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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.

The orthotropic material property in combination with ductility in compression, brittleness in shear and tension, very low shear modulus in radial-tangential (RT) plane etc. requires anisotropic stress failure criteria, as well as their evolution with increasing strains. Three- dimensional failure criteria have been proposed for this purpose, but their validation in the RT plane with interaction of rolling shear stresses has attracted less attention. Corresponding stress interactions are however important for modelling of engineered wood-based products under compression perpendicular to the grain when taking into account influence of the annual ring structure. The work aims at defining failure envelopes for stresses perpendicular to the grain with rolling shear stress interaction based on experimental investigations performed on Norway spruce. The experimental set-up was realized in a biaxial testing frame and consisted of stiff steel plates to transfer load from the testing machine to wood specimen. Mechanical grips prevented rotation and uplifting of the specimen in case of pure shear and tensile loading, respectively. In addition to conventional linear variable differential transformers, a digital image correlation system was used to measure strain fields on the surface of wood specimens and steel plates. Measurements of dog-bone shaped specimens were carried out along different stress interaction paths by displacement controlled loading. The experimental dataset was then compared with commonly used phenomenological failure criteria, namely Tsai-Hill, Tsai-Wu [1], Norris [2] and Hoffman, as well as with regression equations from previous works [3].Experiments revealed that the stress-strain relationship under compression, shear, and biaxial loading differs in radial and tangential directions. None of the three-dimensional stress failure criteria provided good prediction of experiments under compression and rolling shear, but experimental data was closer to the re

The aim of the experimental study presented herein is the assessment and quantification of the behavior of individual dowels in multi-dowel connections loaded by a bending moment. For this purpose, double-shear, steel-to-timber connections with nine steel dowels arranged in different patterns and with different dowel diameters were tested in four-point bending. In order to achieve a ductile behavior with up to 7° relative rotation, the connections were partly reinforced with self-tapping screws. The reinforcement did not influence the global load–deformation behavior, neither for dowel diameters of 12 mm nor for 20 mm, as long as cracking was not decisive. The deformation of the individual dowels was studied by means of a non-contact deformation measurement system. Thus, the crushing deformation, that is, the deformation at the steel plate, and the bending deformation of the dowels could be quantified. In the case of 12 mm dowels, the bending deformation was larger than the crushing deformation, while it was smaller in the case of 20 mm dowels. Moreover, dowels loaded parallel to the grain showed larger bending deformations than dowels loaded perpendicular to the grain. This indicates that the loading of the individual dowels in the connection differs depending on their location.

In timber buildings, elastomers are commonly used to decrease the sound transmission between apartments. Detailed properties of the elastomers are needed in order to model them in a correct yet computational efficient manner. In earlier studies, dynamic experiments have been made on elastomer strips half embedded. However, the sidewise effects need to be further evaluated. In this study, the elastomers are evaluated quasi-statically in different directions, having continuous as well as intermittent distributions, being plane supported or half embedded. An FE-model has been developed using data stemming from the quasi-static tests together with damping estimates stemming from vibrational tests.

The building industry demands ever more effective structural elements with a multitude of requirements at the same time. There is increasing interest for load-bearing glass elements which can be deployed in timber structures, e.g. in the outer façade or as column or beam elements within the building. In an on-going research project, the materials glass, timber and the adhesive combining the former have to be selected to fit each other but also suit the application. The mechanical properties are studied individually as well as in combined small-scale specimens experimentally. Furthermore,large-scale tests on beams and shear walls are performed. This is accompanied by numerical analysis to study a wide range of dimensions and variations as well as specific design situations. The final output of the project will be prototypes to beused in showcase projects., LBTGC - Load bearing timber glass composites

Timber-glass composite shear wall elements were manufactured with different adhesives. The elements were 1200×2400 mm in size. 12 single pane elements and one element with an insulation glass unit (IGU) were manufactured. The load bearing glass pane was in all cases made from 10 mm float glass. The elements were tested in various loading conditions, involving pure vertical load and different combinations of in-plane shear and vertical loading. The test results show that the influence of the adhesive chosen on the ultimate (buckling) load is only of minor importance. This was also confirmed by finite element analyses.

Undersökningen som redovisas i denna rapport har genomförts under hösten 2013 och våren 2014 inom projektet "Nytt paradigm för hållfasthetssortering av konstruktionsvirke". Projektet, som pågår under perioden december 2011 till juni 2014, går ut på att för industriellt bruk utveckla en nyligen föreslagen metod för hållfasthetssortering av konstruktionsvirke, vilken baseras på laserskanning i kombination med dynamisk excitering och densitetsbestämning av virke. Projektet finansieras till 50 % av VINNOVA och till 50 % av de företag som medverkar i projektet, nämligen Innovativ Vision AB (IV), Vida Vislanda AB, Södra Timber AB, Derome Timber AB och Dynalyse AB. Linnéuniversitetet (Lnu) och SP Sveriges Tekniska Forskningsinstitut AB (SP) samverkar med nämnda företag i utförandet av forskningen. Ett syfte med undersökningen är att på ett stort material bestående av många olika virkesdimensioner verifiera de starka statistiska samband som sedan tidigare påvisats för ett begränsat antal plankor och dimensioner, mellan å ena sidan indikerande egenskaper som baseras på mätningar och beräkningar och å andra sidan böjstyrka, elasticitetsmodul och densitet. Ett annat syfte med undersökningen är att visa att nödvändig data kan samlas in av samma utrustning och under samma förhållanden som kommer att gälla vid framtida hållfasthetssortering baserad på den aktuella metoden. Slutligen är ett syfte att samla in och dokumentera data som kan användas för forskning och utveckling både inom och efter det att det aktuella projektet har avslutats.

Föreliggande redogörelse avser en metod och en anordning för utvärdering av en bräda av trä med en ländriktning. Data som indikerar fiberorienteringen över brädans yta inhämtas och för ett antal underpartier hos brädan bestäms en nominell, lokal elasticitetsmodul, MOE, på basis av nämnda fiberorienteringsdata och en nominell materialparameter. En nominell global MOE i längdriktningen för träbrädan i sin helhet genereras och jämförs med en sekundär global MOE. På basis av nämnda fiberorienteringsdata och denna jämförelse genereras en uppskattad lokal elasticitetsmodul, MOE, i nämnda längdriktning för ett flertal underpartier. Dessa data kan användas för exempelvis tillförlitlig hållfasthetsgradering av träbrädor.

From previous research, it is well known that a localized modulus of elasticity (MOE) is a better indicating property (IP) of strength than an MOE averaged across a longer span. In this study, it was investigated to what extent the relationship, in terms of coefficient of determination (R2), between strength and localized MOE was dependent on the length across which the MOE was determined. Localized MOE was calculated with MOE profiles based on dot laser scanning of fiber directions, axial dynamic excitation, and a scheme of integration across a board's cross-section. Two board samples were investigated. Maximum R2 values, which were as high as 0.68 and 0.77, respectively, were obtained for localized MOE determined across lengths corresponding to about half the depth of the investigated boards. Consequently, application of a highly localized bending MOE as an IP will result in very competitive grading.

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.

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.

Timber-glass composite I-beams were manufactured and tested in bending to failure. The glass web of the I-beam was adhesively bonded to the timber flanges using three different adhesives: Epoxy, Acrylate and Silicone. For the webs two types of 8 mm thick glass were used: annealed float and heat heat-strengthened glass. Before testing the beams with heat-strengthened glass, the residual-stress profile through the thickness of the glass panels was measured using a portable scattered light polariscope SCALP. The results show that the beam stiffness was similar for the acrylate and epoxy-bonded beams, despite the difference in adhesive stiffness. The beams bonded with the silicone adhesive showed approximately 25% lower stiffness. In terms of load bearing capacity, the beams made using heat-strengthened glass were approximately 50% stronger than the beams made using annealed float, for the epoxy and acrylate adhesive. Using the silicone adhesive, the increase was approximately 20%., LBTGC - Load bearing imber glass composites

The aim of this three year project, which is part of the WoodWisdom-Net researchprogram, is to develop an innovative load bearing building system composed of timberglasscomposites. The structural loads applied onto these composites will be transferred to, andsupported by, the glass component, in contrary to today’s traditional solutions where glass elementsonly function as an environmental shield. Using such structural elements will make itpossible to largely increase the glass surface in buildings, allowing the presence of more naturallight in personal homes and office buildings. Timber-glass shear walls and beams will be developed taking into consideration long-term behaviorand seismic performance. Design concepts, feasibility studies and performance assessmentsof these components will be performed in order to improve the overall performance. Theproject also includes the development of new design calculations as well as the optimization ofmanufacturing methods. Material properties of timber, glass and adhesives will be determined from small and large scaleexperimental investigations, and will be used as input for theoretical calculations and modelingwork. The projects industrial partners will function as expertise and take part in the developmentand construction of demonstration objects. The project consortium is composed of academic and industrial partners from Austria, Sweden,Germany, Turkey, Slovenia, Chile, and Brazil. This paper presents material specifications andresults from small scale testing performed by the Swedish project partners.

The effect of single-side ion exchange (using a KNO3:KCl mixture) on the ring-on-ring flexural strength of float glass has been studied. Two ion exchanged series, treated at 450 and 515°C, were investigated. The ion exchanged samples showed approximately 160 respectively 100% increases in their arithmetic mean strength compared to as-received float glass. Furthermore, a series of samples containing drilled holes were studied in order to investigate the effect of single-side ion exchange on such common construction elements. The samples that contained drilled holes were ion exchanged at 450°C and showed around 140% increase of the fracture load compared to the untreated samples containing drilled holes. As a general observation, the ion exchange treatment induced ~110 MPa compressive stresses (515°C) and ~180 MPa compressive stresses (450°C). The ion exchanged samples showed no significant increase in stiffness.

Den undersökning som redovisas i denna rapport har genomförts under hösten 2012 och våren 2013 inom projektet "Nytt paradigm för hållfasthetssortering av konstruktionsvirke". Projektet som kommer att pågå under perioden december 2011 till juni 2014 går ut på att för industriellt bruk utveckla en nyligen föreslagen metod för hållfasthetssortering av konstruktionsvirke, vilken baseras på laserskanning i kombination med dynamisk excitering och densitetsbestämning av virke. Projektet finansieras till 50 % av VINNOVA och till 50 % av de företag som medverkar i projektet, nämligen Innovativ Vision AB (IV), Vida Vislanda AB, Södra Timber AB, Derome Timber AB och Dynalyse AB. Linnéuniversitetet (Lnu) och SP Sveriges Tekniska Forskningsinstitut AB (SP) samverkar med nämnda företag i utförandet av forskningen. Syftet med undersökningen är i först hand att utvärdera alternativa sätt för att bestämma densitet för virke och att verifiera implementeringen av programvara för industriellt bruk. Syftet är också att ta fram ett utökat material för att bedöma vilken precision den nya sorteringsmetoden kan erbjuda och för att bedöma hur känslig den är för olika typer förändringar och störningar som kan uppkomma. Undersökningen bygger på ett begränsat material och en mer omfattande undersökning planeras för genomförande under senare delar av projektet.

Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3600 mm, a coefficient of determination as high as 0.68-0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.

The fracture strength of oxide glasses is to a large degree influenced by other factors than the inherent strength of the bonds in the vitreous network such as surface defects. Due to the brittle nature of glass, mechanical processing decreases the strength substantially. The aim of this study was to investigate ion exchange strengthening also known as chemical strengthening of commercially available mechanically processed soda-lime-silicate float glass and to compare it with as-received float glass by means of flexural fracture load. The dimensions of the samples were 66±2 x 66±2 mm and two series had 7 mm diamond drilled holes in the centre of each sample while one series was as-received. Ion exchange of sodium ions by larger potassium ions were performed by treating the air-side of a series of samples with a KNO3:KCl mixture at 450 °C. The flexural fracture load of both untreated and ion exchanged holed samples was measured by means of the coaxial double ring test. The ion exchanged samples showed an arithmetic mean fracture load increase of approximately 140% compared to untreated holed float glass. The drilled hole decreases the arithmetic mean fracture load to approximately 25% of as-received float glass whilst the strengthening effect of the ion exchange improves it to around 65% of as-received float glass.

In a previous research project, carried out during the years 2006-2008, the possibility to manufacture wet glued laminated beams using ungraded laminations of Norway spruce side boards was investigated with very promising results. In the project presented in this report, the performance of the wet glued beams has been further investigated and developed as regards grading of side board laminations, bond line properties and lamination finger jointing. The possibility to use scanning equipment for measurement of fibre angles and prediction of strength and stiffness of boards and beams has been studied and the procedures for technical approval and CE marking have been probed into. Studies concerning market and economy for the beams and layouts for a pilot plant and a full capacity plant, respectively, for production of such beams have also been carried out. The possibility to grade side boards in the wet state using axial dynamic excitation was investigated with a positive result. From such excitation, a board’s stiffness (modulus of elasticity) could be determined. Accordingly, grading criteria regarding axial stiffness, and knot size, was applied to grade side board laminations into two classes; outer and inner laminations. Strength and stiffness tests of beams manufactured from such graded laminations showed that the beams actually could challenge first rate glulam and LVL products available on the market. Regarding beam shape and shape stability, cross section cupping may need further attention. Even if this deformation was small, it was still visible to the naked eye. The problem could probably be overcome if the beams are dried to a moisture content of 12-14% before planing. Results of shear tests show that green glued bond lines can fulfil strength requirements for glulam. However, delamination requirements for service class 3 (outdoors) were not fully met. From small scale tensile testing of glued bonds it was concluded that green glued bonds with high density w

Strength grading of Norway spruce (Picea abies (L.) Karst.) side boards in the wet state was investigated. For a sample of 58 boards, density and dynamic modulus of elasticity in the axial direction, MOEdyn, were determined in the wet state. The boards were then split into two parts and the procedure of determining MOEdyn was repeated both before and after the boards were dried to a target moisture content of 12 %. Finally, tensile strength of the split boards was measured and its relationship to MOEdyn for both wet and dried split boards determined. The investigation also included an evaluation of a so called reversed lamination effect on the stiffness caused by the splitting of boards into two parts. The results show that strength grading of split boards in the wet state can give just as good results as grading performed after drying. The reversed lamination effect on the stiffness of split boards was found to be of lower order., Published online first 1/11-2011

Strength grading of Norway spruce side boards in the wet state was investigated. For a sample of 58 boards of dimensions 25×120×3000 mm3, density and dynamic modulus of elasticity in the axial direction, MOEdyn, were determined in the wet state. The boards were then split into two parts and the procedure of determining MOEdyn was repeated both before and after the boards were dried to a target moisture content of 12 %. Tensile strength of the split boards was finally measured and its relation to MOEdyn for both split and unsplit boards determined. The investigation also included an evaluation of a so called reversed lamination effect on the stiffness caused by the splitting of boards into two parts. The results show that strength grading of split boards in the wet state could give just as good results as grading performed after drying. The coefficient of determination between MOEdyn in wet and dried states was as high as R2=0.92, and the relation between MOEdyn in the wet state and tensile strength in the dried state, σt, was of the same order (R2=0.55) as the relation between MOEdyn in the dried state and σt (R2=0.52). Regarding the reversed lamination effect on the stiffness of split boards, it was found to be of low order.

Strength grading of Norway spruce side boards in the wet state was investigated. For a batch of 58 boards, densities and dynamic modulus of elasticity in the axial direction, MOEdyn, were determined in the wet state. The boards were then split into two parts and the procedure of determining MOEdyn was repeated both before and after the boards were dried to a target moisture content of 12 %. Tensile strength of the split boards was measured and its relation to MOEdyn for both split and unsplit boards determined. A so called reversed lamination effect on the stiffness caused by the splitting of boards into two parts was also evaluated. The results show that strength grading of split boards in the wet state could give just as good results as grading performed after drying. The reversed lamination effect on the stiffness of split boards was found to be of lower order.

Both timber and glass are materials that have aesthetically pleasing properties. An appealing idea is to combine them to overcome the drawbacks and utilise the beneficial mechanical properties. Adhesive bonding with an appropriate adhesive could provide a uniform stress distribution at the transition between the materials. This report presents a study of three different adhesives, silicone, acrylate and polyurethane. Intentionally, adhesives with a wide range of properties were chosen. The adhesive bonds between timber and glass were tested both in tension and in shear with rather small bonds, 800 mm2. Special fixtures were designed both for gluing and testing of the adhesive bond specimens studied. The results presented include a traditional study of strength, failure type and relative displacement measured with LVDT’s, but also an extended study with a non-contact optical 3D-deformation measuring system and finite element modelling. Of the adhesives tested, the acrylate (SikaFast 5215) performed best, both in tension and shear. The mean strength obtained for this adhesive was 3.0 MPa in tension and 4.5 MPa in shear. Even if an important factor when gluing glass is the load distribution ability, the flexible silicone adhesive has too low stiffness and strength for use in structural components, where structural refers to the ability of a component to carry loads other than its own weight., Glas och trä i samverkan - innovativa byggprodukter med mervärde