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  • 751.
    Veljkovic, Milan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Johansson, Bernt
    Design of thin-walled steel column with partially closed cross-section2006In: Proceedings of SDSS 2006: International Colloquium on Stability and Ductility of Steel Structures : [Lisbon, Instituto Superior Técnico, 06 - 08 September 2006] / [ed] Dinar Camotim, Lisboa: Instituto Superior Técnico , 2006, p. 639-647Conference paper (Refereed)
    Abstract [en]

    Cold formed sections can be optimized for different purposes and they are fairly inexpensive to produce in small series. They have an inherent weakness in their small torsional stiffness, which is unfavourable for columns. The solution presented here is to make closed section by adding a thin cover plate connected with self-tapping screws. It is here called a partially closed cross-section because it is not continuously and rigidly connected. The aim of this paper is to evaluate the efficiency of this solution by comparing the behaviour of partially closed and open cross-section. Four columns were tested within the project, two of them with centric axial load and two with eccentricities. Numerical analysis was performed using ABAQUS for establishing the influence of the cover plate on the critical load and the resistance. A good agreement between non-linear FEM and experiments were found. After this verification of the FE model a parametric study was carried out. Results of experiments and numerical analysis were compared with the predicted resistance by Eurocode 3, Part 1-3, and the Direct Strength Method.

  • 752.
    Veljkovic, Milan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Johansson, Bernt
    Design of uniformly compressed stiffened plates: a review of Eurocode 3-1-52000In: Coupled Instabilities In Metal Structures: Proceedings of the Third International Conference Held in Lisbon / [ed] Dinar Camotim; Dan Dubina; Jacques Rondal, Singapore: World Scientific and Engineering Academy and Society, 2000, p. 305-314Conference paper (Refereed)
  • 753.
    Veljkovic, Milan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Johansson, Bernt
    Light steel framing for residential buildings2006In: Thin-walled structures, ISSN 0263-8231, E-ISSN 1879-3223, Vol. 44, no 12, p. 1272-1279Article in journal (Refereed)
    Abstract [en]

    Building systems with light steel members, gypsum plasterboards and mineral wool have a wide spread use in the US, Australia and Japan and are gaining market in some European countries. The systems have often load-bearing walls and the floors may be of lightweight steel profiles or concrete. Such systems are suited for industrial production and can contribute to a more efficient building process. Examples of components and systems are given in the paper. For low and medium rise buildings it is natural to use the walls as stabilising for horizontal loads from wind and imperfections. In Sweden and Finland this has been common practice for single-family timber houses since the 1970s. The paper describes the traditional design model for walls with single-layer gypsum plasterboards and an extension to double layers, which are needed for fire protection in multi-storey buildings.

  • 754.
    Veljkovic, Milan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Johansson, Bernt
    Residual static resistance of welded stud shear connectors2006In: Composite Construction in Steel and Concrete V: Proceedings of the 5th International Conference / [ed] Roberto T. Leon; Jorg Lange, American Society of Civil Engineers (ASCE), 2006, p. 524-533Conference paper (Refereed)
    Abstract [en]

    Headed studs are widely used in composite bridges to provide longitudinal shear force transfer in the interface between concrete deck and steel beam. There is still no theoretical model available to describe the local failure mechanism and the resistance under the monotonic loading of the stud. The standard design of shear studs assumes that the static resistance is independent of fatigue. A test series on 12.5mm studs published by Oehlers however indicates a linear reduction of the static resistance with the number of cycles. In order to shed more light on this question a test series on 22mm studs was performed, which is the common size in bridges. The residual static resistance of shear studs after cyclic loading was measured using push tests according to Eurocode 4-1-1. The test program consisted of two series of tests. Five static tests were performed for establishing a reference static resistance and five residual strength tests were used to measure residual static resistance after cyclic preloading. In order to give an insight into the local failure mechanism under the monotonic loading a realistic 3D FE analysis of a single stud embedded in the concrete is presented. Results obtained from the FE model are compared with experiments and rather good agreement is obtained.

  • 755.
    Veljkovic, Milan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Johansson, Bernt
    Stabilizing light weight steel buildings with shear walls2005In: EUROSTEEL 2005: 4th European Conference on Steel and Composite Structures / [ed] B. Hoffmeister; O. Hechler, Aachen: Verlag Mainz , 2005, p. 1.8/25-1.8/33Conference paper (Refereed)
  • 756.
    Veljkovic, Milan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Johansson, Bernt
    Thin-walled steel columns with partially closed cross-section: tests and computer simulations2008In: Journal of constructional steel research, ISSN 0143-974X, E-ISSN 1873-5983, Vol. 64, no 7-8, p. 816-821Article in journal (Refereed)
    Abstract [en]

    Cold formed sections can be optimized for different purposes and they are fairly inexpensive to produce in small series. They have an inherent weakness in their small torsional stiffness, which is unfavourable for columns. One solution presented here is to make a closed section by adding a thin cover plate connected discretely with self-tapping screws. It is here called a partially closed cross-section because it is not continuously and rigidly connected. The aim of this paper is to evaluate the efficiency of this solution by comparing the behaviour of partially closed and open cross-section. Four columns were tested within the project, two of them with centric axial load and two with eccentricities. Numerical analysis was performed using ABAQUS for establishing the influence of the cover plate on the critical load and the resistance. A good agreement between non-linear FEM and experiments were found. After this verification of the FE model a parametric study was carried out. Results of experiments and numerical analysis were compared with the predicted resistance by Eurocode 3, Part 1-3, and the Direct Strength Method. Both design methods give good predictions of the resistance.

  • 757.
    Veljkovic, Milan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Koukkari, H.
    Borg, R.P.
    Stoian, V.
    Plewako, Z.
    Overview on eco-efficiency of constructions2011In: Summary report of the Cooperative Activities of the Cost Action C25: Sustainability of Constructions. Integrated Approach Towards Sustainable Constructions, 2011, p. 177-187Chapter in book (Other academic)
  • 758.
    Veljkovic, Milan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Koukkari, Heli
    VTT Technical Research Centre of Finland, Espoo.
    Braganca, Luis
    University of Minho, Guimarães.
    Survey on educational material on sustainable constructions2008In: Proceedings of Seminar on Sustainability of Constructions - Integrated approach to life-time structural engineering: COST Action C25, Dresden, Germany 6.-7.10.2008, 2008, p. 1.59-1.67Conference paper (Other academic)
    Abstract [en]

    Higher education of professionals in the construction and real estate sector is in the process of "Greening curricula". Pressures to educate environmentally literate workforce are increasing. The literature survey shows that technical universities worldwide have incorporated modules, courses and programmes of sustainable construction. In general, new teaching methods and approaches are regarded as necessary due to the complexity of the triple bottom-line issues of the sustainable construction. In addition to traditional lecturing and exercises, life-cycle and overall performance matters are taught by methods of team-work, problem-solving and learning-by-doing. The material for this study was gathered from literature and virtual site visits of universities as well as a questionnaire among the participants of the COST C25. First remarks concerning all the material is that there are still few technical universities with a cross-cutting strategy about sustainability.

  • 759.
    Veljkovic, Milan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Limam, Marouene
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Heistermann, Christine
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Rebelo, Carlos
    University of Coimbra.
    Silva, Luis Simoes da
    University of Coimbra.
    Feasibility study of friction connection in tubular towers for wind turbines2010In: Steel structures: culture & sustainability 2010: international symposium, Istanbul, 21 - 23 September 2010, Istanbul: Turkish Constructional Steelwork Association , 2010Conference paper (Refereed)
    Abstract [en]

    In steel tubular towers flange connections are used to assemble two segments of the tower. As an alternative for these fatigue-sensitive joints a new type of friction connection has been investigated both in laboratory and at a production plant where the feasibility study was performed. The specimen used in the feasibility test consists of two tower segments, each about 3m high and 2 m in diameter. The segments are connected by 222 M30 high-strength bolts. The production process and tolerances achieved are briefly explained. The assembling process is modeled using a realistic FEA model to predict the stress in the segments during pretensioning. A simplified FE analysis was performed to assess the influence of the compressive strength of the specimens. This paper presents results of a short parametric study on the influence of the gap between two tower segments exploring possibilities to use higher-strength steel in the towers. Keywords: Finite Element Model, Gap, High Strength Friction Grip Connection, Tubular Steel Tower, Wind Energy Converter

  • 760.
    Veljkovic, Milan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lopez, Nuno
    University of Naples.
    Real, Paulo Vila
    University of Naples.
    Uppfeldt, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Silva, Luis Simoes da
    University of Coimbra.
    Franssen, Jean-Marc
    University of Liège.
    Bouchaïr, Hamid
    Polytech' Clermont-Ferrand.
    Muzeau, Jean-Pierre
    Polytech' Clermont-Ferrand.
    Vassart, O
    Bacinskas, Darius
    Vilnius Gediminas Technical University.
    Kaklaskaus, Gintaris
    Vilnius Gediminas Technical University.
    Gribniak, Viktor
    Vilnius Gediminas Technical University.
    Nigro, Emido
    University of Naples.
    Cvetkovska, M
    Lazarov, L
    Cefarelli, G
    Structural member behaviour and analysis in case of fire2008In: Urban Habitat Constructions under Catastrophic Events: COST Action C26 / [ed] Federico M Mazzolani, Valetta: Editura Universitatii de Vest din Timisoara / University of the West Timisoara Publishing House, 2008, p. 45-50Conference paper (Other academic)
  • 761.
    Vessby, Johan
    et al.
    Linnaeus University, Växjö, Linnéuniversitetet.
    Källsner, Bo
    School of Engineering, Linnæus University, Växjö, Linnéuniversitetet, Linnaeus University, Växjö.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Olsson, Anders
    Faculty of Technology, Linnaeus University.
    Evaluation of softening behaviour of timber light-frame walls subjected to in-plane forces using simple FE models2014In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 81, p. 464-479Article in journal (Refereed)
    Abstract [en]

    The present investigation focuses on evaluating the entire load–displacement relationship, especially the softening part, of light-frame wall segments subjected to in-plane monotonic forces when the load-slip curves of the individual sheathing-to-framing fasteners are considered. Different sheathing-to-framing joint characteristics, including unloading behaviour, and stud-to-rail joint characteristics are incorporated in the analyses. Two loading cases are investigated: Horizontal loading resulting in uplift of the leading stud and diagonal loading representing a fully anchored wall.Two common types of finite element (FE) models for the sheathing-to-framing joints are used for the analyses: A single spring model and a spring pair model, where the joint characteristics valid for the timber properties perpendicular and parallel to the grain are used. The maximum capacity of the wall segments is somewhat overestimated when using the spring pair model compared to that of the single spring model. The softening parts of the load–displacement curves are significantly affected, regardless of whether the perpendicular or parallel characteristics of the joints are used.The results from FE simulations using models with perpendicular and parallel characteristics are compared with full scale test results for walls with a single segment loaded horizontally and diagonally. The behaviour of the wall segments subjected to horizontal loading is dominated by fastener displacements perpendicular to the bottom rail. Hence, FE models including perpendicular characteristics should be used. For diagonal loading the behaviour of the wall segments is dominated by displacements parallel to the framing members, and FE models including parallel characteristics should therefore be used.The analyses were extended to multiple segment walls resulting in the same type of behaviour as single segment walls.

  • 762.
    Vicente, Guiomar
    et al.
    ISISE, Department of Civil Engineering, University of Coimbra.
    Andrade, Pedro
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simões, Rui
    ISISE, Department of Civil Engineering, University of Coimbra.
    Rebelo, Carlos
    ISISE, Department of Civil Engineering, University of Coimbra.
    Silva, Luís Simões da
    ISISE, Department of Civil Engineering, University of Coimbra.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sistema Inovador de Construção Metálica: FRAMEUP2015Conference paper (Refereed)
    Abstract [en]

    The methodology developed under the project FRAMEUP includes the construction of residential buildings from the top to the base, whose compartments are prefabricated modules. The construction begins with the execution of the roof, on the ground level, which is later on lifted, allowing from beneath the construction of the lower floors, while it protects them from the weather. The construction ends with the execution of the ground floor. It is adopted a framed structure with tubular sections for which the beam-to-column connections are developed and the columns-splices designed to facilitate and the use of this constructive methodology.

  • 763.
    Viking, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Byggkravsutredningen missar målet: Industriella byggares syn på särkrav2014In: Samhällsbyggaren, ISSN 2000-2408, Vol. 2014, no 6, p. 38-39Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Vi menar att den definition av termen kommunala särkrav som används av Byggkravsutredningen är för snäv för att vara riktigt meningsfull för det industriella byggandet. De förbättrade förutsättningarna för industriellt byggande som utlovats till följd av de lagändringar som träder i kraft vid årsskiftet riskerar därför till stor del att utebli.

  • 764.
    Viking, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Föreslagna ändringar i plan- och byggprocessen: En workshopdokumentation2014Report (Other academic)
    Abstract [sv]

    Denna rapport är en delrapportering inom ramen för forsknings- och utvecklingsprojektet ATTRACT (Attractive and Sustainable Cities in Cold Climate). Rapporten presenterar resultaten från en workshop som genomfördes 25/2 2014 i Malmberget med temat: Föreslagna ändringar i plan- och byggprocessen. Bakgrunden till workshopen var det större antal statliga utredningar, promemorior, lagrådsremisser och riksdagspropositioner som det senaste året lagt fram förslag på förändringar av den svenska plan- och byggprocessen. Workshopdeltagarna fick möjlighet att diskutera hur dessa förslag skulle påverka plan- och byggprocessen med särskilt fokus på effektivitet och kvalitet, två viktiga aspekter vid samhällsomvandlingarna i Malmfälten.Ett antal återkommande teman dök upp i de diskussioner som hölls och sammanfattningsvis kan sägas att förslagen möttes med blandad entusiasm. Framför allt tyckte deltagarna att det är viktigt att hitta en balans mellan effektivitet och kvalitet. Allt arbete måste göras ordentligt, annars riskerar processen att dras ut av långsamma överklagandeprocesser. Samtidigt är det svårt att utvärdera förslagen eftersom ett större antal intressenter är involverade i plan- och byggprocessen och alla dessa påverkas på olika sätt.Deltagarna menade också att det är viktigt att åstadkomma en röd tråd genom planeringen för hållbarhetsfrågor för att konsekvent och med hjälp av stringent uppföljning och dokumentering kan arbeta strukturerat med att konkretisera hållbarhetsdimensionerna allteftersom processen fortskrider.

  • 765.
    Viking, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Industriella byggföretags syn på kommunalt kravställande2014Report (Other academic)
    Abstract [sv]

    Efter mer än två decennier av otillräckliga produktionsvolymer på bostadsmarknaden lider Sverige nu i allt ökad utsträckning av en brist av bostäder i allmänhet och av små, billiga bostäder i synnerhet. Industriella byggare symboliserar ett sätt att, genom användning av standardiserade processer och byggsystem, bygga bostäder mer kostnadseffektivt än med traditionella metoder men för att uppnå full effekt krävs förutsägbara villkor. Rätten för svenska kommuner att ställa krav på lokala byggprojekt ärcentralt i svensk byggrätt. Sentida samhällsförändringar har dock ökat kommuners behov av att profilera sig själva i en allt hårdare kamp om invånare, företagsetableringar och resurser. Detta har gjort dem mer benägna att tillämpa rätten till kravställning på byggprojekt i en högre utsträckning än tidigare.Bakgrunden till förstudien som presenteras i den här rapporten är att många industriella byggare uttrycker att det finns problem i gränssnittet mellan industriellt byggande och den kommunala planeringen. Denna rapport är en delrapportering inom ramen för projektet och presenterar preliminära resultat och analys av empiriskt material insamlat under en förstudie som genomförts mellan augusti 2013 och januari 2014. Rapporten syftar till att presentera den empiri och de resultat som hittills genererats. Materialet består av intervjuer med representanter från fem industriella byggföretag. Resultaten visar att förekomsten av kommunalt särkravsställande i Sverige idag är tämligen utbredd. Mycket pekar på att byggprojekt situerade i resursstarka centralt belägna kommuner drabbas hårdast av denna företeelse. Industriella byggkoncept bygger på upprepning och stordriftsfördelar och alla individuella krav som tvingar till avsteg från det industriella byggsystemet vara sig i form av tekniska lösningar eller måttsättningar leder till ökade omkostnader som i slutändan återspeglas i boendekostnaderna. Byggarna tillämpar ett antal olika strategier för att hantera kommunal kravställning. En strategi är att försöka förebygga särkravsproblematik genom att ta sig in tidigt i processen, en annan att på förhand försöka inventera vilka särkrav som kan tänkas ställas och på så sätt undvika projekt som väntas bli för krångliga. En tredje strategi verkar vara att identifiera kommuner som är särskilt viktiga och att anpassa sig efter deras särkrav. Gemensamt verkar dock vara en önskan om att föra dialog imening att skapa förståelse och samverkan för att navigera runt de mest snåriga kraven. Det förefaller dock inte som att någon av dessa strategier ger fullständigt tillfredsställande resultat. I detta läge kan man bara spekulera kring orsakerna till kommuners agerande, dock framgår tydligt att faktorer på både individ- och organisationsnivå spelar in. Kommunalt särkravsställande grundar sig i de bästa intentioner men resulterar inte alltid i de bästa utfallen. De industriella byggarna har teorier om varför kommuner agerar som de gör, men har inte en full förståelse för deras situation. De teman som identifierats i intervjumaterialet ger en generell förklaring av grundproblematiken mellan industriellt byggande och kommunal planering men det finns fortfarande en diskrepans mellan dessa och den utförliga intervjudatan. Därför krävs fortsatta analyser för att åstadkomma en ökad förståelse för de bakomliggande orsaker som finns och inte minst de konsekvenser som uppstår till följd av kommunalt särkravsställande. Fortsatta studier bör dessutom belysa det kommunala perspektivet.

  • 766.
    Viking, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lidelöw, Sofia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Exploring industrialised housebuilders' interpretations of local requirement setting using institutional logics2015In: Construction Management and Economics, ISSN 0144-6193, E-ISSN 1466-433X, Vol. 33, no 5-6, p. 484-494Article in journal (Refereed)
    Abstract [en]

    Industrialized housebuilding contractors use standardized processes and building systems to improve time and cost efficiency. Recent governmental investigations argue that Swedish local planning authorities’ requirement setting practices stifle the potential for increased industrialization. Yet, no previous research has accounted for the industrialized housebuilders’ perspective. We aim to explore industrialized housebuilders’ interpretationsof local requirement setting, using institutional logics to increase the understanding of how structure and human agency influence the emergence of local requirements. Interviews were conducted with representatives of fiveindustrialized housebuilders who together span the Swedish multi-family housing market. Findings indicate that industrialized housebuilders do not perceive intentional local requirement setting as problematic, yet struggle tocope with interpretive local requirement setting. Findings also necessitate distinguishing local requirement setting in the exercise of public authority from local requirement setting in public procurement. The agency structure dualism contributes an understanding of interpretive local requirement setting in the exercise of public authority as an expression of agency and of local requirement setting in public procurement as one of structure. Furthermore, using an institutional logics approach is found to provide an accentuation of human agency and the individual level of analysis that is often absent from construction management research.

  • 767.
    Viking, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lidelöw, Sofia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Exploring industrialised house-builders' perceptions of local requirement setting: An institutional logics perspective2014In: Procs 30th Annual ARCOM Conference: 1-3 September 2014, Portsmouth, UK / [ed] Ani Raiden; Emmanuel Aboagye-Nimo, Reading: Association of Researchers in Construction Management , 2014, Vol. 2, p. 1133-1142Conference paper (Refereed)
    Abstract [en]

    Industrialised house-builders (IHBs) are housing contractors who use standardised processes and building systems as a means to time and cost efficiently address the current housing shortage in Sweden. Recent governmental investigations argue that the mandate for local planning authorities (LPAs) to intentionally set stricter requirements than those prescribed in the national building code can stifle the potential for increased industrialisation. The aim of this paper is to explore IHBs’ perceptions of local requirement setting (LRS). It seeks to use the concept of institutional logic to advance the understanding of how LRS affects IHBs. Data was collected through in-depth interviews with representatives of five IHBs encompassing a mix of building systems spanning the Swedish multi-family housing market. From the data we identify three distinct categories of LRS: intentional, interpretive and public procurement-related. The respondents' perceived issues with LRS are found to relate more closely to the process of setting requirements than to the requirements themselves. The political debate about LRS has entirely neglected interpretive LRS, LRS in public procurement as well as the entire process perspective. Institutional logics is shown to offer new and interesting perspectives on the agency/structure dominated cognitive and intra-organisational processes that shape the emergence of local requirements in interpretative LRS and LRS in public procurement respectively. Since LRS is affected both by individual planning officers (agency) and the LPA organisation (structure) further studies will explore their perceptions of LRS.

  • 768.
    Viking, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stehn, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Exploring Swedish local planning authorities' perceptions of standardized housing construction2015In: Procs 31st Annual ARCOM Conference: 7-9 September 2015, Lincoln, UK / [ed] Ani Raidén; Emmanuel Aboagye-Nimo, Reading: Association of Researchers in Construction Management , 2015, Vol. 2, p. 1053-1062Conference paper (Refereed)
    Abstract [en]

    We explore how Swedish Local Planning Authorities perceive standardized housing construction and attempt to use an ideal type typology of institutional logics to describe how Local Planning Authorities make use of the multiple institutional logics available to them. Increased standardization in Swedish housing construction has been suggested as a means to meet the growing need for housing with reasonable rent levels. However, housing contractors that use standardization and repetition of processes and components claim that the variation of requirements set by Local Planning Authorities prevents them from taking full advantage of their standardization. A recent empirical study of standardized housing contractors’ perceptions suggests that Local Requirement Setting, the requirement setting practices of Local Planning Authorities, are interpretational responses to a lack of familiarity with standardized housing construction. Yet, Local Planning Authorities’ perceptions of standardized housing construction have never previously been explored. Empirical material for this on-going study was collected through in-depth exploratory interviews with local planning officers from three municipalities situated in Swedish population growth regions. Findings suggest that Local Planning Authorities perceive potential benefits with standardization, but ultimately expect standardized housing concepts to adapt to local standards for processes and products. In projects with high ambitions for architectural quality standardized housing concepts need to be highly flexible. Conversely, highly standardized housing concepts benefit from project ambitions that favour reasonable rent levels. Therefore, Local Requirement Setting is indicative of a mismatch between the Local Planning Authority’s project ambitions and the standardized housing contractor’s degree of product standardization.

  • 769.
    Viklund, Emma
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Design approaches in industrialized house building: A creativity perspective2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Industrialized house builders strive towards structure and control of their processes, including design. Such structure is seldom sought for in architectural design practice, where individuality and autonomy are considered essential. This is causing a tension in the construction industry as industrialized house builders and architects strive to improve their collaboration. In this licentiate thesis, a first step towards better understanding this tension is taken by exploring different design approaches from a creativity perspective. The analytical framework builds on a theoretical conceptualization of design approach features, including design task, design process, design organization, and knowledge sharing. A creativity perspective is added using heuristic or algorithmic design tasks; divergent or convergent design processes; autonomy or imposed structure from the design organization; and sole designer or teamwork as the basis for knowledge sharing. This framework is used to analyze four empirically explored design approaches, two focusing on platform development and two focusing on project specific design. Three of these are explored using a case study approach, while the fourth is explored through interviews with multiple architects.

    The architectural design approach’s features seem likely to facilitate creativity: the design task is mainly heuristic; the design process enables divergence; and the architects have autonomy in how to go about the design process. However, they experience a lack of knowledge sharing, which could further facilitate creativity. The studied standardized design development approach has the opposite features: the design task is mainly algorithmic; the design process facilitates convergence; and there is a clear structure with instructions of how each subtask should be executed. Hence, this design approach is not likely to facilitate creativity (which was also not its intention). The structure has however improved the design team’s knowledge sharing, which is likely to facilitate creativity.

    The two platform development approaches have a mix of features. Both design tasks are more algorithmic than heuristic and creativity was not expected of the design results. The design processes are clearly convergent. While the house platform development team is multi-functional and work in close collaboration, the design automation platform developers’ knowledge sharing is based on communication with the client’s organization, thus not enabling as many perspectives on the designed product. The design automation platform developers use a support structure with process descriptions and methods to ensure quality, motivated by the variety of platforms that they develop on a regular basis. The house product platform developers on the other hand, were expected to develop only this one platform. Hence, they worked autonomously, using the teamwork setting to progress and converge in the process.

    In summary, the creative intention seems related to how design is approached. If creativity is sought for, the design task is heuristic, and divergence and autonomy is promoted. If creativity is not sought for, structure seem to facilitate other benefits such as reliability and quality control. Knowledge sharing could however be potentially beneficial in most design approaches. By understanding that different design approaches will influence creativity in different ways, a first step has been taken towards understanding why architects and industrialized house builders approach design differently.

  • 770.
    Viklund, Emma
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Sandberg, Marcus
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Lidelöw, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Jansson, Gustav
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Modularization based on commonalities in house-building requirements2017In: ICCREM 2016: BIM Application and Offsite Construction - Proceedings of the 2016 International Conference on Construction and Real Estate Management 2016 / [ed] Wang Y.,Al-Hussein M.,Shen G.Q.P.,Zhu Y., Reston, VA: American Society of Civil Engineers (ASCE), 2017, p. 126-134Conference paper (Refereed)
    Abstract [en]

    Some of the requirements governing the design of houses are common between projects. This opens up for using modularization based on product commonalities. Though modularization is well known in the manufacturing industry, its use in house-building contexts is less studied. Even more scarce is research focusing on how requirement commonalities between one-of-a-kind products are found and managed in a modularization process. In this research, modularization from a requirements management perspective is empirically explored using a case study approach. Though the studied modularization process can be described as sequential, the process steps are highly interrelated, with overlaps and iterations. Commonalities are found by functional decomposition of the customer's portfolio projects, tracing technical solutions back to their initial requirements. These are balanced with the customer's requirements on the product and on the design automation tool. The requirement list is continuously updated based on portfolio analysis and communication of modularization results to the customer

  • 771.
    Vikström, Matilda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Edlund, Desirée
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Byggnadstekniska lösningar för brandskydd på radhusvindar2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 772.
    Völling, Boris
    et al.
    Lehrstuhl für Stahlbau und Leichtmetallbau, RWTH Aachen.
    Sedlacek, Gerhard
    Lehrstuhl für Stahlbau und Leichtmetallbau, RWTH Aachen.
    Pak, Daniel
    Lehrstuhl für Stahlbau und Leichtmetallbau, RWTH Aachen.
    Clarin, Mattias
    Zum Beulverhalten kaltgeformter und geschweisster Rechteckhohlprofile aus hochfestem Stahl2006In: Stahlbau, ISSN 0038-9145, E-ISSN 1437-1049, Vol. 75, no 11, p. 889-896Article in journal (Refereed)
    Abstract [en]

    New structural steels, such as (liquid) quenched and tempered (QT) steels, with extra high strength, good toughness and weldability have been developed in Europe in recent years and are included in Eurocode 3 Part 1-12 for strengths up to S 700. However, extra high strength steels (EHSS) with a yield strength of 1100 N/mm2 so far have not been taken into account in the present version of Eurocode 3 due to insufficient knowledge on their buckling behaviour and fatigue strength and lack of associated experimental data. In this article results of experimental and numerical investigations concerning the local buckling behaviour of cold-formed and welded hollow sections made of EHSS are summarised. The investigations have been carried out within the scope of an European research project. Results have been used to check the applicability of existing design rules for local buckling to EHSS. As a consequence the scope of Eurocode 3, Part 1.12 could be expanded to cover stability rules also for such steels.

  • 773.
    Wahl, Emma
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Buildings in Arid Desert Climate: Improving Energy Efficiency with Measures on the Building Envelope2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Because of the harsh climate of Saudi Arabia, residential buildings on average, consume more than half of the total consumed energy. A substantial share of energy goes to the air-conditioning of buildings. Cooling buildings during summer is a major environmental problem in many Middle Eastern countries, especially since the electricity is highly dependent on fossil fuels. The aim of this study is to obtain a clearer picture of how various measures on the building envelope affects the buildings energy consumption, which can be used as a tool to save energy for buildings in the Middle East.

    In this study, different energy efficiency measures are evaluated using energy simulations in IDA ICE 4.7 to investigate how much energy can be saved by modifying the building envelope. A two-storey residential building with 247 m2 floor area is used for the simulations. The measures considered are; modifications of the external walls, modification of the roof, window type, window area/distribution, modification of the foundation, shading, exterior surface colour, infiltration rate and thermal bridges. All measures are compared against a base case where the building envelope is set to resemble a typical Saudi Arabian residential. First, all measures are investigated one by one. Thereafter, combinations of the measures are investigated, based on the results from single measure simulations. All simulations are carried out for two cities in Saudi Arabia, both with arid desert climate. Riyadh (midlands) with moderately cold winters and Jeddah (west coast) with mild winter.

    The results from simulations of single measures show the highest energy savings when changing the window type from single clear glass to double glass with reflective surface saving 27 % energy (heating & cooling) in Riyadh and 21 % in Jeddah. Adding insulation to an uninsulated roof saved up to 23 % and 21 % energy for Riyadh respectively Jeddah. Improvements of the thermal resistance of the exterior walls show 21 % energy savings in Riyadh and only 11 % in Jeddah. Lowering the window to wall ratio from 28 % to 10 % and changing the window distribution results in 19 % (Riyadh) and 17 % (Jeddah) energy savings. Adding fixed shades saves up to 8 % (Riyadh) and 13 % energy (Jeddah) when dimensioned for the peak cooling load. Using bright/reflective surface colour on the roof saves up to 9% (Riyadh) and 17 % (Jeddah) when the roof is uninsulated. For the exterior walls, bright/reflective surface saves up to 5 % (Riyadh) and 10 % (Jeddah) when the walls are uninsulated. The other single measures investigated show less than 7 % energy savings.

    The results for combined measures show the highest energy savings for two combined measures when improving the thermal resistance of the exterior walls and changing window area/distribution saving up to 52 % (Riyadh) and 39 % (Jeddah). When performing three measures the addition of improved thermal resistance and reflectance of the windows resulted in the highest energy savings, saving up to 62 % (Riyadh) and 48 % (Jeddah). When adding a fourth measure, improving the thermal resistance of the slab shows the highest energy savings, 71 % (Riyadh) and 54 % (Jeddah). Applying all measures on the building envelope results in 78 % (Riyadh) and 62 % (Jeddah) energy savings.

    Significant energy savings can be achieved with measures on the building envelope. Major savings can be made by adding only 50-100 mm of insulation to the exterior walls and roof. Decreased window area and improvements on the thermal resistance and reflectance on the windows result in significant energy savings. Energy savings achieved with shadings and reflective surface colours decrease significantly when the thermal resistance of the roof and external walls are improved. All measures concerning thermal resistance have a higher impact in Riyadh than in Jeddah due to that a large part of the total heating and cooling is air handling unit (AHU) cooling in Jeddah. AHU cooling is not affected significantly by measures on the building envelope. To optimise energy savings, measures on the building envelope should be considered in combination with measures concerning the AHU.  

  • 774. Wald, F.
    et al.
    Moore, D.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Eliášová, M.
    Continuing education in structural connection2004In: Innovative Steel Connections: June 3-5, 2004, Radison SAS H., Amsterdam, Netherlands, Amsterdam: American Institute of Steel structures , 2004, p. 37-44Conference paper (Other academic)
    Abstract [en]

    The European project Continuing Education in Structural Connections (CeStruCo) under Leonardo da Vinci initiative No. CZ/00/B/F/PP-134049 was prepared by partners from seven European countries to disseminate the latest results in research and standardization during the period of transferring the European Pre-Standard into the European Standard. The project has started by a collection of questions from the European practice. The answers to those questions have been prepared in the form of textbooks in the project partners national languages. The material is available as an easily accessible Internet/CD (www.fsv.cvut.cz/cestruco) media, and includes video and audio files, slides and worked examples.

  • 775.
    Wargsjö, Agneta
    Luleå tekniska universitet.
    Plastisk rotationskapacitet hos svetsade stålbalkar1991Licentiate thesis, monograph (Other academic)
  • 776. Wargsjö, Agneta
    et al.
    Johansson, Bernt
    Plastic rotation capacity for steel girders with slender webs1993In: Proceedings, Nordic Steel Colloquium, ECCS Annual Meeting: Odense, Danish Steel Institute, September 1991, Odense: Danish Steel Institute , 1993Conference paper (Other academic)
  • 777.
    Wenicke, Brian
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Lidelöw, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Stehn, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Flow and resource efficiency measurement method in off-site production2017In: IGLC 2017: Proceedings of the 25th Annual Conference of the International Group for Lean Construction 2017 / [ed] Brilakis I.,Walsh K.,Sacks R., The International Group for Lean Construction , 2017, p. 861-868Conference paper (Refereed)
    Abstract [en]

    Although the focus remains primarily on high resource efficiency, the significance of flow efficiency in construction is continuously increasing. Flow and resource efficiency describe two competing target viewpoints, which focus on reducing non-value adding activities and maximizing resource utilization, respectively. Recent research has shown that balancing both perspectives provides a viable solution. However, the exact measurement of flow and resource efficiency in construction remains unclear. Therefore, the aim of this work is to evaluate a possible flow and resource efficiency measurement method in the off-site production context of volumetric element construction, and assess the industrial relevance thereof. Work sampling has been used to collect data from a building project flowing through the off-site production system. The validity of the method has been checked statistically, through a focus-group workshop and with calculation figures from the case company. Work sampling allows flow and resource efficiency measurements in an off-site production system. The method delivers current status figures of companies, yielding a balance between flow and resource efficiency.

  • 778.
    Wernicke, Brian
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Lidelöw, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Foundation for Balancing Resources and Flow Efficiency in Industrialized Construction2017In: ICCREM 2016: BIM Application and Offsite Construction - Proceedings of the 2016 International Conference on Construction and Real Estate Management 2016 / [ed] Wang Y.,Al-Hussein M.,Shen G.Q.P.,Zhu Y., Reston, VA: American Society of Civil Engineers (ASCE), 2017, p. 103-110Conference paper (Refereed)
    Abstract [en]

    Construction companies traditionally try to optimize their resource efficiency to minimize costs. Today's demand for value stream optimization along the whole supply chain cannot be resolved by that approach. To be able to strengthen the performance of the fragmented construction, supply chain measuring flow efficiency is essential to meet the customer's demand of shorter lead times. A literature study and an exploratory case study on a construction company and its supplier have been done to map existing key performance indicators (KPIs) for measuring both resource and flow efficiency. The outcomes from the literature study show possible KPIs and the connections between them. Results from the case study indicate that basic data for flow efficiency measurements exist in companies but these are underutilized. Balancing resource and flow efficiency is a challenge for all companies. Decisions made on how to manage production and construction affect this balance, thus creating a dynamic situation where the balance is different between building projects.

  • 779.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Boundary Conditions in Fire Protection Engineering2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 45-64Chapter in book (Refereed)
    Abstract [en]

    A summary of the three kinds of boundary conditions as outlined in Sect. 1.​1.​3 is shown in Table 4.1. The third kind of BC sometimes called natural BC is by far the most important and common boundary condition in fire protection engineering, while the first and second kinds of BCs can rarely be specified. The third kind of BC may be divided into three subgroups, (a), (b) and (c). The subgroup (b) and (c) are particularly suitable for fire engineering applications. Subgroup (a) is applied when the heat transfer coefficient may be assumed constant as assumed in Chaps. 2 and 3. T g is then the surrounding gas temperature. In fire protection engineering it is, however, generally not accurate enough to assume a constant heat transfer coefficient as in particular heat transfer by radiation is highly non-linear, i.e. the heat transfer coefficient varies with the surface temperature. Therefore the subgroups (3b) and (3c) are the most commonly applied. They consist of a radiation term and a convection term with the corresponding emissivity ε and convection heat transfer coefficient h, respectively. The subgroup (3b) presupposes a uniform temperature T f , i.e. the radiation temperature and the gas temperature are equal. This is assumed, for example, when applying time–temperature design curves according to standards such as ISO 834 or EN 1363-1 for evaluating the fire resistance of structures, see Chap. 12. The subgroup (3c) is a more general version of (3b) as it allows for different gas T g and radiation T r temperatures, so-called mixed boundary conditions. Alternatively σ⋅T 4 r σ⋅Tr4 may be replaced by an equivalent specified incident radiation q . ′′ inc q.inc′′ according to the identity q . ′′ inc ≡σ⋅T 4 r q.inc′′≡σ⋅Tr4 (Eq. 1.​17). As shown in Sect. 4.4 all boundary conditions of subgroup 3 may be written as type 3a. That means momentarily a single effective temperature named the adiabatic surface temperature (AST) with a value between the radiation and gas temperatures as well as a corresponding total heat transfer coefficient can always be defined, see Sect. 4.4.

  • 780.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Fire Exposure of Structures According to Standards2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 185-193Chapter in book (Refereed)
    Abstract [en]

    When exposed to fire structures deform and lose load-bearing capacity which must be considered in design processes. It is then exposures to the more severe fires which are of interest such as post-flashover compartment fires and large flames for longer times. Pre-flashover fires do in general not create thermal conditions that can jeopardize the function of structural elements in a building. For design purposes it is therefore in general exposures relevant for post-flashover compartment fires that are specified in various standards and guidelines in the form of time–temperature curves. These curves are then used for controlling fire resistance test furnaces, see Fig. 12.1.

  • 781.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Heat Transfer by Convection2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 89-105Chapter in book (Refereed)
    Abstract [en]

    In previous chapters heat transfer by convection or just convection was treated only to the extent that it provides a linear boundary condition of the 3rd kind for conduction problems when the heat transfer coefficient is assumed constant. In this chapter the physical phenomenon of convection is described in more detail.

  • 782.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Heat Transfer by Radiation2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 65-87Chapter in book (Refereed)
    Abstract [en]

    Heat transfer by thermal radiation is transfer of heat by electromagnetic waves. It is different from conduction and convection as it requires no matter or medium to be present. The radiative energy will pass perfectly through vacuum as well as clear air. While the conduction and convection depend on temperature differences to approximately the first power, the heat transfer by radiation depends on the differences of the individual body surface temperatures to the fourth power. Therefore the radiation mode of heat transfer dominates over convection at high temperature levels as in fires. Numerical applications of radiation heat transfer in FSE are outlined in Sect. 4.​1.

  • 783.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Heat transfer in fire technology2012Book (Other academic)
  • 784.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Introduction2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 1-16Chapter in book (Refereed)
    Abstract [en]

    Temperature is the dominating factor in determining the rate and extent of chemical reactions including breakdown of organic compounds and deteriorations of strength and stiffness of structural materials such as steel and concrete. Phase change phenomena including ignition as well as severe loss of strength of materials are often related to specific elevated temperature levels. Temperatures of fire gases are also of crucial importance as they initiate gas movements thereby spread of smoke and toxic fire gases. Fire temperatures vary typically over several hundred degrees. Therefore a number of thermal phenomena need special attention such as phase changes of materials and heat transfer by radiation when calculating temperature of fire-exposed materials.

  • 785.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Measurements of Temperature and Heat Flux2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 133-151Chapter in book (Refereed)
    Abstract [en]

    In FSE temperature is nearly always measured with thermocouples as described in Sect. 9.1. Heat flux measured in different ways is most commonly measured as the sum of the net heat flux by radiation and convection to a cooled surface. The principles are briefly outlined in Sect. 9.2. Alternative methods incident radiation heat flux as well AST using so-called plate thermometers has also been developed as a practical alternative to heat flux meters as outlined in Sect. 9.3

  • 786.
    Wickström, Ulf
    SP Technical Research Institute of Sweden, Borås.
    Methods for Predicting Temperatures in Fire-Exposed Structures2016In: SFPE Handbook of Fire Protection Engineering, New York: Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 1102-1130Chapter in book (Refereed)
    Abstract [en]

    The fire resistance of structural elements is traditionally determined by standard fire endurance tests. However, there is also a need to be able to predict the response of structures of various designs when exposed to alternative design fire conditions. Accurate and robust analytical methods are then needed. Such methods may also be used for predicting standard tests of, for example, structural elements that cannot be tested due to their size or for extending test results to modified structures.

  • 787.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    New formula for calculating time to ignition of semi-infinite solids2016In: Fire and Materials, ISSN 0308-0501, E-ISSN 1099-1018, Vol. 40, no 3, p. 464-471Article in journal (Refereed)
    Abstract [en]

    An analytical closed form formula is presented for explicitly calculating time to reach ignition temperature of semi-infinite solids exposed to constant incident radiation and gas temperature as for example in the cone calorimeter. The non-linear boundary condition due to the emitted radiation from the surface being proportional to the surface temperature raised to the fourth power according to the Stephan–Boltzmann law is accurately considered. The formula works for a wide range of the parameter values like the thermal inertia of the solid, the emissivity of the exposed surface and the convective heat transfer coefficient. They are all assumed constant. The new formula contains a single constant coefficient, which has been derived by comparing results obtained by accurate numerical finite element simulations using two different codes, comsol and TASEF, as well as calculations based on a Duhamel superposition scheme. Thus, the formula can be classified as semi-empirical. It offers a simple approximate solution of a non-linear problem that requires cumbersome numerical calculation methods to obtain more exact results. Any exact analytical solution is not available. The new method is carefully verified by comparisons with numerical solutions. However, as it is an analysis of well-defined theoretical methods, any validation and comparisons with test data are not required and has therefore not been made.In comparison with other similar approximation formulas found in the literature, the accuracy as well as simplicity of applying the new formula is outstanding

  • 788.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Numerical Methods2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 107-124Chapter in book (Refereed)
    Abstract [en]

    The analytical methods outlined in Chaps. 2 and 3 presume that the material properties and heat transfer coefficients are constant. That is, however, not possible in most cases in fire protection engineering as the temperature then varies within a wide range and therefore both material properties and boundary conditions vary considerably. Phase changes or latent heat due to water vaporization or chemical reactions of materials (see Sect. 14.​1 on concrete) must in many cases be considered to achieve adequate results. Furthermore in particular radiation heat transfer coefficients vary considerably with temperature. As shown in Sect. 4.​1 it increases with the third power of the temperature level. In addition geometries being considered are not as simple as assumed above. Often they are in two or three dimensions, and then analytical methods can seldom be used for practical temperature analyses. Therefore numerical methods involving computer codes are frequently used in fire protection engineering. In some cases in particular for 0-dimension problems (lumped-heat-capacity) relatively simple so-called spreadsheet codes such as Excel may be used. For problems with more complex geometries and boundary conditions computer codes based on finite difference or finite elements methods are needed. Several computer codes based on these methods are commercially available, see Sect. 7.3.2. The superposition technique as presented in Sect. 7.2 may be seen as a combination of a numerical and an analytical method.

  • 789.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Post-Flashover Compartment Fires: One-Zone Models2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 153-174Chapter in book (Refereed)
    Abstract [en]

    FSE and design of structures and structural elements are in most cases made with a procedure including tests and classification systems. Fire resistance or endurance tests are specified in standards such as ISO 834, EN 1363-1 or ASTM E-119. In these standards time–temperature curves are specified representing fully developed compartment fires to be simulated in fire resistance furnaces for prescribed durations.

  • 790.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Pre-flashover Compartment Fires: Two-Zone Models2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 175-183Chapter in book (Refereed)
    Abstract [en]

    Two-zone models are applied to pre-flashover fires, i.e. compartment fires which have not reached ventilation controlled combustion conditions as defined in Chap. 10. Several more or less advanced computer codes have been developed to calculate temperature under such assumptions. The most fundamental principles of the theory are outlined below.

  • 791.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Steady-State Conduction2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 17-24Chapter in book (Refereed)
    Abstract [en]

    In one dimension in the x-direction the rate of heat transfer or heat flux is expressed according to Fourier’s law as outlined in Sect. 1.​1.q . ′′ x =−k⋅dTdx q.x′′=−k⋅dTdxwhere k is the thermal conductivity. For simplicity the mathematical presentation of the heat transfer phenomena is here in general made for one-dimensional cases only. Corresponding presentations in two and three dimensions can be found in several textbooks such as [1, 2].

  • 792.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Temperature Calculation in Fire Safety Engineering2016Book (Refereed)
    Abstract [en]

    This book provides a consistent scientific background to engineering calculation methods applicable to analyses of materials reaction-to-fire, as well as fire resistance of structures. Several new and unique formulas and diagrams which facilitate calculations are presented. It focuses on problems involving high temperature conditions and, in particular, defines boundary conditions in a suitable way for calculations. A large portion of the book is devoted to boundary conditions and measurements of thermal exposure by radiation and convection. The concepts and theories of adiabatic surface temperature and measurements of temperature with plate thermometers are thoroughly explained.Also presented is a renewed method for modeling compartment fires, with the resulting simple and accurate prediction tools for both pre- and post-flashover fires. The final chapters deal with temperature calculations in steel, concrete and timber structures exposed to standard time-temperature fire curves. Useful temperature calculation tools are included, and several examples demonstrate how the finite element code TASEF can be used to calculate temperature in various configurations. Temperature Calculation in Fire Safety Engineering is intended for researchers, students, teachers, and consultants in fire safety engineering. It is also suitable for others interested in analyzing and understanding fire, fire dynamics, and temperature development. Review questions and exercises are provided for instructor use.

  • 793.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Temperature of Steel Structures2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 195-216Chapter in book (Refereed)
    Abstract [en]

    Steel is sensitive to high temperature. The critical temperature of a steel member is the temperature at which it cannot safely support its load.

  • 794.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Temperature of Timber Structures2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 227-233Chapter in book (Refereed)
    Abstract [en]

    Modelling the thermal behaviour of wood is complicated as phenomenas such as moisture vaporization and migration, and the formation of char have decisive influences on the temperature development within timber structures. Nevertheless it has been shown that general finite element codes can be used to predict temperature in, for example, fire-exposed cross sections of glued laminated beams [52], provided, of course, that apparent thermal material properties and appropriate boundary conditions are used. Other specialized numerical codes for timber structures have been developed, e.g. by Fung

  • 795.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Temperatures of Concrete Structures2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 217-225Chapter in book (Refereed)
    Abstract [en]

    Reinforced concrete structures are sensitive to fire exposure of mainly two reasons. They may be subject to explosive spalling, and they may lose their load-bearing capacity due to high temperatures. Spalling is particularly hazardous as it may occur more or less abruptly and unanticipated. It usually starts within 30 min of severe fire exposure. It may depend on several mechanisms or combinations thereof such as pore pressure, stresses due to temperature gradients, differences of thermal dilatation and chemical degradations at elevated temperatures. Reinforcement bars of steel lose their strength at temperature levels above 400 °C. Prestressed steel may even loose strength below that level. Concrete loose as well both strength and stiffness at elevated temperature.

  • 796.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    The adiabatic surface temperature and the plate thermometer2011In: Fire safety science: proceedings of the 10th international symposium : [held at College Park, MD, 19-24 June 2011], London: International Association for Fire Safety Science, 2011, p. 1001-1011Conference paper (Refereed)
    Abstract [en]

    The concept of adiabatic surface temperature (AST) opens possibilities to calculate heat transfer to a solid surface based on one temperature instead of two as is needed when heat transfer by both radiation and convection must be considered. The adiabatic surface temperature is defined as the temperature of a surface which cannot absorb or lose heat to the environment, i.e. a perfect insulator. Accordingly, the AST is a weighted mean temperature of the radiation temperature and the gas temperature depending on the heat transfer coefficients. A determining factor for introducing the concept of AST is that it can be measured with an inexpensive and robust method called the plate thermometer (PT) even under harsh fire conditions. Alternative methods for measuring thermal exposure under similar conditions involve water cooled heat flux meters that are in most realistic situations difficult to use and very costly and impractical. This paper presents examples concerning how the concept of AST can be used in practice both in reaction-to-fire tests and in large scale scenarios where structures are exposed to high and inhomogeneous temperature conditions

  • 797.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    The term ‘heat flux’ is used ambiguously: Clear definitions are needed on how to express thermal exposure2016In: Fire and Materials, ISSN 0308-0501, E-ISSN 1099-1018, Vol. 40, no 3, p. 507-510Article in journal (Refereed)
    Abstract [en]

    The expression ‘heat flux’ without any qualifier like ‘to a surface at ambient temperature’ as frequently used in fire safety science and engineering literature and standards is ambiguous and misleading. Boundary conditions in fire safety engineering problems cannot be expressed as a given heat flux (or net heat flux), as the heat flux depends on and varies with the exposed surface temperature and thereby the properties of the target body. Therefore, it is important that the terminology is reviewed and that an agreement is reached on how to express thermal exposure in a well-defined and unambiguous way. A proposal is given on how the boundary conditions can be defined in a consistent way that is applicable to fire resistance and reaction-to-fire problems

  • 798.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Thermal Ignition Theory2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 125-132Chapter in book (Refereed)
    Abstract [en]

    The various aspects of the subject ignition of unwanted fires has been thoroughly investigated by Babrauskas and presented in the comprehensive Ignition Handbook. This book is concentrating on the calculation of the development of surface temperature. Despite many limitations, it is often assumed that a solid ignites due to external heating when its exposed surface reaches a particular ignition temperature.

  • 799.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Unsteady-State Conduction2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 25-44Chapter in book (Refereed)
    Abstract [en]

    When a body is exposed to unsteady or transient thermal conditions, its temperature changes gradually, and if the exposure conditions remain constant it will eventually come to a new steady state or equilibrium. The rate of this process depends on the mass and thermal properties of the exposed body, and on the heat transfer conditions. As a general rule the lighter a body is (i.e. the less mass) and the larger its surface is, the quicker it adjusts to a new temperature level, and vice versa. The temperature development is governed by the heat conduction equation (Eq. 1.29) with the assigned boundary conditions. It can be solved analytically in some cases, see textbooks such as [1, 2], but usually numerical methods are needed. This is particular the case in fire protection engineering problems where temperature generally varies over a wide range, often several hundred degrees.

  • 800.
    Wickström, Ulf
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Byström, Alexandra
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Compartment fire temperature: a new simple calculation method2015In: IAFSS - The International Association for Fire Safety Science: proceedings, ISSN 1817-4299, Vol. 11, p. 289-301Article in journal (Refereed)
    Abstract [en]

    In this paper a new simple calculation method for compartment temperatures is derived. The method is applicable to post-flashover ventilation controlled fires. A parameter termed the ultimate compartment fire temperature is defined as the temperature obtained when thermal equilibrium is reached and thick compartment boundaries cannot absorb any more heat from the fire gases. This temperature depends only on the product of the heat of combustion and the combustion efficiency over the specific heat capacity of air. It is, however, independent of the air mass flow rate, and of the fire compartment geometry and the thermal properties of the compartment boundary materials. These parameters on the other hand govern the rate at which the fire temperature is increasing towards the ultimate temperature. It is shown how the fire temperature development as a function of time in some idealized cases may be calculated by a simple analytical closed form formula.The fire temperature developments of two types of compartment boundaries are presented, semi-infinitely thick and thin structures. It is also shown that for the semi-infinite case, the solution resembles the standard ISO 834/EN 1363-1 curve and the parametric fire curves according to Eurocode 1, EN 1991-1-2.

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