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  • 201.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Aktivitet: Studerar värdeflödet i helheten: Forskarporträtt- Jarkko Erikshammar2011Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Jarkko Erikshammars forskning handlar om hur man kan identifiera och optimera värdeflödet vid industriell trähusproduktion så att företagen kan använda dessa fördelar i sin produktutveckling. Projektet ingår i programmen TräIN och LWE.

  • 202.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Aktivitet: Sustainable Wood Building Expo 20132013Other (Other (popular science, discussion, etc.))
  • 203.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Aktivitet: TräIn2009Other (Other (popular science, discussion, etc.))
  • 204.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Aktivitet: Utveckling genom strategisk samverkan och hållbart byggande2012Other (Other (popular science, discussion, etc.))
  • 205.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Aktivitet: Värdeflödesanalys - "ett Lean verktyg för effektivisering av processer" : PLAN Lunch: PLAN Lunch2010Conference paper (Other (popular science, discussion, etc.))
  • 206.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Aktivitet: Värdeflödesanalys: Ett Lean verktyg för effektivisering av processer, A lean tool for improving process effectiveness2009Conference paper (Other (popular science, discussion, etc.))
    Abstract [sv]

    Emneord: Lean, Värdeflödesanalys

  • 207.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Aktivitet: Workshop2014Other (Other (popular science, discussion, etc.))
  • 208.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Aktivitet: Workshop2012Other (Other (popular science, discussion, etc.))
  • 209.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Aktivitet: Workshop med Bygglogistik från LIU2012Other (Other (popular science, discussion, etc.))
  • 210.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Characteristics of supply chain management in systems building and implications for small business2013In: Proceedings of the 7th Nordic Conference on Construction Economics and Organisation, Trondheim: Tapir Akademisk Forlag, 2013Conference paper (Refereed)
    Abstract [en]

    Supply Chain Management (SCM) is an important part of the production process in systems building. The loosely-coupled construction supply chains created by the involvement of many interdependent sub-contractors and suppliers destabilize the production process. Purchasing strategies, used by many construction companies, for controlling the supply chain may not be applicable to small and medium-sized (SME) systems building companies, because the relationship between the buyer and the suppliers is characterized by long-term supply chain relationships rather than short-term project incentives. In order to ensure the reliability of deliveries and product quality, supply strategy in the form of SCM is suggested. The position taken is that systems building SMEs could integrate their supply chain with their customers and suppliers, in order to reduce variation in deliveries. A re-analysis of multiple case study and previously published qualitative data has been performed with SCM characteristics as the unit of analysis. Implications are that systems building SMEs need to have a long-term integration perspective when using SCM. Furthermore, SMEs have limited capacity and capabilities so differences in the maturity of their ‘systems building thinking’ might hinder effective SCM. However, the results do not conclusively prove or disprove the idea that SCM can replace project-based purchasing as the supply strategy for systems building SMEs.

  • 211.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Collaborative Product Development: a Purchasing Strategy for Small Industrialized House-building Companies2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

  • 212.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Kortare tid på taket med prefabricerade takkomponenter2012In: Bygg & Teknik, ISSN 0281-658X, Vol. 104, no 4, p. 51-54Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Det är få som idag projekterar fönster och dörrar, som inte är standardiserade produkter, i en byggnad. Samtidigt envisas aktörer i byggprocessen med att göra både arkitektritningar och konstruktionshandlingar på andra återkommande byggdelar för taket som borde kunna tillverkas som standardiserade produkter. Byggdelar såsom underlagstak, vindskivor och uppstigningslucka designas och konstrueras för varje projekt trots att de är i princip samma produkter. Samtidigt är det svårt för små entreprenörer och små leverantörer att utveckla attraktiva och standardiserade produkter som når acceptans inom byggindustrin. Genom att demonstrera ett produktutvecklingsprojekt mellan en litet sågverk, en underleverantör och en nationell byggentreprenör visar jag på hur aktörerna kan utveckla produkter tillsammans som reducerar tiden på taket, ökar lönsamheten och ökar säkerheten.

  • 213. Erikshammar, Jarkko
    Leverantörer som strategisk resurs för produktutveckling: LTU lic Jarkko Erikshammar berättar om hur LTU och BAC Såg & Hyvleri i samverkan bidrar till att lyfta nivån i byggandet.2012Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    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

  • 214.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Projekt: TräIN2010Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Projektet "TräIN" (Träinnovationsnätverket) är ett EU-finansierat samverkansprojekt mellan IUC Norrbotten och Luleå tekniska universitet (avdelningen för Träbyggnad), som, genom riktade insatser hos SMEföretag inom träbranschen i Norrbotten, ska utveckla och stärka hela den norrbottniska trä-industrins konkurrenskraft och lönsamhet.

  • 215.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Näslund, Ida (Producer)
    Suppliers as a strategic asset for collaborative product development2012Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Populärvetenskaplig presentation av författarens LICCollaborative Product Development : a Purchasing Strategy for Small Industrialized House-building Companies.Speltid: 9 min 35 sek

  • 216.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Supply Chain Integration for Small Sawmills in Industrialized House-Building2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The position taken in this thesis is that a small and medium sized supplier makes a strategic choice to integrate their supply chain with industrialized house-building companies in order to deliver customer value and sustain competitive advantage. Customer values for industrialized house-building means delivery reliability, product quality, supply chain and market flexibility. Supply chain integration is the means for understanding customer requirements and to use supply chain resources efficiently through collaboration. The purpose of this thesis is to explore a small sawmill transition from single-minded focus on raw material optimization and increased production efficiency towards supply chain integration and customer focus in the industrialized house-building context. The thesis basis is a systematic literature review and five appended papers, based on a longitudinal case study at a small Swedish sawmill. Data has been collected through interviews, participant observations, and archival data during the period of 2010-2012. The theoretical gap is formed by the lack of consensus on supply chain integration. Viewing the criticism it is not clear how the constructs that constitute supply chain integration affect the possibility of succeeding with integration, how the integration should be measured, or how it affects the performance. Hence this thesis makes a holistic approach and collect empirical data trough method development on a strategic (business models, supply chain management), tactical (supply chain planning, sales and operations planning) and operational (value stream mapping, lean value delivery, simulation) supply chain integration process within industrialized house-building context. However, the findings do not conclusively prove or disprove the position. Findings indicate that small sawmills with limited resources and capabilities can employ methods of sales and operations planning, business model decomposition and value stream mapping enhanced decision making. The main contribution is the empirical data on supply chain integration divided and analyzed from strategic, tactical and operational process levels synthesized that with understanding of the importance of integrating these three levels dual perspective. Thus contribute with theoretical enhancement and reduction of the still-identifiable fragmentation of supply chain integration theory.

  • 217.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    The ambiguity of value2010Conference paper (Refereed)
  • 218. Erikshammar, Jarkko
    Vad är Lean?: En personlig reflektion2013Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Youtube presentation om min definition av Lean.

  • 219.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Viktiga frågor: En lite blogg i rymden om små viktiga frågor som hållbarhet, fattigdom och rättvisa.2012Other (Other (popular science, discussion, etc.))
  • 220.
    Erikshammar, Jarkko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Värdeflödesanalys: En fallstudie på Polardörren2011Report (Other academic)
    Abstract [en]

    This report is a case study is done, within the research program TräIN, in order to evaluate the modified methodology for Value Stream Mapping. Theoretical frame of reference is within Lean Production. Data has been collected at Polardörren in Öjebyn. The report is focusing on one product; Lapporten. The data has been collected during four workshop days at Polardörren, and by e-mail and telephone. During the visit interviews and the Learning-to-see methodology has been used. Suggestions for improvement in the value stream is that Polardörren should work with a decoupling point by the CNC, which makes the frame assembly free to work with batch oriented production and after the CNC use FIFO (First in, First Out). Polardörren must work with increased availability with the CNC. This report does not consider other products or processes that might affect the result The methodology Learning-to-see works very well with this type of production.

  • 221.
    Erikshammar, Jarkko
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Alestig, Erik
    Prolog AB.
    Lu, Weizhuo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Parametric Value Stream Mapping Framework: A Case Study of a Small Swedish Industrialized House-Building Supplier2014In: Proceedings of IGLC22: 22nd Annual Conference of the International Group for Lean Consruction : understanding and improving project based production / [ed] Bo Terje Kalsaas; Lauri Koskela; Tarcisio Abreu Saurin, Oslo, Norway: Akademika forlag, 2014, Vol. 1, p. 425-436Conference paper (Refereed)
    Abstract [en]

    Industrialized house-building is based on repetitive processes used in the supply, design, manufacturing and erection of pre-configured houses. Industrialized house-building contractors are dependent on many small suppliers and sub-contractors in their supply chain. These small suppliers, with limited resources and capabilities, need to be able to develop products and processes in order to deliver future customer value without wasting development resources on non-viable products. Our question is whether product development by small and medium-sized (SME) industrialized house-building suppliers could be supported by parametric Value Stream Mapping.The objective is to explore a process design framework in which Value stream Mapping (VSM) is used to identify improvements and to generate product development suggestions, based on a set of parameters defined as P1, P2..., Pn.The testing was carried out at a Swedish SME supplier to the industrialized house-building sector, using a newly-developed roofing board with an integrated membrane, with the parameters (P1) customer needs, (P2) waste on construction site and (P3) construction worker safety. Data were collected using interviews and video-recorded participant observations on two construction sites. Findings indicate that VSM cannot describe attributes of a product other than those associated with production flow. However, parametric VSM helped the case study company to stop current development and instead suggest valuable product attributes. The implications are that parametric VSM enhances the application of VSM. Parametric VSM can be used by SME suppliers as an input to product development in order to validate product attributes before launch. However, this is based on a single case study and further research is needed.

  • 222.
    Erikshammar, Jarkko
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bildsten, Louise
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Haller, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Value Stream Mapping: a case study of an inner wall manufacturer2014Report (Other academic)
    Abstract [sv]

    Kartläggning av värdeflöden har blivit ett av de mer använda verktygen inom Lean sammanhang. Dessutom är det ett viktigt verktyg för ständiga förbättringar.Dess framgång är kopplat till skapandet av en stor visuell karta över hela företagets processer och samspelet mellan dessa processer. I arbetet med att göra kartan, fås en djupare kunskap om företaget genom att de som utför arbetet i processerna deltar i arbetet att rita upp värdeflödeskartan.Denna rapport är en fallstudie av Moelven Eurowand, en tillverkare av innerväggssystem för kontor. Syftet med studien var att undersöka möjligheterna att förkorta ledtiden för glasväggar. Företaget besöktes två gånger. Vid det första besöket genomfördes kartläggning av värdeflödet och vid det andra besöket skedde uppföljningen av kartläggningen. Företagets representanter uttryckte att värdeflödesanalysen var givande.

  • 223.
    Erikshammar, Jarkko
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Björnfot, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Gardelli, Viktor
    Luleå University of Technology, Department of Arts, Communication and Education, Education, Language, and Teaching.
    The ambiguity of value2010In: Proceedings IGLC-18: 18th Conference of the International Group for Lean Construction / [ed] Ken Walsh; Thais Alves, Haifa: Technion-Israel Institute of Technology , 2010, p. 42-51Conference paper (Refereed)
    Abstract [en]

    'Value' is a central concept in all of the principles and methods applied in Lean Construction, but it is rather difficult to provide a precise definition of the term. The problem lies in the word value itself: its ambiguity and vagueness make theorization difficult. This paper investigates the philosophical concept of value from a Lean Construction perspective. Several elements that contribute to value are considered, including objective elements such as waste reduction, quality, price and functionality, and more subjective elements such as design. The hypothesis of this paper is that the reduction or removal of elements that detract from value, such as waste and costs, is not the only means by which value may be increased. The Sorites paradox is used to form a cohesive perspective on some different meanings of the word ‗value‘. One of the known ‗solutions‘ of the paradox, utilization theory, is then explored through a case study in off-site construction that illustrates how different actors in the construction process view value, and how utility theory can be used to provide a consensus on value that is acceptable. In practice, ‗value‘ is ambiguous because actors generally value different things and these views seldom converge during projects. Our results indicate that the actors involved strive for value individually. Analysis using utility theory allows the actors to establish a shared conceptualization of value, expressed in monetary terms. The work described in this paper aims to improve our understanding of value and of how to design products in construction to improve value for clients of industrialized housing.

  • 224. Erikshammar, Jarkko
    et al.
    Engelmark, Henrik
    Haller, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Värdeflödesanalys: En pilotstudie på Finsnickeriet AB2010Report (Other academic)
    Abstract [en]

    The background to the report, written under the graduate course "Pilot study: Value Stream Analysis", is to assess the method of value stream mapping. The theory that has been used is from the field of Lean Production. The empirical data is gathered on Finsnickeriet in Råneå AB and the report is a case study of a specific product; the balcony door to Älvsbyhus. Data has been collected during two visits to Finsnickeriet and via phone and email. During visits, the interviews and the methodology of learning-to-see was used. The company's own time measurements for the different process steps have also been used. Improvement proposals suggest that the company should continue working on, good order, for example with 5S and marking of storage areas, changing the layout of the painting in order to create a cell, set up time reduction in the plane, and smaller batches whenever possible. We believe that Finsnickeriet must do so in small steps to reduce the risk.Report does not account for other activities such as order preparation, quality issues and affecting the overall result. The errors we are aware of the study is the uncertainty surrounding collection of the cycle and setup times

  • 225.
    Erikshammar, Jarkko
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lassinantti, Josefin
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    The business model effect on collaborative product development in SME construction companies2010In: Ph.D. Research Workshop on Technology and Innovation in Construction: Held at Department of Civil, Mining and Environmental Engineering, Luleå University of Technology, Porsön, Luleå, 29 September 2010 / [ed] Paul Chan; Ylva Sardén, 2010, p. 32-39Conference paper (Other academic)
    Abstract [en]

    The housing construction industry in Sweden is fragmented with few major actors dominating the housing market and several local or regional small and medium (SME) sized construction companies. This combined with the SME's lack of resources for knowledge consuming activities such as product development and innovations, creates a super competitive situation for the SME companies. Studies show that innovation and business model are tightly linked to each other. A business model that is robust can be used as foundation for innovation. The business model needs to define the market, partnerships, product attributes meeting market requirements and production parameters such as cost, time and quality, which are all necessary input for achieving product innovation.This paper investigates a SME construction company and its suppliers, initially linked by traditional working agreements, when developing a product collaboratively in order to gain increased market shares, This paper elaborates on whether developing the business model might be a possible key success area for SME construction companies, which might enhance their possibilities in offering a more competitive product to the market. The objective is to find a methodology that is applicable and workable for the SME´s in construction industry and to develop a framework for analysis. The work described in this paper aims at improving our understanding of the SME product development process.The result of the product development project has been a new design process with a business model that has longer contractual agreements rather than short term project procurement.

  • 226.
    Erikshammar, Jarkko
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lu, Weizhuo
    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.
    Olofsson, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Discrete event simulation enhanced value stream mapping: an industrialized construction case study2013In: Lean Construction Journal, ISSN 1555-1369, E-ISSN 1555-1369, Vol. 10, p. 47-65Article in journal (Refereed)
    Abstract [en]

    Research Question/Hypothesis: Can a production process design framework created by integrating Value Stream Mapping (VSM) and Discrete Event Simulation (DES) be used to assess the production system performance, as predicted by a future state design of small and medium sized enterprises (SMEs) working in industrialized construction?Purpose: To explore a production process design framework in which VSM is used to identify doable improvements and DES provides analytical evaluation of them.Research Method: The demonstration was carried out at a Swedish SME industrialized construction component manufacturerFindings: VSM is unable to evaluate analytically the performance of the future state design. This inability leads to unnecessary implementation iterations. VSM assumes a deterministic model and cannot describe the dynamic behaviors of a system. The dynamic behavior of the construction processes will result in the future state design not performing as expected. However, by analytically evaluating the future state with DES helped the case company to implement a new production process design.Limitations: DES modeling is still time-consuming and needs skilled professionals, the cost of whom can be prohibitive for SMEs and demonstrated in one case study.Implications: The integration of DES and VSM provides a framework to evaluate and communicate the outcome, hence enhancing the application of VSM.Value for practitioners: A lean framework, which can be used, for industrialized construction processes especially by SMEs with very limited resources, to validate changes before implementing them.

  • 227.
    Erikshammar, Jarkko
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Meiling, John
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jansson, Gustav
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Levander, Erika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Industriellt träbyggande förenar ekonomi och byggbarhet2010In: Samhällsbyggaren, ISSN 2000-2408, no 2, p. 32-35Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Industrialized Timber Housing is based on repetition of the predefined building processes compared with traditional building where the business transaction and the customer are arranged into unique projects. Since the construction process consists of recurring activities, the industrial methods do not only improve the design and production phase, but the positive impact stretches well into the management phase. The market today can be offered cost-effective housing, with higher flexibility and better quality if the client, contractor and supplier takes control of the construction process.

  • 228.
    Erikshammar, Jarkko
    et al.
    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.
    Ökad samverkan i försörjningskedjan genom sälj- och verksamhetsplanering: En analys av ett SME sågverks metod och process2016In: PLANs Forsknings- och tillämpningskonferens 2016: Logistik – teori möter praktik / [ed] Peter Bergling, Helen Forslund, 2016, p. 65-75Conference paper (Other academic)
    Abstract [sv]

    Ökad videraförädling för små och medelstora (SME) sågverk innebär att ett ensidigt fokus på produktionsprocessen och sågutbyte bör kompletteras med ökad kundfokus. Sälj- och verksamhetsplanering (SVP) är en planeringsmetod som balanserar kundkrav med övriga operativa processer på medellång sikt. Syftet med denna artikel är att beskriva en anpassad SVP-metod och en SVP-process som möter sågverkets specifika behov av ökad effektivitet i försörjningskedjan samt beskriva faktorer som kan undersökas vidare för att skapa en ökad förståelse av SVP tillämpningen inom sågverkets kontext. Data som analyserats är från en longitudinell fallstudie på ett svenskt SME sågverk och processen för införandet av en SVP-metod. Sågverket sågar cirka 100000 kubikmeter per år av både gran och tall. Forskningen visar att SVP-metoden bör utvecklas så att den kan balansera i två nivåer; både för sågat färdigvarulager och lager för vidareförädling med hänsyn tagen till divergent och konvergent produktflöde. Den utvecklade metoden visar på sågverkets behov av balanserat råmateriallager, men också behovet av att lösa konflikter mellan sågutbyte och olika marknadskrav. Identifierade faktorer för vidare forskning av SVP, som en tillämpad metod och process, är sågverkets förmåga att linjera interna ekonomiska mål, sågverkets behov av ökad kommunikation i försörjningskedjan, tydligare marknadskrav och engagemang från företagsledningen.

  • 229.
    Erikshammar, Jarkko
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Wetterblad, Jakob
    LTU.
    Wallin, Johan
    LTU.
    Herder, Marcus
    LTU.
    Svensson, Thorbjörn
    LTU.
    Vendor managed inventory: a sawmills potential offering for builders merchants2013Report (Other academic)
    Abstract [en]

    Vendor managed inventory (VMI) is a frequently used method for and a widely discussed partnering initiatives for improving supply chain efficiency. VMI as a program has increased in popularity, especially in the grocery industry, where the supplier, reseller or distributor makes the main inventory replenishment decision for the consuming organization. The objective of implementing VMI programs is to decrease costs for inventory control and management, and create transparency; possibility to collaborative planning and replenishment and efficient consumer response. The theoretical framework presents the basics of VMI, what the effects are and what prerequisites for such a program demands. The theoretical framework is used for the model of analysis when analyzing the possibility to implement VMI from a sawmill perspective to one of their customer segments; builders merchants. This is a case study performed at a small and medium sized sawmill. The purpose of this study was to investigate the possibilities of theoretically implement VMI since the Swedish wood supply chain is in a need for new business models and services since the value refinement is too low. The current system for inventory management and replenishment is summarized and compared to a theoretical construction with VMI. The analysis shows total settlement days could increase with 50%. This has a positive effect on the net cash flow and the inventory turnover per year could almost double. Further does the relationship between Case Company and Builders merchant fulfill the requirements for implementing a VMI program, but there is reason to be aware of the potential pitfalls.

  • 230.
    Ersson, Tina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Balkonger i trähus: Systematisering av konstruktionsarbete2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    House construction today is largely project-based, where the buildings are tailored tounique conditions and locations that are rarely the same as another build on anotherbuilding site. In addition to the building itself and the building site, involved actorsusually also change from project to project. As a result of today's project-basedconstruction, there is a lack of a standardized and systematic work process forconstruction work. A systematic work process could contribute to all the players' pursuitof profit.

    To explore the possibilities of creating an improved work process, this study focusedon balconies of wooden houses.

    The purpose and objectives of the work were therefore designed to evaluate today'sconstruction work for the design of balconies in wooden houses, where possible areasof improvement were evaluated to create a systematic work process for constructorsin designing and dimensioning balconies in wooden houses.In order to achieve the purpose and objectives of the work, four questions have beendeveloped that focus on the production of systematic work processes, the current workprocess of the construction work, design methods and balconies in wooden houses.Existing research and published material were found through a literature and contextstudy to further develop the study’s work.

    Theory regarding systematisation and process development, balconies,dimensioning of supporting structures, etc. was the basis for how the work would becarried out. The systematized work process for balcony design was, however, createdusing information from the qualitative interview study with a total of eight (8)respondents in different roles I house building. The work process was then partiallytested in a quantitative verification.

    The work resulted in a systematic work process in the form of a checklist that includesgeneral tips as well as a chronological workflow that describes how, when, with whomand what should and can be done at the balcony design to get the best possible results.A description of the existing balcony types has also been developed to simplify workand to clarify important points and tasks in the design of a particular type of balcony.

    The workflow is divided into the activities of the design and dimensioning, such asstart-up, design and dimensioning of the balcony's main components, detail designand dimensioning of fastening components, drawing up drawings and assemblydescriptions, and follow-up and development of the work process.

    Based on the results of the study, the questions were answered with a description ofthe four (4) types of balcony, which were based on theory and were strengthened bymeans of empirical data from the respondents. Two (2) of the balcony types are viiiconsidered more common, balconies with pillars to land and rods above the balconyplate, where the latter is considered the most common in wooden houses at present.Today's construction work for designing and dimensioning balconies in woodenhouses is similar in large part, but due to the use of prefabrication and standardizationdegree the work differs from each other.

    The verification of a part of the work process resulted in a balcony solution with crosslaminated timber as a balcony slab and in a comparison between results from aproposed software and hand calculations. The comparison showed that the softwarecan be used for dimensioning balconies with cross laminated timber, with the exceptionthat the dimensioning for fire must be done by hand because of deficiencies in thesoftware's settings.

    The study has shown that systematisation is often based on LEAN Production, whichwas created by the Japanese automotive industry, which focuses on creating efficientwork processes by circularly examining, testing, evaluating and developing workprocesses.

    The conclusion of the work is that it is possible to systematise construction work, butunlike the manufacturing industry, the work process must have adjustment possibilitiesduring the work to meet the commonly occurring changes in house construction.However, in order for the systematisation work to be carried out, increasedunderstanding and involvement from and by other actors than constructors arerequired.

    A systematic work process together with type solutions and standardized calculationmethods can shorten the design time, improve and secure the solutions, and allowmore time for creative thinking to further improve the balcony solutions and the workprocess.

  • 231.
    Evegren, Franz
    et al.
    Fire Research, SP Technical Research Institute of Sweden, Box 857, SE-501 15 Borås.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    New approach to estimate temperatures in pre-flashover fires: Lumped heat case2015In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 72, p. 77-86Article in journal (Refereed)
    Abstract [en]

    This paper presents a model for estimating temperatures in pre-flashover fires where the fire enclosure boundaries are assumed to have lumped heat capacity. That is, thermal inertia is concentrated to one layer with uniform temperature and insulating materials are considered purely by their heat transfer resistance. The model yields a good understanding of the heat balance in a fire enclosure and was used to predict temperatures in insulated and non-insulated steel-bounded enclosures. Comparisons were made with full scale experiments and with other predictive methods, including CFD modeling with FDS and the so called MQH relationship. Input parameter values to the model were then taken from well-known literature and the heat release rates were provided from the experiments. The fire temperature predictions of the model matched very well with experimental data. So did the FDS predictions while the original MQH relationship gave unrealistic results for the problems studied. Major benefits of using the model in comparison with CFD modeling are its readiness and simplicity as well as the negligible computation times needed. An Excel application of the presented pre-flashover fire model is available on request from the author.

  • 232. Falk, Andreas
    Architectural aspects of massive timber: structural form and systems2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The hypothesis of this thesis is that there are rational, technical and architectural gains to be made from interactively developed architectural and structural utilisation of massive timber plates. The aim is to study and describe architectural features of structural applications of massive timber and ways to utilise and develop timber-based plates in building applications by combining an architectural and a structural engineering perspective. The work presented in this thesis concerns the fields of architecture and structural engineering, their interrelations and interaction in building systems based on cross-laminated timber products. Characteristic of the entire work is the search for advantages from material- and product-specific features and how to utilise these architecturally and structurally, unified in a holistic perspective. The work contains two case studies and a theoretical extension. The studies and discussions on development of the utilisation have lead in two directions: towards industrialised residential building construction and towards timber plate structures in combination with steel rods or cables for wide spans. For building systems production, erection methods and system-action are of main importance for the result and a case study comprising four Swedish and two Austrian projects on medium- and high-rise residential blocks has been performed. For advanced structures it is the material and product properties that are of main importance and a case study on timber-structures for wide spans has been performed. One Swedish project has been considered aligned with four Austrian examples. Two- and three-dimensional structures for wide spans of the type treated in the thesis are not yet in production. The results from the case studies and a discussion on form finding, the study of and search for the interplay between force and structural form, have been developed into a theoretical extension of advanced structures with timber-plates in combination with steel rods, cables and trestle structures. The theoretical extension has resulted in a new type of structural element based on timber plates.

  • 233.
    Feldmann, M.
    et al.
    Rheinisch-Westfälische Technische Hochschule Aachen (RWTH).
    Naumes, J.
    Rheinisch-Westfälische Technische Hochschule Aachen (RWTH).
    Pak, D.
    Rheinisch-Westfälische Technische Hochschule Aachen (RWTH).
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Eriksen, J.
    Luleå University of Technology.
    Popa, N.
    ArcelorMittal Belval & Differdange (AM R & D).
    Hechler, O.
    ArcelorMittal Belval & Differdange (AM R & D).
    Seidl, G.
    SSF-Ingenieure AG (SSF).
    Economic and durable design of composite bridges with integral abutments (INTAB+)2012Report (Refereed)
    Abstract [en]

    In the design and construction of bridges, questions of sustainability, maintenance and durability become more and more important for European road administrations in addition to safety and serviceability issues. Therefore integral abutment bridges become highly attractive to designers, constructors and road administrations as they tend to be less expensive to build, easier to maintain and more economical to own over their lifetime. However in Europe less experience in building integral bridges has been gained so far. Therefore in 2005 the European RFCS-projects INTAB has been launched. Within the scope of the project, universities, consulting engineering companies as well as steel producers worked together to develop economic and safe solutions for composite bridges with integral abutments. Significant knowledge has been gained and cost-effective, environmentally friendly and sustainable bridge structures have been developed. Furthermore their durability has been proven to obtain competitive composite bridges for small and medium spans. The outcome of that project was reworked within the scope of the current project to make it available to a larger number of practitioners. To disseminate the knowledge, two workshops have been organised. A design guide was written and translated into German and French. It was completed by a design example as well as CEN-recommendations regarding actual Eurocodes. A software tool was written to help designers to perform some calculations regarding the design of integral abutment bridges.

  • 234.
    Feldmann, M.
    et al.
    Rheinisch-Westfälische Technische Hochschule Aachen (RWTH).
    Naumes, J.
    Rheinisch-Westfälische Technische Hochschule Aachen (RWTH).
    Pak, D.
    Rheinisch-Westfälische Technische Hochschule Aachen (RWTH).
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Eriksen, J.
    Luleå tekniska universitet.
    Collin, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Kerokoski, O.
    Ramböll Sverige AB (Ramböll).
    Pétursson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Verstraete, M.
    Université de Liège.
    Vroomen, C.
    Université de Liège.
    Haller, M.
    ArcelorMittal Belval & Differdange (AM R & D).
    Hechler, O.
    ArcelorMittal Belval & Differdange (AM R & D).
    Popa, N.
    ArcelorMittal Belval & Differdange (AM R & D).
    Economic and durable design of composite bridges with integral abutments2010Report (Refereed)
    Abstract [en]

    In the design and construction of bridges, questions of sustainability, maintenance and durability are becoming more and more important for European road administrations, in addition to safety and serviceability issues. Therefore integral abutment bridges are becoming highly attractive to designers, constructors and road administrations, as they tend to be less expensive to build, easier to maintain and more economical to own over their life time. Bearings and joints are main sources of maintenance costs during a lifetime. These costs vanish because the bridges are joint- and bearing-free. However, this very advantage complicates the design compared to conventional bridges in some crucial respects. Combined with the fact that most European countries have only limited experience with integral bridges to date, this leads to a reluctance of road administrations to use this bridge type. Thus the main objective of the project is to experimentally and theoretically investigate the behaviour of critical points of integral abutment bridges. Regarding the soil-structure interaction, recommendations are elaborated based on monitoring results as well as previous research and monitoring campaigns. Conventional HP piles and sheet piles are investigated as a foundation. Furthermore a hinged HP connection is developed to decrease the stresses in the pile system. An investigation of the design and construction of the slab to pavement approach is also carried out to avoid major damages to the structure. Finally the most important information is condensed into the essential features in form of a 'Design guide for composite bridges with integral abutments'

  • 235.
    Feneuil, Blandine
    et al.
    Aalto University, Concrete Technology Laboratory, Department of Civil and Structural Engineering, School of Engineering, Aalto University.
    Habermehl-Cwirzen, Karin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Contribution of CNTs/CNFs morphology to reduction of autogenous shrinkage of Portland cement paste2016In: Frontiers of Structural and Civil Engineering, ISSN 2095-2430, E-ISSN 2095-2449, Vol. 10, no 2, p. 224-235Article in journal (Refereed)
    Abstract [en]

    In this experimental study, carbon nanotubes (CNTs) and carbon nanofibers (CNFs) were dispersed by intensive sonication in water in the presence of superplasticizer and subsequently mixed with Portland cement with water/ cement ratios varying between 0.3 and 0.4. The autogenous shrinkage in the fresh stage was investigated. The CNTs and CNFs were characterized by high resolution scanning electron microscopy (SEM) and the hydrated pastes were studied by X-ray diffraction and SEM. The results showed a reduction of the autogenous shrinkage by 50% for pastes containing small amounts (0.01 wt%) of nanomaterials. Higher additions appeared to be less effective. The highest reduction of shrinkage was observed for carbon nanofibers which were long, rather straight and had diameters of around 200 nm. The result showed that the addition of nanomaterials accelerated the hydration processes especially in the early stages of hydration. The effect was the most pronounced in the case of functionalized nanotubes. The proposed mechanism resulting in the reduction of the autogenous shrinkage was a combination of nano-reinforcing effects, alterations of hydration and microstructure of the hydrated matrix.

  • 236.
    Filipsson, Tomas
    Luleå tekniska universitet.
    Shear walls with double plasterboards: evalutation of design models2002Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This thesis presents a part of the ECSC-project Development of dry composite construction systems based on steel in residential application that focus on design recommendations for stabilizing buildings by using shear resistance in the walls. The existing design method suggested and used by the Swedish plasterboard manufacturer Gyproc AB is considered as a bit conservative and it does not consider double plasterboards properly. A work within the frame of the ECCS-project performed by Swedish participants was conducted in order to investigate the possibilities for improvements of design recommendations for shear wall design. Therefore a number of tests concerning the behaviour of the connection between plasterboards and steel studs have been carried out. Background information necessary for the project is presented in this report. Experimental investigations and finite element modelling of characteristic specimens and a design model for a shear wall with double plasterboards are described in the report. Furthermore, a short description of a newly established design recommendations proposed in the project are given. The experimental investigation covered various cases of connections between either one layer or two layers plasterboard to a frame made of steel studs. Nine different set-ups using a single fastener herein referred to as fastener tests were tested to get an indication of the fastener resistance in various situations. Three specimens were tested for each setup. Six types of small-scale wall tests (900x900mm) were performed. Different boards are used in specimens, one layer plasterboard or board made of constructional plywood, and two layers plasterboards were fastened with fasteners to both sides of the frame. The full-scale test was performed on the two-storey wall with a door opening. This test was performed to find out the resistance of a shear wall built up by several units using double plasterboards. A structural model for design of shear walls with double plasterboards is given. A MathCad script was written in order to perform a parametric study of the wall. A complete text of the script is given in Appendix B. A comparison between results obtained from the FE model computed using commercially available code, ABAQUS, and results from the structural model were accomplished to validate assumptions used in the structural model. Two types of the small-scale wall test and the full-scale test were modelled by ABAQUS to gain more knowledge about force distribution between the plasterboards and steel frame. Usefulness of the fastener test to provide reliable data for the non-linear analysis was determined since those data were used in the finite element analysis.

  • 237.
    Flodman, Emelie
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Lundberg, Sofia
    Glas som bärande konstruktionsdel: Dimensionering av en glasbalk2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 238. Fontoura, B.
    et al.
    Matos, R.
    Abílio, M.P. Jesus
    Rebelo, C.
    Silva, L. Simões da
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Avaliação da Resistência à Fadiga de Ligações por Atrito em Aço Estrutural de Alta Resistência S6902011In: Construção Metálica e Mista VIII / [ed] L. Simões da Silva; P. Cruz; N. Lopes; J. Almeida Fernandes; A. Batista, Lissabon: CMM Press , 2011, p. 191-200Conference paper (Refereed)
  • 239.
    Fredriksson, Ylva
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Samverkan mellan träkomponenttillverkare och stora byggföretag: en studie av massivträbyggnade2003Licentiate thesis, monograph (Other academic)
    Abstract [sv]

    Under en lång tid har trä tappat marknad till stål och betong vad gäller stommar för flervåningshus, ett skäl till detta är att bristen på kundfokusering lett till att träindustrins sida halkat efter vad gäller framtagandet av effektiva systemlösningar för husbyggandet och helhetsåtagande gällande kvalitetstänkande. I dagsläget upplever träkomponenttillverkarna att byggföretag väljer att använda sig av andra material, framför allt betong, därför att de är vana vid det, även i situationer där massivträlösningar skulle kunna vara ett konkurrenskraftigt alternativ. Byggföretagen menar att det är för osäkert att bygga med massivträ, eftersom man inte vet vilka problem som kan uppstå och hur man kan lösa dem. Licentiatuppsatsen har ett praktiskt syfte att undersöka och visa hur en direkt samverkan mellan träkomponenttillverkare och stora byggföretag kan öka kommunikationen och materialflödet och därmed effektivisera utvecklingen av ett konkurrenskraftigt byggsystem i massivt trä. Ett sådant byggsystem förväntas leda till ökade förtjänstmöjligheter för både träkomponenttillverkare och byggföretag genom att utgöra ett alternativ till stål och betong. En direkt samverkan antas också öka konkurrenskraften för massiva träprodukter samtidigt som det på längre sikt ger större valmöjligheter och därmed också större möjligheter för byggföretaget att kundanpassa sin produktion. Studien ska också leda till en ökad vetenskaplig förståelse för vad som påverkar samverkan mellan tillverkare av massiva träkomponenter och byggföretagen. Företagen som deltagit i studien har visat ett stort intresse för att skapa en samverkansrelation mellan parterna. Resultaten visar att syftet med att samverka, för industrirepresentanterna, är att förbättra ekonomin för båda parter. Detta ska framför allt ske genom att man med ett gemensamt systemperspektiv utvecklar det massiva stomsystemet. Resultaten visar också att företagen måste utveckla nya typer av arbetsformer vilka stödjer kundfokusering för båda parter. Utvecklingen inom dessa områden förväntas bidra till en utveckling på en rad andra områden så som produktutveckling och miljöfokusering. Parterna tror att samverkan måste karakteriseras av en vilja att arbeta tillsammans och att göra det som är bra för båda parter, inte bara för den egna organisationen. För att upprätthålla viljan att arbeta tillsammans krävs effektiva sätt att ta hand om konflikter mellan parterna och att man tydligt definierar syftet med relationen och vilka åtaganden respektive part har, eventuellt genom skrivna avtal.

  • 240. Fredriksson, Ylva
    et al.
    Stehn, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Industrial difficulties and strategies for timber building system development in Sweden2003In: Construction economics and organization: proceedings of the 3rd Nordic Conference on Construction Economics and Organization, 24-24 April 2003, Lund, Sweden / [ed] Bengt Hansson; Anne Landin, Lund: Lund Institute of Technology , 2003, p. 149-158Conference paper (Refereed)
  • 241.
    Försth, Michael
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sjöström, Johan
    SP Technical Research Institute of Sweden, Borås, SP Sveriges Tekniska Forskningsinstitut, Brandteknik.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Andersson, Petra
    SP Technical Research Institute of Sweden, Borås.
    Girardin, Bertrand
    R2Fire Group/UMET-UMR CNRS 8207, Ecole Nationale Supérieure de Chimie de Lille.
    Characterization of the thermal exposure in the en 50399 cable test apparatus2015In: Fire and Materials 2015, 2-4 Feb 2015, San Francisco, USA: proceedings, Interscience Communications, 2015, p. 23-37Conference paper (Refereed)
    Abstract [en]

    The EN 50399 cable test is used for classification of cables within the European construction products regulation. Means to predict a cables performance in this test, based on material data and small scale test results is of great value for the development of new cable materials. A first step in developing a prediction tool should be to understand the heat exposure on the cables in the EN 50399 test apparatus. The heat load in e.g. the cone calorimeter is very well characterized whereas for EN 50399 only the burner power (20.5 kW) is known. In the cone calorimeter the heating is solely by radiation, whereas for the EN 50399 test a large fraction of the heat exposure depends on feed-back from the cable fire. This paper presents a measuring method for characterizing the thermal exposure inside the EN 50399 cable test apparatus without cables and with a cable rated Euroclass Dca. A new instrument for measuring thermal exposure simultaneously in several directions was developed for the purpose, and thereby the non-isotropic exposure on the cables at different position on the ladder could be investigated

  • 242.
    Garzon, Olga
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Resistance of polygonal cross-sections: application on steel towers for wind turbines2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wind power is considered an efficient alternative for production of electrical energy. One advantage that wind power offers compared to conventional ways of producing energy such as fossil energy and nuclear energy is the low emission of carbon dioxide “CO2” during production of electrical energy. In the last two decades extensive research and huge resources have been focused on production of wind power around the world. In the European Union (EU) the installation of wind power has an annual growth rate of over 11% from 3.2 GW in 2000 to 11.9 GW in 2012 [1] A wind power station consists of a tower with a turbine at the top. In the tower equipment used for transforming kinetic energy in the wind and turbine to electrical energy is placed. The cost for the tower is up to 27% of the total building cost. Building higher towers increases the output of wind power as the wind becomes more constant and the wind speed increases with the increase of the tower height. To make the tower hollow to create space for equipment, decrease weight and increase bending stiffness the walls should be as thin as possible. For such thin walled structures stability is one of the most dangerous failure cases, it leads to brittle failure. The tower needs to be stiff enough to prevent instability. In addition to this, it is important to use connections with high fatigue endurance, which is no considered in this analysis.One solution to reduce transportation costs is to manufacture the tower in sections, at least for onshore towers where the access is difficult. These towers can be made from using a lattice (truss) tower or a tubular tower made from steel. By using sections of high strength steel the towers will have more structural strength with more stability and lower cost as less material is used. As many of the tubular and lattice (truss) towers are made from thin elements it is important to study buckling. Therefore, a study of optimization by geometrical analysis and comparison with the actual standards is performed. Thin plates are often made from cold-formed steel with higher yield strength. The focus of this thesis is in the evaluation and the use of thin folded plates that can be combined to form polygonal cross-sections in towers for wind turbines. An initial numerical study of a folded plate with three different polygonal cross-sections was done using the Finite Element software ABAQUS [2]. The results are compared with EN 1993 part 1-3 [3] and EN 1993 part 1-5 [4]. The FEA showed local buckling as failure mode in all cases of the folded plates. The folded plates are designed to be used as section members for tubular and lattice (truss) towers. In the design for lattice towers the thin folded plates may be connected with gusset plates at different distances over the length of the plate to form a semi-closed cross-section column. For tubular towers the plates were designed to be connected by longitudinal connections to form a tube with a polygonal cross-section. The validity of the design rules given in EN 1993 part 1-3[3], EN 1993 part 1-5 [4], EN 1993 part 3-2 [5]and EN 1993 part 1-6 [6] were used.

  • 243.
    Garzon, Olga
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Heistermann, Tim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    A study of an axially compressed cold-formed folded plate2011In: Proceedings of the 6th International Conference on Thin-Walled Structures: Recent Research Advances and Trends, Timisoara, 2011, p. 297-304Conference paper (Refereed)
    Abstract [en]

    Cold formed steel members are new compared to hot rolled material in building construction. Mostly all cold formed elements have open cross sections and the thicknesses of its members are normally small related to their widths. Therefore, local buckling may occur before the section yields. The work presented is based on experiments of axially compressed cold formed folded plates with two different plate thicknesses of 6 mm and 8 mm; for thickness of 6 mm with two different lengths, 400 mm and 900 mm and for 8 mm plate thickness with a length of 400 mm. A nominal steel grade of S355 is used in experiments. The results, carried out in experiments, are compared to Finite Element Analyses (FEA), taking into consideration different yield strength in the cold-formed areas. The commercial software ABAQUS is used and the validity of rules of EN 1993 part 1-3 is checked.

  • 244.
    Gervasio, Helena
    et al.
    University of Coimbra.
    Eriksen, Jörgen
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Silva, Luis Simoes da
    University of Coimbra.
    Comparative analysis of an integral abutment composite bridge and a concrete bridge with expansion joints2008In: Steel bridges : advanced solutions & technologies: 7th International Conference on Steel Bridges ; conference proceedings ; Guimarães, Portugal, 4 - 6 June, 2008 ; [ICSB '08] / [ed] Paulo J. S. Cruz, Brussels: European Convention for Constructional Steelwork, ECCS , 2008Conference paper (Refereed)
    Abstract [en]

    Bridge engineers very often face economic restrictions on their designs in addition to technical requirements. Those requirements are related not only to initial construction costs but also the cost to maintain the bridge condition at the level required by the bridge administration. In standard bridge structures, expansion joints are one of the most expensive components to maintain. In this regard, jointless bridges have major advantages. Integral bridges are built without joints, they span from one abutment to the other abutment, possibly over intermediate piers, without any joints in the deck. The absence of joints and bearings results in savings in initial costs and reduce maintenance efforts. Apart from economical benefits, the reduction of maintenance leads to less disturbance of the traffic over the bridge and thus to smaller environmental and social impacts. In this paper a case study is presented with the purpose of making a comparative life cycle analysis between an integral composite bridge and a concrete bridge with expansion joints. The result of this life cycle analysis will enhance the advantages of the former solution in regard of economical and environmental aspects.

  • 245.
    Gervásio, Helena
    et al.
    ISISE, Department of Civil Engineering, University of Coimbra.
    Rebelo, Carlos
    ISISE, Department of Civil Engineering, University of Coimbra.
    Moura, André
    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.
    Silva, Luis Simões da
    ISISE, Department of Civil Engineering, University of Coimbra.
    Comparative life cycle assessment of tubular wind towers and foundations: Part 2: Life cycle analysis2014In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 74, p. 292-299Article in journal (Refereed)
    Abstract [en]

    In the first part of the paper the design of tubular towers and respective onshore foundations was addressed. The considered solutions were based on steel, concrete and hybrid steel-concrete tubular towers supporting multi-megawatt turbines of 2, 3.6 and 5 MW power with hub heights of 80, 100 and 150 m respectively. In this second part of the paper, the life cycle analysis of the designed case studies is performed and conclusions about their environmental impact are drawn. Two different scenarios concerning the lifetime of the towers were established. The first scenario considers 20 years lifetime and two different construction methods for the connection of the steel segments, the first based in current technology using flange connections and the second using newly developed friction connections. Assuming equal importance for all environmental categories in this scenario, it may be concluded that for heights up to 100 m hybrid towers with friction connections are the most efficient solution. For higher heights, the concrete tower becomes more efficient. The second scenario considers an increased total lifetime of 40 years, assuming the reuse of the tower after 20 years of operation. In this case, the use of friction connections in steel towers enhances the possibility of dismantling and reusing the tower potentiating much better performance in relation to the environmental category of global warming.

  • 246.
    Ghasemi, Yahya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Aggregates in Concrete Mix Design2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The importance of studying the behaviour and properties of concrete can be highlighted by considering the fact that concrete is the most used man-made material in the world. The very first step in making concrete is its mix design and deciding the type and amount of constitutes used in the production of concrete which should fulfil the requirements of the final product. Mix design models are commonly used for the purpose of proportioning concrete ingredients while anticipating the properties of the final product. 

    The current document deals with the commonly used principals in mix design models namely particle packing theory and excess water/paste layer theories. The conducted studies includes an investigation on accuracy of particle packing models (Toufar, 4C, CPM) and also tries to address the issue with measurement of specific surface area of particles as an essential input to water/paste layer theories. 

    It has been observed that the particle packing models can predict the packing density with acceptable margin. However, it should be mentioned that the particle packing models by themselves are not mix design models but should be rather used as a part of a mix design. In addition, it was found that the accuracy of calculating the specific surface area of particles based on their size distribution curve can be further improved by assuming angular platonic solids as uniform shape of aggregate instead of traditional approach of assuming spheres for aggregates’ shape. 

  • 247.
    Ghasemi, Yahya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Flowability and proportioning of cementitious mixtures2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Understanding the role of constituents of cementitious mixtures as the most globally used human-made material and their effect on the flowability of the blends is of great importance. A comprehensive understanding of the ingredients of mixtures allows for optimized proportioning of constituents and can lead to a reduction in cement and water demand of the blends.

    The thesis focuses on relating the flow of mixtures to the specific surface area of the particles through the concepts of excess water layer theory by assuming that the particles are enveloped by a thin film layer that separates the grains and lubricates their surfaces. However, in order to study the film thickness, it is inevitable to consider packing density and specific surface area of the particles. Both of the mentioned parameters and their influence on water requirement of mixtures were investigated as a part of the project.

    The theoretical part of the thesis includes background and explanation of the concepts and theories used in conducting the research including particle packing theory, specific surface area, and excess layer theories. In addition, the thesis attempts at defining and formulating terms and parameters such as representative shape, mixer efficiency, and optimal packing.

    The experimental part of the thesis consists of laboratory measurements of packing density in the loose state, estimation of specific surface area using microtomography and slump tests for mortar and concrete.

    The results of the thesis indicate that the available packing models can estimate the packing density with acceptable accuracy. In addition, it was shown that it is possible to estimate flowability of mixtures based on information about the specific surface area of the constituents. A mix design approach is introduced which predicts flow spread of slump test, a measure that is often used in laboratories and at the building sites.

    Moreover, the research revealed that the estimation of the specific surface area of particles can be improved by assuming a platonic solid shape for the particles instead of spheres. Furthermore, the mixer efficiency was quantified and optimization of mixtures against packing density and water requirement was explained.

    The finding of the project lays a foundation for a simple workability based mix design approach.

  • 248.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    A method for obtaining optimum packing of aggregates for concrete at the onset of flow2017In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017, p. 361-365Conference paper (Refereed)
    Abstract [en]

    Particle packing models have been studied extensively during past decades and led to development of some complex and relatively accurate predictions of packing of granular materials. While the models are capable of calculating the packing density for different volumetric share of constitutes, the concept of optimum packing remains unclear. The study aims to define optimum packing based on particle packing theory and excess water layer theory .The approach makes it also possible to calculate amount of paste that is required to put a concrete mixture at the onset of flow. Some pilot tests conducted in the laboratory showed good agreement with calculated data.

  • 249.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Lulea university of technology.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Lulea university of technology.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    A theoretical study on optimal packing in mortar and paste2019In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605Article in journal (Refereed)
    Abstract [en]

    Packing density of particles is regarded as a key factor affecting workability of cementitious mixtures. While the value can be easily measured, and several models exist for estimating the parameter, no generally accepted definition exist for the optimal packing. Current study aims at exploring the concept of optimal packing in mortars and paste using particle packing and excess water layer theories. A semiempirical method is used for calculating water demand of mixtures based on their specific surface area. The approach allows for estimating optimal packing considering water demand and water to cement ratio of mixtures in addition to packing density. 

  • 250.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Exploring the relation between the flow of mortar and specific surface area of its constituents2019In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 211, p. 492-501Article in journal (Refereed)
    Abstract [en]

    Mortars can be studied as mixtures of solid and flowable phases. The volume of the flowable phase required for deformation depends on the solid phase surface area according to excess layer theories. This paper examines the relation between the specific surface area of constituents in mortars and their flow. The flowable phase volume was divided by the solid phase surface area to obtain the layer thickness surrounding the surface of the particles. The results suggested that the amount of water and paste needed to ensure flow could be estimated from the packing density and specific surface area of the particles.

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