The use of stainless steel in buildings is small but increasing, mainly due to the low maintenance costs, favourable corrosion resistance and aesthetic appearance. It is well known that stainless steel also performs better than carbon steel at elevated temperatures. The improved behaviour is mainly explained by the enhanced material properties and a favourable temperature dependent relationship between strength and stiffness that makes stainless steel less prone to buckling in fire.The objective of this work is to establish and validate a simple design model for Class 4 stainless steel box columns in fire. The proposed design model is verified through parametric studies performed with the finite element software Abaqus and the FE-model used for the parametric studies is validated towards Class 4 stub column tests at both room and elevated temperatures.The failure mode of Class 4 box columns is a combination of local and flexural buckling. The importance of taking the temperature dependent relationship between strength and stiffness into account is clearly seen in the results from the parametric study.The proposed design model is fully consistent with EN 1993-1-1 (2005) and its capability to predict failure loads at different steel temperatures is compared to the design model in EN 1993-1-2 (2005) and EN 1993-1-4 (2006) as well as the Design Manual for Structural Stainless Steel (2006). All design models are then compared to the results of the parametric study. The results show an improvement from a mean of 0,96 and COV=0,17 to a mean of 0,99 with a COV=0,12. Furthermore the proposed design model gives better results than the existing models for all cross-section classes when compared to all available test results. / Användningen av rostfritt stål som stommaterial i byggnader är i nuläget liten. Men, de senaste åren har en viss ökning skett, i huvudsak på grund av låga underhållskostnader, högt korrosionsmotstånd och av estetiska skäl. Nyligen genomförda forskningsprojekt har visat att rostfritt stål motstår höga temperaturer bättre än kolstål. Anledningen till detta beror i huvudsak på att förhållandet mellan styrka och styvhet vid höga temperaturer är mer fördelaktigt vilket gör att rostfritt stål är mindre bucklingsbenäget vid höga temperaturer.Syftet med detta arbete är att utveckla och validera en ny enkel beräkningsmodell för pelare i rostfritt stål av fyrkantrör i tvärsnittsklass 4. Den föreslagna beräkningsmodellen är verifierad med en parameterstudie utförd med finita elementprogrammet Abaqus. Den använda finita elementmodellen är i sin tur validerad mot utförda provningar på pelare i tvärsnittsklass 4 både i rumstemperatur och vid höga temperaturer.Brottmoden för pelare i tvärsnittsklass 4 är en kombination av lokal buckling och knäckning. Vikten av att ta hänsyn till det temperaturberoende förhållandet mellan styrka och styvhet framgår tydligt i resultaten från parameterstudien. Den föreslagna beräkningsmodellen är fullt kompatibel med EN 1993-1-1 (2005) och förmågan att förutspå brottlaster vid olika ståltemperaturer jämförs med beräkningsmodellerna i EN 1993-1-2 (2005) och Design Manual for Structural Stainless Steel (2006). Samtliga beräkningsmodeller jämförs sedan med resultaten från parameterstudien. Resultaten visar på en förbättring från medelvärdet 0,96 med spridningen COV=0,17 till ett medelvärde av 0,99 med spridningen COV=0,12. Beräkningsmodellen ger även bättre resultat än de ovanstående för alla tvärsnittsklasser vid en jämförelse med alla tillgängliga provningar.

The renewal of the existing housing stock is a slow progress and theexisting is quite old. The existing housing stock represents a largeamount of the bought energy need for heating and a simple method forquickly determining the energy performance is needed.There are many different methods for estimating the energyperformance of buildings. In this report the feasibility of using asingle-variate steady state method to investigate energy performancehas been tested. Bought energy need in single-family houses in a coldclimate has been observed during the cold period. The observationshave been made with the help of a measurement system requiring aminimal installation. The heat loss factor of the observed buildingshas been determined using the energy signature approach and differenttime scales have been tried.The result shows that to determine the heat loss factor of single-familybuildings, a single-variate method is valid. Daily averages are a goodtime scale for houses using radiators under the windows to heat thebuilding. Buildings with floor heating in concrete slab need to have alonger time scale, around 3 days.The method does not account for occupancy levels and separateenergy use in specific installations is not easy to estimate with theminimalized measurement setup. A combination of heat sources suchas district heating, electrical heating, heat recovery and/or fire stove isproblematic to handle with the energy signature method if enoughobservations for al heat sources can be achieved.

Purchasing, is an important part of the production process in industrialized house-building. Uncoordinated purchasing is one of the causes for low productivity increase within the sector. Traditional purchasing strategies, used by large construction companies, may not be applicable to small and medium-sized companies. It has been suggested that traditional purchasing strategies are not favorable for small industrialized house-building companies, because the relation between the buyer and the suppliers are characterized by short term project incentives rather that long term relationships.In order to secure low process variation in deliveries, quality and time, long term relationship in a form of supply chain collaboration is suggested. The position taken is that small and medium sized industrialized house-building companies could improve their supply chain process by developing products collaboratively with their customers, suppliers or both.Case studies to analyze the collaborative product development process have been conducted at small and medium sized industrialized house-building companies. The products developed in these cases have varied from simple to complex and the results have been studied from both the supplier and customer perspective in the industrialized house-building supply chain.The results indicate that the actors are valued differently. Value is an ambiguous term. Therefore, process improvements have been studied using ‘value stream mapping’ and simulated with a strategically selected performance measurement such as lead-time. Collaborative product development can be argued to increase purchasing process productivity. However, there are barriers, synthesized from supply chain management theory, that need to be addressed. Barriers to be taken into account in collaborative product development are that small companies have limited resources, that the legal structure does not support collaboration and that differences in maturity in ‘industrialized house-building thinking’ might hinder effective collaboration. However, the results do not conclusively prove or disprove the idea that collaborative product development can be used by small industrialized house-building companies.Further research into the application of purchasing and collaborative product development in the industrialized house-building and construction context with a dynamic model where time on market will affect what processes needed to be developed between the buyer and the supplier. / Inköp, som är en viktig del a tillverkningsprocessen inom industriellt byggande, är en av orsakerna till låg produktivitetsökning inom branschen. Traditionella inköpsstrategier, som används av större företag, är kanske inte tillämpbara för små och medelstora företag. Det har påvisats att dessa strategier inte är gynnsamma då relationen mellan köpare och leverantör karaktäriseras av kortsiktigt projekttänkande istället för långsiktiga relationer.För att säkerställa en låg process variation i form av säkra leveranser, tid och kvalitet, föreslås samverkan inom värdekedjan. Ståndpunkten är att små och medelstora företag inom industriellt byggande skulle kunna öka produktiviteten i värdekedjan genom att utveckla produkter tillsamman med sina kunder och leverantörer.Fallstudier har genomförts hos små och medelstora industriella byggare inom professionellt inköp i syfte att analysera gemensam produktutveckling. Produkter som studerats, både från ett kunds och från ett leverantörs perspektiv, har varierat från enkla till komplexa. Resultaten indikerar att aktörerna ser olika på värde. Värde är mångtydigt begrepp. Därför har process utveckling studerats med värdeflödesanalys och genom att simulera ledtid som ett strategiskt mätetal. Gemensam produktutveckling kan hävdas öka inköpsprocessens produktivitet, men det finns hinder som måste beaktas. Hinder och krav som bör beaktas vid gemensam produktutveckling är att små företag har små resurser, den legala strukturen stöttar inte gemensam produktutveckling och olika mognadsgrader i industriellt tänkande mellan aktörer är också ett hinder. Resultaten varken bevisar eller motsäger inte på ett otvetydigt sätt att gemensam produktutveckling kan användas för små och medelstora företag. Vidare forskning tillämpningen mellan gemensam produktutveckling som en inköpsstrategi inom industriellt byggande i byggomgivningen krävs genom att utveckla en dynamisk modell som är beroende av hur lång tid produkten har varit på marknaden. / TräIN, Lean Wood Engineering

In the present thesis, the application of fracture mechanics in design and assessment of steel structures has been studied.The first case study concerns a ring-flange connection used in wind turbine towers. The flange is rolled from straight steel profile into a complete ring. Subsequently, at the ends of the ring are welded by way of electron beam welding. This weld providing the integrity of the ring-flange was designed against fracture. To avoid potential failure by fracture and/or fatigue, the fracture mechanics approach for engineering assessments (as described in the Swedish handbook for safety assessment of structures containing defects) was implemented to predict the maximum allowable crack size. Material properties along with the design stress and crack size are the three variables that must be taken in account in order to design a structure against fracture. To this end, toughness and mechanical properties of the weld metal were experimentally determined. The results confirmed that the material behaves in a ductile manner and the electron beam welding has a positive effect on material properties. The fatigue performance of the flange was examined using the fatigue load histogram experienced by the flange in its 20years lifetime. Detailed finite element analyses of the flange connection were conducted to determine stress distribution at the most critical location along a hypothetical crack plane. The stresses obtained from the finite element analysis were used to assess the fracture stability of the flange. The fracture and fatigue assessment results confirmed that the flange in question is susceptible to fatigue failure which turns out to be the governing criterion in order to define the maximum allowable crack size. Furthermore, a parametric study was carried out to investigate the effect of parameters such as crack eccentricity, material properties and crack geometry on the integrity of the flange connection.The second case concerned the maintenance problem of roller bearings of relatively old bridges. These tend to rupture and no satisfactory explanation exists in the literature. Two broken specimens were supplied by the Swedish Transportation Authority (Trafikverket). These were first subjected to fractographic examination to determine the crack initiation location. Afterward, Charpy, compact tension, tensile and chemical composition specimens were machined out of the broken roller pieces and the respective tests were conducted. The results showed a very brittle material but no deviations from the prescribed material properties that were set forth in the 1967 certificate of application (Zulassung) of the rollers in question. To explain the observed failures a mechanical over-stressing condition was sought. Two such over-stressing sources were investigated. First the Hertz contact solution traditionally used in the design of roller bearings (both DIN 4141 and EN 1337-4) is valid for an infinite length cylinder. At the edges of the roller contact zone, stress singularities of the sort appearing in the case of a rectangular rigid body indenting an elastic half-space are likely to appear: three-dimensional finite element analyses were conducted and a 30% edge stress increase was established. As a second source of over-stressing the imperfections of welded I-beams according to EN 1090-2 were introduced into the FE model including, as before, the girder end, the roller assembly and the abutment. A wedge-type imperfection between the lower flange of the bridge girder and the lower support plate of the roller can create detrimental stress concentrations even at values no higher than 50% of the EN 1090 limits. Finally, the effect of the contact stresses in the roller was examined with a linear elastic fracture mechanics approach. It was found that surface cracks at the roller edge may become unstable in Mode-II when traversing the limits of the contact zone as this is the area of maximum shear stress: daily thermal cycles cause such cracks to go through a full plastic cycle as they are forced to swing past both edges of the contact area of the roller. This causes plastic strain accumulation at the crack tip of even small stable cracks: this mechanism causes them to grow until they become critical. A fracture assessment diagram for one of the broken rollers was computed.

In the majority of university cities in Sweden, a strong demand for student accommodations has initiated various development and research projects focusing on costs reduction and fast execution. The present thesis brings up a solution based on the development of a feasible assembly concept and process, for a Modular Building erection, where prefabricated 3D Modules are assembled into a sway steel frame. The concept has been initiated within FRAMEUP project: Optimization of Frames for Effective Assembling (RFCS contract RFS-PR-10121). One of the main project objectives was to investigate and develop a competitive structural system suitable for fast in-situ execution and dismounting. Thus, in order to streamline the construction process, the use of optimized prefabricated frames and room 3D modules has become a very attractive alternative. The building is designed considering a six-story building, as it has been seen as the suitable choice of industrial partners in the project on market demands for the optimal payoff time. The use of Intensive Use of Steel together with Modular Construction enhances the conditions for industrialization of the construction process towards the cost reduction.The development of the whole concept is described and followed up by a 4D construction sequence. The concept is based on the original structural system for which calculations, drawings and feasibility test at full scale are made to prove the credibility of the system. The 3D Modules are designed by Norrbotten based SME, which has influenced the global concept design. In addition, development of a novel joint, by means of laboratory tests and finite element models, is shown in the thesis. It is believed that its use in the frame, for the column splice connection, may be advantageous for the execution process. The issue of execution tolerances has been addressed by advanced FEA, which has been validated by experiments. / I majoriteten av svenska universitetsstäder har stark efterfrågan på studentbostäder initierat flera utvecklings- och forskningsprojekt med fokus på kostnadsbesparingar och snabbt uppförande. Föreliggande uppsats behandlar en lösning baserad på utveckling av ett koncept med prefabricerade byggnadsmoduler vilka monteras i ett ramverk av stål. Konceptet har initierats inom FRAMEUP-projektet Optimization of Frames for Effective Assembling (RFCS contract RFS-PR-10121). En av de främsta målsättningarna var att utveckla ett konkurrenskraftigt konstruktivt system som är lämpligt för såväl snabb montering som snabb nedmontering på plats. I syfte att effektivisera konstruktionsfasen är användning av optimerade prefabricerade ramar och rumsmoduler att attraktivt alternativ. Byggnaden är dimensionerad för sex våningar eftersom det har ansetts som ett optimum ur ett återbetalningsperspektiv av medverkande industriella partners. Användningen av koncepten Intensive Use of Steel och Modular Construction förbättrar möjligheterna till industrialisering av konstruktionsprocessen vilket möjliggör kostnadsbesparingar.Utvecklingen av hela konceptet är beskriven och följs upp med en 4D konstruktionssekvens. Konceptet är baserat på det ursprungliga konstruktiva systemet för vilket beräkningar, ritningar och genomförbarhetsprov i fullskala är utförda. Modulerna är konstruerade av SME i Norrbotten vilket har påverkat det övergripande konstruktionskonceptet. Därutöver redovisar uppsatsen utvecklingen av en ny typ av förband vilket undersöks med provning och FE-beräkningar. Det är tänkbart att användande av detta förband i ramverkets pelarskarvar kan leda till ett optimerat uppförande. Frågan om utförandetoleranser har adresserats med avancerade FE-beräkningar vilka har validerats med provningar. / FRAMEUP - Optimization of frames for effective assembling

Construction clients have the position to continuously improve new-built from a life cycle perspective. Furthermore, they can contribute to advancement and improved competition in construction by putting more explicit and distinct requirements and by a willingness to try new, non-local contractors and new construction methods (Statskontoret 2009). Conventional construction is argued to constitute a barrier to change (Dulaimi et al. 2003). Industrialised building, with its off-site characteristics and process-orientation, is seen as a means to attain advancement in construction (e.g. Statskontoret 2009). Industrialised multi-dwelling timber framed (ITF) housing entail all of the identified advantages of industrialisation. Nonetheless, clients are not actively driving change towards industrialised construction (e.g. Engström et al. 2009) and it was indicated that one possible explanation could be that clients are uncertain (Höök 2005). The aim of this thesis is to identify client organisations' uncertainties concerning ITF housing and property, find mechanisms for why they arise and propose measures to manage uncertainty within clients' organisations. The thesis is based on three appended papers and a detached technical report (Levander 2010). Empirical data consist of interviews, economic data, documentation and a questionnaire, they have been collected from in total 27 Swedish client organisations and on 44 ITF properties, and are analysed in two case studies and one field study.The results show that the great majority of client organisations' uncertainties are a matter of equivocality. The mechanisms for the high equivocality are the high complexity and uncertainty in construction in conjunction with the novelty encompassed by ITF housing and property. The current information processing practice within the studied client organisations does not support resolving equivocality.The general conclusion is that ITF housing and property is a radical change seen from clients' perspective and represents novelty in construction technology. Thus, the ITF alternative challenges and goes beyond clients' known frame of reference and thereby causes equivocality. In order to manage and resolve equivocality, client organisations need to enable translation and transfer of frameworks and their activities must constitute challenges to their normal practice. Thus it is proposed that in order to manage uncertainty and equivocality, and thereby contribute to advancements in construction, client organisations need to work with uncertainty management. / Fastighetsägare har i rollen som beställare möjligheten att ständigt förbättra nybyggnation från ett livscykelperspektiv. Dessutom kan de bidra till utveckling och ökad konkurrens inom byggbranschen genom ett tydligare kravställande och med en vilja att prova nya, icke-lokala entreprenörer och nya produktionsmetoder (Statskontoret 2009). Traditionellt byggande hävdas utgöra ett hinder för förändring (Dulaimi et al. 2003). Industriellt byggande, med byggande i fabrik och processorientering, ses som ett sätt att nå framsteg byggandet (ex Stadskontoret 2009). Industriellt byggande av flerbostadshus med trästomme för med sig samtliga fördelar med industriellt byggande. Trots detta är inte beställarna en aktiv kraft (Engström et al. 2009), en möjlig förklaring är att kunderna är osäkra (Höök 2005).Syftet med forskningen är att identifiera fastighetsägarorganisationernas osäkerheter om den industriella träbyggnadsprocessen och om industriellt byggda flerbostadshus med trästomme (ITF-alternativet), hitta mekanismer för varför osäkerheterna uppstår och föreslå åtgärder för att hantera osäkerhet inom kundorganisationer. Avhandlingen bygger på tre bifogade artiklar och en fristående teknisk rapport (Levander 2010). Empiriska data består av intervjuer, ekonomiska data, dokumentation och en enkät som har samlats in från totalt 27 svenska fastighetsägarorganisationer och på 44 ITF fastigheter, och sedan har analyseras inom två fallstudier och en fältstudie.Resultaten visar att kundernas osäkerheter främst är en fråga om tvetydighet (equivocality). Mekanismerna bakom denna är den höga komplexitet och osäkerhet inom byggbranschen generellt, tillsammans med det nya och annorlunda som ITF-alternativet medför. Det nuvarande sättet att hantera information och kommunikation inom de studerade fastighetsägarorganisationerna stödjer inte hantering av tvetydighet.Den allmänna slutsatsen är att ITF-alternativet är en radikal förändring sett ur kundernas perspektiv och representerar nyhet i flera dimensioner. Således går ITF-alternativet utanför kundernas kända referensram och medför därigenom tvetydighet. För att lösa tvetydighet krävs att kundorganisationerna möjliggör överföring av referensramar och aktivt utmanar sina nuvarande arbetssätt. Det föreslås därför att kundorganisationer behöver arbeta med osäkerhetshantering, detta för att kunna hantera och lösa både osäkerhet och tvetydighet, och därigenom bidra till framsteg inom byggandet.

During the last few decades the demand for renewable energy has led to a myriad of innovative solutions. The present assembling solution between two segments of a tubular tower is accomplished by conventional ring flange connection. This connection suffers from economical and technological barriers. One possible improvement could be achieved by implementing friction connections. Performance of this connection exposed to static loading is considered in this thesis. FEM is used as the main tool to improve understanding of the friction connection behaviour for application in towers for wind turbines. This new solution consists of the upper tower segment, where normal clearance holes are made and where bolts can be pre-installed, and the lower tower segment where opened slotted holes are made. It is easier to produce and 80% less expensive than traditional flange connection which leads to a total reduction of 10% to 15% of the tower costs.The influence of the level of assembling tolerances and the loss of pretension force in the bolts has been thoroughly investigated by a large number of FE models in the search for a model that is the most successful match with regards to its comparison with test data. Experiments are performed in an international project financed by RFCS, HISTWIN.The starting point is a small scale friction connection, best described as a single shear lap joint. This specimen represents a strip of the friction connection of a tubular tower. The ability of the FE models to capture three-dimensional contact problems, with realistic modelling of the assembling process and effects of the secondary bending during the loading are investigated. Resistance according to European codes, EN 1993-1-8, for the preloaded bolts is compared with the FE solutions.The second type of specimen is a down-scaled bending test of the beam. The test is used to check the performance of the connection and to calibrate the FE model. A very realistic FE model is created and compared with results from experiments. Failure modes and the respective ultimate resistances are predicted by FEA. The same model is used to investigate the influence of the gap between tubular segments and the influence of residual stresses generated in the segment which contains slotted holes on the tower resistance in bending, as well as in compression and tension. / Efterfrågan på förnyelsebar energi har under de senaste decennierna drivit fram ett stort antal innovativa lösningar. Idag är flänsar den vanligaste lösningen vid skarvar i rörformade vindkraftstorn. Det är en lösning som har både ekonomiska och tekniska brister. Friktionskoppling kunde vara en möjlig förbättring. I detta arbete studeras hur en sådan koppling skulle fungera under statisk last. FEM används som det viktigaste verktyget för att skapa förståelse för hur en sådan friktionskoppling fungerar i ett rörformat vindkrafttorn. Den föreslagna friktionskopplingen består av en övre del som har hål med bultar i längs nedre kanten, och en undre del som har skåror. Det är en konstruktion som är enklare att tillverka och som kostar 80% mindre än en traditionell flänskoppling. Det ger en total besparing för ett torn på mellan 10 och 15%. Betydelsen av det extra spelrum som tillåts för att förenkla monteringen och vad förlusten av förspänning i bultarna betyder har studerats i ett antal FEMmodeller för att hitta en modell som ger så bra överensstämmelse som möjligt med mätdata från försök gjorda i projektet HISTWIN som finansierats av RFCS. Första försöket är en liten del av hela friktionskopplingen, enklast beskriven som ett skjuvförband. FEM-modellens förmåga att beskriva den tredimensionella kontakten, en realistisk sammanfogning samt de olika böjfenomen som uppträder undersöks. De förspända bultarnas bärförmåga enligt Europakoden EN 1993-1-8 jämförs med FEM-lösningen. Den andra modellen är ett nedskalat böjtest på en balk. Modellen används för att undersöka hur friktionskopplingen fungerar och för att kalibrera FEMmodellen. En mycket realistisk FEM-modell skapas och beräkningsresultaten jämförs med gjorda försök. FEM-beräkningen ger både brottmod och brottlast. Samma modell används också för att studera betydelsen av glappet mellan de olika delarna i tornet samt betydelsen av spänningstillståndet i delen med skårorna när den belastas i både tryck och drag.

In this thesis the performance of different constitutive models in ratchet simulation is investigated. Ratcheting is accumulated plastic strains which may occur when a structure is subjected to a constant load in combination with cyclic loading. In the assessment of nuclear class 1 pressure retaining component ratcheting is one of the three failure modes that are addressed and may limit the design life of nuclear pressurized components and piping systems.A steel structure subjected to a constant load in combination with cyclic loading into the plastic region undergoes a change of the material characteristics in several aspects. These cyclic material characteristics are complex and may vary for different load situations, load levels, temperatures and materials. In addition to this, the presence of a mean stress may also affect the material cyclic characteristics.In previous numerical investigations on ratcheting there has not been a sufficiently robust case of simulation. However, in most of these investigations, the simulation response is compared with ratcheting experiments which either are conducted under load levels which are not common for a nuclear pressurized component, the experimental specimen is not comparable with a pressurized component or only a few experimental tests have been conducted. Hence, it has not been settled which material characteristics need to be considered to accurately simulate ratcheting in a pressurized piping component under load levels common in a nuclear power plants. As a result of this, it is not obvious which types of constitutive material models is needed and how the model parameters should be calibrated in order to simulate ratcheting in a nuclear component accurately.As part of this thesis an extensive experimental program has been conducted on pressurized tube specimens. In total 30 test specimens made of two different materials, 316L and P235, have been manufactured and tested. In order to determine material properties, monotonic tensile load and internal pressure experiments have been performed. The remaining test specimens have been used for ratcheting experiments.The experimental results show ratcheting in the hoop direction when the tube is subjected to certain combinations of internal pressure and cyclic axial strains. The higher the pressure is and the larger the strain ranges are, the higher the ratcheting response becomes. In addition to this, also the cyclic hardening and softening behavior in the tubes axial direction and the direction of the incremental plastic strain tensor is investigated. The results show that the material cyclic hardening or softening behavior and direction of the plastic strain vector varies strongly depending on the level of primary and secondary loads.Measured ratcheting strains are compared to numerical simulations using different constitutive models. In this thesis the interrelated models of Prager, Armstrong-Frederick and Chaboche are investigated. In addition to these, the Besseling model is investigated. Among the constitutive models investigated, the Besseling multi-linear model shows by far the best agreement with the ratcheting experiments. The more advanced models are able to capture the material ratchetingbehavior, but overestimate the hoop strain in the tube tests.Investigation results also indicate that significant cyclic hardening material behavior influence the direction of the plastic stain vector and, hence, affect the accuracy of predicted results when disregarded. This effect is most apparent for the experiments subjected to high pressure and high deformation controlled loads. In the tests which experience significant cyclic hardening, the direction of the plastic strain vector starts to deviate after roughly 20 loading cycles.Simulation of ratcheting should be done with an as simple constitutive model as possible, while still capturing the essential response. Important reasons are that simple models are easier to understand and work with, and that fewer tests are needed for determining model parameters. Based on this the Besseling constitutive model is recommended for simulation of pressure equipment subjected to cyclic plastic deformation. However, if shake-down does not occur at relative early stage, effects related to cyclic softening or hardening may need to be taken into consideration.

Combining computer fluid dynamic, CFD, models with finite element, FE, models to calculate temperature in fire exposed structures can reduce design temperatures in structures while still obtaining the level of structural fire safety stipulated by society. A better understanding of heat transfer and the concept of adiabatic surface temperatures, AST, the transition of data between models can be simplified and more accurate temperature predictions can be made.The thesis focuses on heat transfer calculations by employing AST in particular, and how this can be used as a means of coupling any CFD and FE-analysis code. The thesis presents a method for performing FE-analysis of the thermal response with input data calculated with the computer code FDS, Fire Dynamics Simulator. Parallel to this, the heat balance equation in FDS is tested and an alternate numerical algorithm is developed and tested.Firstly, a verification model is developed to test the radiative and convective part of the existing heat balance equation in FDS. An alternate numerical algorithm for calculation of the heat transfer at surfaces is developed as a more homogenous alternative for CFD codes.Secondly is a study on how to extract AST from an arbitrary point with direction in a CFD calculation using an infinitesimal surface. Instead of modeling numerous small surfaces for extracting AST, a post processor is developed to calculate AST independent of any modeled surface. For CFD codes, such as FDS that depend on a rectilinear grid, this enables calculation of AST in any direction, not only directions normal to the Cartesian planes.Finally, a comparison is made between different methods for calculating temperatures in steel with AST from numerical fire dynamics/modeling calculations. In this thesis there is a comparison between simplified Eurocode techniques, simple finite element analysis and advanced finite element analysis. This study shows the benefit of understanding heat transfer in numerical codes and to implement the concept of AST in a proper way.This way, the concept of combining numerical fire dynamics calculation with numerical (or simplified) thermal calculations can be better understood and implemented.

During recent years wind energy has established as an alternative to commonenergy sources. To advance its competitiveness, the costs for the constructionof a wind tower have to be reduced. One possible option is the use of frictiongrip joints instead of flange connections to join various tower segments in atubular steel tower. Additionally, the time necessary for installation andmaintenance of the bolts in these connections can be decreased, not only forimplementation in tubular towers but also in lattice towers.Four different bolt types have been investigated with respect to the ease ofinstallation and maintenance on the one hand and structural applicability on theother hand. The latter one is mainly defined by the behaviour of the pretensionforce in the bolts. Various influences on the reduction of clamping force areexperimentally checked, such as the type and thickness of coating, thethickness of the clamping package and external loading.The slip factor, which plays an important role in friction connections, isexperimentally achieved in a test on a double shear lap joint. The experiment isthoroughly examined by a finite element analysis, which models the interactionbetween bolts and plates.In various numerical analyses the influence of steel grade and possibleassembling tolerances on the resistance of a friction joint is investigated bothfor single and double shear lap joints.Shortages of EN 1993 parts 1-8 and 1-12 for the use of slip critical joints areidentified. / På senare år har vindenergi blivit ett allt vanligare alternativ till de mertraditionella energikällorna. För att ytterligare stärka konkurrenskraftenbehöver installationskostnaden för vindkraftverken minskas. Ett sätt att göradetta är att använda friktionsförband istället för att sammanfoga flänsarna hosde olika segmenten i vindkraftverk uppbyggda av stålrör. Man kan dessutomminska den erforderliga tiden för att montera och underhålla skruvarna i dessaförband, vilket inte bara gäller för rörkonstruktioner utan även förvindkraftverk av fackverkstyp.Fyra olika sorters skruvar har undersökts, å ena sidan avseende hur enkla de äratt montera och underhålla, å andra sidan avseende den strukturellatillämpligheten. Den senare beror huvudsakligen på beteendet hosförspänningskraften i skruvarna. Olika sorters påverkan påfastspänningskraften har undersökts experimentellt, exempelvis ytskiktenstjocklek, klämlängden samt den påförda yttre lasten.Friktionskoefficienten vid glidning, som har en viktig roll i friktionsförband,har erhållits experimentellt genom försök med ett tvåskärigt skjuvförband.Försöken har utvärderats noga med FE-analyser, där interaktionen mellanskruvar och plattor har modellerats.Inverkan av vald stålsort samt utförandetoleranser har undersökts genomnumeriska analyser för både enskäriga och tvåskäriga skjuvförband.Brister i EN-1993 del 1-8 och 1-12 har identifierats vid användning av förbandsom är känsliga för glidning