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Florisson, S., Ormarsson, S. & Vessby, J. (2019). A numerical study of the effect of green-state moisture content on stress development in timber boards during drying. Wood and Fiber Science, 51(1), 41-57
Open this publication in new window or tab >>A numerical study of the effect of green-state moisture content on stress development in timber boards during drying
2019 (English)In: Wood and Fiber Science, ISSN 0735-6161, Vol. 51, no 1, p. 41-57Article in journal (Refereed) Published
Abstract [en]

Timber boards manufactured with a traditional sawing pattern often contain both heartwood andsapwood. In such boards, internal constraints can occur during drying because of a radial variation in greenstate(GS) MC between the heartwood (30-60%) and sapwood region (120-200%). Despite such knowledge,the initial MC is seldom considered when evaluating kiln-drying schedules. The effect of GS MC on thedevelopment of tangential tensile stress during drying is studied for four types of timber boards. A numericalmodel was developed that can simulate transient nonlinear orthotropic moisture flow and moisture–inducedstress and distortion in wood with the use of the finite element method. The stress analysis considers elastic,hygroscopic, and mechano-sorptive strain. The study shows that the GS MC does not significantly influencethe maximum stress state, but that it does influence the time at which the maximum tangential tensile stressoccurs at different exchange surfaces. This results in several periods in the drying schedule where unfavorablehigh stress situations in the tangential direction arise, which could lead to crack propagation.

Place, publisher, year, edition, pages
Society of Wood Science and Technology, 2019
Keywords
Green state, Nonlinear, Numerical, Moisture transport, Transient, Timber drying, Tangential stress
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-80214 (URN)
Available from: 2019-02-05 Created: 2019-02-05 Last updated: 2019-02-25Bibliographically approved
Ormarsson, S. & Johansson, M. (2018). Finite element simulation of global structural behaviour of multifamily timber buildings using prefabricated volume modules. In: WCTE 2018 - World Conference on Timber Engineering: . Paper presented at WCTE 2018, World Conference on Timber Engineering, August 20-23, 2018, Seoul, South Korea. World Conference on Timber Engineering (WCTE)
Open this publication in new window or tab >>Finite element simulation of global structural behaviour of multifamily timber buildings using prefabricated volume modules
2018 (English)In: WCTE 2018 - World Conference on Timber Engineering, World Conference on Timber Engineering (WCTE) , 2018Conference paper, Published paper (Refereed)
Abstract [en]

The potential of building multi-storey timber buildings has changed in recent decades. The building of apartment houses with fully prefabricated volume modules in wood is an industry sector that is rapidly increasing its capacity. A number of house manufacturers that have delivered volume modules, primarily for single family homes, are now expanding their production to multi-storey buildings up to 6-8 floors. This is a challenging task for producers, since the available design procedures for timber buildings have not yet been fully implemented for these types of buildings.The aim of the work is to develop an efficient and flexible finite element model to analyse the three-dimensional structural behaviour of multi-storey buildings using prefabricated volume modules made by wooden stud-and-rail structure. The model will be used to study the global structural behaviour of various timber walls, volume modulus and modular-based multi-storey buildings when subjected to different types of loading. The model will also be used for detailed analysis and design (using so-called adaptive modelling) of the most critical (weak) parts of the structure.

Place, publisher, year, edition, pages
World Conference on Timber Engineering (WCTE), 2018
Keywords
Wood, multi-storey timber buildings, volume modules, finite element modelling
National Category
Construction Management Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-82135 (URN)2-s2.0-85058174258 (Scopus ID)
Conference
WCTE 2018, World Conference on Timber Engineering, August 20-23, 2018, Seoul, South Korea
Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-05-24Bibliographically approved
Florisson, S., Ormarsson, S. & Vessby, J. (2018). Modelling of mechano-sorption in clear wood by using an orthotropic non-linear moisture flow and stress model. In: WCTE 2018 - World Conference on Timber Engineering: 2018 World Conference on Timber Engineering, WCTE 2018; COEX Convention and Exhibition CenterSeoul; South Korea, 20-23 August 2018. Paper presented at 2018 World Conference on Timber Engineering, WCTE 2018; COEX Convention and Exhibition CenterSeoul; South Korea, 20-23 August 2018. World Conference on Timber Engineering (WCTE)
Open this publication in new window or tab >>Modelling of mechano-sorption in clear wood by using an orthotropic non-linear moisture flow and stress model
2018 (English)In: WCTE 2018 - World Conference on Timber Engineering: 2018 World Conference on Timber Engineering, WCTE 2018; COEX Convention and Exhibition CenterSeoul; South Korea, 20-23 August 2018, World Conference on Timber Engineering (WCTE) , 2018Conference paper, Published paper (Refereed)
Abstract [en]

The European design standard for timber structures provides, besides obligatory safety requirements, a set of general serviceability requirements. Despite their generality, they have been proven important in design of timber structures, especially in varying climatic conditions, where the time dependent deflection can have a dominant role in long term performance. The total deformation consists of instantaneous elastic deformation, hygroscopic deformation, time dependent creep and mechano-sorptive deformation. The three latter deformations are influenced by climate, and when the change in climate is considerable over time, the deflection will significantly increase. In this paper a test-setup is created to study the effect of mechano-sorption on the global deflection of clear wood samples. The samples are loaded in a three-point bending test subjected to a constant mechanical load combined with a cyclic climatic load. The moisture induced stress and bending distortion were simulated by taking into account elastic, hygroscopic and mechano-sorptive strain. The non-linear moisture flow was simulated using Fick’s law. A parametric study was performed to obtain a better understanding of the constitutive equation, especially the term related to the moisture and temperature dependent diffusion coefficient. In addition to the simulations, an experiment was performed to verify the global deflection and mass change. The obtained results show that the mechano-sorption behaviour of the tested clear wood samples can be modelled, but an improvement of both the experimental setup and the model is required to come to more accurate conclusions on this type of long-term material behaviour.

Place, publisher, year, edition, pages
World Conference on Timber Engineering (WCTE), 2018
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-80218 (URN)2-s2.0-85058165472 (Scopus ID)
Conference
2018 World Conference on Timber Engineering, WCTE 2018; COEX Convention and Exhibition CenterSeoul; South Korea, 20-23 August 2018
Available from: 2019-02-05 Created: 2019-02-05 Last updated: 2019-05-27Bibliographically approved
Sejkot, P., Ormarsson, S. & Vessby, J. (2018). Numerical and experimental study of punched metal plate connection used for long-span pitched timber roof truss structure. In: WCTE 2018 - World Conference on Timber Engineering: . Paper presented at WCTE 2018, World Conference on Timber Engineering, August 20-23, 2018, Seoul, Rep. of Korea. World Conference on Timber Engineering (WCTE)
Open this publication in new window or tab >>Numerical and experimental study of punched metal plate connection used for long-span pitched timber roof truss structure
2018 (English)In: WCTE 2018 - World Conference on Timber Engineering, World Conference on Timber Engineering (WCTE) , 2018Conference paper, Published paper (Refereed)
Abstract [en]

According to the harmonized European design code for timber structures, Eurocode 5, all pitched timber trusses used in load bearing roofs are designed as in-plane structures which means that a bracing system must be designed and put in place to prevent the out-of-plane instability. Results from numerical 3D stability analyses of the whole roof structure indicate that the out of plane stability is often the critical factor. Therefore, influence of stiffness properties of that system is studied in detail herein for long-span timber roofs. Focus is put on how the stiffness of the mechanical connections in the roof structure influences the load carrying capacity of the roof. The punched metal plate connections are modelled as non-coupled spring elements connecting the various beam elements in the timber truss respectively. The spring stiffness of the connections is derived from full-scale tests, which were made for all in- and out-of-plane degrees of freedom. To evaluate the experimental testing, a digital image correlation method was used. The results from the digital image correlation tests were compared with numerical simulations of the experimentally tested connections to check the potential of using the numerical simulations instead of the experimental testing to get the stiffness properties of various connections used in the whole roof stability analysis. Based on such analysis, punched metal plate fasteners showed to be an important contributor to the roof stability because of its relatively high stiffness in all six degrees of freedom.

Place, publisher, year, edition, pages
World Conference on Timber Engineering (WCTE), 2018
Keywords
Timber truss structures, punched metal plate connections, numerical analysis, top chord buckling length
National Category
Construction Management
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-82136 (URN)2-s2.0-85058165120 (Scopus ID)
Conference
WCTE 2018, World Conference on Timber Engineering, August 20-23, 2018, Seoul, Rep. of Korea
Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-05-27Bibliographically approved
Ormarsson, S. (2018). Parameterized and adaptive modelling of structural behaviour of innovative modular-based multi-storey timber buildings of wood. In: Presented at EMI 2018, Engineering Mechanics Institute Conference, May 29 - June 1, 2018, MIT, Cambridge, USA: . Paper presented at EMI 2018, Engineering Mechanics Institute Conference, May 29 - June 1, 2018, MIT, Cambridge, USA.
Open this publication in new window or tab >>Parameterized and adaptive modelling of structural behaviour of innovative modular-based multi-storey timber buildings of wood
2018 (English)In: Presented at EMI 2018, Engineering Mechanics Institute Conference, May 29 - June 1, 2018, MIT, Cambridge, USA, 2018Conference paper, Oral presentation with published abstract (Refereed)
National Category
Construction Management Building Technologies
Research subject
Technology (byts ev till Engineering), Sustainable Built Environment
Identifiers
urn:nbn:se:lnu:diva-82133 (URN)
Conference
EMI 2018, Engineering Mechanics Institute Conference, May 29 - June 1, 2018, MIT, Cambridge, USA
Note

Ej belagd 190508

Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-05-08Bibliographically approved
Ormarsson, S. & Johansson, M. (2017). FE-modell av en volymmodul - spännings- och stabilitetsanalys : Förstudie.
Open this publication in new window or tab >>FE-modell av en volymmodul - spännings- och stabilitetsanalys : Förstudie
2017 (Swedish)Report (Other academic)
Abstract [sv]

Trä är ett mycket användbart, prisvärt och förnyelsebart material som rätt utnyttjat har en extremt hög industriell potential inom området byggnadskonstruktion. Det finns ett stort intresse i Sverige att utforska nya sätt att utnyttja trä som huvudlastbärande material i olika typer av flervåningshus. Detta är en stor utmaning för träbyggnadsindustrin, forskare och konstruktörer eftersom det inte finns någon traditionell beräknings- och designprocedur för dessa typer av byggnader.

I denna förstudie har en parametrisk FE-modell framtagits för att studera strukturmekaniska egenskaper (deformationer och styvhet) hos en typisk volymmodul som används för byggande av flerbostadshus i trä. Modellen är uppbyggd av olika typer av strukturelement (fjädrar, balk- och skalelement) för att den skall vara så snabb och flexibel som möjligt. Modellen inkluderar ett stort antal konnektor- och kopplingselement för att på ett optimalt sätt kunna simulera alla spik-, skruv- och bultförband i modulen. Modellen är också ganska flexibel eftersom den är parameterstyrd via ett antal geometriska parametrar. Modellen har använts för att studera globala deformationer och styvhetsegenskaper hos olika vägg- och volymelement när de belastas med olika mekaniska laster. Att få en uppfattning om hur styvhetsegenskaper hos de mekaniska förbanden (svaga delar i konstruktionen) påverkar det globala deformationsbeteendet hos olika vägg- och volymelement har varit en viktig del i denna förstudie.

Modellen visar ett deformationsbeteende hos vägg- och volymelementen verkar rimliga men en experimentell verifiering återstår. Ett exempel på resultat är att väggelement som belastas i planskjuvning har en tydlig tendens att böja ut ur planet eftersom det finns gipsskiva enbart på insidan av regelstommen. Studien visar också att för volymmoduler med en gles skruvförbindning mellan vägg- och bjälklagselementen uppkommer stora gliddeformationer mellan elementen. En av de viktigaste slutsatser från denna förstudie är att det gick att skapa en snabb och effektiv strukturmekanisk tredimensionell FE-modell för den här typen av konstruktion. Beräkningstiden för en volymmodul var endast 5.5 minuter på en vanlig laptop computer. Dessa resultat visar därför att det finns goda förutsättningar för att kunna simulera och analysera hela flerbostadshus inom rimliga beräkningstider.

Publisher
p. 16
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-68221 (URN)
Available from: 2017-10-05 Created: 2017-10-05 Last updated: 2017-10-16Bibliographically approved
Nilsson, J., Ormarsson, S. & Johansson, J. (2017). Moisture-related distortion and damage of lightweight wood panels: experimental and numerical study. Journal of the Indian Academy of Wood Science, 14(2), 99-109
Open this publication in new window or tab >>Moisture-related distortion and damage of lightweight wood panels: experimental and numerical study
2017 (English)In: Journal of the Indian Academy of Wood Science, ISSN 0972-172X, Vol. 14, no 2, p. 99-109Article in journal (Refereed) Published
Abstract [en]

This study was conducted to increase the knowledge of moisture-related distortion and damage in the field of wood-based lightweight panels. By increasing the possibilities of predicting moisture-related distortion and damage, the possibilities of using lightweight wood materials could increase. The study was performed through experiments and modelling work on a wooden panel product with numerous struts and two thin outer-face sheets of beech-wood glued tightly onto the struts, as well as reference panels of solid wood. During the testing period the results showed the density of the studied lightweight panels to vary from 170 to 290 kg/m3. These panels shrunk and swelled less than the solid wood panels and reacted faster to changes of surrounding humidity and temperature. Moisture related distortions such as twist and bow were not inferior compared to the solid wood panels. Shrinkage or swelling produced moisture related stresses. This may mean that the panel will have a risk of serious damage in the form of cracks or glue release between the outer face sheet and the struts when it is exposed to intense drying. The experimental tests also followed how various damages arose in the panels. Until the damage occurred, the deformation results showed a strong agreement between the experimental and the model findings. Better knowledge of how this type of panel reacts to climate variations is important for the further design and development of this type of product.

Place, publisher, year, edition, pages
Springer, 2017
Keywords
Sandwich panel, Stresses, Shape stability, Numerical modelling, Finite element method (FEM)
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-68220 (URN)10.1007/s13196-017-0193-y (DOI)000449592600001 ()2-s2.0-85036588702 (Scopus ID)
Available from: 2017-10-05 Created: 2017-10-05 Last updated: 2019-08-29Bibliographically approved
Sejkot, P., Ormarsson, S. & Vessby, J. (2017). Numerical and experimental study of punched metal plate connections to obtain spring stiffness needed for 3D buckling analysis of long-span timber trusses. In: Presented at CompWood 2017 – ECCOMAS Thematic Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber, June 7-9, 2017, Vienna, Austria: . Paper presented at CompWood 2017 – ECCOMAS Thematic Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber, June 7-9, 2017, Vienna, Austria..
Open this publication in new window or tab >>Numerical and experimental study of punched metal plate connections to obtain spring stiffness needed for 3D buckling analysis of long-span timber trusses
2017 (English)In: Presented at CompWood 2017 – ECCOMAS Thematic Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber, June 7-9, 2017, Vienna, Austria, 2017Conference paper, Oral presentation with published abstract (Refereed)
National Category
Construction Management
Identifiers
urn:nbn:se:lnu:diva-68219 (URN)
Conference
CompWood 2017 – ECCOMAS Thematic Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber, June 7-9, 2017, Vienna, Austria.
Available from: 2017-10-05 Created: 2017-10-05 Last updated: 2017-10-19Bibliographically approved
Ormarsson, S. & Johansson, M. (2017). Numerical simulations of structural behaviour of volume modules used for construction of multifamily timber houses. In: CompWood 2017 : Computational Methods in Wood Mechanics – from Material Properties to Timber: Programme & Book of abstract. Paper presented at CompWood 2017 – ECCOMAS Thematic Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber, June 7-9, 2017, Vienna, Austria..
Open this publication in new window or tab >>Numerical simulations of structural behaviour of volume modules used for construction of multifamily timber houses
2017 (English)In: CompWood 2017 : Computational Methods in Wood Mechanics – from Material Properties to Timber: Programme & Book of abstract, 2017Conference paper, Oral presentation with published abstract (Refereed)
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-68217 (URN)9783903024496 (ISBN)
Conference
CompWood 2017 – ECCOMAS Thematic Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber, June 7-9, 2017, Vienna, Austria.
Available from: 2017-10-05 Created: 2017-10-05 Last updated: 2017-10-16Bibliographically approved
Florisson, S. & Ormarsson, S. (2017). The effect of surface emission, diffusion and initial moisture profiles on stress development in timber boards. In: CompWood 2017 : Computational Methods in Wood Mechanics – from Material Properties to Timber: Programme & book of abstract. Paper presented at CompWood 2017 – ECCOMAS Thematic Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber, June 7-9, 2017, Vienna, Austria.. TU Verlag
Open this publication in new window or tab >>The effect of surface emission, diffusion and initial moisture profiles on stress development in timber boards
2017 (English)In: CompWood 2017 : Computational Methods in Wood Mechanics – from Material Properties to Timber: Programme & book of abstract, TU Verlag , 2017Conference paper, Oral presentation with published abstract (Refereed)
Place, publisher, year, edition, pages
TU Verlag, 2017
National Category
Wood Science
Identifiers
urn:nbn:se:lnu:diva-68218 (URN)9783903024496 (ISBN)
Conference
CompWood 2017 – ECCOMAS Thematic Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber, June 7-9, 2017, Vienna, Austria.
Available from: 2017-10-05 Created: 2017-10-05 Last updated: 2017-10-16Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5591-1045

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