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  • 1.
    André, Alann
    et al.
    Swerea SICOMP AB.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Flax fibre-reinforced glued-laminated timber in tension perpendicular to the grain: experimental study and probabilistic analysis2010In: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 22, no 9, p. 827-835Article in journal (Refereed)
    Abstract [en]

    The weak mechanical properties of wood in tension perpendicular to the grain are often the origin of catastrophic brittle failure. In order to enhance the tension strength perpendicular to the grain and achieve a more ductile failure, flax fibre and glass fibre reinforced polymer (FRP) composites were used to strengthen glued-laminated (glulam) timber specimens. Three series of specimen of glulam timber (flax fibre reinforced, glass fibre reinforced and unreinforced), with a grand total of 28 specimens, were tested in tension perpendicular to the grain. For an approximate amount of FRP reinforcement of 1.2- in volume (thickness ~ 0.7 mm), an increase of the tensile strength up to 74- was shown, with a stiffness increase up to 41-. For all reinforced specimens, semi-ductile failures were observed. A parametric study was carried out using both the Monte Carlo method (MC) and the First Order Second Moment method (FOSM). It is shown that the mean values obtained during experiments are in agreement with those from the MC simulation. However, the standard deviations from the MC simulation are larger. From the FOSM analysis, it is demonstrated that the variation in glulam stiffness perpendicular to the grain is not the first parameter driving the variation for the reinforced system. The variation in mechanical properties of the flax fibres appeared to be the driving parameters for the strength of the system.

  • 2.
    Björnfot, Anders
    et al.
    Faculty of Technology, Economy and Management, Gjøvik University College.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simonsson, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    'Find-think-write-publish': Lean thinking in scientific paper writing2012Conference paper (Refereed)
    Abstract [en]

    Construction research supports long-term development of the construction industry and the society. Thus it is important to evaluate research against existing knowledge and to constantly develop new knowledge. The main mechanism for doing so is publishing scientific papers. In Sweden, praxis has developed that a Ph.D. consists of a handful of scientific papers. The average time period for a Ph.D. is five years after which the funding situation changes drastically. Previously, the duration of Ph.D. studies at Luleå University of Technology, Sweden often exceeded the planned five years, disrupting the flow of Ph.D. examinations. To increase awareness and interest in paper writing, a method was sought to visualise and manage the writing process. This paper investigates how an Oobeya room can be implemented in construction research to support paper writing. Experiences of working with the Oobeya room in three separate research divisions prove that it is possible and fruitful to better manage knowledge in academic institutions. Even though research is creative, it can be properly managed without hampering scientific freedom. Evidence from managing scientific paper writing using the Oobeya room shows that proper management of research will actually create better research that is more publishable with shorter lead times!.

  • 3.
    Caprolu, Giuseppe
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Källsner, Bo
    Linnaeus University, Växjö.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Test on the splitting failure capacity of the bottom rail due to uplift in partially anchored shear walls2012In: World Conference on Timber Engineering: Final Papers - Architecture and Engineering Case Studies / [ed] Pierre Quenneville, New Zealand Timber Design Society , 2012, p. 189-194Conference paper (Other academic)
    Abstract [en]

    Källsner and Girhammar have developed a new plastic design method for wood-frame shear walls at ultimate limit state. The method is capable of calculating the load-carrying capacity of partially anchored shear walls, where the leading stud is not necessarily anchored against uplift. In fully anchored shear walls, the leading stud needs to be anchored using some kind of hold-downs to resist uplift and the bottom rail needs to be fixed by anchor bolts to resist horizontal shear forces. In partially anchored shear walls, where hold-downs are not provided, the uplifting force is resisted by the sheathing-to-framing joints along the bottom rail. Hence, it is important that the bottom rail is anchored to the floor structure or foundation by anchor bolts and, therefore, able to transmit the forces to the structure below. Because of the eccentric load transfer, transverse bending is developed in the bottom rail and splitting of the bottom rail can occur. In order to use the plastic design method, a ductile behaviour of the sheathing-to-framing joints must be ensured. In this paper, results of tests on the splitting capacity of the bottom rail due to uplift in partially anchored shear walls are presented. Specimens with single-sided sheathing were tested, varying the size of washer, pith orientation of the bottom rails and anchor bolt position along the width of the bottom rail. The aim of the tests was to evaluate the influence of these parameters in order to avoid splitting failure of the bottom rail. Two types of brittle failure modes occurred during testing: (1) a crack opening from the bottom surface of the bottom rail and (2) a crack opening from the edge surface of the bottom rail along the line of sheathing-to-framing joints. These failure modes were mainly dependent on the washer size and the location of the anchor bolt. The results show that the distance between the edge of the washer and the loaded edge of the bottom rail has a decisive influence on the maximum load and the failure modes of the bottom rail.

  • 4.
    Caprolu, Giuseppe
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Källsner, Bo
    School of Engineering, Linnæus University, Växjö.
    Lidelöw, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Splitting Capacity of Bottom Rail in Partially Anchored Timber Frame Shear Walls with Single-Sided Sheathing2014In: The IES Journal Part A: Civil & Structural Engineering, ISSN 1937-3260, E-ISSN 1937-3279, Vol. 7, no 2, p. 83-105Article in journal (Refereed)
    Abstract [en]

    Plastic design methods can be used for determining the load-carrying capacity of partially anchored shear walls, where hold-downs are not provided. In order to use these methods, a ductile behaviour of the sheathing-to-framing joints must be ensured. Since the forces in the anchor bolts and the sheathing-to-framing joints do not act in the same vertical plane, the bottom rail will be subjected to bending and shear in the cross-wise direction, and splitting of the bottom rail may occur. In this article, results of two experimental programmes on the splitting capacity of the bottom rail due to uplift in partially anchored shear walls are presented. Two brittle failure modes occurred during testing: (1) a crack opening from the bottom surface of the bottom rail and (2) a crack opening from the edge surface of the bottom rail along the line of the sheathing-to-framing joints. The results show that the distance between the edge of the washer and the loaded edge of the bottom rail has a decisive influence on the maximum load and the failure modes of the bottom rail.

  • 5.
    Edskär, Ida
    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.
    Wind-Induced Vibrations in Timber Buildings-Parameter Study of Cross-Laminated Timber Residential Structures2017In: Structural Engineering International, ISSN 1016-8664, E-ISSN 1683-0350, Vol. 27, no 2, p. 205-216Article in journal (Refereed)
    Abstract [en]

    A current trend (2016) to construct high-rise timber buildings is seen. In order to understand the limitations posed by the timber material, wind-induced dynamic behaviour causing vibrations in the serviceability limit state has to be studied. The aim of this research is to calculate the natural frequency and acceleration levels of timber buildings having a cross-laminated timber structure to further the understanding of its behaviour and how a change in parameters affects building performance as reflected against comfort criteria. The results were calculated through finite element modelling using commercial software and by performing a modal analysis. The parameters under scrutiny were material stiffness, wall density, damping ratio, building height, and building footprint. The results show that even at moderate building heights (12-14 storeys), the comfort criteria are not fulfilled. Furthermore, the interaction between stiffness and mass for timber buildings needs to be explored further. And since the change of building footprint has a strong influence on the dynamic behaviour, the interplay between architectural and structural design becomes more important. Finally, more data on measurements of damping in timber buildings need to be collected to further validate simulation models.

  • 6.
    Jansson, Gustav
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Johnsson, Helena
    Concurrent engineering in educational projects: case study Svartöberget2008In: CIB-W78: International Conference on Informations Technology in Construction, Universidad de Talca , 2008, p. 1-12Conference paper (Refereed)
    Abstract [en]

    Each year, Luleå University of Technology teach 40 civil engineering students and 45 architectural engineering students basic knowledge in the construction process through a simulated real-life situation. In the third year, the grand total of 85 students is brought together and taught their respective professional roles through acting as experts within 6 different fields in the realization of a residential area. Research in the last decades has identified concurrent engineering as a possible method for streamlining the design phase in the construction process. The student project was therefore planned with a concurrent engineering approach, where all student groups start their work at the same time. The pedagogy was to teach students a new approach to working in large projects, with the side effect of testing if concurrent engineering is feasible also in educational projects. Information is shared between groups through live documents on a project portal. Project coordination and communication is handled by 21 project leaders who meet regularly to exchange information between groups and detect missing information needed from other groups. Project planning is made through a method adopted from lean construction; Look Ahead Planning, which is part of the Last Planner method. IT-support is used to produce data and perform calculations but also as a tool for quality assurance across groups. All data is eventually summed up and presented in a virtual reality model of the new residential area. The VR model is gradually refined and the structure for delivering information into the model is drawn up by 6 appointed IT coordinators

  • 7.
    Jansson, Gustav
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Engström, Dan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Platform use in systems building2014In: Construction Management and Economics, ISSN 0144-6193, E-ISSN 1466-433X, Vol. 32, no 1-2, p. 70-82Article in journal (Refereed)
    Abstract [en]

    The practice of reusing processes and technical solutions leads to the formation of product platforms in house building. Product platforms originate from industries employing a make-to-order production strategy, e.g. the automotive industry. To test how the product platform concept is useful in engineer-to-order production strategies, a case study at two Swedish house-builders was made. Key factors that affect platform use in systems buildings were sought. The smaller company operates a supplier-led platform focusing on commonalities in process knowledge. There is less definition of the product itself to allow for distinctiveness in the product offer. The larger company has a decentralized business and operates a client-driven platform with fragmented standardization. Focus is put on creating commonality through defining the product and handling distinctiveness through an iterative design procedure. Product families were not in use at the case study companies. The companies transform standardized platform solutions into project uniqueness by using support methods. Four platform support methods emerged from the case studies: design planning, collaborative design, design optimization, and requirements iteration. The balance between commonality and distinctiveness in the platform is important to attend to in each house-building project. The engineer-to-order production strategy hinders the implementation of a fully parameterized platform. The product platform concept is therefore expanded with support methods to handle distinctiveness, i.e. project uniqueness. The product platform assets: components, processes, relationships and knowledge, are present also in platforms used in systems building

  • 8.
    Jansson, Gustav
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jensen, Patrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Modularization in a housing platform for mass customization2013Conference paper (Other academic)
    Abstract [en]

    The problem of combining production efficiency with flexible product offers in housing design is well known. The platform concept is applied in housing to support design and production with predefined solutions. Modularization can be useful to meet both client demands on flexibility and production requirements on standardisation. To identify the module drivers in housing, ten projects at one off-site housing company were analysed. Furthermore, the cycle time for the modules was recorded. Client, design, purchasing, production and suppliers have different module drivers. When module drivers concur, modules are identified by; identifying clear and few interfaces, the availability of a supplier, and the cycle time for the design and production of the module in relation to the production pace. The results from the case study further show that fixed geometry on modules is a less successful concept than parameterised modules in housing. The ability to outsource technical solutions increased, when the module drivers were combined with a long term relationship with the supplier. Variant modules were successfully applied in the studied company to respond to client demands. Further research is needed on how to configure generic modules.

  • 9.
    Jansson, Gustav
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Söderholm, Erik
    Johnsson, Helena
    Design process organisation at industrial house builders: a case study of two timber housing companies in Sweden2008In: Proceedings 24th Annual ARCOM Conference: 1-3 September 2008, Cardiff, UK, Association of Researchers in Construction / [ed] Andrew Dainty, Reading: Association of Researchers in Construction Management , 2008, Vol. 1, p. 135-144Conference paper (Refereed)
    Abstract [en]

    In industrial construction companies the design process tends to be the bottleneck for further streamlining of the entire manufacturing process. The demands posed on this particular design process are diverse; should feed the production process with data, should satisfy the client with documentation and should document the project for experience feedback. Further complications arise from the internal notion of being a manufacturing company opposed to the external view of the company being a traditional building firm. In this work, the design process at two industrial builders was studied in-depth. The two companies have chosen opposing strategies for their design departments; one have specialised functions where all projects pass and the other have more general designers who work in parallel with similar tasks. With the support from lean production theory, the consequences of these two strategies on succeeding with design of industrial built houses are analysed. The results show that increased specialisation is beneficial in daily work, but can pose a sensitive design process if key competences suddenly vanish.

  • 10.
    Jansson, Gustav
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Viklund, Emma
    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.
    Design management using knowledge innovation and visual planning.2016In: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 72, no 3, p. 330-337Article in journal (Refereed)
    Abstract [en]

    An open platform used for industrialised house-building imposes restrictions on the flexibility of the product offering when developing design standardisation. How design process standardisation incorporates variations in products has not been widely studied. The aim of this research is to explain how design breakdown enables Lean Product Development Flow (LPDF) and look-ahead planning in an industrialised house-building context where an open platform is used. A case study was conducted of how one of the leading industrialised house-building companies in Sweden introduced the LPDF tool Knowledge Innovation/Visual Planning (KI-VP) into their design process. The implementation of KI-VP led to an increased cross-functional understanding of relationships between activities, which are an important factor in achieving flexibility and a synchronised workflow. By using design standardisation, look-ahead planning was implemented and used in the management of design flow. Standardisation through design breakdown provides a basis for knowledge innovation that enables improvement of the open platform using a bottom-up approach and increases the production flow. 

  • 11.
    Jensen, Patrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lidelöw, Helena
    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.
    Product Configuration in Construction2015In: International Journal of Mass Customisation, ISSN 1742-4208, Vol. 5, no 1, p. 73-92Article in journal (Refereed)
    Abstract [en]

    Construction is traditionally a trade that produces unique, one-off products designed specifically for the project in an engineer-to-order process. However, the development of flexible product platforms, based on the theory of mass customization, can offer product flexibility with affordable costs. The degree of commonality can also be increased if applying the products-in-products concept. This study aims to conceptualize and test theories of mass customization through modularization for applications in the construction industry. This is examined for three cases, with different specification processes (modify-to-order, configure-to-order and select-variant) incorporating bothbuilding and infrastructure products. The results show that the products-in-products concept is useful for enabling mass customization in construction. While the design can be integral in the select-variant type of specification process, the architecture needs to have a modular structure to enable a modify-to-order or configure-to-order type of customization.

  • 12.
    Jensen, Patrik
    et al.
    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.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Configuration through the parameterization of building components2012In: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 23, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Many construction companies have developed building systems, based on prefabrication strategies, to enhance productivity. Current practice coupled with the difficulties of introducing these systems early in the design process often leads to ad hoc solutions and problems downstream along the value chain. In 2008 a multi-storey timber building system based on modularization principles was developed. The customization process used in this system is illustrated herein using a configurable timber floor slab module. The downstream flow of design information and upstream flow of constraints on, and rules for, the building system are described from three product viewpoints: the customer view, the engineering view and the production view. Using a manufacturing CAD tool, design automation is implemented in the engineering view and connected to an architectural CAD tool. The demonstration software shows that manufacturing CAD tools can be used to create design automation alternatives for modularized building systems within the construction industry.

  • 13.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Construction Purchasing and Supply Chain Management2012In: Construction Management and Economics, ISSN 0144-6193, E-ISSN 1466-433X, Vol. 30, no 12, p. 1105-1107Article in journal (Other academic)
  • 14.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Fånga det industriella byggandet2013Report (Other academic)
    Abstract [sv]

    Det industriella byggandet i Sverige har under senare år rönt ett ökande intresse. Fortfarande råder tveksamhet kring vad industriellt byggande egentligen innebär. I den här rapporten sammanställs intervjuer med personer som har lång erfarenhet av olika satsningar på industriellt byggande. Gemensamt kommunicerar intervjuerna ett par teman som sammanfattar vad industriellt byggande omfattar:‐ För att industriellt byggande skall fungera måste hela kedjan, frånmarknadssidan, över projektering, till produktion och montage samt logistikfungera och gå i takt. Det innebär att tekniska lösningar som väljs måste vararobusta och gångbara i alla led. Ofta leder det till att lösningen inte är heltoptimal för något led, men det fungerar i kedjan.‐ Kopplingen mellan det erbjudande företaget har mot marknaden och deprodukter man kan leverera måste vara helt i överensstämmelse med varandra.Säljarbetet i ett industriellt byggande skiljer sig avsevärt från säljarbetet itraditionellt byggande. I ett industriellt byggande handlar det om att arbetainom byggsystemet tillsammans med kunden och förklara vilka kostnader somuppkommer om man går utanför systemet. I ett traditionellt byggande handlarsäljarbetet om att fånga kundens behov och tillfredsställa dem, även om detinnebär nya produktionsmetoder.‐ Långsiktigheten i en satsning på industriellt byggande kan inte överskattas. Ett företag som satsar måste vara förberett på att de första åren visar sämre ekonomiska resultat. Där måste finnas en tålighet för att orka med utvecklingsinsatser samtidigt som full produktion pågår. Vägen fram till ett fungerande och etablerat koncept måste ske i mindre steg och i en takt så att likviditeten i företaget inte blir lidande.‐ Ett unikt erbjudande är inte en fördel för industriellt byggande. Det handlarsnarare om att erbjuda en vara som uppfyller alla funktionskrav enligt normenpå ett trovärdigt och verifierat sätt. Det unika ligger i själva processen där t.ex.korta tider på byggplats kan vara ett erbjudande.‐ Relationerna i värdekedjan är mycket långsiktiga i industriellt byggande. Avtalom samarbete skrivs ibland över flera år. Underleverantörerna, både konsulteroch materialleverantörer, är ovana att arbeta på detta sätt i byggbranschen.Särskilt konsulternas affärsmodell att ta betalt per timme krockar medlångsiktiga samarbeten som bygger på ständiga förbättringar och upprepning av lösningar.Tidigare modeller för industriellt byggande har lagt för lite fokus på marknadens betydelse, affärsmodeller och kundmöten. Byggare generellt är ovana att hantera marknadsfrågor och att ha kundrelationer som sträcker sig bortom inlämnande och diskussioner kring anbud. Denna ovana kommer sig av att det bara är under de senaste 20 åren som Sverige haft en avreglerad bostadsmarknad. För industriellt byggande är marknadskopplingen om möjligt ännu viktigare och detta område behöver utvecklas avsevärt framgent.

  • 15.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Plug shear failure in nailed timber connections: avoiding brittle and promoting ductile failures2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mechanical timber connections can fail both in a brittle and a ductile manner depending on the joint layout. Plug shear failure in nailed timber connections is a brittle failure mode, which shall be avoided in timber structures. This failure mode occurs in nailed connections loaded in tension parallel to the grain, for instance in the lower chord of a timber truss. The failure mode is not described in the Swedish building code of today, but there is an informative annex in the upcoming Eurocode 5 concerning the subject. In the thesis, plug shear failure is studied and a new prediction model developed based on experimental work on nailed steel-to-timber connections. The experiments were short-term experiments and the effect of long-term conditions is not considered. The total amount of joints tested was 86, which together with results from other researchers formed the base for the prediction model. The stress state and the effect of fastener placement were analysed and showed that plug shear failure is initiated at the nail farthest from the free end of timber. Increased spacing between fasteners lessens the risk for plug shear failure to occur, especially the spacing perpendicular to the grain is important. The prediction model is based on structural mechanics and suggests that the plug shear resistance R = blfv, where b is the joint width, l the joint length and fv the shear strength of wood. The shear strength is determined through fv = KAs-0.25, where As = bl and K is a constant. Furthermore, an analysis based on fracture mechanics was performed showing the importance of the softening behaviour of the joint failure. The overall goal with the development of a prediction model is to avoid brittle failures and promote ductile failures. As a tool to promote ductile failures, a measure was developed to aid the designer in designing ductile and strong joints. Recommendations on nail spacing and overall design of the joint are finally given with the aim to avoid plug shear failure.

  • 16.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Plug shear failure in nailed timber connections: experimental studies2003In: Meeting thirty-six - CIB-W18, International Council for Research and Innovation in Building and Construction, Working Commission W18 - Timber Structures: Meeting thirty-six - CIB-W18, International Council for Research and Innovation in Building and Construction, Working Commission W18 - Timber Structures / [ed] Rainer Görlacher, Karlsruhe: Lehrstuhl für Ingenieurholzbau und Baukonstruktionen, Univ. Karlsruhe , 2003Conference paper (Refereed)
  • 17.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Plug shear failure: the tensile failure mode and the effect of spacing2004In: Meeting thirty-seven - CIB-W18, International Council for Research and Innovation in Building and Construction, Working Commission W 18 - Timber Structures: Edinburgh, Scotland, August 2004 / [ed] Rainer Görlacher, Karlsruhe: Lehrstuhl für Ingenieurholzbau und Baukonstruktionen, Univ. Karlsruhe , 2004Conference paper (Refereed)
  • 18.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Production strategies for pre-engineering in house-building: Exploring product development platforms2013In: Construction Management and Economics, ISSN 0144-6193, E-ISSN 1466-433X, Vol. 31, no 9, p. 941-958Article in journal (Refereed)
    Abstract [en]

    Construction is a trade where the dominating production strategy is engineer-to-order. House-builders can pre-engineer their design to different degrees, resulting in variations of the engineer-to-order strategy: design-to-order, adapt-to-order, and engineer-to-stock. This variation causes different settings for the use ofplatforms in house-building. The aim of this research is to diversify the engineer-to-order production strategy and its consequences for platform organization by studying its use in house-building. The multiple case study on four engineering/contractor firms reports the core capabilities for engineer-to-order firms: procurement and tendering, market knowledge, engineering, multi-skilled manufacturing, and coordination of sales and manufacturing. Design-to-order, adapt-to-order and engineer-to stock were shown to be production strategies in use in house-building. In design-to-order platforms parts of the platform are undefined while engineer-to-stock platforms are fully predefined. Coordination between market and manufacturing is a crucial capability when engaging in platform organization. When an engineering firm and a contractor collaborate to fulfil client needs, the coordination capability between market and manufacturing was shown to be low. The case study shows that specialized contractors who integrate the supply chain towards a specific market segment benefit fully from the platform concept, while contractors with a wider scope could focus on standardization of processes rather than products.

  • 19.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Systematic design of glulam trusses2001Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The design of a structure should be regarded as the design of a system. In this licentiate thesis a method (concurrent engineering) for the design of systems is studied parallel with the development of the system itself. The purpose of the work is twofold: To study the application of concurrent engineering (CE) as a method to manage the design work for the design of a glulam truss. To develop a glulam truss and investigate if it can be made competitive on the Swedish market. The qualitative study started with the formation of a CE team consisting of an architect, a contractor and a manufacturer of glulam with the researcher as the project manager. The idea in CE is to let members from different parts of the design work (design, production and manufacturing) solve the problem together. Through the concurrent work of these members a proposal of a glulam truss was posed. The proposal was then verified and refined by the CE team through several iterations between resistance considerations and production issues. The qualitative study showed that the members of the CE team are equally important for the success of the development project. The project manager needs to be independent and have a wide knowledge base. Furthermore, the production issues were investigated early in the design process, which is an advantage for the manufacturer of the truss. The quantitative study focused heavily on the solution for the joint in the glulam truss. A connection type new to the Swedish market was proposed; nails with slotted-in steel plates. The joint consists of steel plates placed in internal slots in the glulam member which is assembled by shooting the nails through the glulam and the steel plates with a nailer. Medium-sized joints were tested in tension parallel to the grain and the resistance was found to be on average 8.35 kN/nail and two steel plates. Production considerations for the joint type revealed that sawing the slots to accommodate the steel plates could be a problem and this was further investigated in laboratory tests on full-scale joints. The full-scale tests were performed using the theory of statistical experimental design aiming to show tendencies in the behaviour rather than performing a parameter study. The specimens were designed without eccentricities in the joint. The results showed that buckling tendencies of the steel plates must be suppressed and therefore the design of the full-scale joint was adjusted to counteract this. Tension perpendicular to the grain in the joint was qualitatively studied. The results showed that the occurrence of a compressive force close to the tensile force does not affect the resistance in tension perpendicular to the grain for this joint design and this failure mode will not set any demands on the resistance of the truss. The glulam truss was optimised with respect to material cost to investigate the competitiveness on the Swedish market. First order theory was used assuming linearly elastic material behaviour. The rotational capacity of the joints was included in the analysis. Together with estimates for the production cost of a joint, the results showed that a glulam truss using this connection type would have a production cost of approximately 19,200 SEK/truss. The competitiveness of this cost must be judged by the market, but steel trusses have a production cost of about 15,600 SEK/truss while other glulam structural elements range from 18,300-31,000 SEK/element.

  • 20.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    The building system as a strategic asset in industrialised construction2011In: Proceedings of the 6th Nordic Conference on Construction Management and Organisation: Shaping the Construction/Society Nexus / [ed] Kim Haugbølle; Stefan Christoffer Gottlieb; Kalle E. Kähkönen; Ole Jonny Klakegg; Göran A. Lindahl; Kristian Widén, Danish Building Research Institute, Aalborg University , 2011, Vol. 3 . Construction in Society, p. 541-552Conference paper (Refereed)
    Abstract [en]

    The growing industry segment within construction focusing on industrialisation, meet new challenges traditional construction firms never have encountered. The choice of a building system (technical and process platform) defines not only what resources and technology are needed, but also the organisation within the company, its market position, and possible growth. Using a resource-based view, the building system can be seen as a strategic asset for an industrialised construction company. In this paper, the characteristics of a strategic asset is identified and used to analyse two building systems as being a strategic asset at two industrialised construction companies in Sweden. Two companies participated in the case study, one specialised contractor and one more general contractor, both active in the housing segment. The building system is clearly a strategic asset in all aspects for the specialised contractor, while the asset for the general contractor lies more in the organisational power of the company than in the technical solutions. The company strategy should therefore differ. The specialised contractor should strive to clarify and strengthen their total offer to the client, while the more general contractor should continue to exploit its human resources, moving towards a more unique offer to their client.

  • 21.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    The Daily Life of a Construction Contractor: Multiplicity in Production Strategies2013In: Proceedings from 7th Nordic Conference on Construction Economics and Organisation 2013: Green Urbanisation - Implications for value Creation : Trondheim June 12-14, 2013 / [ed] Ole Jonny Klakegg, Trondheim: Akademika forlag, 2013, p. 404-414Conference paper (Refereed)
    Abstract [en]

    For a contractor, two main contractual agreements are used to meet the client; open bidding or design-build contracts. Viewing construction as a production system, this implies different production strategies are active; engineer-to-order and make-to-order. Theory suggests that this is difficult to handle within the same firm. The research aims to identify concurrent production strategies at a contractor and to elaborate on the consequences for the internal capabilities when acting according to several strategies. The in-depth case study is performed at a large contractor, active on the construction market in several European countries. The core capabilities of the case firm are analysed using theory capturing needed capabilities in the engineer-to-order and make-to-order situations. Generalisation is made by describing the atypical capabilities and consequences. The case study firm operates four concurrent production strategies. To cope, manufacturing is organised in flexible, multi-skilled teams to optimise the manufacturing resource utilization. When introducing industrialization in construction, the manufacturing flexibility hinders streamlining of the supply chain.

  • 22.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Alerby, Eva
    Luleå University of Technology, Department of Arts, Communication and Education, Education, Language, and Teaching.
    Hyyppä, Kalevi
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Jonsson, Håkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Karlberg, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Stenberg, Magnus
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Human Work Science.
    Strömberg, Thomas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    En pedagogisk idé för ingenjörsutbildningarna vid Luleå tekniska universitet2009Conference paper (Refereed)
    Abstract [sv]

    Utmärkande för Luleå tekniska universitet (LTU) har länge varit närheten mellan studenterna och lärarna vilket har manifesterats genom klassrumsundervisning, lärartillgänglighet, mindre studiegrupper, koncentrerade campus etc. Undervisningsformerna har dock ändrats till att idag omfatta dels klassiska föreläsningar i stora studentgrupper, men också projektarbete i team där totalt sett 1/3 av all undervisning vid Luleå tekniska universitet sker i projektform. En fråga har ställts: Har Luleå tekniska universitet idag en gemensam pedagogisk idé för ingenjörsutbildningarna? I så fall är ytterligare en fråga hur denna pedagogiska idé tar sig uttryck i organisationen?Intervjuer med 40 aktiva lärare vid Luleå tekniska universitet har genomförts av projektgruppen (tillika författarna) varpå svaren har grupperats och analyserats i fjorton olika teman. Från dessa teman har sedan fyra hörnstenar i en definition av en pedagogisk idé aggregerats. Formuleringen av den pedagogiska idén lyder: Ett aktivt lärande för yrkeslivet – i branschnära projekt och med god vetenskaplig grund tränas förmågan att arbeta som ingenjör genom coachning från lärare i ett nära och öppet klimat. Idén har antagits av den tekniska fakultetsnämnden vid Luleå tekniska universitet och verifierats på institutionerna. Exempel på implementering och hur den pedagogiska idén aktivt verkar presenteras i artikeln.

  • 23.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Carolin, Anders
    Glulam members strengthened by carbon fibre reinforcement2007In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 40, no 1, p. 47-56Article in journal (Refereed)
    Abstract [en]

    Glulam members often become large in cross section where heavy loads should be carried. In some applications this may cause problems if limitations on height are posed. A possible solution is to reinforce the member by e.g. bonding fibre reinforced polymer (FRP) on the beams or between the glulam lamellas. The aim of this paper is to investigate the possibility of strengthening glulam beams by the use of pultruded rectangular carbon fibre rods and to establish the anchoring length for this system. Tests were performed in three different series completed by a reference series, 10 specimens altogether. All tests were performed as short-term experiments in four-point bending. The experimental results were compared to analytical models in several aspects. The overall capacity of the beam was established using an analogy with concrete beams. Special attention was made to establishing the anchoring length of the reinforcement bar, since this is governing to avoid premature failures. The anchorage length was tested and an analytical model established. The agreement between the analytical critical anchoring length and the test result was satisfactory. The proposed reinforcement method increased the short-term flexural load-carrying capacity by 49-63% on average.

  • 24.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Engström, Susanne
    Ett industriellt byggande kräver aktiv beställare2009In: Husbyggaren : bygg, el, VVS, anläggning, ISSN 0018-7968, Vol. 51, no 7, p. 6-8Article in journal (Other (popular science, discussion, etc.))
  • 25.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Janols, Henrik
    Stehn, Lars
    3D computer visualisation in timber construction: some important parameters2006In: Architectural Engineering and Design Management, ISSN 1745-2007, E-ISSN 1752-7589, Vol. 2, no 3, p. 161-175Article in journal (Refereed)
    Abstract [en]

    Timber building structures are seldom considered because of a lack of timber construction knowledge among many clients and professionals. 3D computer visualization (3D VIZ) is a possible way of communicating the aesthetics of a visible timber structure and visualizing complex timber connections. This paper investigates the potential for 3D VIZ to communicate visible timber structures during the different phases of the construction process. Furthermore, important parameters (controllable in 3D VIZ) for communicating a timber structure are identified. Through an Internet-based Delphi study, the usefulness of 3D VIZ for timber structures has been evaluated by professionals representing different competencies in the construction process. The results show that structural complexity, intended beholder (professional or non-professional) and current construction phase influence the benefit of 3D VIZ. The level of detail in the visualization is heavily dependent on whether the communication is internal (between professionals) or external (between professionals and clients/users). The impact of parameters needed, such as textures, surface structures and realistic lighting, have been described.

  • 26. Johnsson, Helena
    et al.
    Lukaszewska, Elzbieta
    Stehn, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nailed timber joints with a thick interlayer2004In: 8th World Conference on Timber Engineering: WCTE 2004. Proceedings, 2004, p. 281-284Conference paper (Refereed)
  • 27.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Malmgren, Linus
    Division of Structural Engineering, Lund Institute of Technology och Tyréns AB.
    Persson, Stefan
    Division of Structural Engineering, Lund Institute of Technology och Tyréns AB.
    ICT support for industrial production of houses: the Swedish case2007In: Bringing ITC knowledge to work: proceedings, Maribor: Faculty of Civil Engineering , 2007, Vol. 1, p. 407-413Conference paper (Refereed)
    Abstract [en]

    The Swedish construction sector is currently undergoing great changes. The large costs for labour have forced the construction companies to rationalise and minimise labour intense work operations. Therefore, the current trend in construction to adopt the principles of lean production and transform it into lean construction, suits the Swed-ish way of working and the entire Swedish construction sector has caught on. A growing market is the prefabrication of building elements that are transported to site and then erected. The development has been taken so far that modular houses i.e. vol-umes/rooms are prefabricated. Companies in the prefabrication industry within construction fall between two sectors; the construction industry and the manufacturing industry. In terms of IT support the contradiction between the two sectors become evident. Software developed for the construction sector seldom provide enough detailing to suffice as a basis for industrial production, while software supporting the manufacturing industry are incapable of delivering standard construction documenta-tion. The current study presents a multiple case study where six Swedish industrial manu-facturers of timber houses were studied. The process from tender acceptance to mod-ule delivery is described. Alongside, a survey of the building sys-tem revealed that much still needs to be done in terms of documenting a building system. The results show that the ques-tion of IT support is more a question of consequent information strategies than eloquent IT tools. The pressing need for a method for documenting building systems is stressed and different methods are discussed.

  • 28.
    Johnsson, Helena
    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.
    Defects in off-site construction: timber module prefabrication2009In: Construction Management and Economics, ISSN 0144-6193, E-ISSN 1466-433X, Vol. 27, no 7, p. 667-681Article in journal (Refereed)
    Abstract [en]

    The construction industry is based on craftsmanship. Quality control and assurance procedures applied in manufacturing cannot usually be readily applied in construction, where there are higher degrees of uniqueness in each project. One category of companies, industrialized housebuilders, is attempting to bridge some of the gaps between construction and manufacturing. These companies prefabricate building modules for later assembly at the building site. Since they are wholly responsible for large parts of the building process, these companies have greater opportunities to control and improve quality in a more consistent way than ordinary construction companies. Thus, it could be hypothesized that the frequency and severity of defects should be lower in industrialized housing than in ordinary construction. The aim of the study presented here is to examine this hypothesis by measuring and characterizing defects in industrialized housing. The design and manufacturing processes at two Swedish timber module prefabrication firms has been analysed through interviews, site visits and document reviews. Quality audits from three phases of the building process were compiled, analysed and categorized to provide statistical measures of defects in industrialized housing. The results show that the case study companies are better in terms of product quality than conventional housing.

  • 29.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Parida, Gabriela
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Prediction model for the load-carrying capacity of nailed timber joints subjected to plug shear2013In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 46, no 12, p. 1973-1985Article in journal (Refereed)
    Abstract [en]

    Timber joints can experience ductile failures as modeled by Johansen in the European Yield Model adapted in Eurocode 5, or they can fail in a brittle manner. In nailed or screwed joints where the fastener does not protrude through the timber, plug shear failure can occur where an entire plug defined by the perimeter of the joint is torn away from the timber. The brittle plug shear failure, which can occur in joints loaded in tension parallel to the grain, results in a lower joint resistance than the ductile failure modes. The aim of this study is to evaluate existing prediction formulas for plug shear failure in timber connections, compare them to test results and observations, and propose a new prediction formula. Test results from four different experimental studies are presented. Using hypothesis testing, a prediction formula for plug shear failure is proposed based on 92 experiments. The resistance of the tensile failure mode of plug shear failure is best modelled by the tensile resistance of the end face of the plug. The resistance of the shear failure mode of plug shear failure is best modelled by the shear resistance of the bottom area of the plug taking into account the volume effect on shear strength. The model currently in Annex A of Eurocode 5 is overestimating the plug shear resistance compared to the test results analysed in this research. To avoid plug shear failure, short and wide joints are preferred, minimising the number of fasteners in line with the load and grain direction

  • 30.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Persson, Stefan
    Lunds tekniska högskola, LTH.
    Malmgren, Linus
    Tyréns IT.
    Tarandi, Väino
    Eurostep AB.
    Bremme, Jesper
    Inbrix AB.
    IT-stöd för industriellt byggande i trä2006Report (Other academic)
    Abstract [sv]

    Delar av den svenska träbyggnadsindustrin har stora möjligheter att utveckla det industriella byggandet. Villor har lång tradition av att prefabriceras i fabriker för senare transport och montage på byggplats. Volymbyggnadsteknik där prefabriceringen även innefattar ytskikt och installationer har ökat prefabriceringsgraden avsevärt. Fortfarande är dock tillverkningen hantverksbetonad och genomförs med samma dokumentation och styrning som råder på ett platsbygge. Ett industriellt angreppssätt kräver en metodutveckling inom tillverkningen med styrning och kvalitetskontroll som nyckelord för att dra nytta av den upprepningseffekt som troheten till ett byggsystem skapar. Om ett IT-verktyg skall stötta en process, måste processen utformas och beskrivas på ett entydigt sätt som är repeterbart. Införandet av IT-verktyg betyder nästan alltid att processen förändras. Träbyggindustrin har en situation som definierar deras dilemma: man tillhör bygg-branschen och har anammat deras metoder och IT-verktyg, men tillverkningen är en indu-striell process som inte stöds av byggbranschens arbetssätt utan liknar tillverkningsindustrins serietillverkning. Flera företag har implementerat affärssystem och börjat utnyttja dess material- och planeringsfunktioner, en metod som är vanlig i tillverkningsindustrin. Data som skapas i projekteringen vore till nytta för affärssystemet, t.ex. mängder och antal komponenter. Tyvärr är inte byggbranschens IT-verktyg uppbyggda för att kommunicera med affärssystem via databaser. Tillverkningsindustrin har löst detta problem genom att arbeta med PDM-system, där data kring själva produkten hanteras (CAD-ritningar, komponenter). Affärssystemet kan sedan tanka av önskat data från PDM-systemet. Idag saknar träbyggindustrin en effektiv hantering av den egna produkten, byggsystemet. De beskrivningar som finns består av ritningar och endast 50- 70% av den information som behövs för att beskriva byggsystemet kan hämtas från ritningar. Den resterande delen är regler för systemet som sällan dokumenteras, utan existerar som arbetsmetoder inom varje företag. Byggsystemet förvaltas idag genom ett kontinuerligt användande i projekt efter projekt. Det betyder att överblicken över själva byggsystemet försvinner och möjligheterna till strategisk produktutveckling inte tas till vara. Som förvaltningsverktyg av byggsystem vore ett PDM-system lämpligt. Där förvaras och uppdateras data kring själva byggsystemet, som därifrån appliceras i olika projekt. Produktutveckling som idag sker i projekten, sker istället med byggsystemet som bas och informationen blir direkt tillgänglig för nästa projekt. Projekterings- och produktutvecklingsprocessen måste ändras från projektbaserad, upprepande projektering till strukturerad hantering av byggkomponenter i databas som kombineras på nya sätt i projekten. Inom föreliggande projekt har process och byggsystem hos 6 företag inom träbyggindustrin kartlagts. Baserat på företagens tolkade behov som beskrivits ovan utvecklades tre demon-stratorer (mjukvaror) för att utröna applicerbarheten av ett PDM-system inom träbygg-industrin. Intelligenta GDL- objekt skapades som utgjorde stommen i data för en PLCS-struktur som kan användas som ett PDM-system och kompletteras med ytterligare data. En koppling på databasnivå mellan CAD-data från träbyggindustrin och ett PDM- system testades också. Demonstratorerna visade att det är möjligt att utveckla dagens IT-verktyg till att stödja en industriell träbyggnadsprocess. Det kommer dock att kräva ett förändrat arbetssätt hos företagen. För att starta förändringen krävs att företagen dokumenterar sina processer och byggsystem. Högskolorna kan stötta med framtagning av metoder för processkartläggningar och beskrivning av byggsystem.

  • 31.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sardén, Ylva
    Industrialised timber housing: from trial to production2008In: Proceedings 24th Annual ARCOM Conference: 1-3 September 2008, Cardiff, UK, Association of Researchers in Construction / [ed] Andrew Dainty, Reading: Association of Researchers in Construction Management , 2008, Vol. 1, p. 155-64Conference paper (Refereed)
    Abstract [en]

    Increased cost and declining quality within the construction industry has resulted in a growing interest in industrialised housing construction. During the past 15 years Swedish timber housing has been in a start-up phase where the frame system has been adapted to fulfil the demands of the building regulations. Still, potential clients and building owners are uncertain of long-term financial costs and functional performance of timber houses. To take timber frame housing from the level of unique experimental projects to competitive industrialised production, manufacturers will have to face the challenge of convincing the market that timber is an equally sufficient frame material as the more traditional concrete and steel. This paper presents a summary and analysis of the research conducted within the field of industrialised timber housing at Luleå University of Technology. The summary is made through a literature review of research reports, theses, papers and statistic references. The results are put in relation to lean theories and the development of industrialised timber housing in Sweden, with the aim of establishing current knowledge and identifying future research needs. Industrialised housing in Sweden is a growing market with good potential to provide low-cost housing of good quality. The results points out organising the design process to support production, working on customer interaction and to providing information that decreases the uncertainty for future customers as challenges for the industrialised house builders. Further research within industrialised housing should address the quality concept in housing, reduction of uncertainties in customer relations and new business models. Support of the technical development with efficient stabilisation methods for high-rise buildings and simple joining methods during assembly is another important issue.

  • 32.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stehn, Lars
    A linear fracture mechanics evaluation of plug shear failure2004In: Proceedings, The 8th World Conference on Timber Engineering: WCTE 2004, 2004, Vol. 1, p. 253-258Conference paper (Refereed)
  • 33.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stehn, Lars
    Effect of joint geometry on the shear-plug failure in nailed timber connections2002In: 7th World conference on timber engineering: WCTE 2002, Penerbitan Publications , 2002, Vol. 2, p. 320-327Conference paper (Refereed)
  • 34.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stehn, Lars
    Plug shear failure in nailed timber connections: load distribution and failure initiation2004In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 62, no 6, p. 455-464Article in journal (Refereed)
    Abstract [en]

    Brittle failures in mechanical timber joints should be avoided, because this often results in low capacity and brittle failure of the structure. Nailed joints experience three ultimate failure modes: embedding, splitting or plug stear failure. To avoid plug shear failure, short and wide joints are preferred, limiting the number of fasteners in line with the load and grain direction. Plug shear failure was examined in short-term experiments on nailed steel-to-timber joints in glulam loaded in tension parallel to the grain with five different joint geometries. The aim of the study was to examine if the fastener group layout can be adjusted to avoid plug shear failure and to gain an insight into the causes of failure initiation. Using spring models, it is shown that the load distribution creates pronounced stresses at the last nail in the joint, which probably initiates the plug shear failure. Test results are compared with prediction models found in the literature. It was found that fasteners placed in groups can be a successful way of reducing the risk of plug shear failure. The failure is probably initiated at the nail farthest from the free end, where tensile stresses perpendicular to grain occur.

  • 35. Johnsson, Helena
    et al.
    Stehn, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Säkra våtrumsgolv2004In: Bygg & Teknik, ISSN 0281-658X, no 8, p. 51-52Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Badrumsgolv av kompositmaterial, ett projekt i samarbete mellan Lindbäcks Bygg, APC Composite, Tirsén & Aili Arkitekter och Luleå tekniska högskola.

  • 36.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stehn, Lars
    Lukaszewska, Elzbieta
    Connections for prefabricated timber-concrete composite systems2006In: 9th World Conference on Timber Engineering: WCTE 2006. Proceedings, 2006Conference paper (Refereed)
  • 37.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Söderholm, Erik
    Industriell projektering2009In: Samhällsbyggaren, ISSN 2000-2408, no 2, p. 38-40Article in journal (Other (popular science, discussion, etc.))
  • 38. Johnsson, Helena
    et al.
    Tlustochowicz, Gabriela
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Vilken skillnad gör en skiva?2010In: Samhällsbyggaren, ISSN 2000-2408, no 2, p. 16-18Article in journal (Other (popular science, discussion, etc.))
  • 39.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Åhlén, Johan
    Trästomme allt vanligare i hallar och kontorshus2009In: Husbyggaren : bygg, el, VVS, anläggning, ISSN 0018-7968, no 3, p. 8-10Article in journal (Other (popular science, discussion, etc.))
  • 40. Larsson, Tobias
    et al.
    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.
    Isaksson, Ola
    Projekt: Regelbaserad projektering för trävolymbyggande2010Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Syfte  Byggföretag inom industriellt trävolymbyggande behöver effektivisera sitt projekteringsarbete för att öka sin konkurrenskraft på byggmarknaden. Idag sker projekteringen ofta ostrukturerat och byggsystemet utvecklas på ett sätt som försvårar återanvändning och kontroll, vilket leder till onödiga produktionskostnader. För att kunna återanvända information från tidigare projekt krävs en strukturerad informationshantering så att informationen blir tillgänglig för alla samtidigt som personberoendet minskas. I detta projekt studeras hur knowledge-based engineering (KBE) och liknande kunskapsintensiva metoder (t ex Case-based reasoning) kan bidra till nya arbetssätt och ny informationsstruktur för trävolymbyggnad som ett alternativ till att införa nya programvaror. 

  • 41.
    Lidelöw, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Offsite construction in Sweden: From technology-driven to integrated processes2017In: Offsite Architecture: Constructing the future / [ed] Ryan E Smith; John D Quale, London: Taylor & Francis, 2017, p. 214-223Chapter in book (Refereed)
  • 42.
    Lidelöw, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    The ER design simulation game: Experience and reflect2017In: 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. 515-522Conference paper (Refereed)
    Abstract [en]

    Most simulation games that exist are targeted towards experiencing and reflecting on Lean principles such as tact time, pull, Kanban, continuous improvements etc. The design phase in construction is characterised by information not being available, iterative work, specialized work tasks, and high uncertainty. The research aim is to develop and test a design simulation game that explains the design principles: lack of information, iterative work, and specialized work in order to let inexperienced people experience and reflect (ER) on the design phase. The method to develop the ER design game was to alter an already existing production sequence simulation game developed to illustrate one-piece flow. Action cards were entered into the game, changing work tasks and their sequencing as the game progressed. The ER design game demonstrates the difficulties in characterising and improving the design flow, but it does not show any methods to improve it. Lack of information, iterative work, specialized work, stop-start effects, and tact time issues all surfaced during playing the ER design game. The time frame for the game set was 45 minutes, which makes it feasible to incorporate in Lean method training.

  • 43.
    Lidelöw, Helena
    et al.
    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.
    The effect of pre-engineering on design management methods2017In: 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. 523-530Conference paper (Refereed)
    Abstract [en]

    Several methods exist for design management such as Agile project management, the Last Planner System®, and configuration in diverse variants. Construction can be realized using different degrees of pre-engineering i.e. different production strategies, which can affect the design management method. The research aim is to describe different design management methods and discuss their capacity to function in existing production strategies in construction. Data was collected as secondary data from earlier publications on Agile project management, the Last Planner® system, configuration, and visual planning. Agile project management has a strong focus on customer value and lends itself well to situations with little pre-engineering. The Last Planner System® in design has a strong focus on the co-creation of flow and coordination of actions. In industrialised housing a dialect of Last Planner System® named KI-VP is implemented drawing upon predefinition of design tasks through standardized work. Configuration is the ultimate predefined design stage, where everything can be automated based on product variants.

  • 44.
    Lidelöw, Helena
    et al.
    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.
    Stehn, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Lindbäck, Hans
    Lindbäcks Bygg AB, Sverige.
    Projekt: Industriell byggprojektering2010Other (Other (popular science, discussion, etc.))
  • 45.
    Lidelöw, Helena
    et al.
    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.
    Viklund, Emma
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Design Breakdown in Industrialized Construction: Supporting Lean Manufacturing2015In: Proceedings of the 2015 Modular and Offsite Construction (MOC) Summit & 1st International Conference on the Industrialization of Construction (ICIC) / [ed] Mohammed Al-Hussein; Osama Moselhi; Sunkuk Kim; Ryan E. Smith, Edmonton, Canada: University of Alberta Press , 2015, p. 255-262Conference paper (Refereed)
    Abstract [en]

    A turn-key commitment towards the client compels the contractor to optimize the entire supply chain from design to delivery of the finished building. Industrialization of residential construction can be accomplished using either an open or a closed platform. In the case of an open platform, the client can greatly affect design solutions and the subsequent production phase. The aim of this research is to explain how design process breakdown into activities and deli-veries supports Lean manufacturing in an open platform situation. The most successful industria-lized contractor in Sweden was studied through mapping their design process of modular buildings using their visual planning display. Describing the improvement strategy, the visual content, and the standardization efforts in design revealed the support for Lean manufacturing. Analyzing each activity for repetitive elements identified the base for standardization. The conclusion is that design breakdown is a successful method that effectively supports Lean manufacturing and provides a base for standardization in an open platform context.

  • 46.
    Lidelöw, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Olofsson, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    The Structure and Predefinition of the Industrialized Construction Value Chain2017In: 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. 117-125Conference paper (Refereed)
    Abstract [en]

    Industrialized construction means predefinition of products and processes. The level of predefinition is balanced against the level of needed flexibility to create the desired customer value. There is a range from no predefinition up to complete predefinition. This pattern can be repeated in different dimensions defining several decoupling points in the value chain. The aim of this paper is to map different situations of predefinition in design, supply, and production dimensions in order to understand the structure of industrialized construction value chains. A multiple case study was organized using secondary data collection from earlier work of the authors originally collected through interviews with key actors in industrialized construction companies in Sweden. The results show that long-term supplier agreements and cooperations are important to sustain industrialization of construction. A high degree of predefinition in design is a prerequisite to succeed in construction industrialization. However, there is no coupling between a high degree of predefinition in design and a high degree of mechanization and automation in production

  • 47.
    Lidelöw, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Parida, Gabriela
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Åhlén, Johan
    Moelven Töreboda, Sverige.
    Projekt: Pelar-balksystem för höga trähus2010Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Syftet med projektet är - att utveckla en optimeringsmetod för pelar-balksystem i limträ som tar hänsyn till fenomenen i både bruks- och brottgränstillstånd och - att undersöka hur optimeringsmetoder kan användas i projekteringsskedet för flervåningshus i trä. 

  • 48.
    Lidelöw, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Simu, Kajsa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Lean construction as an emergent operations strategy2016In: IGLC 2016 - 24th Annual Conference of the International Group for Lean Construction, National Pingtung University of Science and Technology , 2016, p. 153-162Conference paper (Refereed)
  • 49.
    Lidelöw, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simu, Kajsa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lean construction as an operations strategy2015In: Proceedings of IGLC 23: 23rd Annual Conference of the International Group for Lean Construction: Global Knowledge - Global Solutions, Perth, Australia, 28 - 31 July 2015 / [ed] P. Arroyo; O. Seppanen; V.A. Gonzalez, International group for lean construction , 2015, p. 486-495Conference paper (Refereed)
    Abstract [en]

    All companies have an operations strategy; a pattern of decisions made in operations with the purpose to support the business strategy. Lean Construction can be seen as an operations strategy. The aim of this research is to present the generic decision categories in an operations strategy and discuss their characteristics in contrast to the Lean Construction framework. A literature study identified ten decision categories: process technology, capacity, facilities, vertical integration, human resources, organization, quality, production control, product development, and performance measurement. Data was collected through in-depth interviews with managers on the tactical level at three construction companies with a Lean implementation. The results indicate that Lean construction companies emphasize quality, production planning, and vertical integration in their operations strategy. Facilities, process technology, capacity, and organization receive less attention. Quality, production planning, and vertical integration are keywords also in Lean Construction, while it is intriguing that organization receives little attention. Facilities, process technology, and capacity are ever changing between construction projects and are candidates for decision categories that could be less relevant for formulating an operations strategy in construction.

  • 50.
    Lidelöw, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Simu, Kajsa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Project: Flow Efficiency in Construction2014Other (Other (popular science, discussion, etc.))
12 1 - 50 of 87
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