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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
621

Impact of moisture on long term performance of insulating products based on stone wool

Vrána, Tomás January 2007 (has links)
<p>Demands for energy have been increasing in the whole world. According to higher consumption, the price of energy rises yearly too. This evokes usage of insulating products in a wider range. By adding insulation, we lower the amount of energy needed to heat our homes, resulting in fewer associated greenhouse gas emissions and a lower monthly heating bill. Savings depend on insulation thicknesses and on conditions, in which the insulant is kept. Mineral insulation based on stone wool is also a member of building insulants that defends buildings and constructions against temperature changes of the ambient. However, even when we use modern technologies and building techniques to reduce high energy losses, we can never provide unimpeachable protection of stone wool from damage. During a construction process on a building site or at fast climate changes, it often happens that stone wool is exposed to rain precipitaions or other climate effets. This brings water to the insulating structure. Besides the loss of insulating qualities, the stone wool is left permanently wet. Even the fibres of stone wool are inorganic, they still can be attacked by degradation processes due to organic agents fixing fibres together. Analysis of damaged flat-roof constructions using stone wool and verification of material properties is a starting point of this licentiate thesis.</p><p>The attached paper section can be divided into two parts:</p><p>In-situ practice that notes troubles with insulating materials based on stone wool with inbuilt moisture on a building site</p><p>Laboratory measurement that observe material properties of stone wool under varying conditions</p>
622

Testing large samples of PCM in water calorimeter and PCM used in room applications by night-air cooling

Bellander, Rickard January 2005 (has links)
<p>The latent-heat-storage capacity in Phase-Change Materials can be used for storing or releasing energy within a small temperature interval. Upon the phase transition taking place in a narrow temperature span, the material takes up or releases more energy compared to sensible heat storage. For an ideal phase-change material, the transition temperature is a single value, but for the most common phase-change materials on the market, used in building applications, the transition temperature is distributed within a temperature range of several degrees.</p><p>Integration of phase-change materials in building applications can be effected in several ways, for example by impregnating phase-change materials into porous building materials like concrete, wallboards, bricks or complements of the building structure. Integrating storages filled with phase-change materials makes other implementations, for instance accumulating tanks or envelopes as presented in this thesis, in an air heat exchanger. An appropriate phasetransition temperature of the supposed application is critical to the functionality of the material. For example, in cooling applications, the transition temperature of the material should be a few degrees lower than the requested comfort temperature in the building, and the opposite for heating applications.</p><p>In order to assess the thermal properties and the durability of the material, a watercalorimetric equipment was developed and employed in an accelerated testing programme. The heat capacity of the material and in particular possible change in the heat capacity over time, after thermal cycling of the material, were measured. In the thermal cycling of the material from solid to liquid phase, the temperature rise and required energy supply were recorded. The testing programme was undertaken according to control procedures and documents. In order to be able to utilize the heat-storage capacity in the best way, it is necessary to gain knowledge about thermal properties of the material, especially the long-term behaviour of the material and the deterioration rates of the thermal properties.</p><p>A semi-full-scale air heat exchanger based on phase-change material was developed and tested under real temperature conditions during the summer of 2004. The test results were used to compare and verify computer simulations made on a similar plant. The air heat exchanger utilises the ambient diurnal temperature swing to charge and discharge the phasechange material. The material tested in the calorimeter and in the air heat exchanger has an estimated phase-change temperature of about 24 °C.</p>
623

Steel-to-timber dowel joints : Influence of moisture induced stresses

Sjödin, Johan January 2006 (has links)
<p>Joints are critical parts of timber structures, transmitting static and dynamic forces between structural members. The ultimate behavior of a loaded building depends strongly on the structural configuration and the capacity of the joints. The collapse of a whole building or less extensive accidents that may occur is usually starting as a local failure inside or in the vicinity of a joint. Such serious failures have recently occurred in our Nordic countries. Especially the collapse of two large glued laminated timber structures clearly indicates the need of an improved joint design. The trend toward larger and more complex structures even further increases the importance of a safer design of the joints.</p><p>An aim of this partly experimental and partly numerically based thesis has been to investigate if steel-to-timber dowel joints are affected by moisture-induced stresses. The experimental results showed that the load-bearing capacity of the joints is reduced by such a moisture influence. Most of the decrease in load-bearing capacity observed was found in joints initially exposed to restrained shrinkage deformations caused by the presence of dowel fasteners in the joint area. The load-bearing capacity was, however, also found to decrease in joints exposed to an initial decrease in moisture without any fasteners present in the specimens during storage before loading. An explanation of this unexpected behavior is that moisture gradients cause tensile stresses. It is shown by numerical simulations that the moisture-induced stresses are so large that they may have a considerable influence on the joint behavior.</p><p>Use of contact-free measurement methods, used in some of the experimental tests, was in many ways found to be superior to traditional measurement techniques, but was also found to be a valuable complement to the numerical analysis performed. From numerical results obtained in combination with results from contact-free measurements several observations of considerable interest were made. For dowel-type joints loaded in tension parallel to the grain a strongly non-uniform strain distribution was found in the joint area. It was further observed that the shear and tensile strains were concentrated close to the fasteners in the joint area. These concentrations will influence the failure mode of the joint. A general observation was that the larger sized joints failed in a brittle manner.</p><p>Keywords: constraint stresses, contact-free measurement, dowel-type joints, humidity variations, moisture-induced deformations, timber structures</p>
624

Livscykelanalys och optimering av isoleringstjocklek för moderna byggnader : - med fokus på kv Limnologen i Växjö

Johansson, Martin, Kanellos, Konstantin January 2007 (has links)
<p>Syftet med denna rapport är att visa hur en ökning av isolertjockleken i ett hus påverkar kostnader och energiåtgång för isoleringen i ett livscykelperspektiv, samt för husets bruksskede. I studien har en optimering av isoleringen på ett pågående byggprojekt i Växjö, kv Limnologen, utförts. Total energiåtgång för isoleringens livscykel har tagits fram från tidigare utförda livscykelanalyser (LCA). Husets värmebehov har beräknats mha information från ritningar och kontakter med personer i anknytning till kv Limnologen. En ekvation har utformats för att finna ett teoretiskt optimum för isolertjockleken med inriktning mot total energiåtgång, koldioxidutsläpp och ekonomi. Resultatet för optimeringen av total energiåtgång visar att optimum ligger vid den dubbla tjockleken för tak och grund, samt tredubbla för väggarna. För koldioxidutsläpp och ekonomin är resultatet mer beroende av husets uppvärmningskälla. Fjärrvärme med biobränslen är mer miljövänligt och ekonomiskt idag i jämförelse med fossila bränslen. Det innebär att hus som är oljeuppvärmda bör isoleras betydligt mer. I denna studie sammanställs en del faktorer såsom energi, koldioxid och ekonomi vilket gör det lättare att analysera och värdera dem. Att isolera till vårt framräknade optimum vore inte relevant då detta är ett teoretiskt värde och inte tar hänsyn till förändringar i konstruktionen och andra problem som kan uppstå. Optimeringskurvan visar att vinsten ökar snabbast de första centimetrarna av tilläggsisolering och om konstruktionen inte påverkas nämnvärt skulle det vara möjligt att utföra detta tillägg. Slutsatsen är att husen som byggs på kv Limnologen är välisolerade enligt dagens förutsättningar.</p> / <p>The aim with this report is to show how an increase of the thickness of insulating in a house influences the costs and the energy consumption for the insulation in a life cycle perspective and for the usage stage of the house. An optimization of the insulation on an ongoing construction project in Växjö, Limnologen has been carried out in the study. Total energy consumption for the insulation’s life cycle has been taken from earlier accomplished life cycle assessments (LCA). The house's heat need has been calculated on the basis of information from blueprints and contacts with persons in connection to Limnologen. An equation has been formulated in order to find a theoretical optimum for the insulating thickness regarding total energy consumption, carbondioxide and economy. The result of the optimization for total energy consumption shows that optimum lies at the the double thickness for ceilings and foundation, and triple for the walls. For carbondioxide and the economy the result is more depending on the house's heating source. District heating with biomass fuel is more environmentally friendly and economic today compared with fossil fuel. It means that houses that are oil heated should be insulated considerably more. In this study a compilation of some factors have been made, such as energy, carbondioxide and economy which makes it easier to compare them. Insulating to the calculated optimum is not relevant because the optimum is a theoretical value and does not take into consideration structure solutions and other problems that can arise. On the other hand the optimization curve shows that the profit increases rapidly at the first centimetres of additional insulation and if the structure is not affected markedly this addition would be profitable to carry out. The conclusion is that the buildings raised at Limnologen are well insulated with the presumptions of today.</p>
625

Förstärkta strävor i trätakstolar för ökad tryckkapacitet : En laborativ undersökning / Reinforced compression members in wooden roof trusses : An experimental investigation

Karlsson, Tomas, Fromell, Johan January 2007 (has links)
<p>I vissa takstolskonstruktioner kan det ibland uppstå stora tryckkrafter i diagonala reglar. I Sverige löser man oftast detta med hjälp av stagning tvärs diagonalen för att hindra utböjning i veka riktningen. Ibland när det är svårt att på plats trä in strävor på grund av utrymmesbrist och dylikt kan man spika eller skruva på en regel för att på så sätt förstärka den diagonala strävan. Detta examensarbete har undersökt två olika förstärkningsalternativ, rektangulärt- och T-tvärsnitt, med hjälp av reglar med dimension 45x95 mm2 vilka skruvas respektive spikas ihop. Detta har gjorts laborativt genom att trycka provkroppar i en provningsram och undersöka hur mycket den axiala kapaciteten ökar med förstärkning. De två olika förstärkningslösningarna bygger på att man på plats kan förstärka strävor med enkla medel.</p><p>Testbitarna har levererats till Växjö universitet och är av oklassat virke. Provbitarnas E-modul har undersökts för att på teoretisk väg undersöka hur stor axialkraftskapacitet den primära strävan har utan förstärkning. Provkroppar tillverkades och konditionerades i klimatrum, med temperaturen 20°C och 65 % RF, i ca tre veckor före provtryckning.</p><p>De laborativa värdena visar att den axiella kapaciteten ökar med 1,9 – 2,7 ggr för de rektangulära tvärsnitten och 2,5 – 4,0 ggr för T-tvärsnitten. Förstärkningsfaktorn är beroende av längd, förstärkningsalternativ och sammanfogning. Förstärkningseffektiviteten är högst för de längre strävorna.</p> / <p>In wooden roof trusses there sometimes may occur buckling in compressed web members. In most cases in Sweden this is solved by bracing between two webs to prevent buckling of the minor axis. Sometimes it is hard to brace between webs because of lack of space. Then it is possible to nail or screw a side member on the compressed web to increase the capacity. This diploma work has examined two different ways of bracing, rectangular cross section and T-bracing, with webs 45x95 mm2. Experimental tests have been made on compression webs and examine the bracing efficiency. It is important that the bracing alternatives are easy to use with simple tools.</p><p>Ungraded lumber were delivered to Växjö University. The Youngs modulus of the test pieces has been examined so the critical buckling load of the main member without bracing could be calculated theoretically. The lumber was conditioned to equilibrium moisture content of approximately 12 percent in a room maintained at 65 percent relative humidity and 20°C in three weeks before testing the critical buckling load.</p><p>The experimental results show that the critical buckling load increases with a factor of 1,9 – 2,7 for the rectangular cross sections and with a factor of 2,5 – 4,0 for the T-bracing. The bracing efficiency is dependent on length, bracing alternative and type of connectors.. The bracing efficiency increases for longer webs.</p>
626

Utvärdering av styvhetsegenskaper hos ett nyutvecklat träbjälklag av limmade sidobräder / Evaluation of stiffness properties of a novel wooden floor system of glued side boards

Wadefur, Tommy, Karlsson, Viktor January 2007 (has links)
<p>Idag blir det allt vanligare med träbyggnader högre än två våningar. Detta tillsammans med en modern arkitektur som ger stora öppna planlösningar ställer höga krav på bjälklagen i träbyggnader. Problematiken med långa spännvidder för bjälklag i trä är att klara kraven för svikt och nedböjning. Dessa krav måste uppfyllas för att säkerställa funktioner hos andra byggdelar och för att människor inte ska uppleva att golvet sviktar eller vibrerar på ett obehagligt sätt.</p><p>Ett träbjälklag bestående av limmade balkar av sidobräder har utvecklats. Bjälklaget är utformat av balkar med I-tvärsnitt i primärriktningen och rektangulära balktvärsnitt i sekundärriktningen. Examensarbetet omfattar laborativa provningar och beräkningar dels för att bestämma en böjelasticitetsmodul för varje enskild limmad balk och dels för att bestämma styvhetsegenskaperna för bjälklaget.</p><p>De limmade träbalkarna ingår i ett forskningsprojekt vid Växjö universitet finansierat av KK-stiftelsen, som syftar till att undersöka möjligheterna att tillverka en konkurrenskraftig produkt genom att i grönt tillstånd (otorkat) limma ihop bräder från stockens yttre delar till balkar. Balkarna levererades limmade och hyvlade till universitet där en böjelasticitetsmodul först bestämdes för varje enskild balk. Därefter monterades balkarna ihop till ett fullskaligt bjälklag som provades med olika försöksuppställningar/lastfall varvid deformationen mättes upp. Dessa deformationer blir underlag för att bestämma bjälklagets styvhet.</p><p>Böjstyvheten i primärriktningen uppgår till 17,55 x 1012 Nmm2/m enligt beräkningar baserade på laborativa resultat. Böjstyvheten i sekundärriktningen uppgår till 4,5 % av primärriktningens böjstyvhet, dvs. 0,79 x 1012 Nmm2/m. Sammanfattningsvis kan man säga att böjstyvheten är hög i båda riktningar i jämförelse med vanliga träbjälklag.</p> / <p>In Sweden it becomes more and more common with wood buildings higher than two floors. This along with a modern architecture that gives big open plan solutions sets high requirements on the floor systems in wood buildings. The complexes of problems with long spans for floor systems in wood are to match the requirements for elasticity and deformation. These requirements must be met in order to ensure functions of other construction components, and not be unpleasant for people to walk on with respect to vibrations.</p><p>A wooden floor system consisting of green glued side wood sections has been developed. The floor system is made with I-profiled beams in the primary direction and rectangular cross-sections in the secondary direction. This diploma work is based on that through elaborative testing and numeric calculations to decide the stiffness properties for each individual green glued side wood section and for the floor system.</p><p>The glued side wood sections are included in a project at Växjö University, which is financed by the KK-foundation. The sections were delivered glued and planed to the university where the stiffness properties were first determinded for each individual section. Then, the sections were assembled to one fully sized floor system that was exposed to different experiments as the deformation was measured. These deformations were later used in order to decide the stiffness of the floor system.</p><p>The stiffness in the primary direction was prescribed to 17,55 x 1012 Nmm2/m after calculations using results from the tests. The stiffness in the secondary direction amounts to 4,5% of the primary directions stiffness, i e. 0,79 x 1012 Nmm2/m. To sum up, one can say that the stiffness is high in both directions compared to regular wooden floor systems.</p>
627

Passivhusen på Oxtorget

Brandt, Fredrik, Jonsson, Mathilda January 2008 (has links)
<p>Syftet med vårt examensarbete är att undersöka hur passivhus eller så kallade nollenergihus skiljer sig i funktion samt uppbyggnad från konventionella hus.</p><p>I vår undersökning tar vi upp hur utformning, orientering, material samt ett väl fungerande klimatskal påverkar energiförbrukningen.</p><p>Vi har tittat närmare på faktorer som sparar energi samt hur ett typiskt passivhus är uppbyggt. För att se hur teorin fungerar i praktiken har vi tittat närmare på befintliga passivhus, nämligen de på Oxtorget i Värnamo.</p><p>Vi har kommit fram till att passivhus fungerar och vi anser det som väldigt viktigt att man fortsätter driva fram arbetet och informera om dess betydelse för miljön.</p><p>Passivhus blir mer och mer uppmärksammat. De är något dyrare att bygga, men man tjänar in det i längden. Lönsamheten är dock inte det viktigaste utan känslan av att man gör något bra för miljön.</p> / <p>The main purpose with our diploma work is to examine how passive houses or so called zero energy houses differ in function and construction compared to conventional houses. In our research we present different things such design, orientation, materials and how a fully functional climate shell affects the energy consumption.</p><p>We’ve looked closer at some factors that save energy and how a typical passive house is constructed. To see how theory works in practice we have looked at existing passive houses, and that is the passive houses on Oxtorget in Värnamo.</p><p>We have come to the conclusion that the passive houses works and we believe that it is very important that we continues to carry on the work and inform people about its importance to the environment. Passive houses are becoming more and more noticed. They are somewhat more expensive to build but in time you will earn the money spent back. The profit is not the most important but the feeling that you do something good for the environment.</p>
628

Energideklaration av Svenska kyrkans byggnader i Växjö : utredning, deklaration och fördjupning nattkyla

Ericsson, Stefan, Evertsson, Torbjörn January 2008 (has links)
<p>Detta examensarbete syftar till att utreda vilka av Svenska kyrkans byggnader i Växjö som ska energideklareras samt utföra en energideklaration av en kontorsbyggnad. I energideklarationen ingår det även att ge åtgärdsförslag för olika energibesparingsmöjligheter. En fördjupad studie i nattkylning av stommen har också utförts. Examensarbetet är uppdelat i tre huvuddelar, indelning av byggnader, utförande av energideklaration samt fördjupad studie av nattkyla. I den första delen delas byggnaderna in i grupper utifrån verksamhet och byggnadstyp och därefter utreds om de ska energideklareras. Målet med denna indelning av byggnader är att Svenska kyrkan ska få vetskap om vilka av deras byggnader som berörs av lagen om energideklarationer. I andra delen görs en energideklaration för en kontorsbyggnad. Det visar sig att det finns en hel del energibesparande åtgärder som kan göras i kontorsbyggnaden. En del av åtgärderna är endast enkla åtgärder som inte kräver något större ingrepp i byggnaden för att utföras. I den tredje delen genomförs en fördjupad studie i nattkylning av stommen i byggnader, där tung och lätt stomme jämförs gentemot varandra. För att utföra jämförelsen används simuleringsprogrammet IDA Klimat och Energi. Resultatet av simuleringen visar ingen besparing av energi till följd av nattkylning av stommen i den simulerade byggnaden, vilket leder fram till en parameterdiskussion om hur olika parametrar påverkar lönsamheten vid nattkyla.</p> / <p>This diploma work aims to investigate which of the Swedish church’s buildings in Växjö that needs to be energy declared and also to perform an energy declaration of an office building. In the energy declaration there’s also included measures for various energy-saving potential. An in-depth study of night-cooling of the framework has also been performed. This diploma work is divided into three main parts, classification of buildings, carrying out the energy declaration and a depth study of night-cooling of the building’s framework. In the first part buildings where divided into different groups on the basis of activities and type of building and then investigated whether to be energy declaration or not. The objective of this classification of buildings is that the Swedish church will know which of their buildings that’s affected by the law concerning energy declarations. The second part is an energy declaration of an office building. It turns out that there are a lot of energy-saving measures that can be done in the office building. Some of them are only simple measures that don’t require any major interference in the building to be performed. In the third part is carried out an in-depth study of night-cooling of buildings’ frameworks, where heavy and light frames are compared against each other. In order to carry out the comparison the simulation program IDA Climate and Energy was used. The results of the simulation shows no saving of energy as a result of night-cooling of the building frame in the simulated building, which leads to a parameter discussion on how various parameters affecting the profitability of night-cooling.</p>
629

Hur följs kraven på tillgänglighet vid nybyggande av bostäder? : - En studie av utvalda bostadsprojekt i tre närliggande kommuner

Axelsson, Therese January 2008 (has links)
<p>The purpose of this study is to find out how housebuilding meets the demands of availability for people with some sort of disability. The rules and demands of availability are stated in Boverkets byggregler, BBR and the Swedish standard, SS 91 42 21:2006 (publ.5). The projects in this study are compared to the rules and demands of BBR and SS 91 42 21:2006 (publ.5). The rapport studies three different house projects in three different municipalities and the result shows that only three of these nine projects meet the demands of availability for disabled people.</p>
630

Shear walls for multi-storey timber buildings

Vessby, Johan January 2008 (has links)
<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>

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