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  • 301.
    Haller, Martin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stehn, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Increasing the Accuracy of a Prefab Building Design Process Simulation Using Simulated Annealing2014In: Automation and robotics for construction: proceedings : CC2014 / [ed] Miklós Hajdu ; Mirosław J. Skibniewski, Budapest: Diamond Congress Ltd , 2014, p. 408-413Conference paper (Refereed)
  • 302.
    Haller, Martin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stehn, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Increasing the Accuracy of a Prefab Building Design Process Simulation Using Simulated Annealing2014In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 85, p. 214-221Article in journal (Refereed)
    Abstract [en]

    Monte-Carlo simulation analysis has been discussed in project management literature as tool for proactive scheduling and to gain better insights into projects which are characterized by a high level of complexity and uncertainty, such as the design phase of prefab building projects. The application of simulation as proactive scheduling tool in construction projects is hampered by limited accessibility of proper input data, though, because of long project duration, the often temporary organization and multidisciplinary nature of such projects. In this study we use simulated annealing to adjust parameters of a simulation model for which the simulation outcome is sensitive to data perturbation by making use of data from related parameters which is easier to estimate. The applicability of the approach was demonstrated on a real life project, the construction of a 1100 m2 residential building in Sweden. More precisely, we used Design Structure Matrix simulation, i.e. an activity network based Monte-Carlo simulation technique with which stochastic project evolution (deviations from the planned activity sequence due to unexpected iteration of sub-processes) can be simulated, to model the workflow of the design process of the observed project. Then, by means of the simulated annealing approach, we adjusted the rework probabilities (model parameter) such that the frequencies of executed activities in simulated activity sequences fitted the frequencies as observed in the real project. Adjusting input data by using prior knowledge of the dependencies of the project activities and cross analysis with related data that is easy to estimate would help to increase the accuracy of simulations when access to statistical data of the input variable in question is limited. The suggested approach is interesting for practitioners who work with standardized design processes (e.g. as part of standardized building systems) and continuous improvement

  • 303.
    Haller, Martin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stehn, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Standardizing the pre-design-phase for improved efficiency in off-site housing projects2010In: ARCOM twenty-Sixth Annual Conference 2010, September 6-8, Leeds / [ed] Charles O. Egbu; Eric Lou, Reading: Association of Researchers in Construction Management , 2010, Vol. 2, p. 1259-68Conference paper (Refereed)
    Abstract [en]

    Long erection times on-site and project-specific design work, performed by consultants, generally accounts for a large part of correction and building costs in construction projects. In a typical Swedish housing project, the pre- and design phase accounts for about 10-12 % of the total costs. Due to a lack of standardized conceptualization procedures, much of the design work is reiterated in each project, and thus avoidable costs are incurred. In order to minimize these problems an open building system, called MFB, which exploits standardized technical solutions, design and construction processes for off-site prefabricated housing is under development. The MFB system developer will provide a process manual that describes, in detail, standardized design, construction, and erection processes. The open building system relies on close cooperation with local, often small to medium-sized, enterprises that can efficiently undertake “local” building projects. Here, we present and analyse a standard procedure for the pre-design-phase to incorporate in a MFB-process manual. The pre-design-phase of a MFB-building project was recorded and analysed in terms of efficiency. A detailed process map is presented, showing that 122 process steps were logged from the first contact with the client until the generation of the tender. By standardizing the pre-design-phase, the number of essential activities could be reduced by 47%. An improvement in time efficiency of the pre-design-phase with co-instantaneous generation of effective cost estimates should lead to lower building costs in general. Furthermore, by tightly standardizing and controlling the process, it should be possible to repeat projects (or many aspects of projects), without repeating much of the pre-design-phase, even if the actors change.

  • 304.
    Hamon, Emile
    et al.
    Tyréns AB.
    Jensen, Patrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lessing, Jerker
    Tyréns AB.
    Utvecklar ett byggsystem för flerbostadshus i trä2009In: Husbyggaren : bygg, el, VVS, anläggning, ISSN 0018-7968, no 3, p. 12-17Article in journal (Other (popular science, discussion, etc.))
  • 305.
    Hassan, Osama A B
    et al.
    Umeå University. Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Human-induced vibrations in composite timber floors2012In: Proceedings of the 15th European Conference on Composite Materials, Venice, 24-28 June 2012 / [ed] Marino Quaresimin; Laszlo Kollar; Leif Asp, Venice, 2012Conference paper (Refereed)
    Abstract [en]

    The authors investigate the human induced vibrations in typical composite timber floors in residential buildings. Assessment methods given in different design codes and guidelines, such as the Eurocode, are discussed. A case study analysis based on the different methodologies is carried out to assess the acceptability of a specific timber floor. Two extreme cases are considered: full and non-composite action. It is shown that composite action improves the floor acceptability for general residential applications. The limitations of the different criteria given in the codes and guidelines for assessing floor vibrations in timber floor structures are discussed and, also, the possible improvement of these criteria

  • 306.
    Hassan, Osama A B
    et al.
    Umeå University. Department of Applied Physics and Electronics.
    Schedin, Staffan
    Umeå University. Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Experimental analysis of composite timber-concrete wall element2012In: Proceedings of the 15th European Conference on Composite Materials, Venice, 24-28 June 2012 / [ed] Marino Quaresimin; Laszlo Kollar; Leif Asp, Venice, 2012Conference paper (Refereed)
    Abstract [en]

    The authors present an experimental and theoretical study on a composite or hybrid element used in residential and agricultural buildings. The composite wall element consists of timber studs connected to a concrete plate by means of nail plate shear connectors. Experimental results are presented and compared with an analytical model for partial composite action. A good agreement is obtained between the analytical and experimental results. Also, some suggestions to improve the design of the composite element are discussed.

  • 307.
    Hassan, Osama A.B.
    et al.
    Umeå University. Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Assessment of footfall-induced vibrations in timber and lightweight composite floors2013In: International Journal of Structural Stability and Dynamics, ISSN 0219-4554, Vol. 13, no 2Article in journal (Refereed)
    Abstract [en]

    In this paper, the footfall-induced vibrations in typical timber and lightweight composite floors in residential buildings are investigated. The two-floor structures have approximately comparable distributed mass and that the transverse flexural stiffnesses of the two structures are not substantially different. An analysis is carried out to assess the floor acceptability of the two structures, based upon derived expressions as well as some design codes and guidelines such as the Eurocode. For the analysis, two cases are considered for each floor structure: a composite action and noncomposite action. It has been shown that use of composite action, under certain conditions, has more advantages than its noncomposite counterpart with respect to the floor acceptability for general residential applications. Moreover, the limitations of the different criteria of the codes, guidelines for assessing floor vibrations in timber and lightweight floor structures, and possible improvements of these criteria are discussed in this paper

  • 308.
    Hassan, Osama A.B.
    et al.
    Umeå University. Department of Applied Physics and Electronics.
    Grundberg, Staffan
    Umeå University. Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Dynamics of partially interacting composite beams2012In: Proceedings of the 15th European Conference on Composite Materials, Venice, 24-28 June 2012 / [ed] Marino Quaresimin; Laszlo Kollar; Leif Asp, Venice, 2012Conference paper (Refereed)
    Abstract [en]

    The dynamic behaviour of layered composite beams with partial interaction is analysed using variational calculus. The theoretical results are compared with those from dynamic tests on simply supported beams with varying shear connection stiffness between the layers. The influence of the shear connection stiffness on the flexural natural frequencies, flexural deflection and damping is investigated. A good agreement between the analytical and experimental results is obtained

  • 309.
    Haugum, Dag
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Linköpings universitet.
    Långtidsstudie av byggnader i trä i kallt klimat2019Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    För 30 år sedan uppfördes en svensk forskningsstation, Wasa, i Antarktis. Huvudbyggnaden konstruerades utifrån erfarenheter från svenska fjällstugor. Ett av syftena var att visa att svensk träbyggnadsteknik fungerade väl i det arktiska klimatet. Initiala byggfysiska mätningar gjordes. Att använda en träkonstruktion till en forskningsstation i Antarktis var unikt vid denna tidpunkt. Under sydsommaren 2019-20 finns möjlighet att för första gången sedan 1990 göra en uppföljande undersökning av byggnadens påverkan av klimatet som kännetecknas av stora dygnsvariationer i temperatur och av stora vindlaster i kombination med stark kyla och drevsnö. Analys görs av byggnadens uttorkning/täthet och hur detta påverkar inträngning av fukt i form av drevsnö. Byggnadens utformning gör att vi kan jämföra olika konstruktionslösningar på plats. Jämförelse kommer att göras med den intilliggande finska stationen som är byggd enligt helt andra principersamt med motsvarande byggnader i Skandinavien.

  • 310.
    Hedgren, Erika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Overcoming organizational lock-in in decision-making: Construction clients facing innovation2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The role of clients in construction innovation is receiving increasingresearch attention due to their perceived tendencies to adhere to conventional practices preserving the status-quo. The aim of this thesis is to improve understanding of construction client organizations’ behaviour that affects their ability to overcome organizational lock-in in their new-build decision-making processes, and thus their ability to adopt innovation. A more specific aim is to compare and contrast the behaviour and decision-making processes of innovation adopters and non-adopters. The theoretical frame of reference integrates organizational information processing and three discrete, but mutually dependent decision-making schools of thought. The methodological approach acknowledges the importance of human interpretation. Most of the empirical data are qualitative, and were collected mainly through in-depth face-to-face interviews with key decision-makers of professional Swedish multi-dwelling client organizations with a property portfolio, both private and public. The research addresses clients’ practices for information processing and new-build decision-making, and their impact on their adoption of more radical innovation, as well as their perceptions and behaviour when facing the radical innovations of industrialized construction of timber-framed multi-dwelling buildings (IB) that extends beyond their frames of reference. The results show that Swedish clients’ perceptions about IB innovations are affected by both uncertainty and equivocality (i.e. the human problem of managing multiple meanings of information and conflicting interpretations). Thus, managing equivocality appears to be essential for making judgments about radical innovation alternatives. Both individual- (cognitive) and organizational-level barriers to the adoption of IB innovations are identified. These barriers create an organizational lock-in to conventional a lternatives because they lead to decision-makers not recognizing the need to revise their heuristics, question given meanings and make different interpretations that would enable them to reach different conclusions. Finally, the results show that the behaviour of innovation adopters differs from that of non-adopters in terms of how they manage uncertainty and equivocality in their new-build decision-making processes. The conclusion is that to overcome the organizational lock-in that hinders radical innovation adoption, organizations must manage equivocality through information-processing practices that allow for multiple meanings and different interpretations to surface and interact with their new-build decision-making. The research findings show that practices that support decision-making on conventional alternatives can simultaneously present organizational lock-in. These findings indicate that the current research assumptions regarding the negative impact of uncertainty and positive impact of experience may have to be reversed in decision-making about radical innovation. They also encourage application of an interpretative approach. The research may contribute to further understanding of means to overcome barriers to the adoption of other types of radical construction innovations, such as sustainable building.

  • 311.
    Hedgren, Erika
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stehn, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    The impact of clients’ decision-making on their adoption of industrialized building2014In: Construction Management and Economics, ISSN 0144-6193, E-ISSN 1466-433X, Vol. 32, no 1-2, p. 126-145Article in journal (Refereed)
    Abstract [en]

    Previous research has shown that client organizations’ decision-making about new-build creates individual-level and organizational-level barriers to the adoption of Swedish industrialized building (IB). However, it has been proposed that clients may overcome barriers on both levels by allowing multiple meanings and conflicting interpretations to surface and interact with their decision-making. The aim is to test this proposition. Based on the theoretical fields of decision-making and organizational information processing, a framework for analysis has been developed. In the framework, three decision-making approaches are operationalized: rational, judgments and managing multiple meanings. Data were collected using in-depth interviews with key decision-makers from four Swedish professional clients differing on when and if they adopted IB: one early-adopter, two late-adopters and one non-adopter. The empirical findings support the proposition and show a relationship between how clients manage multiple meanings in their decision-making and their adoption of IB. The research adds to the understanding of how clients may overcome barriers to the adoption of IB on both individual and organizational levels. Moreover, it increases understanding about how clients might better cope with radical changes and innovations.

  • 312.
    Hedlund, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hörte, Sven-åke
    Changes in development approaches of technological and work organization and the impact on performance2000Report (Other academic)
    Abstract [en]

    The paper analyses the joined data and results of two separate studies together covering the change actions of 49 Swedish manufacturing companies during a ten-year period, 1988-1997. The purpose is to reveal the long-term change patterns of synchronous or non-synchronous change of technology and work organisation. The results are that during the studied ten-year period a lesser percentage of companies pursue synchronous change than non-synchronous. The general change pattern is indicating more focus on change of organisation than on technology, and this tendency has grown stronger in resent years. The results presented in this paper also indicate that synchronously changing companies during 1988-1997 tend to have had greater performance increases during recent years than non-synchronously changing companies.

  • 313.
    Hedlund, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hörte, Sven-åke
    Changes in development approaches of technology and work organization and the impact on performance2000In: Operations Management "Crossing Borders and Boundaries: The Changing Role of Operations": Papers from the 7th International Conference of the European Operations Management Association Ghent, Belgium June 4-7 2000 / [ed] Roland Van Dierdonck; Ann Vereecke, Ghent: University, Faculty of economics and business administration , 2000, p. 267-274Conference paper (Refereed)
  • 314.
    Hedlund, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hörte, Sven-åke
    Technological and organisational development and its management1999In: Managing Operations Networks: Venice, Italy, June 7th-8th 1999 / [ed] Emilio Bartezzaghi; Roberto Filippini; Gianluca Spina; Andrea Vinelli, Padova: Servizi Grafici Editorali , 1999, p. 829-836Conference paper (Refereed)
  • 315.
    Hedlund, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hörte, Sven-åke
    Technological and organizational development and its management1999Report (Other academic)
    Abstract [en]

    The technological- and organisational development 1992-1997, and the corresponding changes of seven internal and four external performance measures of 56 Swedish firms are analysed, as well as the way the change efforts are managed. The general results are that the firms have moved towards higher levels of decentralisation and automation. The internal performance of the firms has improved if firms have upgraded the technology, or both their technology and organisation. Investments in increased automation tend to improve the quality performance of the firms, while the opposite result is associated with the introduction of a more decentralised organisation. The results for the external performance support that higher automation is related to higher quality, but this is at the expense of less flexibility in product change. The managerial implications discussed are if firms should focus on improved technology, organisation or both, and how to manage the change process.

  • 316.
    Hedlund, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hörte, Sven-åke
    Teknologi, Organisation och Management (TOM): slutrapport2000Report (Other academic)
  • 317.
    Heistermann, Christine
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Behaviour of pretensioned bolts in friction connections: towards the use of higher strength steels in wind towers2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    During recent years wind energy has established as an alternative to commonenergy sources. To advance its competitiveness, the costs for the constructionof a wind tower have to be reduced. One possible option is the use of frictiongrip joints instead of flange connections to join various tower segments in atubular steel tower. Additionally, the time necessary for installation andmaintenance of the bolts in these connections can be decreased, not only forimplementation in tubular towers but also in lattice towers.Four different bolt types have been investigated with respect to the ease ofinstallation and maintenance on the one hand and structural applicability on theother hand. The latter one is mainly defined by the behaviour of the pretensionforce in the bolts. Various influences on the reduction of clamping force areexperimentally checked, such as the type and thickness of coating, thethickness of the clamping package and external loading.The slip factor, which plays an important role in friction connections, isexperimentally achieved in a test on a double shear lap joint. The experiment isthoroughly examined by a finite element analysis, which models the interactionbetween bolts and plates.In various numerical analyses the influence of steel grade and possibleassembling tolerances on the resistance of a friction joint is investigated bothfor single and double shear lap joints.Shortages of EN 1993 parts 1-8 and 1-12 for the use of slip critical joints areidentified.

  • 318.
    Heistermann, Christine
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Resistance of Friction Connections with Open Slotted Holes in Towers for Wind Turbines2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The most common solutions for in-situ connections of steel tubular towersegments of onshore wind turbines are ring flange connections. These havecertain drawbacks, such as e.g. costly production, long delivery time and ratherlow fatigue endurance. Friction connections with long open slotted holes havepreviously been proven to be a competitive alternative. In this work, the newtype of connection is investigated in various scales: segment tests, down-scaledexperiments and full-scale models. The influence of tower cross-section shape,execution tolerance (horizontal gap between the tower segments) and length ofthe connection on the bending resistance is thoroughly studied. In addition,buckling behaviour of the shell in the vicinity of the friction connection intowers with circular and polygonal cross-sections is analysed in order to checkpossible advantages of either cross-section. The influence of two types of theexecution tolerances on the connection strength is investigated: inwards bent“fingers”, leading to inclined gaps, and a parallel gap created by differentdiameters of the tower segments. Based on validated finite element analysesrecommendations for execution tolerances are proposed.A closer look is taken at the level of bolt forces under load application for thenew friction connections as well as for the ring flange connection. For theformer case, the influence of slotted holes on the joint resistance is checked.For both types of connections, comparison is drawn to hand calculation modelsused in engineering practice. Additionally, the distribution of meridionalstresses in the shell in the vicinity of the connection is studied.Based on the findings from the above described investigations,recommendations for the design of friction connections with open slotted holesin steel tubular towers for onshore wind turbines are given.

  • 319.
    Heistermann, Christine
    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.
    Limam, Marouene
    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.
    Finite element analysis of a single lap joint2012In: Nordic Steel Construction Conference 2012: September 5-7, 2012 Oslo, Norway : Proceedings, Oslo: Norwegian Steel Association , 2012, p. 673-682Conference paper (Refereed)
    Abstract [en]

    A single shear lap joint of steel grade S355 is modelled with finite elements to investigate the influence of externally applied tensile loading on the loss of pretension in the engaged bolts. Additionally, a parameter study is performed to understand the effect of various steel grades on the loss of pretension. It is found that the slip resistance of the specimen depends on the steel grade of the clamped plates. Besides, the final resistance of the single shear lap joint has been found to increase after a slip of 0,15 mm has occurred due to a secondary bending moment. However, the final resistance of the specimen has been found to depend on the size of assembling tolerances; the bigger the distance between the clamped plates, the lower the resistance.

  • 320. Heistermann, Christine
    et al.
    Heistermann, Tim
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Remaining pretension force in friction connections2010In: Proceedings of the 4th International Conference on Steel and Composite Structures: 21 - 23 July 2010, Sydney, Australia / [ed] Brian Uy, Singapore: Research Publishing Services, 2010, p. 275-278Conference paper (Refereed)
  • 321. Heistermann, Christine
    et al.
    Husson, Wylliam
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Flange connection vs. friction connection in towers for wind turbines2009In: Nordic Steel Construction Conference: Proceedings : September 2.-4., 2009, Malmö, Sweden, Stockholm: Stålbyggnadsinstitutet , 2009, p. 296-303Conference paper (Refereed)
    Abstract [en]

    The paper deals with connections used to assemble sections of tubular steel towers supporting wind turbines. The design of current ring flange connections is briefly presented. An alternative option for the assembling connection is to use single overlapping friction connection. This is introduced in on-going research project "HISTWIN- High-Strength Steel Tower for Wind Turbine, 2006-2009". The main characteristic of the friction connection is long open slotted holes. Design example for equivalent design load at ultimate load of the friction connection is compared to the flange solution on a particular example of REpower Tower MM92. The benefits of the new connection in terms of design simplicity, fatigue strength and material costs are discussed.

  • 322.
    Heistermann, Christine
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Pavlovic, Marko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Andrade, Pedro
    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.
    Rebelo, Carlos
    ISISE, Department of Civil Engineering, University of Coimbra.
    Silva, Luís Simões da
    ISISE, Department of Civil Engineering, University of Coimbra.
    Finite Element Analysis of Lap Joints in Steel Tubular Towers2014In: Eurosteel 2014: 7th European Conference on Steel and Composite Structures / [ed] Raffaele Landolfo; Frederico M. Mazzolani, Brussels, Belgium: European Convention for Constructional Steelwork, ECCS , 2014, p. 291-292Conference paper (Refereed)
  • 323.
    Heistermann, Christine
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Pavlovic, Marko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Delft University of Technology, Faculty of Civil Engineering & Geoscience.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Delft University of Technology.
    Pak, Daniel
    Institute for Steel Construction, RWTH Aachen University.
    Feldmann, Markus
    Institute for Steel Construction, RWTH Aachen University.
    Rebelo, Carlos
    ISISE; Department of Civil Engineering, University of Coimbr.
    Silva, Luís Simões da
    ISISE; Department of Civil Engineering, University of Coimbr.
    Influence of execution tolerances for friction connections in circular and polygonal towers for wind converters2017In: Advanced steel construction, ISSN 1816-112X, Vol. 13, no 4, p. 343-360Article in journal (Refereed)
    Abstract [en]

    Friction connections with long open slotted holes have been proven to be a competitive alternative to the conventional flange connections in steel tubular towers for wind energy converters. As full-scale tests are not available, results of Finite Element Analysis (FEA) of the real-scale tower geometry are used in this paper to investigate the influence of tower cross section shape, execution tolerance (gap between the shells) and length of the connection on the bending resistance. Buckling behaviour of the shell in the vicinity of the friction connection in circular and polygonal towers is compared. The friction connection is thoroughly examined and recommendations for execution tolerances are given. The influence of two types of the execution tolerances on the connection strength is considered: inward bended "fingers", leading to inclined gaps, and a parallel gap created by different tower diameters.

  • 324.
    Heistermann, Christine
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Tran, Anh Tuan
    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.
    Rebelo, Carlos
    ISISE, Department of Civil Engineering, University of Coimbra.
    Flangeless Connections in Steel Tubular Wind Towers2014In: Proceedings of the METNET Seminar 2013 in Luleå: Metnet Annual Seminar in Luleå, Sweden, on 22 - 23 October 2013 / [ed] Kuldeep Virdi; Lauri Tenhunen, Hämeenlinna: HAMK University of Applied Science , 2014, p. 157-168Conference paper (Other academic)
    Abstract [en]

    Extensive research is conducted on the improvement of renewable energies. One field is the use of wind energy, where the tower construction is one of the main issues. This paper deals with new ideas and ongoing research in this area. To raise the height of steel tubular towers, fatigue as the design limit and constraints due to transportation issues have to be overcome. Changes in the cross-section are considered as one of possible solutions. This work presents an extensive finite element study dealing with different ways to improve shell stability, which become the limiting criteria if a friction connection substitutes the common flange connection between two tower segments. The use of circular and polygonal cross-sections is briefly described and will be investigated in an experimental program.

  • 325.
    Heistermann, Christine
    et al.
    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.
    Bolts for slip resistant joints in towers for wind turbines2012In: Proceedings of the METNET Seminar 2012 in Izmir: Metnet Annual Seminar in Izmir, Turkey, on 10 - 11 October 2012 / [ed] Kuldeep Virdi; Lauri Tenhunen, Hämeenlinna, Finland: HAMK University of Applied Science , 2012, p. 31-39Conference paper (Other academic)
    Abstract [en]

    This paper deals with a new solution to connect various segments in a tubular steel tower for wind power plants. Tests are performed to determine appropriate bolts for such connections. They focus on checking the development of pretension forces in the bolts during a period of one week. The behaviour of four different types of bolts is described and evaluated. For one type of bolt the force reduction is monitored for two different clamping lengths. Finally, recommendations for further tests are given.

  • 326.
    Heistermann, Christine
    et al.
    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.
    Loss of pretension in bolted connections: influence of loading2011In: Proceedings of the 6th European Conference on Steel and Composite Structures: Eurosteel 2011, August 31 - September 2, 2011, Budapest, Hungary, Budapest: European Convention for Constructional Steelwork, ECCS , 2011, p. 399-404Conference paper (Refereed)
    Abstract [en]

    A common problem in bolted connections is the self-loosening effect of bolts over time. Therefore the remaining strength in a slip resistant connection can only roughly be estimated for a certain point of time. A possible solution ot avoid self-loosening is the use of lockbolts, which have been studied in order to achieve recommendations for connections which are "free from maintenance". The pretension force in the bolt unavoidably reduces over time due to creep of primer, forces in bolts and in plates. These effects are experimentally studied. For all types of connections this effect is very important and in this paper the focus is brought on lap joints, where the influence of various types of loading is examined.

  • 327.
    Heistermann, Christine
    et al.
    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.
    Simões, R.
    ISISE, Department of Civil Engineering, University of Coimbra.
    Rebelo, C.
    ISISE, Department of Civil Engineering, University of Coimbra.
    Silva, L. Simões da
    ISISE, Department of Civil Engineering, University of Coimbra.
    Design of slip resistant lap joints with long open slotted holes2013In: Journal of constructional steel research, ISSN 0143-974X, E-ISSN 1873-5983, Vol. 82, p. 223-233Article in journal (Refereed)
    Abstract [en]

    Current design procedures for slip resistant connections according to Eurocodes and American specifications are reviewed. Although failure of a slip resistant connection is defined at different levels of slip, 0.15 mm and 0.5 mm respectively, the calculation of the resistance is similar. Most of the research is performed on bolts in normal clearance holes. A testing program was conceived to evaluate the influence of long open slotted holes on the behavior of slip resistant lap joints with tension control bolts because of possible use of such connections in towers for wind turbines. In comparison to specimens with normal clearance holes it is found that the friction coefficient is about 4% lower. This reduction is lower than suggested by the current correction factors. Since none of the design procedures takes the reduction in bolt forces by time into account, the loss of pretension force is experimentally studied and an approximation is proposed. A second testing program was carried out with friction standard specimens in order to determine the slip factor for different surface treatments and steel grades in range between S275 and S690. The achieved slip factors for different surface preparations are in accordance with the classification of friction surfaces in EN 1090-2:2008 and differences obtained are addressed to variations in exposure to weather conditions. The steel grade does not have a significant influence.

  • 328.
    Heistermann, Tim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stiffness of reverse channel connections at room and elevated temperatures2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A frame structure exposed to fire undergoes two types of changes due to the resulting temperature fields. The first is the thermal expansion of the structural members and the second is the degradation of the material strength and stiffness as temperature rises. Initially the thermal expansion dominates the response and the structural member (beam) is exposed to compressive forces due to restrained expansion, thus precipitating flexural buckling. At higher temperatures the mechanical material properties degrade. This fact, together with the high compressive forces in the bottom flanges of the beam often results in local buckling, followed by the formation of a plastic hinge close to the support region. The combination of transverse loads and the rising temperature leads to the development of excessive deflections in the beam. When temperature rises enough for the bending resistance of the beam to become insufficient, catenary action is introduced. The result is that the beam transitions to a stage where tensile forces appear due to the catenary action. In these different stages of the response of the structure the beam-to-column connection plays a crucial role and its robustness will determine if the structure will be able to maintain its integrity.The robustness of a structure in a fire situation greatly depends on the rotational capacity of the connection region. High rotational capacity is required at elevated temperatures since the steel beams lose their bending stiffness and exhibit increasingly large deflections under constant load. Beam deflections result in increasing rotations at the supports and may lead to collapse due to connection failure. Other possible failure modes may occur in the structural members, for example due to yielding in tension of the beam. The reverse channel has been proposed as a practical alternative to assemble beams to tubular columns. In a simple implementation, the bending moment generated in the joint due to rotation of the beam may be neglected; however, research efforts are being attempted to quantify the level of constraint. The typical arrangement of the connection type consists of a reverse channel with its flanges welded onto the face of concrete-filled tubular columns and the web bolted to the endplate of a beam. Thicknesses and depths of the reverse channel determine the level of rotational restraint at high temperature. The reverse channel has the ability to undergo catenary deformation in the tensile zone due to the applied rotation at the support and similarly it is relatively ductile in the compression zone. Overall, the reverse channel connection response is rather ductile in terms of its ability to undergo large rotational deformation as long as bolt failure is avoided through proper design.Various tests have been performed to study the behaviour of this type of connection such as full scale buildings, sub-frames, isolated joints and individual sections. The aim of these tests was to capture the connection behaviour in relation to other structural components in fire. This thesis focuses on the tests carried out on the connection components and their finite element modelling. A comprehensive parametric study was performed to assess the influence of different parameters on the behaviour of the connection component at elevated temperatures. The results from the finite element analyses have been utilized to validate analytical models that describe the behaviour of this type of connection at ambient and elevated temperature. Insight into the analytical models provides proper background to a structural designer to estimate the initial stiffness and understand the behaviour of the reverse channel in the connection.

  • 329.
    Heistermann, Tim
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Iqbal, Naveed
    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.
    Lopes, Fernanda
    University of Coimbra, Department of Civil Engineering.
    Santiago, Aldina
    University of Coimbra, Department of Civil Engineering.
    Silva, Luís Simões da
    University of Coimbra, Department of Civil Engineering.
    Reverse channel connections at elevated temperature: finite element modelling2011In: Proceedings of the 6th European Conference on Steel and Composite Structures: Eurosteel 2011, August 31 - September 2, 2011, Budapest, Hungary, Budapest: European Convention for Constructional Steelwork, ECCS , 2011, p. 1587-1592Conference paper (Refereed)
  • 330.
    Heistermann, Tim
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Koltsakis, Efthymios
    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.
    Lopes, Fernanda
    University of Coimbra, Department of Civil Engineering.
    Santiago, Aldina
    ISISE, Department of Civil Engineering, University of Coimbra.
    Silva, Luís Simões da
    Virginia Polytechnic Institute and State University, Universidade de Coimbra , ISISE, Department of Civil Engineering, University of Coimbra.
    Initial stiffness evaluation of reverse channel connections in tension and compression2015In: Journal of constructional steel research, ISSN 0143-974X, E-ISSN 1873-5983, Vol. 114, p. 119-128, article id 4268Article in journal (Refereed)
    Abstract [en]

    The so-called Reverse Channel connection has been conceived for the purpose of accommodating the thermal expansion of beams so that premature failure due to thermal buckling is avoided. The connection is made of a channel-shaped element, welded along the tips of its flanges onto the face of a hollow section column; an endplate welded on the beam is bolted onto the web of the channel. In a fire situation, the thermal expansion of a reverse-channel supported beam causes extensive bending deformation of the connection, therefore preventing the development of significant axial stress in the beam. Furthermore, this connection offers a high rotational capacity, if designed properly, which is beneficial in a fire situation where excessive deflections of beams can be expected. This paper aims to provide analytical stiffness assessment tools for reverse channel connections in compression and tension under uniform temperatures. The proposed analytical models are compared to results of Finite Element simulations, which in turn have been benchmarked with experiments. In addition, a comprehensive parametric study is conducted in order to identify all influencing factors on the initial stiffness response: reverse channel geometry and thickness, plate thickness, bolt position, and bolt diameter. Correction factors that account for 3D effects and bolt size are presented and discussed. The obtained expressions for the reverse channel stiffness are found to provide an accuracy that is acceptable for structural applications and can, therefore, be used as a design tool

  • 331.
    Heistermann, Tim
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Koltsakis, Efthymios
    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.
    Lopes, Fernanda
    University of Coimbra, Department of Civil Engineering.
    Santiago, Aldina
    ISISE, Department of Civil Engineering, University of Coimbra.
    Silva, Luís Simões da
    Universidade de Coimbra , ISISE, Department of Civil Engineering, University of Coimbra.
    Initial Stiffness of Reverse Channel Connections2014In: Eurosteel 2014: 7th European Conference on Steel and Composite Structures, September 10-12, 2014, Naples, Italy / [ed] Raffaele Landolfo; Federico M. Mazzolani, Brussels: European Convention for Constructional Steelwork, ECCS , 2014Conference paper (Refereed)
    Abstract [en]

    The robustness of a structure in a fire situation greatly depends on the rotational capacity of the connection region. High rotational capacity is required at elevated temperatures since the steel beams lose their bending stiffness and exhibit increasingly large deflections under constant load. Beam deflections result in increasing rotations at the supports and may lead to collapse due to connection failure. The reverse channel has been proposed as a practical alternative to assemble beams to tubular columns. In a simple implementation, the bending moment generated in the joint due to rotation of the beam may be neglected; however, research efforts are being attempted to quantify the level of constraint. The typical arrangement of the connection type consists of a reverse channel with its flanges welded onto the face of concrete-filled tubular columns and the web bolted to the endplate of a beam. Thicknesses and depths of the reverse channel determine the level of rotational restraint at high temperature. The reverse channel has the ability to undergo catenary deformation in the tensile zone due to the applied rotation at the support and similarly it is relatively ductile in the compression zone. Overall, the reverse channel connection response is rather ductile in terms of its ability to undergo large rotational deformation as long as bolt failure is avoided through proper design.Various tests have been performed to study the behaviour of this type of connection such as full scale buildings, sub-frames, isolated joints and individual sections. The aim of these tests was to capture the connection behaviour in relation to other structural components in fire. This paper, however, focuses on the derivation and verification of analytical models to assess the initial stiffness of reverse channel/partial-depth endplate connections. The results from finite element analyses have been utilized to validate analytical models that describe the behaviour of this type of connection at ambient and elevated temperature. Insight into the analytical models provides proper background to a structural designer to estimate the initial stiffness and understand the behaviour of the reverse channel in the connection.

  • 332.
    Holmlund, Sara
    et al.
    Luleå tekniska universitet.
    Jansson, Gustav
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lennartsson, Martin
    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 i praktiken: en studie av produktionen på Englundshus AB2008Report (Other academic)
    Abstract [sv]

    Bakgrunden till projektet som resulterat i denna rapport, ligger i ett behov att förbättra effektiviteten i fabriken hos Englundshus AB. Syftet är att se över fabrikslayouten, hitta flöden, flaskhalsar och slöseri. Den teoribas som använts, finns inom ramen för Lean Production även kallat Lean Construction inom byggbranschen. Studien har genomförts i tre steg med lika många företagsbesök. Vid det första besöket studerades hela fabrikslayouten och samtliga delprocesser. Besöket resulterade i ett konstaterande att det som i teorierna beskrivs som 5S snabbt skulle skapa mervärde till hela fabriksprocessen. I samband med det andra besöket fokuserades på de två största processerna som är vägg- och golvtillverkning. Ur företagets tidsuppföljning konstaterades att väggtillverkningen var flaskhalsen för delprocesserna. Under besöket drogs även slutsatsen att materialflödet är kritiskt och bör ses över.För att hitta aktiviteten som orsakar flaskhalsen i väggtillverkningen gjordes under besök tre en värdeflödeskartläggning. Den visade att den sista stationen, där panel monteras, är flaskhalsen inom delprocessen.För att minska slöseriet och få ett bättre flöde genom fabriken och därmed minska effekten av flaskhalsen har ett förslag på ny fabrikslayout tagits fram. Förslaget innebär att borden omplaceras så att varje station ges möjlighet till ett bättre materialflöde.

  • 333. Hosseini-Hashemi, Sh.
    et al.
    Atashipour, Seyed Rasoul
    Fadaee, M.
    An exact analytical approach for in-plane and out-of-plane free vibration analysis of thick laminated transversely isotropic plates2012In: Archive of applied mechanics (1991), ISSN 0939-1533, E-ISSN 1432-0681, Vol. 82, no 5, p. 677-698Article in journal (Refereed)
    Abstract [en]

    In this article, the governing equations of motion of thick laminated transversely isotropic plates are derived based on Reddy’s third-order shear deformation theory. These equations are exactly converted to four uncoupled equations to study the in-plane and out-of-plane free vibrations of thick laminated plates without any usage of approximate methods. Based on the present analytical approach, exact Levy-type solutions are obtained for thick laminated transversely isotropic plates and, for some boundary conditions, the exact characteristic equations hitherto not reported in the literature are given. Also, the in-plane and out-of-plane deformed mode shapes are plotted for different boundary conditions. The present solutions can accurately predict both the in-plane and out-of-plane natural frequencies and mode shapes of thick laminated transversely isotropic plates.

  • 334. Hosseini-Hashemi, Sh.
    et al.
    Atashipour, Seyed Rasoul
    Fadaee, M.
    On the buckling analysis of isotropic, transversely isotropic and laminated rectangular plates via Reddy plate theory: an exact closed-form procedure2012In: Proceedings of the Institution of mechanical engineers. Part C, journal of mechanical engineering science, ISSN 0954-4062, E-ISSN 2041-2983, Vol. 226, no 5, p. 1210-1224Article in journal (Refereed)
    Abstract [en]

    Based on Reddy's third-order shear deformation theory, an exact closed-form solution is proposed to describe linear buckling of transversely isotropic laminated rectangular plates under either mono- or bi-axial compressive in-plane loads. To this end, the coupled governing equations are exactly converted to two sets of uncoupled equations for in-plane and transverse deformations of symmetric laminated plates. The new uncoupled equations are analytically solved by applying both Navier and Lévy-type solution methods. The validity and high accuracy of the current exact solution are evaluated by comparing the present results with their counterparts reported in literature.

  • 335.
    Hosseini-Hashemi, Sh.
    et al.
    School of Mechanical Engineering, Iran University of Science and Technology, Narmak.
    Atashipour, Seyed Rasoul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Fadaee, M.
    School of Mechanical Engineering, Iran University of Science and Technology, Narmak.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    An exact closed-form procedure for free vibration analysis of laminated spherical shell panels based on Sanders theory2012In: Archive of applied mechanics (1991), ISSN 0939-1533, E-ISSN 1432-0681, Vol. 82, no 7, p. 985-1002Article in journal (Refereed)
    Abstract [en]

    This paper deals with closed-form solutions for in-plane and out-of-plane free vibration of moderately thick laminated transversely isotropic spherical shell panels on the basis of Sanders theory without any usage of approximate methods. The governing equations of motion and the boundary conditions are derived using Hamilton's principle. The highly coupled governing equations are recast to some uncoupled equations by introducing four potential functions. Also, some relations were presented for the unknowns of the original set of equations in terms of the unknowns of the uncoupled equations. According to the proposed analytical approach, both Navier and Lévy-type explicit solutions are developed for moderately thick laminated spherical shell panels. The efficiency and high accuracy of the present approach are investigated by comparing some of the present study with the available results in the literature and the results of 3D finite element method. The effects of various shell parameters like shear modulus ratio of transversely isotropic materials and curvature ratio on the natural frequencies are studied. Clearly, the proposed solutions can accurately predict the in-plane and out-of-plane natural frequencies of moderately thick transversely isotropic spherical shell panels

  • 336. Hosseini-Hashemi, Sh.
    et al.
    Atashipour, Seyed Rasoul
    Karimi, M.
    Es'haghi, M.
    Free vibration analysis of functionally graded elliptical plates2012In: International journal of Maritime Technology, ISSN 2345-6000, Vol. 8, no 15, p. 43-60Article in journal (Refereed)
    Abstract [en]

    This paper deals with a free vibration analysis of functionally graded elliptical plates with different classical boundary conditions on the basis of polynomial-Ritz method and classical plate theory. The proposed admissible function is capable to obtain accurate natural frequencies of various classical boundary conditions namely, clamped, free and simply supported edges. The mechanical properties of the FG plate are assumed to vary continuously through the thickness of the plate and obey a power law distribution of the volume fraction of the constituents. The convergency of applied polynomial-Ritz method is investigated. In order to verify the accuracy of the present solution, a comprehensive comparison study is performed with the available results in the literature for homogeneous elliptical plate and FG circular plate. Also, the numerical results of the present solution for FG elliptical plate are compared with those of the finite element method (FEM). Finally, the effects of the plate geometry and inhomogeneity on the natural frequencies are investigated and some vibrational mode shapes related to symmetric-symmetric, symmetric-antisymmetric, antisymmetric- symmetric and antisymmetric- antisymmetric states are presented.

  • 337.
    Hosseini-Hashemi, Sh.
    et al.
    School of Mechanical Engineering, Iran University of Science and Technology, Narmak.
    Rezaee, V.
    School of Mechanical Engineering, Iran University of Science and Technology, Narmak.
    Atashipour, Seyed Rasoul
    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.
    Accurate free vibration analysis of thick laminated circular plates with attached rigid core2012In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 331, no 25, p. 5581-5596Article in journal (Refereed)
    Abstract [en]

    This paper deals with the free vibration behavior of laminated transversely isotropic circular plates with axisymmetric rigid core attached at the center. The governing equations of motion are obtained based on Mindlin's first-order shear deformation plate theory. Two possible categories of vibration modes related to up-down translation of the core and wobbly rotation of the core about a diameter are studied. Accurate natural frequencies hitherto not reported in the literature are presented for a wide range of thickness-to-radius ratio, inner-to-outer radius ratio, mass and moment of inertia ratios of the core and various boundary conditions at the outer edge of the plate. Numerical results are compared with those of a three-dimensional finite element method (3-D FEM) to demonstrate the high accuracy and reliability of the current analysis.

  • 338. Hosseini-Hashemi, Sh.
    et al.
    Salehipour, H.
    Atashipour, Seyed Rasoul
    Exact three-dimensional free vibration analysis of thick homogeneous plates coated by functionally graded layer2012In: Acta Mechanica, ISSN 0001-5970, E-ISSN 1619-6937, Vol. 223, no 10, p. 2153-2166Article in journal (Refereed)
    Abstract [en]

    Exact closed-form solutions are carried out for both in-plane and out-of-plane free vibration of thick homogeneous simply supported rectangular plates coated by a functionally graded (FG) layer, based on three-dimensional elasticity theory. The elasticity modulus and mass density of the FG coating are assumed to vary exponentially through the thickness of the coating layer, whereas Poisson’s ratio is remaining constant. The equations of motion are solved using two proposed displacement fields for the in-plane and out-of-plane vibration modes. By inserting the displacement fields in the 3-D elasto-dynamic equations, some independent ordinary equations are obtained and solved analytically. Natural frequencies are extracted by satisfying boundary conditions of interface and surfaces of the structure. The solution procedure is validated by comparing the obtained results with corresponding results of a 3-D finite element analysis. Finally, the influence of the FG coating layer on the natural frequencies of the structure is investigated and discussed. Clearly, the present closed-form solutions can exactly predict both in-plane and out-of-plane vibration modes of thick FG coated plates.

  • 339.
    Hosseini-Hashemi, Sh.
    et al.
    School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Islamic Azad University, Tehran South Campus, Islamic Azad University, Hamedan University of Technology, School of Mechanical Engineering, Iran University of Science and Technology, Tehran.
    Salehipour, H.
    School of Mechanical Engineering, Iran University of Science and Technology, Narmak.
    Atashipour, Seyed Rasoul
    School of Mechanical Engineering, Iran University of Science and Technology, Narmak.
    Sburlati, Roberta
    Department of Civil, Chemical and Environmental Engineering, Genoa University.
    On the exact in-plane and out-of-plane free vibration analysis of thick functionally graded rectangular plates: Explicit 3-D elasticity solutions2013In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 46, p. 108-115Article in journal (Refereed)
    Abstract [en]

    In this paper exact closed-form solutions of 3-D elasticity theory are presented to study both in-plane and out-of-plane free vibrations for thick functionally graded simply supported rectangular plates. The solution procedure of the transverse vibration utilizes Levinson’s representation form to describe the displacement; in this way, the 3-D elasto-dynamic equations are written in terms of some suitable independent functions satisfying ordinary differential equations. A similar procedure is presented for in-plane vibration by introducing an appropriate displacement field. In each case, the obtained ordinary differential equations are analytically solved and boundary conditions are satisfied. The proposed solutions are validated by comparing some of the present results with corresponding results known in the literature as well as with 3-D Finite Element Method. Finally, the influence of inhomogeneity on the natural frequencies for a thick functionally graded rectangular plate is discussed.

  • 340.
    Huber, Johannes Albert Josef
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Review of Robustness in Timber Buildings2017Conference paper (Refereed)
    Abstract [en]

    Timber buildings today aim for taller and larger dimensions to accommodate increased numbers of occupants.  In tall buildings, more human lives are at risk if large portions of the structure collapse progressively during catastrophic failure events. To safeguard timber structures from disproportionate collapse due to localised failures, the aspect of robustness in particular needs to be considered. In the literature about building structures the term robustness seems to be contemplated in diverse ways. Several possible approaches to define and analyse this property can be found. However, certain consensus as to what characterises a robust structure seems to exist. A review of the concept of robustness for building structures in general and timber structures in specific is presented in this paper. Certain commonly applied terminology and definitions in the context of robustness are analysed. In the literature, risk-based, reliability-based and performance-based concepts for robustness appear to be established. The first two concepts are briefly summarised. The performance-based concept is treated in greater detail to highlight different procedures of deterministic robustness analyses. Common general characteristics of robust buildings which seem to be agreed upon are summarised. Robustness provisions for timber buildings in specific are described and compared to provisions in other building materials such as steel and concrete. The development of alternate load paths during local failure seems to play an essential role in preventing progressive collapse in buildings. The literature about robustness seems to be comprehensive concerning general considerations and concerning structures built in concrete or steel but appears to be rather limited in regards to timber structures. Evaluations of robustness in timber structures seem to be focused on risk-based and reliability-based concepts in literature.

  • 341. Husson, Wylliam
    Friction connections with slotted holes for wind towers2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In a constantly increasing and competitive market the efficiency of the whole wind power plant is an issue. The tubular steel towers supporting wind turbines account for about 15 to 20% of the total installation costs and their optimization may lead to substantial savings with regard to costs and use of material. One important aspect of the design is the connection between tower's sections. The currently used solution with bolted ring flanges is prone to low fatigue resistance which imposes limitations that can impair the overall efficiency. Improvement could be achieved by implementing friction connections. This idea is investigated and the principles of a new type of friction connection are presented. Long open slotted holes are used to facilitate assembly and the segments are clamped with Tension Control Bolts which can safely and easily be tightened from within the tower. In the first part, the behaviour of segment specimens is investigated experimentally by mean of static and long term tests as well as numerical analyses. Two types of surfaces are considered: ethyl silicate zinc rich paint and corroded weathering steel. The influence of hole's geometry as well as connection configuration are studied. Particular focus is given to the variations of bolt force and the slip resistance. In the second part, the resistance function of the tested connections is derived from statistical analysis according to Annex D of EN1990. The influence of environmental parameters and workmanship on the pretension achieved by TCBs is also investigated to provide recommendation on optimal handling and design pretension. Finally, a method is proposed to design friction connections for wind towers. It is compared to the design of current L flange connections. One example of a 80m-high tower is shown. It highlights the potential benefits of using friction connections as the design is made simpler and material costs savings of up to 80% could be achieved.

  • 342. Husson, Wylliam
    et al.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Behaviour of a friction connection using TCB in long slotted holes2007In: Proceedings of the 9th International Conference on Steel, Space and Composite Structures, Singapore: CI-Premier Pte Ltd, 2007Conference paper (Refereed)
    Abstract [en]

    With constantly increasing demand for renewable energies the cost optimization of steel towers supporting multi-mega-watt wind turbines becomes important. Luleå University of Technology currently coordinate European research project (RFCS), including partners from 5 countries, which aim is to ensure the high competitiveness of the next generation of steel towers produced in Europe. One innovation investigated within this project is the use of friction grip connection with long slotted holes to connect the steel tower sections. This paper presents a part of ongoing experimental program and result of three segment tests performed with weathering steel plates and M20 Tension Control Bolts. Experimental results are compared to the prediction according to European structural code EN 1993-1-8 Furthermore a three dimensional numerical model was used to describe behaviour of the connection with a long slotted hole together and a thick cover plate FE-analysis of the preliminary experiments was used to endorse conclusions from the experiments.

  • 343. Husson, Wylliam
    et al.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Innovative connections in tubular steel towers: experiments on segment specimens under static loading2008In: Proceedings / Eurosteel 2008: 5th European Conference on Steel and Composite Structures - Research, Eurocodes, Practice - Graz, Austria, September 3 - 5, 2008 / [ed] Robert Ofner; Darko Beg; Josef Fink; Richard Greiner; Harald Unterweger, European Convention for Constructional Steelwork, ECCS , 2008, Vol. A, p. 651-656Conference paper (Refereed)
  • 344. Husson, Wylliam
    et al.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Performance of a high-strength friction grip connection with open slotted hole2008In: Connections in Steel Structures VI: Proceedings of the 6th international workshop, 2008, p. 585-596Conference paper (Refereed)
  • 345.
    Häggkvist, Andreas
    et al.
    SP Technical Research Institute of Sweden, Borås.
    Sjöström, Johan
    SP Technical Research Institute of Sweden, Borås.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Using plate thermometer measurements to calculate incident heat radiation2013In: Journal of fire sciences, ISSN 0734-9041, E-ISSN 1530-8049, Vol. 31, no 2, p. 166-177Article in journal (Refereed)
    Abstract [en]

    The plate thermometer is a device used mainly to measure temperatures in fire resistance tests according to ISO 834-1 and EN 1363-1 and to measure the so-called adiabatic surface temperature. However, it can also be used to measure incident radiant heat flux (q̇″inc) as a simpler, more robust and less-expensive alternative to water-cooled heat flux meters. The accuracy of the measured q̇″inc is subject to simplifications in the heat transfer analysis model and uncertainties of parameters such as convective heat transfer coefficients, emissivities and ambient gas temperatures. This study investigates the accuracy of the model itself, isolated from the uncertainties of the physical surrounding, by comparing a simple one-dimensional model to the results of finite element modelling. The so-obtained model includes a heat transfer coefficient due to heat losses of the plate thermometer, found to be KPT = 8 W/m2 K and a heat storage lumped heat capacity CPT = 4200 J/m2 K for an ISO/EN standard plate thermometer. The model is also compared to real field experiments.

  • 346.
    Hällmark, Robert
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Prefabricated composite bridges: a study of dry deck joints2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with prefabricated composite bridges in general, and prefabricated concrete deck elements with dry joints in particular.As outlined in Paper I and Chapter 2 prefabrication has several advantages over in situ construction, and has hence been discussed for decades in the construction business. Further, the house building sector has taken large steps towards a more industrialized approach, in which prefabrication, lean thinking and Building Information Modelling (BIM) are all important components. Numerous studies have also examined the applicability of such an approach in the bridge sector, and several types of prefabrication techniques have been tested. Nevertheless, in many countries the bridge sector seems to lag far behind in the general shift towards more industrialized construction processes. One of the reasons for the relatively slow progress may be the fact that bridges are often unique objects with unique specifications and constraints. This hinders the standardisation that is often regarded as a key to industrialised construction.Chapter 2-3 and Paper I, presents evidence from a literature review together with information gathered from a Workshop, attended by bridge designers and researcher in Europe and the US, that prefabricated deck elements are still quite rarely used in bridge construction. Deck elements with dry transverse joints are even rarer. Few examples have been reported. In addition, the degree of prefabrication and the rate of progress towards more industrialised construction processes seem to vary substantially from one country to another.However, as described in Chapter 3 and Paper II, a prefabricated concrete deck element system with dry joints has been developed in Sweden for constructing composite bridges. The transverse joints are completely dry, and all forces are transferred by contact pressure between concrete surfaces. This implies that no tensional forces can be transferred over the transverse joints. Shear forces are transferred by overlapping concrete shear keys, designed as a series of male-female connections. The research presented in this thesis is focused on the structural behaviour of this deck element system. In order to investigate this, laboratory tests have been performed as well as field monitoring.Results of large-scale laboratory tests, presented in Chapter 4 and Paper V, show that a bridge of this type is less stiff than a similar bridge with an insitu cast deck slab. The concrete elements’ contributions to stiffness are negligible in sections with hogging moments, but make some contribution to global stiffness in sections with sagging moments. At moderate load levels, the interacting concrete area is much smaller than in a similar in-situ cast section. This is believed to be due to the combined effects of small gaps in the joints and continuous in-situ cast concrete in the injection channels.After the channels have been injected, existing gaps will be more or less permanent, since the in-situ cast concrete must be compressed up to a certain limit before the rest of the joint will be closed. Destructive testing showed that the differences in stiffness and stresses between a deck of this type and an in-situ cast bridge deck are much smaller in the ultimate limit state. In this case it could even be reasonable to design a cross-section according to Eurocodes, neglecting effects of the joints.As shown in Chapter 5 and Paper III, the overlapping shear keys are a critical detailing in this deck system. Therefore, they were tested in the laboratory to determine how they fail and evaluate their load capacity. The tests revealed two failure modes. The first is a rather ductile failure, activating the shear reinforcement. This was the expected failure mode for shear keys of this design. The second failure mode observed was a quite brittle failure in the concrete covering layer. It has only been observed in small-scale tests, and might be related to the test set-up. Nevertheless, overlapping of the rebars in the male-female shear key connection is strongly recommended to assure the robustness of shear transfer if failure occurs in the concrete covering layer.To complement the laboratory tests, a single span bridge was monitored in the field (Chapter 6 and Paper IV). The bridge was built in 2000, using the prefabricated deck system that this thesis is focusing on, and was tested in both 2001 and 2011. The tests, and subsequent Finite Element analyses, showed that under moderate loading the interacting concrete area is smaller than for a similar in-situ cast bridge. No significant long-term effects were observed, except that under eccentric loading the distribution of the deflection between the girders decreased slightly during the 10 years between tests. This indicates that the joint gaps may have narrowed and at least partly closed during this time.Chapter 7 summarises the research and presents recommendations for dealing with general issues related to the design and construction of a bridge of this type. The design methods are generally the same as for a conventional composite bridge with an in-situ cast deck slab. However, the Eurocodes require some modification for the design of prefabricated deck elements with dry joints, particularly regarding global analysis and the resistance of cross-sections. Finally, conclusions, a general discussion and suggestions for further research are presented in Chapter 8.

  • 347.
    Hällmark, Robert
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Trafikverket, Luleå.
    Collin, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Ramböll, Luleå.
    Möller, Mikael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SSESAB, Luleå/Helsingborg.
    Testing of coiled spring pins as shear connectors2017In: IABSE Symposium, Vancouver, 2017: Engineering the Future, Zürich, Switzerland: IABSE - International Association for Bridges and Structural Engineering , 2017, p. 1209-1216Conference paper (Refereed)
    Abstract [en]

    A few decades ago, steel-concrete composite bridges were quite rare structures, whereas steel girder bridges with non-composite concrete decks were rather common. For the latter type of structure, composite action can be obtained long after the bridges were constructed by post installation of shear connectors. Most installation procedures involve reconstruction of pavement and concrete deck, which will result in traffic disturbance. There are however some types of shear connectors that can be installed from underneath, connecting the top flanges to the concrete deck, without affecting the upper surface. This means that the bridge can be strengthened during traffic. One type of such a shear connector is the coiled spring pin, which is an interference fit connector. This paper presents the results from push-out tests conducted in order to find the static capacity and the load-slip behaviour of coiled spring pins used as shear connectors.

  • 348.
    Hällmark, Robert
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Collin, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Möller, Mikael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    The behaviour of a prefabricated composite bridge with dry deck joints2013In: Structural Engineering International, ISSN 1016-8664, E-ISSN 1683-0350, Vol. 23, no 1, p. 47-54Article in journal (Refereed)
    Abstract [en]

    This paper describes the monitoring of a one-span composite bridge in northern Sweden. The bridge was built in 2000, with prefabricated deck elements connected to steel girders, and the back walls as well as the piers were also prefabricated. The monitoring was required to clarify the doubts regarding whether a bridge with dry deck joints can be expected to perform as a conventional composite bridge, with in situ cast deck and sections with sagging moments. To get a better understanding of the long-term structural behaviour, the bridge was monitored both during 2001 and 2011, instrumented with equipment measuring the deflections and strains in the steel cross section. The bridge was loaded with a truck in midspan having a total weight of 25 t. When the truck was centred between the girders, the results showed a symmetric behaviour, with respect to deflections and stresses. For the case with the truck stationed right above one of the steel girders, anti-symmetric behaviour was observed and studied by means of finite element calculations, taking into account the stiffness of the composite section as well as the end screens and the earth pressure below them.

  • 349.
    Hällmark, Robert
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Collin, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Large-scale tests on a composite bridge with prefabricated concrete deck and dry deck joints2013In: Stahlbau, ISSN 0038-9145, E-ISSN 1437-1049, Vol. 82, no 2, p. 122-133Article in journal (Refereed)
    Abstract [en]

    This paper describes the large-scale tests on a composite bridge with prefabricated deck elements and dry joints between the elements. The work is part of the European R&D project ELEM (RFCS-CT-2008-00039). This type of bridge has been used for three single-span bridges in Sweden and has contributed to minimizing construction time as well as disturbance to traffi c. The behaviour at midspan and the behaviour over an internal support of a continuous bridge were studied in the tests, and the results analysed by FEM and discussed. Conclusions regarding the design of this type of bridge are drawn, with respect to the global analysis as well as cross-section capacity.

  • 350.
    Hällmark, Robert
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Trafikverket, Luleå.
    Collin, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Ramböll, Luleå.
    Petersson, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Andersson, Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Monitoring of a bridge strengthened with post-installed coiled spring pins2017In: IABSE Symposium, Vancouver, 2017: Engineering the Future, Zürich, Switzerland: IABSE - International Association for Bridges and Structural Engineering , 2017, p. 1201-1208Conference paper (Refereed)
    Abstract [en]

    Many existing bridges were not originally designed for the traffic loads and the number of load cycles which they now experience. In order to increase the load capacity of non-composite steel-concrete bridges, post installed shear connectors can be used. This paper describes a field monitoring of a steel-concrete bridge which have been strengthened with post-installed coiled spring pins as shear connectors. During the monitoring, the bridge was loaded with a 31 tonnes truck placed in specific positions while strains were measured in the steel main girders, together with the horizontal slip at the steel-concrete interface. The results indicate that the coiled spring pins prevent the slip and that they can be used for strengthening purpose. It is also observed that the friction in the steel-concrete interface can contribute quite a lot to the composite action, even though that effect cannot be accounted for in the design.

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