Background:      Previous experience with the construction industry tells us that it’s often conservative and slow to adopt changes or use radical new ideas. This is a problem faced by Cross-Laminated Timber (CLT), as it’s provides a new way of working with wooden construction, that is still unfamiliar to most companies. Marketing this new solution is therefore hard, especially since a lot of the public is still unsure about the qualities and properties of the product. Purpose:               The purpose of this thesis is to identify the different selling points of CLT to see how this product can be marketed towards an audience that is still sceptical towards the wooden material. Method:                Results are gathered with the help of an interview study with six different companies that all in some way worked with CLT. The results are then put through a grounded analysis. Conclusion:                   The results show us that the most important thing to do when marketing a product that few people know of, or are sceptical towards, is to make sure that information about the benefits of using the product gets out. The most important marketing point for CLT seems to be the environmental advantage compared to concrete and the speed of which buildings can be erected.

The increasing demand for more sustainable construction has led to the development of new structural systems that include wood as building material. Cross laminated timber (CLT) has been identified as a potential system to address this need and to provide alternative options in the range of low- to medium-rise construction. The appeal in using CLT as a shearwall is driven by the combination of the rigid panels and small dimension fasteners, which allows for significant energy dissipation in the structure. However, there is currently no reliable analytical model to accurately predict the behaviour of multi-segment CLT shearwalls. The current study aims to develop an analytical model capable of predicting the elastic and plastic phases associated with the behaviour of multi-panel CLT shearwalls. The model describes the wall behaviour as a function of the connectors’ properties in terms of stiffness, strength and ductility. This dependency means that the only input required in the model is the behavioural parameters of the connections. The proposed model contains six cases with a total of 36 different failure mechanisms. Two final wall behaviours were developed, and it was found that behaviour (i.e. single wall) could be achieved if the yielding in the hold-down occurred prior to yielding in the panel joints. Inversely, the other behaviour (i.e. coupled panels) was achieved if the yielding in the vertical joint occur prior to yielding in the hold-down. The analytical model was validated using a numerical model, and the results of the comparison showed very close match between the two models. The study proposed simplified design provisions with the aim to optimize the walls ductility (CP behaviour) or strength and stiffness (SW behaviour).

Previous studies have mainly focused on the behaviour of timber under uniformly distributed compression perpendicular to the grain (CPG) loads. However, there are many practical applications in which timber is loaded by non-uniformly distributed CPG loads. Different design and test codes like the Eurocode 5 (EC5), DIN 1052:2004, ASTM D143- 94 and EN-408:2010 only account for load configurations where timber is subjected to uniformly distributed loads. For specific uniformly distributed load (UDL) configurations the bearing capacity of timber (solid softwood timber or Glulam) in compression is adapted by using a load configuration factor (kc,90) according to EC5, the European code for design of timber structures. EC5 has no guidelines for cross-laminated timber (CLT) under UDL with the exception of the Austrian National Regulations for EC5. In this work, an experimental and numerical study on the bearing capacity and displacement behaviour of CLT subjected to non-uniformly distributed loading (NuDL) is conducted on eight different load configurations. A steel-CLT connection in which the CLT is partially loaded is used in this study. Finite element modelling, performed using the commercial software Abaqus CAE is used as the numerical simulation of the experimental study and is validated by experimental results. Load configuration factors (kc,90) from experimental results are compared with values from the Swedish CLT handbook (KL-Trähandbok). The outcome of the study shows that load configuration factor for NuDL cases is higher than for UDL cases. Hence, for same load configurations a lower CPG strength is required in NuDL than in UDL. Moreover, numerical results feature overall good congruence with the elastic phase of the experiments and have the potential to augment experiments in further understanding other complex steel-CLT connections

The aim of this master thesis is to design a building consisting of joiner workshop and administration part of furniture factory. Building is located in Brno, cadastral area Horní Herpšice. In terms of funcion as well as structure is building devided in two parts, joiner workshop and administration part containing hygienic facilities for workers, canteen for employees and furniture showroom. Joiner workshop is single-deck skelet structure made of glued laminated timber. Administration part has two above-grade floors. Cross laminated timber panels are used for vertical and horizontal bearing structures. Building facade is designed as ventilated, partly made of cement fiber boards, partly of timber boarding along with green panels. The building has one-layer green roof.

In the light of today’s effort to achieve sustainable future of the planet, timber as building material makes a comeback on the construction market. Since the requirements on the buildings and the internal comfort increase, there is a need for finding new solutions and products; one of them is cross-laminated timber (CLT), which has the potential to be used for high-rise buildings due to its mechanical properties. The aim of this work was to study the vibration performance of CLT floors as it is often the governing factor in design of CLT structures unlike for other common building materials. The orthotropic mechanical properties of CLT were determined by the shear analogy method and verified with a finite element (FE) model of a simply supported beam compared to hand calculations of shear forces, bending moments and deflections. The properties based on Timoshenko’s approach were evaluated as less precise regarding the deflection. The non-composite structural behaviour of a steel-CLT hybrid floor structure was predicted for FE dynamic analysis based on a comparison between modelling exercise and hand calculations. Two different methods, the Concrete Society (SC) and Steel Construction Institution (SCI) methods, both seemed to be applicable for determination of the response factor first since the mechanical properties are not used as input in the calculations. These two methods differ in certain aspects, and based on FE analysis of simply supported slab even the resulting response factor for the CLT differs significantly. Moreover, the hand calculation results were similar to those of the FE analysis for the CS method, but in less agreement for the SCI method. Nevertheless, it is not recommended to reject the latter method based on this study and further studies should be performed on real structures with response factor known from on-site measurements. A part of the first floor of Canary Wharf College was modelled and analysed, and previous measurements of the frequency and response factors enabled a validation of some assumptions. The SCI approach showed to be inadequate for this type of structure and therefore only the CS method was applied further. Analysis of the floor structures supported by walls demonstrated similar results from both the measurements and the dynamic analysis. However, if the floor slab was supported by beams, the response factor was significantly overestimated although on the conservative side. This difference suggests that the modelling of such conditions are not satisfactory. The CS method appears to assess correctly the magnitude of the response factor for CLT floors supported by walls but overestimates it in case of beam supports. The first finding shall be confirmed through analysis of other structures and a more extensive research should focus on the latter one to determine more exact behaviour of the model under different conditions.

Woodbe Engineering AB is a freshly started company that has developed a new type of joint for cross-laminated timber (CLT). The joint does not include any metallic fasteners, which improves sustainability, the ergonomics for the workers and time efficiency. The joint is designed to connect floor and wall elements in multi-storey buildings, by milling a dovetail in the floor element, and a fitting track in the wall element using a CNC machine. Before the product can be used on the market, it needs to be verified. This verification can either be done using physical tests, calculations, or a combination of both. The company has performed experimental small-scale tests, where the load-bearing capacity was tested. Later this year, large scale tests are to be performed. The purpose of this work is to develop a simulation model that can predict the results of the physical test. A simulation model that yields accurate results can be a good substitution for physical testing, due to a lower cost, better time efficiency, and parameters that can easily be changed. CLT is made up of several layers of wooden plates with different directions. The wood itself is quite complex to model. It has different properties in different directions, both ductile and brittle fracture modes and a large scatter of material properties. To capture this behaviour, a material model which incorporates orthotropic elasticity with linear fracture mechanics has been used. The behaviour of the material model has been evaluated with tests in both tension and compression in different directions. The accuracy of the material model was investigated by a simulation of the small-scale tests where the load-bearing capacity and the mode of fracture was investigated. A simulation of the large-scale experiment has also been conducted, where predictions of the load-bearing capacity and the first mode of failure was investigated. Also, a calculation script has been developed, which calculates the shear stress in the dovetail.  The results of the simulations clearly show the capability of the material model. Load-displacement graphs show ductile and brittle behaviour in compression and tension respectively. The strength is the highest along the fibres of the wood, with a fast decrease as the angle is increased. The simulation of the small-scale tests showed the initiation of rolling shear damage in the bottom transverse layer of the dovetail at a load level of 87 kN. The load continued to rise until a maximum load of 112 kN, while the damaged region grew upwards into the next layer. As compared to the physical tests, the mean maximum capacity of the joint was 125 kN, where rolling shear cracks could be found in the upper transverse layer in all tested specimens. Some of the tested specimens showed damage initiation at a load level of 84 kN. For the larger experiment, the same mode of damage was initiated at a load level of 161 kN which continued to rise until a maximum load level of 165 kN. The calculated values of the shear stress showed a critical shear force of 26 kN per dovetail. This value is 60 and 63 % of the simulated critical shear forces. The results of the simulation are in good agreement with the reference experiment in terms of damage initiation and maximum load. However, a large scatter of material properties, approximations of material orientations and interactions between individual layers results in a low level of predictability in terms of damage evolution and ductility in the material. / Woodbe Engineering AB är ett nystartat företag som har utvecklat en ny typ av knutpunkt för korslimmat trä (KLT). Förbandet innefattar inga metalliska förbindare, vilket förbättrar hållbarheten, ergonomin för arbetarna och tidseffektiviteten. Förbandet är konstruerat för att binda samman golv- och väggelement i flervåningsbyggnader, genom att fräsa tappar i golvelementen och motsvarande spår i väggelementen med hjälp av en CNC-maskin. Innan produkten kan användas på marknaden, behöver den verifieras. Verifikationen kan antingen ske genom fysiska tester eller beräkningar, alternativt en kombination av båda. Företaget har gjort experimentella tester i mindre skala där bärförmågan provades. Senare i år ska prover i större skala utföras. Syftet med arbetet är att utveckla en simuleringsmodell som kan förutspå resultaten hos de fysiska proverna. En simuleringsmodell som ger tillförlitliga resultat kan vara ett bra substitut till fysiska prover genom en lägre kostnad, de är mer tidseffektiva och parametrar kan enkelt ändras. KLT är uppbyggt av flera lager av träskivor med olika riktningar. Träet själv är relativt komplext att modellera. Det har olika egenskaper i olika riktningar, samtidiga duktila och spröda brottmoder och har en stor spridning av materialegenskaper. För att fånga upp dessa egenskaper, har en materialmodell som innefattar ortotrop elasticitet och linjär brottmekanik använts. Beteendet hos materialmodellen har utvärderats med tester i både drag och tryck i olika riktningar. Noggrannheten hos materialmodellen har undersökts genom en simulering av redan testade småskaleprover, där bärförmågan och brottmoden undersöktes. En simulering av fullskaleproverna har också gjorts, där en förutsägelse av bärförmågan och den första brottmoden har gjorts. Dessutom har ett beräkningsskript tagits fram som beräknar skjuvspänningen i tappen. Resultaten av simuleringarna visar tydligt förmågan hos materialmodellen. Kraft-förskjutningskurvor visar duktila och spröda beteenden i tryck respektive drag. Hållfastheten är högst i fiberriktningen, med en snabb minskning när vinkeln till fibrerna ökar. Simuleringen av småskaleproverna visade initiering av rullskjuvningsbrott i det undre tvärgående lagret i tappen vid en last av 87 kN. Lasten ökade till den maximala lasten 112 kN, medan det skadade området växte uppåt in i nästa lager. I jämförelse med de fysiska testerna var den maximala medellasten 125 kN, och rullskjuvningssprickor i det övre tvärgående lagret kunde hittas i alla provexemplar. Några av de provade exemplaren visade brottinitiering vid en last av 84 kN. Simuleringen av den större uppställningen visade samma typ av brottinitiering vid en last av 161 kN som ökade till en maximal last av 165 kN. Beräknade värden av skjuvspänning i tappen visade en kritisk skjuvkraft av 26 kN per tapp. Detta värde är 60 och 63 % av de simulerade kritiska skjuvkrafterna. Resultatet av simuleringen stämmer bra överens med referensexperimentet gällande brottinitiering och maxkapacitet. Dock, på grund av en stor spridning av materialegenskaper, approximationer gällande materialriktningar och samverkan mellan individuella lager, är nivån av förutsägbarhet låg gällande brottillväxt och duktilitet i materialet.

Cross-Laminated Timber (CLT) has recently become a popular construction material for building timber structures. One advantage of CLT is, that it can be used as floor, beam and wall element. As the arrangements of layers in CLT is in perpendicular direction to each other, it exhibits remarkable strength properties in both in-plane directions. However, the low stiffness and strength properties in compression perpendicular to the grain hinder application of CLT in high rising building, since forces are usually transferred from the wall elements through floor elements perpendicular to the grain. Thus, the aim of this thesis is to get a thorough understanding of the mechanical properties of such connections for different setups, including wood-wood connections, connections with acoustic layers and connections with screws. In addition, the wall was place at different positions on the CLT-floor element. Mechanical tests and numerical simulations, by means of finite element modelling (FEM) were carried out. CLT floor elements, consisting of 5-layers, were loaded by 3-layered CLT wall elements. Displacement and deformation were continuously measured by Potentiometers/LVDTs and an optical measurement system, respectively. Based on the experimental results compressive strength, slip curve and stiffness of the CLT connections were evaluated. Subsequently, results from FE-modelling were compared with experimental findings, which show a good agreement in elastic stiffness. Experimental results exhibited a pronounced influence of the wall position and connection setup on strength and stiffness. Central position of the wall showed higher mechanical properties than edge position. Highest strength and stiffness were found for screwed connections, where the wood-wood connections showed similar results. Connections with acoustic layers exhibited the lowest mechanical properties.

Bygg- och fastighetssektorn är en bidragande faktor till växande koldioxidutsläpp och det krävs därför klimatbaserade innovationer för att arbeta mot ett hållbart och långsiktigt samhälle. På senare år har råvaran trä använts i form av KL-trä som konstruktionsmaterial i allt fler och större byggnader. Parallellt med utvecklingen av KL-trä har även en strävan att behålla materialet oskyddat och synligt växt fram. För att möta kraven på brandsäkerhet i konstruktioner av KL-trä, arbetas nya dimensioneringsregler fram. I detta arbete studeras hur bärförmågan vid brand i nuvarande Eurokod 5 EN 1995-1-2:2004 och kommande version prEN 1995-1-2:2025 dimensioneras hos konstruktioner av KL-trä med synliga ytor. Syftet med arbetet är att ta fram skillnader och likheter mellan respektive version, samt vilken inverkan de kan få. Målet med arbetet är klargöra hur branddimensionering kommer påverkas och på så sätt kunna vara ett underlag för vidare studier och användning inom området. Dimensionering görs på vägg- och bjälklagselement med uppbyggnad av 5 st 40 mm lameller respektive 7 st 20 mm lameller för båda elementen. Dimensionerande brandexponeringstid som beaktas är 60 minuter, men även 90 minuter för väggelementen som krävs för att byggnader med mer än åtta våningar. Beräkningar och jämförelser görs på element av olika uppbyggnader för att tydliggöra relationen mellan typen av lim och bärförmågan. KL-träelement med icke brandtåligt lim uppvisar lägre bärförmågor än element med brandtåligt lim. Detta stämmer särskilt vid element med uppbyggnader av tunnare lameller. Orsaken till detta är att icke brandtåligt lim ger upphov till delaminering som minskar det effektiva tvärsnittet på grund av en ökad förkolningshastighet. Delamineringen ger även upphov till värmeökning då det sker en ny övertändning. Beräkningar visar att det är fördelaktigt med en tjockare yttre lamell för att minska risken för delaminering under brandexponeringstid 60 minuter och 90 minuter. Resultaten jämförs också med resultat från avancerade beräkningsmetoder i de fall där korrekta underlag fanns tillgängligt. Vid framtagning av det icke lastupptagande skiktet enligt kommande version påvisas markant skillnad jämfört med den nuvarande versionen. Enligt kommande version tas det hänsyn till aspekter som tvärsnittshöjd, lamelltjocklek, lamellriktning, om ytan är initialt skyddat eller ej, om den brandexponerade sidan utsätts för tryck- eller dragspänningar m. m. Utöver det tillkommer vissa eventuella avdrag på det resterande tvärsnittet beroende på vart det icke lastupptagande skiktet befinner sig. Nuvarande version anger alltid det icke lastupptagande skiktet som 7 mm. Framtagning av bärförmågan i den kommande versionen bygger likt den nuvarande versionen på den effektiva tvärsnittsmetoden. Det som däremot skiljer versionerna åt är förkolningsdjupet, samt införandet av ny metod för framtagning av det icke lastupptagande skiktet, som nämnt ovan. I kommande version har beräkningsgången för dessa delar uppdaterats och därmed beaktas även fler parametrar som icke brandtåligt lim. Förkolningsdjupet för kommande version beräknas enligt den europeiska förkolningsmodellen som beror på limtyp. Då endast brandtåligt lim beaktas i EN 1995-1-2:2004 bör en direkt tillämpning på KL-trä göras med försiktighet. Arbetet lyfter även fram generella konsekvenser för synligt KL-trä vid brandexponering. / The construction and property sector is a contributing factor to growing emissions of carbon dioxide and climate-based innovations are therefore required to work towards a sustainable and long-term society. In recent years, the raw material wood has been used in form of CLT (Cross Laminated Timber) as a construction material in an increasing number of buildings. Along the development of CLT, the desire to keep the material unprotected and visible has also grown. To meet the requirements for fire safety in CLT-buildings, new design standards are under development. In this study, the firedesign method and results of load-bearing elements of CLT with visible surfaces are compared between the current Eurocode 5 EN 1995-1-2:2004 and the upcoming version prEN 1995-1-2:2025. The purpose of the work is to highlight the differences and similarities between the two versions, and in that way provide basis for future studies and usages. Firedesign is calculated on wall and floor elements with a structure of 5 and 7 laminates respectively for both elements. The fire exposure time considered is 60 minutes, but also 90 minutes for the wall elements which is to clarify the relationship between the type of adhesive and the load-bearing capacity. The fire exposure time considered is 60 minutes, but also 90 minutes for the wall elements which is required for buildings with more than four stories, according to the Swedish building code BBR and to clarify the relationship between the type of adhesive and the load-bearing capacity. CLT elements with non-fire-resistant adhesive have lower load-bearing capacities than elements with fire-resistant adhesive. Calculations according to the upcoming version contains more parameters like non-fire-resistant adhesive and a more complex non-load-capacity layer, which are deficient in the current Eurocode. Since non-fire-resistant adhesive are not included in EN 1995-1-2:2004, a direct application on CLT should be done with caution. The study also highlights general consequences when using visible CLT in buildings.

In Sweden, a large share of residential buildings was built more than 50 years ago. Consequently, old materials, poor maintenance, and corrosion can affect the structural performance of these buildings. Additionally, these buildings do not meet the latest energy efficiency and Eurocode regulations. Building retrofits can improve structural strength and resident safety, as well as the energy efficiency of the buildings. Common retrofitting methods are unsustainable in terms of costs, duration, and disruptions to resident’s lives. A sustainable method for structural and energy upgrades is needed in order to retrofit such kind of structures in an efficient way. This master thesis aims to identify an innovative structural and energy retrofitting solution for reinforced concrete buildings that are reaching the end of their service life as well as to provide an environmental impact assessment of this whole process. A multi-family building built in 1972 in Ronneby, Sweden, with reinforced concrete load-bearing walls and slabs was considered as a case study. An integrated retrofitting strategy based on an addition of cross-laminated timber (CLT) panels, insulation, and claddings to the external walls to increase the horizontal load-bearing capacity and energy efficiency of the building was applied in this study. Steel tubes and fiber-reinforced polymers (FRP) are used to increase the load-bearing capacity of the internal load-bearing walls and slab compared to the original ones, mostly for vertical loads. For the structural analysis based on the Eurocode regulations, the software RFEM was used to model and analyze the building before and after retrofitting. In addition to that, dynamic thermal simulation was performed with VIP-Energy software to analyze the service life energy consumption before and after retrofitting of the building. Life cycle assessment following the European standard SS-EN 15978 was used to assess the environmental impacts including global warming potential (GWP), acidification potential (AP), and eutrophication potential (EP). The environmental impact of the existing building was compared with the retrofitted case, during a 50-year service life. The results show that after the retrofitting in the load-bearing walls, the internal shear forces induced by wind loads decreased by 38%. Also, the load-bearing capacity of the slabs was increased by 350% in the critical areas. Regarding GWP, AP and EP all decreased by 30% in the retrofitted case. The results indicate that by retrofitting the building, structural performance and safety increase, and moreover the environmental impact of the building is minimized.

Biomaterials such as wood and bamboo are in high demand as a building material with the push for building with green technology. The wood product industry accounts for approximately 4% of the total U.S. manufacturing GDP (Gross Domestic Product), which is more than $100 billion. The industry supports over 752,000 full-time equivalent jobs, most of which are in rural areas where employment opportunities are limited. The estimated global market value of bamboo is estimated to be $60 billion annually. This research will explore the use of wood and bamboo in different end use products. The objectives of this research will 1) evaluate the behavior of two single bolt connections in the post-to-rail joint in a hardwood stairway system; 2) the potential of post-treating pre-fabricated cross-laminated timber (CLT) panels with two different copper based preservative treatments; and 3) estimated design values for a commercially sourced bolt laminated bamboo industrial mat. To accomplish these objectives, this dissertation is divided into five sections: 1) Introduction, 2) Structural performance of the post-to-rail connectors in a hardwood stairway handrail, 3) Development of preservative-treated cross-laminated timber: effects of panel layup and thickness on bonding performance and durability when treated with copper-azole (CA-C) and micronized copper-azole (MCA), 4) Strength and stiffness of 3-ply industrial bamboo matting, 5) Conclusion.