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  • 1.
    Werner Åström, Petter
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Experimental study on innovative connections for large span structural timber trusses2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Large span timber trusses are usually built with glulam. One problem with large span glulam trusses is that the connections needed to transfer the load between truss members are often complex and expensive. Another issue is transportation. Building large span trusses out of structural timber instead, could be a way of simplifying the connections and at the same time increase the degree of on-site construction and thereby solving the transportation problem.In this study, a total of 18 laboratory tests were performed with the purpose of investigating the tensile strength and the load slip behavior of different connection designs for large span structural timber trusses. Six different test groups corresponding to six different connection designs were tested. The materials used include members made of C24 timber and gusset plates made of birch plywood, aluminum, and steel. Screws were used as fasteners for five test groups and adhesive was used for one group. The influence of different reinforcement techniques including reinforcement screws and added aluminum sheets was studied.The results showed a ductile failure behavior for all test groups except for the group where adhesive was used. However, a decrease of ductility was observed for groups were aluminum sheets were used on the outsides of the mid placed plywood gusset plate. A 12-17 % increase in capacity was observed due to the presence of aluminum sheets. The reinforcement screws had no significant effect on the capacity. However, the presence of reinforcement screws did lead to a reduction in scatter both regarding capacity and stiffness.

  • 2.
    Rask, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Life Cycle Assessment and comparison of the climate impact of structural members and floor systems constructed in concrete, steel and timber2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this report the climate impact is determined for some basic structural elements made in steel,>mber and concrete. The aim is to compare the climate impact of these three building materials byquan>fying the emissions related to the produc>on and construc>on of some typical structures.The comparison comprise two parts, were one is the comparison of members in bending,compression and tension and the other part is the comparison of a couple of floor structures.The emissions are determined through a Life Cycle Assessment, LCA. The members are comparedwith respect to their load bearing resistance and the floor structures is compared per square meter.The mo>va>on for this inves>ga>on is that the construc>on industry is a large contributor to the totalamount of greenhouse gas emissions and in order to reduce these emissions new solu>ons andprac>ses must be adopted. A more thoughVul choice of the materials used in structures has thepoten>al of reducing the emissions.The method of determining the climate impact is based on first determining the material quan>>esfor all the inves>gated structures and then calcula>ng the amount of carbon dioxide equivalentsrelated to the produc>on of these materials with the help of a Life Cycle Assessment.The material quan>>es of the structural members is determined based on the load. The dimensionsof the cross sec>on is determined with respect to the required load resistance. The materialquan>>es of the floor structures is based on some exis>ng solu>ons from manufacturers.The study show that the >mber based design solu>ons almost always has a smaller climate impactand that the differences can be considerable. Members made in steel oZen result in very largeamount of greenhouse gas emissions but the sca[er in the results indicate that the origin of the steelhas great importance. Primary steel has a much larger impact as opposed to recycled steel.The comparison of the floor designs show that beyond the material choice itself, also the materialefficiency is important. The hollow core slab made in concrete is a very material efficient design andmay in some cases be on par with >mber based designs.The massive >mber floors made of Cross Laminated Timber, CLT, has a fairly large climate impactbecause of the sheer volume of material and may be on the same level as the floor made in concretefor some scenarios. There is however a wide range in the result based on whether the material istransported a long distance and depending on the choice of insula>on material. If these choices isop>mised, the emissions of the CLT floor is instead on a much lower level, closer to that of the otherlightweight floors inves>gated.The process of evalua>ng and comparing the material choices and structural designs form a lifecycleperspec>ve can be u>lised during the design in order to reduce the emissions. With a be[erknowledge of the climate impact of the design, be[er choices can be made in order to reduce theemissions.

  • 3.
    Sjölund, Magdalena
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Stenis, Nelly
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Limträhybrider av acetyleradbjörk och obehandlad gran: En experimentell och numerisk analys av vissamekaniska egenskaper och fuktbeteende2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    I Sverige finns en lång tradition kring användandet av trä för konstruktionsändamål. I den storskaligabyggindustrin har det dock kommit att handla mycket om stål och betong och detta gäller inteminst för konstruktioner utomhus såsom broar. I träkonstruktioner har speciellt infästningarna storbetydelse då dessa är svåra att skydda från fukt, vilket gör att träets begränsande beständighetblir en anledning att välja andra material. Genom kemisk modifiering av trä, så kallad acetylering,kan detta beständighetsproblem lösas, dock med risk för kraftigt ökade materialkostnader. Syftetmed detta arbete var att undersöka möjligheterna kring så kallade limträhybrider av kemiskt modifieradbjörk och omodifierad gran. Tanken är att erhålla god beständighet i svårskyddade delarav en limträbalk, t.ex. vid knytpunkter, utan att behöva använda modifierat trä i hela balken.Genom att fingerskarva samman de två materialen kan det acetylerade materialet användas justintill infästningen och sedan övergå till obehandlat trä i områden som lättare kan skyddas från riskför röta med hjälp av till exempel konstruktionstekniskt träskydd. Mer specifikt handlar arbetetom att studera hur en sådan typ av hybridkonstruktion beter sig när den testas i fyrpunktsböjning.Speciellt undersöktes hur och var brottet uppkom samt balkarnas böjhållfasthet och styvhet.Dessutom undersöktes, med hjälp av småskaliga tester, hur acetyleringen av björk påverkar dessE-modul och hållfasthet.Studien är baserad på både experimentella försök och numerisk analys. Fyrpunktsböjning användesvid försök på hybridbalkarna och materialtesterna. Finita elementmetoder användes för attförutspå var brott kommer att uppstå samt hur området vid fingerskarvarna påverkas av den storaskillnaden i svällningsegenskaper mellan obehandlat trä och det mer dimensionsstabila modifieradeträet.Resultaten indikerade att den acetylerade björken hade större spridning med avseende på det undersöktamaterialegenskaperna jämfört med omodifierad björk. Testerna av hybridbalkarna visadepå stora problem kring fingerskarvarna beroende på problem vid limningen och även lokala defekter.Resultaten visade även en klar förbättring gällande balkarnas styvhet då limträbalkarnasmittpartier bestod av björk.Även de finita elementberäkningarna indikerade att brott kan förväntas i fingerskarvarna samtatt problem kan uppstå som följd av att limträet av omodifierad gran sväller vid uppfuktning ijämförelse med limträet av acetylerad björk. Vidare forskning föreslås bland annat kring utvecklingav lim som lämpar sig för såväl barr- som lövträ, obehandlat- som acetylerat material samtfingerskarvning. Resultaten av studien visar på goda utsikter att förbättra limträets styvhet ochböjhållfasthet samt en möjlighet till att lösa problem med fukt kring infästningar.

  • 4.
    HELGADÓTTIR, KRISTÍN
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    BJÖRNSDÓTTIR, RAGNHEIÐUR
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    The Nordic Prediction Method For Railway Traffic Noise: Improvements of the current corrections forrailway bridges, switches and crossings2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Railway noise is a very important and growing health hazard in today´s society.Railway systems pass through towns and cities and create noise. When trainsride through or over railway bridges, switches and crossings the noise increasessubstantially, causing great annoyance to the residents in the area.At the present time, acoustic regulations exist in most countries and are set to achievea good environmental quality in residential areas, schools, hospitals, offices andhotels.A few calculation models exist for railway traffic noise, such as The NPM 1996,NORD2000 and Cnossos-EU. The NPM 1996 is currently used in Sweden to calculatenoise propagation from railway traffic. To uphold the regulations set, it is importantthat the method used is as precise as possible. All of these calculation modelsare based on several correction factors. Today, the current corrections for trackconditions, that is railway bridges, switches and crossings, are not very accurate andneed to be reconsidered.The aim of this project was to investigate and quantify the error of the NPM correctionfactors and give some indication of how they should be adjusted. This is done to makethe noise prediction from railway traffic more accurate and thus protect the residentsfrom these health risks.The specific objective was to perform significant amount of field measurements ofnoise from trains on different steel bridges, switches and crossings, as well as on afew concrete bridge according to the measurement standard Nordtest NT 098. Thefield work was carried out over the period March to May, when weather conditionsmet the criteria for field measurements, in and around the Stockholm area.The results obtained revealed that the correction factors for steel bridges andcrossings are considerably lower in the NPM than measured in this project. However,the correction factors for switches and concrete bridges are similar to the ones inthe NPM. In this thesis, a part of the correction factors have only been invalidatedto a degree. It has been shown that each bridge is unique and perhaps there is apossibility of finding similarities between some type of bridges. However, much moreiv |measurements are needed to see any correlation between each bridge type. Thus,further and more comprehensive measurements have to be carried out in order toestablish new accurate correction factors for track conditions in the Nordic PredictionMethod.

  • 5.
    Wincrantz, Christian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Finger-jointing of acetylated Scots pine using a conventional MUF resin2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Acetylation of wood is a modification technique that chemically alters the wood substance and enhances several properties of wood. The basic principle is to impregnate wood with acetic anhydride to react and replace OH-groups with acetyl groups in the wood cell wall. In this way, the hygroscopicity of the modified wood is significantly reduced resulting in increased dimensional stability and durability compared with unmodified wood.The objective of this work was to study finger-jointing of acetylated Scots pine (Pinus sylvestris L.) using a conventional melamine urea formaldehyde (MUF) adhesive. Two different types of acetylated pine specimens were investigated, acetylated pine sapwood (APS) and acetylated juvenile pine (AJP), the latter originating from young forest thinning trees (ca 20-30 years). The goal was to evaluate the bending strength, i.e. modulus of rupture (MOR), of such finger-jointed samples, in particular when the acetylated wood was combined with unmodified wood, in this case, Norway spruce (Picea Abies L. Karst) (US). The finger-jointing were performed at Moelven Töreboda by applying their existing industrial procedures. In total, five different of finger jointed sample groups were prepared combining the different specimens: APS-APS, AJP-AJP, US-US, APS-US, and AJP-US. Standardized procedures were used to determine the MOR of the finger-jointed samples, both unexposed at the factory condition state and after a water-soaking-drying cycle. In addition, the experiments also included determination of the moisture content (MC), density, and modulus of elasticity (MOE) (in bending along the grain) of the individual specimens.At the unexposed state, the APS-APS samples showed the highest MOR of 63,1 MPa, while those of the AJP-AJP showed the lowest value of 42,4 MPa. The corresponding values for the US-US, AJP-US and APS-US samples was 56,7, 47,5 and 46,9 MPa, respectively. In contrast to a typical wood failure for the US-US samples, a low amount of wood failure was observed in all cases involving the acetylated wood, indicating a low adhesive anchoring in the wood substrate at the finger-joint, although a surprisingly high strength was obtained for the APS-APS samples. A significantly lower MC content of 4,9 % and a remarkably low value of 1,7 %, was found for the APS and AJP, respectively, compared with 9,2% for the US. The significantly lower MC combined with an assumed increased hydrophobicity of the acetylated wood possible causes a less effective MUF-wood bonding, or adhesion, compared with that of the unmodified wood. Possible, so-called over penetration of the MUF resin in the acetylated wood could also be an explanation for the poor wood-adhesive anchoring. The MOE of the individual APS, AJP and US specimens was 12,6, 8,3 and 11,4 GPa, respectively, indicating a significantly lower mechanical performance of AJP, and hence also of finger-joints of AJP, despite its very low MC, possible due to a higher microfibril angle in the cell walls in juvenile wood compared with mature wood. No clear correlation was found between the MOR and density of the acetylated samples.For the samples exposed to a water-soak-drying cycle, the highest MOR, and lowest reduction of 14 % compared with the unexposed state, was obtained for the US-US samples, whereas all samples involving the acetylated wood showed a distinctly higher reduction. The MOR of the AJP-AJP and AJP-US samples were reduced with 47 % and 50 %, respectively, while the MOR of the APS-APS and APS-US samples were reduced with 43 % and 23 %, respectively. It should be emphasized, however, that after the standard drying-time, which was the same for all samples, the acetylated samples, compared with the untreated ones, did not dry out to the same level as for the dry unexposed state, i.e. the acetylated samples had a high MC of ca 30-40% in these MOR tests. This high MC level could be the main reason for the dramatic strength losses. Furthermore, a less efficient wood-MUF adhesion as well as the drying under acidic conditions may also be possible causes for the reduced bending strength of the finger-jointed samples with acetylated wood.

  • 6.
    Nordlöf, Jennifer
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Stenberg, Linda
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Vinklade lättbalkar i bjälklag: - En lösning till minskad bjälklagshöjd2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 7.
    Kristjánsdóttir, Rut
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Design of Heavy DutyPavements2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This research is focused on design of Heavy Duty Pavement which is when a pavement loading exceeds highway levels. The environment where these conditions occur are for example at ports, industrial areas and airport because of the use of heavy vehicles as handling of containers by Straddle Carriers, Front Lift Trucks or Reach Stackers, airplanes and more. The main emphasis here will be on heavy duty pavements for ports. Different design methods are discussed and compared for the pavement design of ports. In this research two different design methods are thoroughly analyzed, the British Ports Associations Heavy Duty Pavements Manual which is a chart based procedure and the HIPAVE program which is an Australian Heavy Duty Pavement Design Guide. Both those methods are widely used around the world. Furthermore, an analysis is performed to research the plastic properties of the pavement. In most design methods, the material properties of the granular materials are assumed as elastic when they are not, they are elasto-plastic. A Finite Element Analysis is performed to determine if this assumption has significant effect on the design of pavements by comparing models of a design pavement section with elastic granular materials and elasto-plastic granular materials. The main conclusions from the comparison study of different pavement design methods are when using the HIPAVE program the total thickness of the design pavement section is smaller than using the British Ports Manual. Smaller thickness result in less materials needed for and therefor lower cost for the pavement section. Regarding the plasticity analysis, it is concluded that the assumption to model the behavior of unbound granular materials as elastic in pavement design is correct. The Finite Element Analysis determined that plasticity does have effect on the behavior of the materials with respect to elastic behavior, but there is not a considerable difference in pavement displacement between the two analysis.

  • 8.
    Tapparo, Alessandra
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Engineered wood glass combination: Innovative glazing façade system2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Buildings require a lot of energy during all their lifetime, from the construction site to the use and demolition. The building sector contributes to a large part of the total emissions of greenhouse gases and consume a large amount of water and energy resources, so the material components used in the building sector have gained an important role in the discourse of sustainability. The tendency is to use natural renewable materials that generates lower environmental impact than conventional ones and are able to fulfil the required structural and architectural needs.

    Wood is a traditional material with a long and proud history and has been reintroduced in the construction site thanks to its sustainable characteristics. Wood used for building applications, i.e. timber, is capable to capture CO2 from the atmosphere and incorporate so-called carbon storage. Moreover, low process energy requirements and high recyclability increase the potential of timber to become a major building material. On the other hand, the considerable growing demand for highly transparent envelopes has recently resulted in massive introduction of glass as a façade component. The main objective of this thesis was therefore to elaborate on the question if it is possible to merge the positive aspects of these two materials.

    The thesis starts with a discussion on hybrid, composite and combined materials. The key concept is to merge two or more materials with different characteristics, which result in a finished product with better overall properties than the starting constituents. However, such building material systems are not well categorized and a new term is therefore introduced to describe the combination between wood and glass: engineered wood glass combination (EWGC).

    The product is then described presenting the characteristics and properties of wood and glass and the structural benefits of the whole panel. The EWGC product possesses some advantageous properties like transparency, stiffness and strength for glass and the ductile nature of timber when used under compression. Moreover, this wood-glass element enables load transfer of horizontal forces through the glass pane so that the additional metal bracing elements for stiffening the building can be omitted.

    Then the study goes deeper in the architectural possibilities and different potential types of assembly are described. However, only few profiles have been tested and this has resulted in the market production of only one type of panel that is currently used in the construction site. Moreover, the shape of the EWGC is suitable to integrate systems that can control the ventilation rate and solar gains, allowing the development of advanced integrated façades that ensure the comfort condition inside the building.

    EWGC is also seen to be highly potential as an ecological alternative to conventional structural sealant aluminium-glass façade. For this reason, the life cycle assessment (LCA) of different materials is discussed in order to evaluate their environmental impacts. LCA results are strongly dependent on the calculation boundaries and the choice of database, but it stands out that aluminium, as a construction material for glazing elements, requires up to 4 times higher primary energy demand and produces up to 16 times more CO2 emission than timber based combined panels. Despite some weak points, e.g. the lack of standardized regulations and people’s preconceptions about wood, the overall conclusion is that EWGC has the potential to be used for future building envelopes of multi-storey timber buildings.

  • 9.
    Babic, Nino
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Flyttbara byggnader för bostadsändamål: Kompatibla med de nya tidsbegränsade byggloven2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Bostadsbyggandet i Sverige står inför kommande utmaningar. Bostadsbristen ökar och många av landets kommuner anser att de redan nu har en stor bostadsbrist. En orsak som ofta pekas ut är tiden det tar för kommunen att arbeta fram en detaljplan. Samtidigt skärps kraven avseende energiförbrukning för byggnader som byggs efter år 2020. Som en motåtgärd har riksdagen nyligen röstat igenom en lag som utökar möjligheterna att utnyttja de tidsbegränsade byggloven för att bygga tillfälliga bostäder. Tidsbegränsade bygglov kan då utnyttjas för att tillfälligt tillgodose behovet samtidigt som kommunen kan arbeta fram en detaljplan dit byggnaderna sedan flyttas. I detta examensarbete undersöks det hur detta skulle kunna implementera, och samtidigt bibehålla prestandan som byggnaderna är tänkte att ha.

     

    Syftet med detta arbete är att undersöka om KL-trä kan användas på ett tidigare outnyttjat sätt, genom att bygga flyttbara moduler som är kompatibla med tidsbegränsade bygglov för att på ett snabbt sätt kunna tillgodose det stora bostadsbehovet. Den stora frågan som detta examensarbete försöker att besvara är ”Hur kan man bygga flyttbara bostadshus med KL-trä som når den nya miljömålen som kommer år 2020?”. Målet är därför att göra en kartläggning och presentera lösningar på de frågor och tveksamheter som kan finnas kring flyttbara byggnader med KL-trästomme, både innan och efter flytt.

    Trä har länge använts som ett byggmaterial i norra Europa. I Sverige förstördes många städer under 1700- och 1800-talet av bränder. För att förhindra brand och brandspridning mellan byggnader infördes år 1874 ett förbud mot att bygga fler än två våningar i trä, ett förbud som varade i mer än 100 år. Detta ledde till att andra material utvecklades och tog stora marknadsandelar i flerbostadshusmarknaden. År 1994 tilläts det än en gång att bygga högt i trä i samband med att Sverige gick med i EU. Att använda trä som stommaterial har många fördelar, men innebär också specifika områden som är viktiga att ägna uppmärksamhet. KL-trä är ett relativt nytt stommaterial i Sverige och utvecklingen har lett till praktiska lösningar på de problem som är förknippade med trästommar. 

    Genom att utnyttja fördelarna som KL-trä innebär kan flerbostadshus byggas med volymelement som lever upp till dem krav som ställs på flerbostadshus enligt Boverkets byggregler, BBR. Fördelarna är bland annat låg egenvikt, låg värmekonduktivitet och en trevlig arbetsmiljö. Arbetets slutsatser är bland annat:

    • För att nå ett gott resultat i hela processen är det viktigt att planeringen håller hög kvalitet.
    • Stor vikt bör läggas på utformning av brandskydd och akustisk prestanda som lever upp till kraven på platsen för det tidsbegränsade bygglovet och på återuppställningsplatsen.*
    • I projekteringsskedet är det viktigt att se till att de valda tekniska lösningarna är lätta att installera och plocka isär. 
  • 10.
    Zaccaro, Vito Lorenzo
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Timber-concrete hybrid innovations: A framework to evaluate economical and technical factors for the construction market2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays, the focus of the construction market is on sustainability aspects, for which purpose, the employment of wood seems promising. Nevertheless, in countries having high potentiality like Sweden, the timber construction market finds difficulties in growing. The reason lies in the lack of standards for design and industrialization and on the strong competition of the concrete industry. The timber-concrete hybrid solution is presented in this study as a solution beneficial for both the timber and the concrete markets: the former would benefit of a pulling action towards standardization and larger market, while the latter would fulfil the environment-friendly requirements and better differentiate in the competitive landscape.

    Therefore, the objective of this thesis is to provide a framework to evaluate innovations in construction market, highlighting the characteristic issues related to the matching of timber and concrete constructions, and detecting the main economic and technical factors to help in the decision-making process. This framework will help to organize and evaluate all the information and the boundary conditions about the introduction of a concrete-timber hybrid construction solution, which eventually would enhance the timber construction market itself through a preliminary association with concrete market.

    Firstly, some consideration on the market areas and on the general perceptions towards the timber construction are presented; then, the focus is moved onto the dynamics of concrete and timber supply chains, highlighting similarities, diversities, and possible reciprocal benefits, to finally detect the market indicators to be considered for a decision-making path related to the timber-concrete hybrid construction.

    From the technical side, a conceptual design is proposed, considering the industrialization of such hybrid solution. Annex A shows how standardization and modularity of the products would enable compatibility and interchangeability between timber and concrete, on account of the open system within the construction market. Annex B displays a schematic picture of how the exploitation of timber and concrete’ properties, with the industrialization of these two materials, can be best employed for a hybrid building. A preliminary technical evaluation of the timber-concrete hybrid is carried out by dividing the building into modular units and focusing on the main systems (horizontal loadbearing system, vertical loadbearing system, external envelope, inner partitions), while making consideration on structural design, fire protection, building technology details, building service systems integration, construction plan, and costs.

    The innovations within the construction market are often hindered by the fear to undertake a high-risk project. The proposed framework allows to increase the awareness on the general factors to be evaluated, and to undertake a gradual adoption of the “new” timber construction solution. The key points underlying the whole timber-concrete hybrid problem are standardization and modularity, necessary for a quality-oriented production. Further studies need to be carried out with an applicative intent: application of the general framework to real cases and pilot projects; automatic tools for the design and construction optimization including economic and technical factors; innovative and original hybrid solutions, which better exploit the timber-concrete synergy.

  • 11.
    Johansson, Malin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    A study of potential climate impacts from maintenance and replacements in timber buildings: From a lifecycle perspective2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The building sector contributes to a large part of the total emissions of greenhouse gases, which demands for increased sustainability in all phases of a buildings’ lifecycle. Choices of building materials and the respective required maintenance and replacements are becoming more important if further reductions of climate impacts should be obtained.

    Folkhem is a Swedish construction company who constructs multi-storey buildings made of wood. The company has shown interest in developing knowledge about how the selection of building materials effects the impacts on climate, the extent of necessary maintenance and replacement work as well as economic consequences. The aim of this master thesis was to evaluate the potential climate impacts and costs for different scenarios of maintenance and replacements of selected exterior building components for Folkhem’s planned building in Stadshagen, in Stockholm. The façade, roof, windows and balconies have been in focus. To fulfill the aim of this study, life cycle assessment and a simplified cost analysis have been carried out.

    With the basis of the results from this study, recommendations of building materials for the chosen building components in Folkhem’s planned building have been stated. A façade made of pine impregnated with boiled linseed oil is recommended as façade cladding, and OrganoWood is recommended for the balcony decking. Folkhem planned to use wooden windows, but it is recommended that these are substituted to aluminum coated wooden windows. No recommendation could be provided for the roof from this study. The following conclusions have been made;

    • More attention should be payed to the phases of maintenance and replacement when carrying out LCAs for timber buildings, since general assumptions could be misleading.
    • The origin of the building materials could have a significant climate impact if several replacements need to be performed, since this includes a large number of transports of materials.
    • Different building materials or building components have different lifespans and needs for maintenance. To reduce costs and potential climate impacts, long lifespans with little need for maintenance are desired. Planning for a specific lifespan of the building and the required maintenance and replacements may contribute to reduce the potential climate impacts.
    • Maintenance is recommended for timber buildings, since this could reduce the need for replacements, which could reduce the potential climate impacts.
    • LCA can be a useful tool for Folkhem to plan for maintenance and replacements of their timber buildings if improvements are performed regarding LCA data quality.
    • LCA can provide guidance for Folkhem to choose sustainable building materials, with regards to maintenance and replacements at an early stage in the design process.

    A future study could be to perform a more detailed LCA of the materials and products that required assumptions in this study, for instance the surface treatments for maintenance. A more detailed LCA of all maintenance that should be conducted in a building could be of interest as well, and to investigate the impacts from excluded processes in this study. Alternative building materials for the exterior building components could be evaluated as well as different percentages of painting area. More impact categories than climate change could also be evaluated. Impacts from the building lifecycle phases of repair and refurbishment could also be interesting to evaluate in order to receive an overview of the total potential climate impacts and costs from all parts of the lifecycle of a building. Another approach could be to investigate if maintenance and replacement are carried out as described from technical literature and manufacturers in reality. Finally, a more thorough cost analysis could be carried out, evaluating how a housing society would be affected from costs from maintenance and replacement. 

  • 12.
    Nilsson, Alexander
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Olsson, Matilda
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Trästommar på den svenska marknaden: En undersökning av leverantörer och den industriella byggprocessen2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    I dagens samhälle är miljö- och hållbarhetsfrågor viktiga på grund av de pågående klimatförändringarna och detta har skapat en konkurrensfördel för användandet av trä som stommaterial då trä är det enda förnyelsebara materialet på marknaden. Trots detta byggs det idag främst med andra stommaterial, såsom stål och betong. Syftet med detta examensarbete är att få fler byggentreprenörer och byggherrar att uppföra fler byggnader i trä genom att sprida kunskap om trä och skapa en förståelse för materialet och dess fördelar. Målet med detta examensarbete är att göra en undersökning av användandet av trästommar på den svenska marknaden. Metoderna som använts till detta är litteraturstudie, undersökning av ett fallstudieobjekt, enkätstudie och en intervjustudie.

    Litteraturstudien visar att de byggprodukter som främst används i trästommar är konstruktionsvirke, KL-träskivor, limträ, LVL och lättbalkar samt att flervåningshus i trä främst uppförs med stomsystemen massiv trästomme, pelar-balksstomme och regelstomme. Den visar även att trä lämpar sig väl till den industriella byggprocessen då träets låga densitet möjliggör transport av stora plan- och volymelement som prefabriceras. Leverantörer av trästommar kan arbeta med olika affärssystem, vilket leder till att de fungerar som komponentleverantör, delsystemleverantör och/eller systemleverantör. Erfarenheter från fallstudieobjektet visar att det vid uppförandet av en trästomme förekommer flertalet miljö- och kostnadsfördelar samtidigt som de mest kritiska aspekterna är akustik, brand och fukt.

    Resultatet av enkätstudien visar att det på den svenska marknaden idag finns en variation bland leverantörerna gällande affärssystem, uppdelningen av projektering och montage samt hur högt de byggt, vilket i de aktuella fallen handlar om mellan 2 och 8 våningar. Resultatet visar även att leverantörerna arbetar med lean-produktion för att förstärka fördelen som trä har i ett industriellt byggande.

    Resultatet av intervjustudien visar att det i dagsläget är vanligast att leverantören projekterar och att byggentreprenören utför montaget av stommen. Resultatet visar även att leverantörer av trästommar har erfarenhet och lösningar för att uppfylla krav på akustik, brand och fukt, men att det är av vikt att montaget utförs korrekt för att kraven ska uppfyllas. Vidare visar resultat att byggentreprenörens roll kan anpassas beroende på kunskap och erfarenhet gällande projektering och montage. Till sist visar resultatet att leverantörer bedriver forskning och utveckling för att träet ska vara ännu mera konkurrenskraftigt i framtiden.

    Slutsatsen av de utförda studierna är att trä erbjuder flexibilitet genom olika stomsystem och genom möjligheten att kombinera stomsystem, att en beställare, med lite erfarenhet, kan utnyttja leverantörers kunskaper kring trästommar, att trä är konkurrenskraftigt på grund av miljövänlighet och applicerbarhet i den industriella byggprocessen samt att forskning pågår för att göra träet mer konkurrenskraftigt i framtiden.

  • 13.
    Harmachova, Karolina
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Vibration performance of hybrid steel-CLT floors2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    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.

  • 14.
    Dahlström, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology. KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Giesen, Emma
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology. KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Mould resistance design for external wood frame wall systems: Simulation and evaluation of wall structures under varying conditions of exposure using the MRD model2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Moisture induced damages to building envelopes can result in microbial growth possibly affecting the health and wellbeing of occupants. Recent failing structures and damaged buildings indicate a lack of tools to estimate risk of mould growth and moisture damage. In this work a so-called mould resistance design (MRD) model has been applied for mapping the risk for mould growth on a number of wood-containing wall structures. The MRD model introduces an engineering approach to moisture safety design in a similar way as for structural design, where load and resistance is compared. The MRD model introduces and quantifies the concepts of climatic exposure and material resistance and compares them through an MRD index. This MRD index incorporates a limit state, which gives the critical dose of exposure for a given resistance to initiate onset of mould growth.

     

    Three conceptual wall structures were evaluated and analyzed in terms of MRD index: two wall systems with an air gap and one wall system without. A parametric study investigating the effect of parameter variation on MRD index was conducted. Evaluated parameters were: climate (geographic location), orientation, air changes per hour in the air gap, driving rain penetrating the facade layer, exterior plaster properties and wood type. The simulations were performed using the hygrothermal calculation software WUFI. The results indicate that the wall systems with a ventilated air gap performs better in terms of MRD index i.e. suggests a lower risk of initiation of mould growth than the wall system without air gap. The results of orientation variation show that wall systems perform differently dependent on layering structure. The inherent water sorption properties of the exterior plaster are shown to have a large effect on the results. In addition, uncertainties were found on how to accurately include hydrophobicity as a parameter in the model. The report concludes that geographical location and its specific climate is the most important parameter to consider when designing for moisture safety. The MRD model is recommended to be used in combination with traditional moisture safety evaluation.

  • 15.
    Tjernberg, Frida
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wind-induced dynamic response of a 22-storey timber building: Options for structural design of the Hallonbergen project2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Folkhem is a Swedish company exclusively building timber residential buildings in the Stockholm area. The company is currently in the planning stages of what would be the world’s tallest timber building, a 22-storey timber residential buiding in Hallonbergen, Sundbyberg. In this master thesis, this proposed building has been analyzed with regards to its wind-induced dynamic response. The work includes studies of stabilization of tall structures, case studies of existing buildings and developed systems for tall timber construction and analyzed options for structural design of the Hallonbergen project. Eleven different structural systems have been investigated with regards to their displacement at the top and their peak acceleration when subject to wind loading. The peak acceleration has been calculated using both Eurocode and ISO 4354. The values have been assessed against ISO 6897 and ISO 10137. The results indicate that it is possible to construct the Hallonbergen project without risk of unacceptable dynamic response, using any of the following options;

    • The Martinson’s system with 259 mm CLT plates
    • The Kauffmann system
    • The structural system presented in “The Case for Tall Wood Buildings”
    • The structural system presented in “The Timber Tower Research Project”
  • 16.
    Eriksson, Maria
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Studie av impregnerbarhet hos trä2010Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 17.
    Källman, Malin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Korrosion hos fästdon i brandsskyddat trä2009Independent thesis Basic level (professional degree), 30 credits / 45 HE creditsStudent thesis
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