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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:kau:diva-74373 (URN)10.22382/wfs-2019-005 (DOI)
Available from: 2019-08-28 Created: 2019-08-28 Last updated: 2019-09-23Bibliographically 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: . 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, 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
Keywords
Climate change, creep, deflection (structures), sorption, timber, wood products
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:kau:diva-74374 (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: 2019-08-28 Last updated: 2019-10-21Bibliographically 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:kau:diva-74386 (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: 2019-08-16 Created: 2019-08-16 Last updated: 2019-08-16
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:kau:diva-74387 (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: 2019-08-28Bibliographically approved
Ormarsson, S. & Vessby, J. (2016). Geometric nonlinear analysis of a pitched roof structure of wood. In: Eccomas 2016 Proceedings: . Paper presented at ECCOMAS Congress 2016 VII European Congress on Computational Methods in Applied Sciences and Engineering, June 5–10, 2016 Crete Island, Greece..
Open this publication in new window or tab >>Geometric nonlinear analysis of a pitched roof structure of wood
2016 (English)In: Eccomas 2016 Proceedings, 2016Conference paper, Oral presentation with published abstract (Refereed)
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:kau:diva-74381 (URN)
Conference
ECCOMAS Congress 2016 VII European Congress on Computational Methods in Applied Sciences and Engineering, June 5–10, 2016 Crete Island, Greece.
Available from: 2017-10-05 Created: 2019-09-19Bibliographically approved
Ormarsson, S., Vessby, J., Källsner, B. & Filchev, I. (2016). Numerical analysis of failure modes and force distribution in a pitched roof structure of wood. In: J. Eberhardsteiner, W. Winter, A. Fadai, M. Pöll (Ed.), Proceedings of the 2016 World Conference on Timber Engineering (WCTE): . Paper presented at WCTE 2016 World Conference on Timber Engineering, August 22-25, 2016, Vienna, Austria. Vienna: Vienna University of Technology
Open this publication in new window or tab >>Numerical analysis of failure modes and force distribution in a pitched roof structure of wood
2016 (English)In: Proceedings of the 2016 World Conference on Timber Engineering (WCTE) / [ed] J. Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Vienna: Vienna University of Technology , 2016Conference paper, Published paper (Refereed)
Abstract [en]

Instability failures of timber elements and timber structures are reported relatively frequently although there are some suggestions available how to prevent such failures. These types of failures are characterized by sudden deformations that typically lead to failure in a single loadbearing element or collapse of the entire structure. This paper deals with buckling analysis and geometric nonlinear stress analysis of pitched roof structures of wood. A FE- model has been developed and used to study how different parameters influence the buckling modes and force distribution in the lateral bracing system of the roof structure. The simulated forces in the bracing system are also compared with results based on a simple design method given in Eurocode 5 (EC5) and a method where the compressed top chord is treated as a beam on a continuous elastic foundation. The buckling simulations showed the out-of-plane buckling to be the critical failure mode for the truss structure studied and the geometric nonlinear analysis showed the bracing stiffness and the bracing forces to be significant lower than those calculated by hand according to EC5.

Place, publisher, year, edition, pages
Vienna: Vienna University of Technology, 2016
National Category
Construction Management
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:kau:diva-74382 (URN)2-s2.0-85010932009 (Scopus ID)978-3-903039-00-1 (ISBN)
Conference
WCTE 2016 World Conference on Timber Engineering, August 22-25, 2016, Vienna, Austria
Available from: 2017-10-05 Created: 2019-08-28Bibliographically approved
Vessby, J., Källsner, B. & Ormarsson, S. (2016). Stabilisering av takkonstruktioner i trä: arbetet med ny handbok. Bygg & teknik (4), 60-63
Open this publication in new window or tab >>Stabilisering av takkonstruktioner i trä: arbetet med ny handbok
2016 (Swedish)In: Bygg & teknik, ISSN 0281-658X, no 4, p. 60-63Article in journal (Other (popular science, discussion, etc.)) Published
Place, publisher, year, edition, pages
Foerlags AB Bygg & Teknik, 2016
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:kau:diva-74400 (URN)
Available from: 2017-10-05 Created: 2019-08-16Bibliographically approved
Sejkot, P., Ormarsson, S., Vessby, J. & Kuklik, P. (2015). Determination of Load Bearing Capacity for Spatial Joint with Steel Angle Brackets. In: Sahmenko, G; Rucevskis, S; Bajare, D (Ed.), 2ND INTERNATIONAL CONFERENCE ON INNOVATIVE MATERIALS, STRUCTURES AND TECHNOLOGIES: . Paper presented at 2nd International Conference on Innovative Materials, Structures and Technologies (IMST), SEP 30-OCT 02, 2015, Riga, LATVIA. Institute of Physics Publishing (IOPP), Article ID UNSP 012070.
Open this publication in new window or tab >>Determination of Load Bearing Capacity for Spatial Joint with Steel Angle Brackets
2015 (English)In: 2ND INTERNATIONAL CONFERENCE ON INNOVATIVE MATERIALS, STRUCTURES AND TECHNOLOGIES / [ed] Sahmenko, G; Rucevskis, S; Bajare, D, Institute of Physics Publishing (IOPP), 2015, article id UNSP 012070Conference paper, Published paper (Refereed)
Abstract [en]

The design of spatial connections in load bearing timber structures with steel angle brackets has insufficient support in the existing design standards. Therefore, research has been necessary to improve this state of the art. In the current paper an experimental study on two designs of angle brackets is presented and the results from full-scale experiments are compared to numerical and analytical computational models.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015
Series
IOP Conference Series-Materials Science and Engineering, ISSN 1757-8981 ; 96
National Category
Civil Engineering
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:kau:diva-74388 (URN)10.1088/1757-899X/96/1/012070 (DOI)000365029600070 ()2-s2.0-84960415614 (Scopus ID)
Conference
2nd International Conference on Innovative Materials, Structures and Technologies (IMST), SEP 30-OCT 02, 2015, Riga, LATVIA
Available from: 2015-12-11 Created: 2019-08-16Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5591-1045

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