Cross-laminated timber (CLT) is an emerging sustainable engineered material with unique properties that in many ways make it superior to conventional construction material. CLT was invented in the 1990s and the volume produced have increased worldwide since then. It can be used in the load bearing structure for walls and floor slabs in the different typologies, e.g. residential and office buildings.The hygroscopic nature of wood allows it to exchange moisture with the surrounding environment. This may lead to an alteration of properties of wood-based materials such as CLT and can be accompanied by deformations and stresses. These effects influence the CLT’s structural stability, durability and safety.This study focuses on the consequences of moisture content variations in CLT structures, including mechanical properties like modulus of elasticity and bending stiffness (EI). Temperature and relative humidity were measured over three years in three positions along the thickness direction of a slab element on the first floor of House Charlie, a four-storey timber office building located in Växjö, Sweden.The investigation was carried out by mathematical modelling applying MATLAB® software aiming to find the moisture content as a function of time and thickness from the real-world data of House Charlie. The focus was on determining changes in modulus of elasticity and bending stiffness in response to moisture variation. The results showed that the moisture content within a slab of the building varied periodically following the seasonal variation throughout the years. The moisture content at the bottom of the slab was significantly lower compared to two other positions. According to the linear regression analysis, a linear relationship between the moisture content (MC) and positions across the CLT slab at each time step was defined. High R2 values, above 0.9, show the goodness of the fitted model. Applying the MC as a function of time and thickness into an available relationship of modulus of elasticity (E) could predict stiffness versus varied MC in the next step. The modulus of elasticity decreased with an increase in the moisture content over the studied period with a higher variation range at the bottom of the slab. In the final step, bending stiffness was assessed as a function of the changed moisture content. Bending stiffness increased periodically over time, attributed to overall more dry-out of the slab with time.The reported results of the present study give new insight into the behaviour of CLT structure over longer time periods. The recurring pattern in alterations stems from the reliance of bending stiffness on the modulus of elasticity function, which is in turn influenced by the linear relationship with moisture content exhibiting cyclic characteristics. The minimum and maximum values for EI were 3.5×1012 Nmm2 and 3.71×1012 Nmm2, respectively, a variation of approximately ±2.5% around the average. As the time steps increased, the bending stiffness also increased, given the progressive growth of the modulus of elasticity over time.

The Vertically Oriented Interlocking Timber (VOIT) panel is a new solid wood panel similar to Interlocking Cross Laminated Timber (ICLT) and the more commonly known Cross Laminated Timber (CLT). Like ICLT, VOIT panels use timber connections instead of the adhesives or metal fasteners common to CLT. The difference of VOIT is the orientation of the layers. Where CLT and ICLT panels alternate the orientation of each layer, VOIT panels orient all the layers in the same direction. The vertically oriented layers are then attached to one another by smaller horizontal dovetail members.Two types of VOIT panels were provided to be tested for in-plane lateral loading. Type I had three rows of horizontal dovetail members connecting the layers and Type II had four rows of dovetail members as well as two diagonal members to provide stiffness. Two panels of each type were provided, measuring 8 ft. wide, 8 ft. tall, and 13.75 in. thick. Each panel was disassembled after monotonic lateral in-plane loading to determine possible failure modes. Testing results suggest the VOIT panels to be comparable in shear strength to other wood shear walls, including light frame, CLT, and ICLT walls. A two-part analytical model was created to determine the deflection of the wall when loaded as well as the shear strength of the wall. The model predicted deflection and wall strength reasonably well. Due to the small sample size, additional testing is necessary to confirm the results of the Type I and Type II VOIT panels. Additional testing with more variations of the panel and member geometries is also needed to validate the scope of the model.

I denna studie studerades det hur ett 14 våningar högt bostadshus med en kärna av korslaminerat trä (KL-trä) och färdiga lägenhetsmoduler med regelstomme kan byggas på ett industrialiserat och enkelt sätt. Våningsantalet och produktionstypen fastslogs tidigt, i samråd med RISE, för att effektivt kunna granska ett sannolikt sätt att bygga hus i en nära framtid. Dynamiska modalanalyser utfördes för byggnadens olika modeller i FEM-programmet Robot Structural Analysis (kommer fortsättningsvis även beskrivas som Robot) för att ta fram egenfrekvenser. Sedan följdes en beräkningsgång från Eurokod och EKS för att ta fram den toppacceleration som vind orsakar på byggnadens högsta plan. Detta värde jämfördes sedan med det rekommenderade komfortkravet från ISO 10137. Byggnaden som studerades är ett punkthus med en central kärna och 14 moduler, av storlek 4 x 8 meter, per våning. Dessa placeras runt den 8 x 8 meter stora kärnan, vilket gav ett totalt fotavtryck på 24 x 24 meter. Över 20 olika datormodeller studerades där bland annat variationer av placering och mängd av KL-trä i fasad, placering och andel betong i huset och påverkan från gipsskivor i inner- och ytterväggar. Även infästning mellan moduler tillhör några av de ändringar som studerades. Resultatet visar att det är möjligt att bygga den modell som benämns 1400KL i vindlastzon 24 och terrängtyp tre, förutsatt att den mekaniska dämpningen är satt till 2 procent.  Det framgår även att modulernas egna lägenhetsavskiljande väggar har signifikant betydelse för stommens totala stabilitet och att en ökning av styvheten i dessa är ett effektivt sätt att förbättra de dynamiska egenskaperna. Betydelsen av mycket massa högt upp i byggnaden är också tydlig utifrån detta arbete. Det framkommer även att stabila betongvåningar nederst i stommen bidrar mycket till att förhindra att översta våningen i huset rör sig obehagligt mycket vid stor vindbelastning på byggnaden. Detta är en beprövad teknik i basen av flertalet hus som byggs idag. Rotation har visat sig vilja förekomma i de tidigare modeller som använts i denna rapport. Detta är något som måste testas specifikt för alla varianter av basmodellen då rotation är ofördelaktigt ur dynamisk aspekt, då det saknas beräkningssätt för dynamiskrotation i teorin från Eurokod. Generellt kan tillägas att ett 14 våningar högt trähus i vindlastzon 26 och terrängtyp 0 har väldigt svårt att klara av de dynamiska förutsättningar som krävs utan att husets stabiliserande element till största del består av betong. Däremot finns flera trä-modeller i denna rapport som klarar vindlastzon 25 och terrängtyp tre, en mycket mer vanlig situation. Enklare statisk analys antyder att limträpelares dimensioner möjliggör montage mellan moduler utan större produktionsanpassning. Även korslaminerat trä inkluderas fördelaktigt i kärna och fasad, innanför och utanför modulerna, utan att det påverkar de traditionella konstruktionsmetoderna för vare sig moduler eller KL-stomme väsentligt. / In this study, it was examined how a 14-story tall residential building with a core of cross laminated timber (CLT) and prefabricated apartment modules can be built in an industrialized manner. The number of floors and production type were determined early, in consultation with RISE, in order to effectively examine a likely way of building houses in the near future. Dynamic modal analyses were performed for the building's various models in the FEM program Robot Structural Analysis to generate eigen frequencies. Then the method provided in Eurocode and EKS were followed to calculate the top acceleration that the wind causes at the buildings highest floor. This value was then compared with the recommended comfort requirement from ISO 10137. The studied building is a high-rise tower block house with a central core and 14 modules of size 4 x 8 meters per floor. These were placed around the 8 x 8-meter-wide core, giving a total footprint of 24 x 24 meters. Over 20 different computer models were studied with variations in placement and amount of CLT in facade, placement and number of concrete floors and walls. The impact of gypsum inner and outer walls is also being tested. Connections between modules also belongs to some of the changes that were being made between models. The result shows that it is possible to build the model named 1400KL in wind zone 24 and terrain type III, with the mechanical dampening set at two percent. It is also apparent that the walls of modules separating apartments have considerable significance for the overall stability of the frame and that increasing their stiffness is an effective way of improving dynamic properties. It can be concluded from this study that placing a substantial mass at the top of the building is of high importance. It also appears that rigid concrete stories at the bottom of the core contribute greatly to prevent the top floor of the house from exceeding the comfort criteria under high wind loads. This is a widely used technique in the base of houses being built today. Rotation has been shown to appear in the models used in this work. This is something that must be tested specifically for all variants of the base model since rotation is disadvantageous from a dynamic aspect. This is due to the fact that the codes do not consider dynamic rotation. In general, a 14-storey high-rise wooden house in wind zone 26 and terrain type 0 does not fulfil the comfort requirements without most of the stabilizing elements of the house being concrete. On the other hand, there were several wooden models in this study that can endure wind zone 25 and terrain type III, a much more common situation. A simplified static analysis suggests that glulam columns can have dimensions that allow them be placed between modules without major adaptation in production. Also, cross-laminated timber is advantageously included in the core and facade, inside and outside the modules, without significantly affecting the traditional design methods for modules or the cross-laminated frame.

Guadua angustifolia Kunth (Guadua) is a bamboo species native to South and Central America that has been widely used for structural applications in small and large-scale buildings, bridges and temporary structures. Currently, its structural use is regulated within seismic resistant building codes in countries such as Peru and Colombia. Nevertheless, Guadua remains a material for vernacular construction associated with high levels of manual labour and structural unpredictability. Guadua buildings are limited to two storeys due to the overall flexibility of the slender and hollow culms and its connection systems. Its axial specific stiffness is comparable to that of steel and hardwoods, but unlike wood, Guadua’s hollow structure and lack of ray cells render it prone to buckling along the grain and to transverse crushing. As a result, Guadua’s mainstream use in construction and transformation into standard sizes or engineered Guadua products is scarce. Therefore, this work focussed on the development of standardised flat industrial structural products from Guadua devising replicable manufacturing technologies and engineering methods to measure and predict their mechanical behaviour. Cross-laminated Guadua panels were developed using thermohydro-mechanically modified and laminated flat Guadua strips glued with a high performance resin. Guadua was subjected to thermo-hydro-mechanical (THM) treatments that modified its microstructure and mechanical properties. THM treatment was applied to Guadua with the aim of tackling the difficulties in the fabrication of standardised construction materials and to gain a uniform fibre content profile that facilitated prediction of mechanical properties for structural design. Densified homogenous flat Guadua strips (FGS) were obtained. Elastic properties of FGS were determined in tension, compression and shear using small-clear specimens. These properties were used to predict the structural behaviour of G-XLam panels comprised of three and five layers (G-XLam3 and G-XLam5) by numerical methods. The panels were assumed as multi-layered systems composed of contiguous lamellas with orthotropic axes orientated at 0º and 90º. A finite element (FE) model was developed, and successfully simulated the response of G-XLam3 & 5 panels virtually loaded with the same boundary conditions as the following experimental tests on full-scale panels. G-XLam3 and G-XLam5 were manufactured and their mechanical properties evaluated by testing large specimens in compression, shear and bending. Results from numerical, FE predictions and mechanical testing demonstrated comparable results. Finally, design and manufacturing aspects of the G-XLam panels were discussed and examples of their architectural and structural use in construction applications such as mid-rise buildings, grid shells and vaults are presented. Overall, this research studies THM treatments applied to Guadua in order to produce standardised engineered Guadua products (EGP), and provides guidelines for manufacturing, testing, and for the structural analysis and design with G-XLam panels. These factors are of key importance for the use of Guadua as a mainstream material in construction.

House construction today is largely project-based, where the buildings are tailored tounique conditions and locations that are rarely the same as another build on anotherbuilding site. In addition to the building itself and the building site, involved actorsusually also change from project to project. As a result of today's project-basedconstruction, there is a lack of a standardized and systematic work process forconstruction work. A systematic work process could contribute to all the players' pursuitof profit. To explore the possibilities of creating an improved work process, this study focusedon balconies of wooden houses. The purpose and objectives of the work were therefore designed to evaluate today'sconstruction work for the design of balconies in wooden houses, where possible areasof improvement were evaluated to create a systematic work process for constructorsin designing and dimensioning balconies in wooden houses.In order to achieve the purpose and objectives of the work, four questions have beendeveloped that focus on the production of systematic work processes, the current workprocess of the construction work, design methods and balconies in wooden houses.Existing research and published material were found through a literature and contextstudy to further develop the study’s work. Theory regarding systematisation and process development, balconies,dimensioning of supporting structures, etc. was the basis for how the work would becarried out. The systematized work process for balcony design was, however, createdusing information from the qualitative interview study with a total of eight (8)respondents in different roles I house building. The work process was then partiallytested in a quantitative verification. The work resulted in a systematic work process in the form of a checklist that includesgeneral tips as well as a chronological workflow that describes how, when, with whomand what should and can be done at the balcony design to get the best possible results.A description of the existing balcony types has also been developed to simplify workand to clarify important points and tasks in the design of a particular type of balcony. The workflow is divided into the activities of the design and dimensioning, such asstart-up, design and dimensioning of the balcony's main components, detail designand dimensioning of fastening components, drawing up drawings and assemblydescriptions, and follow-up and development of the work process. Based on the results of the study, the questions were answered with a description ofthe four (4) types of balcony, which were based on theory and were strengthened bymeans of empirical data from the respondents. Two (2) of the balcony types are viiiconsidered more common, balconies with pillars to land and rods above the balconyplate, where the latter is considered the most common in wooden houses at present.Today's construction work for designing and dimensioning balconies in woodenhouses is similar in large part, but due to the use of prefabrication and standardizationdegree the work differs from each other. The verification of a part of the work process resulted in a balcony solution with crosslaminated timber as a balcony slab and in a comparison between results from aproposed software and hand calculations. The comparison showed that the softwarecan be used for dimensioning balconies with cross laminated timber, with the exceptionthat the dimensioning for fire must be done by hand because of deficiencies in thesoftware's settings. The study has shown that systematisation is often based on LEAN Production, whichwas created by the Japanese automotive industry, which focuses on creating efficientwork processes by circularly examining, testing, evaluating and developing workprocesses. The conclusion of the work is that it is possible to systematise construction work, butunlike the manufacturing industry, the work process must have adjustment possibilitiesduring the work to meet the commonly occurring changes in house construction.However, in order for the systematisation work to be carried out, increasedunderstanding and involvement from and by other actors than constructors arerequired. A systematic work process together with type solutions and standardized calculationmethods can shorten the design time, improve and secure the solutions, and allowmore time for creative thinking to further improve the balcony solutions and the workprocess.

<p>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.</p><p>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.</p><p>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.</p><p>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.</p><p>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.</p>

Engineered timber products are becoming increasingly popular in the construction industry due to their attractive aesthetic and sustainability credentials. Cross-laminated timber (CLT) is one such engineered timber product, formed of multiple layers of timber planks glued together with adjacent layers perpendicular to each other. Unlike traditional building materials such as steel and concrete, the timber structural elements can ignite and burn when exposed to fire, and thus this risk must be explicitly addressed during design. Current design guidance focusses on the structural response of engineered timber, with the flammability risk typically addressed by encapsulation of any structural timber elements with the intention of preventing their involvement in a fire. Exposed structural timber elements may act as an additional fuel load, and this risk must be adequately quantified to satisfy the intent of the building regulations in that the structure does not continue burning. This can be achieved through timber’s natural capacity to auto-extinguish when the external heat source is removed or sufficiently reduced. To address these issues, a fundamental understanding of auto-extinction and the conditions necessary to achieve it in real fire scenarios is needed. Bench-scale flammability studies were undertaken in the Fire Propagation Apparatus to explore the conditions under which auto-extinction will occur. Critical conditions were determined experimentally as a mass loss rate of 3.48 ± 0.31 g/m2s, or an incident heat flux of ~30 kW/m2. Mass loss rate was identified as the better criterion, as critical heat flux was shown by comparison with literature data to be heavily dependent on apparatus. Subsequently, full-scale compartment fire experiments with exposed timber surfaces were performed to determine if auto-extinction could be achieved in real fire scenarios. It was demonstrated that auto-extinction could be achieved in a compartment fire scenario, but only if significant delamination of the engineered timber product could be prevented. A full-scale compartment fire experiment with an exposed back wall and ceiling achieved auto-extinction after around 21 minutes, at which point no significant delamination of the first lamella had been observed. Experiments with an exposed back and side wall, and experiments with an exposed back wall, side wall, and ceiling underwent sustained burning due to repeated delamination, and an increased quantity of exposed timber respectively. Firepoint theory was used to predict the mass loss rate as a function of external heat flux and heat losses, and was successfully applied to the bench-scale experiments. This approach was then extended to the full-scale compartment fire experiment which achieved auto-extinction. A simplified approach based on experimentally obtained internal temperature fields was able to predict auto-extinction if delamination had not occurred – predicting an extinction time of 20-21 minutes. This demonstrates that the critical mass loss rate of 3.48 ± 0.31 g/m2s determined from bench-scale experiments was valid for application to full-scale compartment fire experiments. This was further explored through a series of reduced-scale compartment fire experiments, demonstrating that auto-extinction can only reliably be achieved if burnout of the compartment fuel load is achieved before significant delamination of the outer lamella takes place. The quantification of the auto-extinction phenomena and their applicability to full-scale compartment fires explored herein thus allows greater understanding of the effects of exposed timber surfaces on compartment fire dynamics.

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.

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).