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  • 1.
    Bader, Thomas K.
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Modeling displacement path dependence in nailed sheathing-to-framing connections2017Ingår i: CompWood 2017 - Computational Methods in Wood Mechanics - from Material Properties to Timber Structures: Programme & Books of Abstracs / [ed] Josef Füssl, Thomas K. Bader, Josef Eberhardsteiner, Vienna: TU verlag , 2017Konferensbidrag (Refereegranskat)
  • 2.
    Bader, Thomas K.
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Enquist, Bertil
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Path dependence in OSB sheathing-to-framing nailed connection revealed by biaxial testing2018Ingår i: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 144, nr 10, artikel-id 04018197Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    OSB sheathing-to-wood framing connection, as typically used in light-frame shear walls, was experimentally examined in a novel biaxial test setup with respect to possible path dependence of the load-displacement relation. The connection with an annular-ringed shank nail was loaded under displacement control following nine different displacement paths within the sheathing plane, which coincided at a number of points. In intersection points, resultant connection force, its orientation and work performed on the connection system to reach the specific point were calculated and compared. Evaluation of experiments revealed significant path dependence with respect to orientation of force resultants at path intersection points. However, magnitude of the forces and the work carried out showed relatively small dependence of the displacement path undertaken. Comparison of uniaxial connection tests with the European yield model demonstrated strong contribution of withdrawal resistance of the ringed shank nail to its lateral strength. Results of this type are a valuable basis to build better models when simulating such connections in wood structures.

  • 3.
    Florisson, Sara
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Ormarsson, Sigurdur
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    A numerical study of the effect of green-state moisture content on stress development in timber boards during drying2019Ingår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 51, nr 1, s. 41-57Artikel i tidskrift (Refereegranskat)
    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.

  • 4.
    Florisson, Sara
    et al.
    Linnéuniversitetet, Växjö.
    Ormarsson, Sigurdur
    Linnéuniversitetet, Växjö.
    Vessby, Johan
    Linnéuniversitetet, Växjö.
    Modelling of mechano-sorption in clear wood by using an orthotropic non-linear moisture flow and stress model2018Ingår i: WCTE 2018 - World Conference on Timber Engineering, World Conference on Timber Engineering (WCTE) , 2018Konferensbidrag (Refereegranskat)
    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.

  • 5.
    Habite, Tadios
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Florisson, Sara
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Numerical Simulation of Moisture-Induced Crack Propagation in Dowelled Timber Connection Using XFEM2018Ingår i: 2018 World Conference on Timber Engineering (WCTE), August 20-23, 2018, Seoul, Republic of Korea, World Conference on Timber Engineering (WCTE) , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    At times dowelled glulam timber connections experience crack development in the fibre direction. The main reason for this is moisture variation in the timber elements which induces a stress perpendicular to the fibre direction. The aim of this paper is to study the influence of different moisture conditions and vertical dowel spacing on crack development through numerical simulations by use of the finite element method in three dimensions. A transient non-linear Fickian moisture diffusion model is implemented to simulate the moisture state within the glulam beam. The moisture gradient in the diffusion model was created by adopting a physical scenario by assuming what conditions the considered glulam beam will go through, from the factory up to installation. Further, an extended finite element method (XFEM) for two different vertical dowel spacing, 100 mm and 300 mm, with a linear elastic fracture mechanics (LEFM) approach was applied for the crack simulation. The results reveal that the moisture variation in combination with unfavourable placement of dowels can cause a crack to develop in the glulam timber beam. Moreover, it was shown that a moisture induced crack development may be modelled successfully by use of an Extended Finite Element Method (XFEM) approach.

  • 6.
    Ormarsson, Sigurdur
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Geometric nonlinear analysis of a pitched roof structure of wood2016Ingår i: Eccomas 2016 Proceedings, 2016Konferensbidrag (Refereegranskat)
  • 7.
    Ormarsson, Sigurdur
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Källsner, Bo
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Filchev, Ivan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Numerical analysis of failure modes and force distribution in a pitched roof structure of wood2016Ingår i: Proceedings of the 2016 World Conference on Timber Engineering (WCTE) / [ed] J. Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Vienna: Vienna University of Technology , 2016Konferensbidrag (Refereegranskat)
    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.

  • 8.
    Reynolds, Thomas
    et al.
    University of Bath, UK.
    Bolmsvik, Åsa
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Chang, Wen-Shao
    University of Bath, UK.
    Harris, Richard
    University of Bath, UK.
    Bawcombe, Jonathan
    Cambridge, UK.
    Bregulla, Julia
    Building Research Establishment (BRE), UK.
    Ambient vibration testing and modal analysis of multi-storey cross-laminated timber buildings2014Ingår i: World conference on timber engineering (WCTE), World conference on timber engineering (WCTE) , 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    The ambient movement of three multi-storey cross-laminated timber (CLT) buildings have been measured and used to determine natural frequencies, mode shapes and damping ratios. This information, obtained by a simple, unobtrusive series of tests, can give insights into the structural performance of this form of building, as well as providing information for the design of future, taller timber buildings for dynamic loads. For two of the buildings, the natural frequency has been related to the lateral stiffness of the structure, and compared with the stiffness based on simple calculation. In future tall timber buildings, a new design criterion is expected to become important: deflection and vibration serviceability under wind load. Design standards give techniques for prediction and mitigation of wind-induced movement, but require an estimate of the mass, stiffness and damping ratio of the structure to make an accurate prediction. For multi-storey timber buildings there is no empirical basis to use for damping estimation, and there is little information for stiffness. This study therefore provides an insight into the modal properties for lateral vibration of multi-storey CLT construction which could inform the design of taller buildings in the future.

  • 9.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Constrained displacement boundary condition in embedment testing of dowel-type fasteners in LVL2017Ingår i: Strain, ISSN 0039-2103, E-ISSN 1475-1305, Vol. 53, nr 6, artikel-id e12238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of the loading orientation with respect to the grain direction of wood and the influence of the lateral dowel displacement boundary condition on the embedment behaviour of steel dowels in laminated veneer lumber (with parallel-laminated veneers) are investigated in this study. For limit states of the lateral boundary condition, the load-displacement behaviour was experimentally studied by means of full-hole embedment tests on screw-reinforced laminated veneer lumber, for two dowel diameters and up to large dowel displacements. A novel biaxial test set-up is proposed for embedment tests with constrained lateral dowel displacement boundary condition, in order to quantify laterally evoked reaction forces. Corresponding forces were found to change orientation with increasing dowel displacement and amounted to about 20% and 40% of the vertical reaction force for dowel displacements of 5 mm and twice the dowel diameter, respectively. The influence of the lateral displacement boundary condition was highlighted by comparison of the test data with a previously established data set for unconstrained embedment testing. Constrained loading showed a stiffer response and higher nominal embedment stresses, as well as a more pronounced displacement hardening, compared to unconstrained loading.

  • 10.
    Sejkot, Petr
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Ormarsson, Sigurdur
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Numerical and experimental study of punched metal plate connection used for long-span pitched timber roof truss structure2018Ingår i: WCTE 2018 - World Conference on Timber Engineering, World Conference on Timber Engineering (WCTE) , 2018Konferensbidrag (Refereegranskat)
    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.

  • 11.
    Sejkot, Petr
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Ormarsson, Sigurdur
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Numerical and experimental study of punched metal plate connections to obtain spring stiffness needed for 3D buckling analysis of long-span timber trusses2017Ingår i: Presented at CompWood 2017 – ECCOMAS Thematic Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber, June 7-9, 2017, Vienna, Austria, 2017Konferensbidrag (Refereegranskat)
  • 12.
    Sejkot, Petr
    et al.
    Czech Tech Univ, Czech Republic.
    Ormarsson, Sigurdur
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Kuklik, P.
    Czech Tech Univ, Czech Republic.
    Determination of Load Bearing Capacity for Spatial Joint with Steel Angle Brackets2015Ingår i: 2ND INTERNATIONAL CONFERENCE ON INNOVATIVE MATERIALS, STRUCTURES AND TECHNOLOGIES / [ed] Sahmenko, G; Rucevskis, S; Bajare, D, Institute of Physics Publishing (IOPP), 2015, artikel-id UNSP 012070Konferensbidrag (Refereegranskat)
    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.

  • 13. Sejkot, Petr
    et al.
    Ormarsson, Sigurdur
    Vessby, Johan
    Källsner, Bo
    Numerical out-of-plane stability analysis of long span timber trusses with focus on buckling length calculations2020Ingår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    According to the harmonized European design code for timber structures, Eurocode 5, all pitched timber trusses are designed as an in-plane structure, meaning that the bracing systems used are assumed to prevent the out-of-plane failure of the truss if sufficient strength and stiffness are provided. The present paper studies how the stiffness of a wooden bracing system contributes to the out-of-plane stability of a trussed roof structure. Results from numerical simulations indicate that significant bracing forces may occur in compressed structural members for long-span timber structures. As well, the values obtained from the calculations according to Eurocode 5 are occasionally far from the results obtained by numerical simulations.

  • 14.
    Serrano, Erik
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Enquist, Bertil
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Long term in-situ measurements of displacement, temperature and relative humidity in a multi storey residential CLT building2014Ingår i: WCTE 2014 - World Conference on Timber Engineering, Proceedings, World Conference on Timber Engineering (WCTE) , 2014, s. 398-405Konferensbidrag (Refereegranskat)
    Abstract [en]

    In a multi-storey residential housing project comprising of four 8-storey timber buildings, the bottom storeybeing designed with concrete and storeys 2-8 in timber, the vertical relative displacement, the temperature and the relativehumidity (RH) along one vertical channel in the external wall of one building has been monitored. Measurements startedduring construction and presented herein are results of 6.5 years of in-situ measurements. Displacement data was monitoredstorey-by-storey, with a sampling frequency of 1 measurement every 10-60 minutes. In another of the four buildingsadditional temperature and relative humidity measurements have been ongoing for about 5.5 years. These temperature andRH measurements were performed at six different locations in the building, at each location in eight positions through theexterior wall with a sampling frequency of 1 measurement every 15 minutes. The results show that the total verticaldisplacement over six storeys after 6.5 years of service life is approximately 23 mm as a yearly average, and over the yearthe displacement varies from this value by approximately ±2 mm. The main cause for the relative displacement is thedecrease of moisture content in the wood material leading to shrinkage after completion of the building. The resultsobtained show also that the exterior wall design of the building behaves well in terms of not comprising a general risk fordamp or mould in the timber core of the external walls.

  • 15.
    Serrano, Erik
    et al.
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Enquist, Bertil
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Vessby, Johan
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Vertical relative displacements in a medium-rise CLT-building2010Ingår i: Structures and Architecture: Proceedings of the First International Conference and Architectures, ICSA / [ed] Paulo J.S. Cruz, Taylor & Francis, 2010, s. 388-395Konferensbidrag (Refereegranskat)
    Abstract [en]

    Four buildings with clt-panels in their load bearing structure were built at the block Limnologen in Växjö, Southern Sweden. Their architecture is an example of the new ar-chitecture possible with this building system. Properties of these new structures are sought, one of these being their relative vertical displacement over time. These displacements are measured continuously for six storeys, up to now for just over two years. So far, the total measured dis-placements have reached a maximum of 21.1 mm over the 17.95 meter measuring length. Annu-lar variations of the displacements corresponding to the varying climate may be observed in the data.

  • 16.
    Serrano, Erik
    et al.
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Vessby, Johan
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Olsson, Anders
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Modeling of fracture in the sill plate in partially anchored shear walls2012Ingår i: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 138, nr 10, s. 1285-1288Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study relates to the topic of anchorage of shear walls. At times, eccentric forces between the sheathing and the anchoring devices may be introduced in the sill plate. In severe cases, such forces may cause the sill plate to split and to fail in a brittle manner. In this study, fracture mechanics are applied to develop a simple closed-form hand-calculation expression for estimation of the ultimate load capacity of the sill plate. Finite-element analyses using both linear elastic fracture mechanics (LEFM) theory and a nonlinear fictitious crack model are also used to predict the ultimate load-bearing capacity of the sill plate. The hand-calculation model is compared with the finite-element models, and good agreement is obtained. The results obtained with the various fracture mechanics models are compared with results available from previously performed experimental tests, and again good agreement is obtained. A general conclusion is that the LEFM theory is an adequate approach for the case studied and that the hand-calculation expression developed could be useful for structural design.

  • 17.
    Vessby, Johan
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Analysis of shear wallsfor multi-storey timber buildings2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This doctoral thesis addresses questions of how wind loads acting on multistoreytimber buildings can be dealt with by structural design of such buildings.The conventional use of sheathing either nailed or screwed to a timberframework is considered, together with other stabilizing structures such ascross-laminated timber panels.The finite element method was employed in simulating the structuralbehaviour of stabilizing wall units. A series of studies was carried out of walls inwhich the sheathing was nailed to a timber frame. Different structural levelswere studied starting with modelling the performance of single sheathing-toframingconnections, to the use of models for studying the overall structuralbehaviour of walls. The results of calculations using models for simulation ofwalls subjected to different loading agree reasonably well with experimentalresults. The structural properties of the connections between the sheathing andthe frame, as well as of the connections between the members of the frame,were shown to have a substantial effect on the simulated behaviour of shearwall units. Both these types of connections were studied and described inappended papers.Regarding cross-laminated timber wall panels, it was concluded that walls witha high level of both stiffness and strength can be produced by the use of suchpanels, and also that the connections between the solid wall panels can bedesigned in such a way that the shear forces involved are transmitted from onepanel to the next in an efficient manner.Other topics in the thesis include the properties of connections between shearwalls and the rest of the building. Typically high tension forces occur at specificpoints in a timber structure. These forces need to be transmitted downwards inthe structure, ultimately connecting them to the substrate. A lap-joint that maybe used for this purpose has been studied using generalized Volkersen theory.Finally the maximum capacity of a conventional rail to substrate connection hasbeen examined using linear and nonlinear fracture mechanics.

  • 18.
    Vessby, Johan
    Växjö universitet, Institutionen för teknik och design.
    Shear walls for multi-storey timber buildings2008Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Wind loads acting on wooden building structures need to be dealt with adequately in order to ensure that neither the serviceability limit state nor the ultimate limit state is exceeded. For the structural designer of tall buildings, avoiding the possibly serious consequences of heavy wind loading while taking account at the same time of the effects of gravitation can be a real challenge. Wind loads are usually no major problem for low buildings, such as one- to two-storey timber structures involving ordinary walls made by nailing or screwing sheets of various types to the frame, but when taller structures are designed and built, serious problems may arise.

    Since wind speed and thus wind pressure increases with height above the ground and the shear forces transmitted by the walls increase accordingly, storey by storey, considerable efforts can be needed to handle the strong horizontal shear forces that are exerted on the bottom floor in particular. The strong uplift forces that can develop on the wind side of a structure are yet another matter that can be critical. Accordingly, a structure needs to be anchored to the substrate or to the ground by connections that are properly designed. Since the calculated uplift forces depend very much upon the models employed, the choice of models and simplifications in the analysis that are undertaken also need to be considered carefully.

    The present licentiate thesis addresses questions of how wind loads acting on multi-storey timber buildings can be best dealt with and calculated for in the structural design of such buildings. The conventional use of sheathing either nailed or screwed to a timber framework is considered, together with other methods of stabilizing timber structures. Alternative ways of using solid timber elements for stabilization are also of special interest.

    The finite element method was employed in simulating the structural behaviour of stabilizing units. A study was carried out of walls in which sheathing was nailed onto a timber frame. Different structural levels were involved, extending from modelling the performance of a single fastener and of the connection of the sheathing to frame, to the use of models of this sort for studying the overall structural behaviour of wall elements that possess a stabilizing function. The results of models used for simulating different load cases for walls agreed reasonably well with experimental test results. The structural properties of the fasteners binding the sheathing to the frame, as well as of the connections between the members of the frame were shown to have a strong effect on the simulated behaviour of shear wall units.

    Regarding solid wall panels, it was concluded that walls with a high level of both stiffness and strength can be produced by use of such panels, and also that the connections between the solid wall panels can be designed in such a way that the shear forces involved are effectively transmitted from one panel to the next.

  • 19.
    Vessby, Johan
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Enquist, Bertil
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Källsner, Bo
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Directional dependency in an OSB sheathing-to-framing mechanical connection2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Nailed connections are commonly employed for connecting sheathings to the framing used in shear walls. Although many aspects of such connections have been investigated thoroughly within the research community generally, the effect the loading direction has on connections of this sort has been much less investigated. In the present study experimental tests were carried out for determining in detail the effects the loading has on different sheathing-to-framing connections. The results obtained indicated the degree of loading to which a nail fastened to an oriented strand board (OSB) sheathing is subjected to not be strongly affected by which of the two main loading directions is involved, but that the effects of loading direction are found to be much greater if the timber element in question is also included in the testing carried out. The dependency of the loading effect on the loading direction at different loading stages and for different directions - parallel to the fibres, perpendicular to them, at some angle between these two main directions - was investigated here.

  • 20.
    Vessby, Johan
    et al.
    Växjö universitet, Institutionen för teknik och design.
    Enquist, Bertil
    Växjö universitet, Institutionen för teknik och design.
    Petersson, Hans
    Växjö universitet, Institutionen för teknik och design.
    Alsmarker, Tomas
    Tyréns.
    Experimental study of cross-laminated timber wall panels2009Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 67, nr 2, s. 211-218Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of cross-laminated structural timber elementsis becoming increasingly popular. The number of layersvaries normally from three upwards. The structural performanceof five-layer cross-laminated timber elements was investigated.The five layers consisted of 19mm thick boards,laid successively at right angles to each other and gluedtogether with PU-adhesive, layers 1, 3 and 5 lying in onedirection and layers 2 and 4 in the other. The stiffness andstrength of four cross-laminated timber elements (4955mmlong, 1250mm wide and 96mm thick) were studied duringin-plane bending. Two of the elements were first partitionedinto two parts that were reconnected in two different waysprior to testing. The influence of the way in which the crosslaminatedtimber elements were reconnected was studied,the behaviour observed being compared with the test resultsfor the unpartitioned specimens with respect to both strengthand stiffness. The experimental tests performed showed thecross-laminated timber elements to possess a high degree ofstiffness and strength. There was also found to be a markeddifference in behaviour between the two different ways inwhich the elements were connected to each other. One of thetwo connecting methods studied, being of less good designbut earlier frequently used in Sweden, showed as expectedpoor structural performance, whereas the other one appliedas a safer alternative performed well.

  • 21.
    Vessby, Johan
    et al.
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Källsner, Bo
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Girhammar, Ulf Arne
    Umeå universitet, Institutionen för tillämpad fysik och elektronik.
    Influence of contact stress between sheets on strength and stiffness of timber frame shear walls2010Ingår i: Proceedings of the 11th World Conference on Timber Engineering / [ed] Ario Ceccotti, 2010Konferensbidrag (Refereegranskat)
  • 22.
    Vessby, Johan
    et al.
    Växjö universitet, Institutionen för teknik och design.
    Källsner, Bo
    Växjö universitet, Institutionen för teknik och design.
    Olsson, Anders
    Växjö universitet, Institutionen för teknik och design.
    Influence of initial gap between timber members on stiffness and capacity of shear walls2008Ingår i: 10:th World Conference on Timber Engineering, 2008Konferensbidrag (Refereegranskat)
  • 23.
    Vessby, Johan
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Källsner, Bo
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Girhammar, Ulf Arne
    Luleå Univ Technol.
    Evaluation of softening behaviour of timber light-frame walls subjected to in-plane forces using simple FE models2014Ingår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 81, s. 464-479Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present investigation focuses on evaluating the entire load displacement relationship, especially the softening part, of light-frame wall segments subjected to in-plane monotonic forces when the load-slip curves of the individual sheathing-to-framing fasteners are considered. Different sheathing-to-framing joint characteristics, including unloading behaviour, and stud-to-rail joint characteristics are incorporated in the analyses. Two loading cases are investigated: Horizontal loading resulting in uplift of the leading stud and diagonal loading representing a fully anchored wall. Two common types of finite element (FE) models for the sheathing-to-framing joints are used for the analyses: A single spring model and a spring pair model, where the joint characteristics valid for the timber properties perpendicular and parallel to the grain are used. The maximum capacity of the wall segments is somewhat overestimated when using the spring pair model compared to that of the single spring model. The softening parts of the load displacement curves are significantly affected, regardless of whether the perpendicular or parallel characteristics of the joints are used. The results from FE simulations using models with perpendicular and parallel characteristics are compared with full scale test results for walls with a single segment loaded horizontally and diagonally. The behaviour of the wall segments subjected to horizontal loading is dominated by fastener displacements perpendicular to the bottom rail. Hence, FE models including perpendicular characteristics should be used. For diagonal loading the behaviour of the wall segments is dominated by displacements parallel to the framing members, and FE models including parallel characteristics should therefore be used. The analyses were extended to multiple segment walls resulting in the same type of behaviour as single segment walls. (C) 2014 Elsevier Ltd. All rights reserved.

  • 24.
    Vessby, Johan
    et al.
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Källsner, Bo
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Ormarsson, Sigurdur
    Linnéuniversitetet, Institutionen för byggteknik (BY).
    Stabilisering av takkonstruktioner i trä: arbetet med ny handbok2016Ingår i: Bygg & teknik, ISSN 0281-658X, nr 4, s. 60-63Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 25.
    Vessby, Johan
    et al.
    Växjö universitet, Institutionen för teknik och design.
    Olsson, Anders
    Växjö universitet, Institutionen för teknik och design.
    Stabilizing strategies for multi-story timber frame structures2006Ingår i: 9th World Conference on Timber Engineering, Oregon State University, Portland, OR 97331, U.S.A 2006 , 2006Konferensbidrag (Refereegranskat)
  • 26.
    Vessby, Johan
    et al.
    Växjö universitet, Institutionen för teknik och design.
    Olsson, Anders
    Växjö universitet, Institutionen för teknik och design.
    Enquist, Bertil
    Växjö universitet, Institutionen för teknik och design.
    Contact-free strain measurement of bi-axially loaded sheathing-to-framing connection2008Ingår i: 10:th World Conference on Timber Engineering, 2008Konferensbidrag (Refereegranskat)
  • 27.
    Vessby, Johan
    et al.
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Serrano, Erik
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Enquist, Bertil
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Contact-free measurement and numerical and analytical evaluation of the strain distribution in a wood-FRP lap-joint2010Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 43, nr 8, s. 1085-1095Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wood specimens to each of which alaminate of carbon fibre reinforcement polymers(FRP) was glued (creating a lap joint in each case)were loaded to failure. A total of 15 specimens ofthree types differing in the glued length (anchoragelength) of the FRP laminate (50, 150 and 250 mmrespectively) were tested, their strength, stiffness andstrain distribution being evaluated. Synchronizeddigital cameras (charge-coupled devices) used intesting enabled strain fields on surfaces they weredirected at during the loading procedure to bemeasured. These results were also evaluated bothanalytically on the basis of generalized Volkersentheory and numerically by use of the finite elementmethod. The lap joints showed a high level ofstiffness as compared with mechanical joints. A highdegree of accuracy in the evaluation of stiffness wasachieved through the use of the contact-free evaluationsystem. The load-bearing capacity of joints ofthis type was found to be dependent upon theanchorage length in a non-linear fashion. The experimental,analytical and numerical results were shownto be in close agreement with respect to the strengthand the strain distribution obtained.

  • 28.
    Vessby, Johan
    et al.
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Serrano, Erik
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Olsson, Anders
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Coupled and uncoupled nonlinear elastic finite element models formonotonically loaded sheathing-to-framing joints in timber based shear walls2010Ingår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 32, nr 11, s. 3433-3442Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Four different elastic models for sheathing-to-framing connections are presented and evaluated on asingle connection level and on a shear wall level. Since the models are elastic in their nature they aresuitable mainly for cases where the sheathing-to-framing connections are subjected to monotonicallyincreasing displacements. Of the four models one is uncoupled and the others are coupled with respect tothe two perpendicular displacement directions in a two-dimensional model. Two of the coupled modelsare non-conservative, while the third is conservative, indicating a path independency with respect to thework done to reach a defined state of deformation. When the different models are compared it is obviousthat the uncoupled model gives strength and stiffness values higher than the others; however it is notobvious which of the models to use in a shear wall analysis, each of the models having its advantages anddisadvantages. For the experimental data used as input in the analyses of this study however, a couplednon-conservative model seems the most appropriate.

  • 29.
    Vessby, Johan
    et al.
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Serrano, Erik
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Olsson, Anders
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Girhammar, Ulf Arne
    Luleå University of Technology.
    Källsner, Bo
    Linnéuniversitetet, Institutionen för teknik, TEK.
    Simulation of bottom rail fracture in partially anchored shear walls using XFEM2012Ingår i: INTERNATIONAL COUNCIL FOR RESEARCH AND INNOVATIONIN BUILDING AND CONSTRUCTION, WORKING COMMISSION W18 - TIMBER STRUCTURES (CIB-W18): Meeting forty-five, Växjö, Sweden, August 2012, 2012Konferensbidrag (Refereegranskat)
1 - 29 av 29
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