high efficiency and accuracy. This building method has many advantages, though more research regarding wind stabilization of both individual and assembled modules is still needed. To study the racking stiffness and strength of such timber modules, a numerical model of their shear walls was created and verified based on experimental results from specially prefabricated test modules. A new test facility was built for this work, where several potentiometers and a digital image correlation system collected the data used to verify the simulation model. The results from the simulations agree well with the experimental findings, which indicate that the three-dimensional finite element model works with reasonable accuracy for this application. © WCTE 2021. All rights reserved.

Place, publisher, year, edition, pages
World Conference on Timber Engineering (WCTE), 2021
Keywords
FE-modelling, Modular-based timber building, Shear wall, Test module, Competition, Finite element method, Shear walls, Three dimensional computer graphics, Timber, Voltage dividers, Construction method, Experimental verification, FE modeling, Light frames, Model verification, Modulars, Test modules, Timber buildings, Wooden buildings
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-112578 (URN)2-s2.0-85120737763 (Scopus ID)
Conference
World Conference on Timber Engineering 2021, WCTE 2021, 9-12 August 2021
Available from: 2022-05-08 Created: 2022-05-08 Last updated: 2022-05-09Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-5591-1045

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