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  • 251.
    Schmid, Joachim
    et al.
    Swiss Federal Institute of Technoogy, Institute Structural engineering, Zurich.
    Brandon, Daniel
    SP Wood Building Technology Sustainable Built Environm, Borås.
    Santomaso, Alessandro
    University of Trieste.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Frangi, Andres
    Swiss Federal Institute of Technoogy, Institute Structural engineering, Zurich.
    Timber under Real Fire Conditions: the Influence of Oxygen Content and Gas Velocity on the Charring Behavior2016Inngår i: Structures in Fire 2016: Proceedings of the Ninth International Conference - June 8-10, 2016, Princeton University / [ed] Garlock, Maria E. Moreyra; Kodur, Venkatesh K. R., Lancaster: DEStech Publications , 2016, s. 692-699Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As for any building material, verification of fire resistance is mandatory for separating and loadbearing timber members. While non-standard fire design for steel members has long tradition, the corresponding possibilities for timber members are limited. Reasons for this can be found in the degree of complexity of the material and the limited research done in the field. This paper summarizes selected outcomes of tests investigating the influences on the charring behavior varying the oxygen content and the gas velocity. Besides the charring rate the char layer depth was the focus of this study to investigate char contraction (consumption of the char layer). In general, measurements are in line with previous results reported in literature. Results show that charring is predominantly depending on the fire compartment temperature. Results show further that for gas oxygen contents below 15 percent the gas velocity has no influence on the charring. However, at higher oxygen rates char contraction was observed affecting the protective function of the char layer. Thus, the charring and the temperature distribution was affected and the residual cross-section was decreased. In fully developed fires increased charring due to char contraction may not be observed due to the low oxygen contents. Contrary, in travelling fires or in the decay phase char contraction may be considered. This may have significant impact to Performance Based Design using non-standard temperature fire curves where the complete fire duration has to be taken into account.

  • 252.
    Schmid, Joachim
    et al.
    Institute of Structural Engineering, ETH Zurich.
    Santomaso, Alessandro
    Commissario delegato per l’emergenza della mobilità riguardante l’A4, Trieste.
    Brandon, Daniel
    RISE, Research Institute of Sweden.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Frangi, Andres
    (Institute of Structural Engineering, ETH Zurich, Zurich.
    Timber under Real Fire Conditions: the influence of oxygen content and gas velocity on the charring behavior2018Inngår i: Journal of Structural Fire Engineering, ISSN 2040-2317, E-ISSN 2040-2325, Vol. 9, nr 3, s. 222-236Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose

    The purpose of this study is to investigate the influencing factors on the charring behaviour of timber, the char layer and the charring depth in non-standard fires.

    Design/methodology/approach

    This paper summarizes outcomes of tests, investigating the influences on the charring behavior of timber by varying the oxygen content and the gas velocity in the compartment. Results show that charring is depending on the fire compartment temperature, but results show further that at higher oxygen flow, char contraction was observed affecting the protective function of the char layer.

    Findings

    In particular, in the cooling phase, char contraction should be considered which may have a significant impact on performance-based design using non-standard temperature fire curves where the complete fire history including the cooling phase has to be taken into account.

    Originality/value

    Up to now, some research on non-standard fire exposed timber member has been performed, mainly based on standard fire resistance tests where boundary conditions as gas flow and oxygen content especially in the decay phase are not measured or documented. The approach presented in this paper is the first documented fire tests with timber documenting the data required.

  • 253.
    Shu, Jiangpeng
    et al.
    Department of Civil and Environmental Engineering, Chalmers University of Technology .
    Bagge, Niklas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. WSP Sverige AB.
    Plos, Mario
    Department of Civil and Environmental Engineering, Chalmers University of Technology.
    Johansson, Morgan
    Department of Civil and Environmental Engineering, Chalmers University of Technology.
    Zandi, Kamyab
    Department of Civil and Environmental Engineering, Chalmers University of Technology.
    Shear Capacity of a RC Bridge Deck Slab: Comparison between Multilevel Assessment and Field Test2018Inngår i: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 144, nr 7, artikkel-id 04018081Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For reinforced concrete (RC) slabs without shear reinforcement, shear and punching can be the governing failure mode at the ultimate limit state if subjected to large concentrated loads. Shear and punching of RC slabs without shear reinforcement has been a challenging problem in assessment based on current standards. To examine a previously developed enhanced analysis approach, this study was conducted by applying a multilevel assessment strategy to a 55-year old RC bridge deck slab subjected to concentrated loads near the main girder in a field failure test. This strategy clearly provides the engineering community a framework for using successively improved structural analysis methods for enhanced assessment in a straightforward manner. The differences between analysis methods at different levels of assessment were discussed regarding one-way shear and punching shear behavior of the slab. The influences of parameters, such as boundary conditions, location of concentrated loads, and shear force distribution, were investigated.

  • 254.
    Shu, Jiangpeng
    et al.
    Chalmers University of Technology.
    Plos, Mario
    Chalmers University of Technology.
    Nilenius, Filip
    Chalmers University of Technology.
    Zandi, Kamyab
    Chalmers University of Technology.
    Bagge, Niklas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Johansson, Morgan
    Chalmers University of Technology.
    Punching/Shear Strength of a full-scale tested bridge deck slab2017Inngår i: IABSE Symposium, Vancouver, 2017: Engineering the Future, Zürich, Switzerland: IABSE - International Association for Bridges and Structural Engineering , 2017, s. 1750-1757Konferansepaper (Fagfellevurdert)
    Abstract [en]

    For reinforced concrete (RC) slabs without shear reinforcement, shear and punching can be the governing failure mode at ultimate limit state if subjected to large concentrated loads. Punching of RC slabs without shear reinforcement has been a challenging problem in assessment based on current standards. To examine a previously developed enhanced analysis approach, this study was conducted by applying continuum FE analyses to a 55-year old RC bridge deck slab subjected to concentrated loads near the main girder in a field failure test. The influence of parameters such as boundary conditions, location of concentrated loads and shear force distribution were investigated.

  • 255.
    Sjöström, Johan
    et al.
    SP Technical Research Institute of Sweden, Borås, SP Sveriges Tekniska Forskningsinstitut, Brandteknik.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Byström, Alexandra
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Validation data for room fire models: Experimantal background2016Rapport (Annet vitenskapelig)
    Abstract [en]

    A series of room fire tests for enclosures with different wall materials have been conducted for the purpose of supplying validation data for enclosure fire models. The wall materials are varied between light weight concrete, mineral wool insulation, bare 3 mm steel, and finally insulated steel. All tests used a propane gas burner with a well-defined mass flux as a fire source. Temperatures of thermocouples and plate thermometers were measured as well as oxygen concentrations in the opening. For some tests the heat release rate (by oxygen consumption calorimetry) as well as O2, CO2 and CO concentrations were measured in addition.This report describes the instrumentation, fire scenarios, enclosure materials, and results from all the tests. All results are readily available as spreadsheet data for downloading. The report also contains short description showing the influence of different factors such as wall materials, heat release rates and burner placements.

  • 256.
    Snefuglli Sondell, Kerstin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Korpinen, Hampus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Framgångsfaktorer för räddningstjänstens operativa arbete vid brand i bostad2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Bränder som innefattar många drabbade eller ger stor förstörelse är oftast de som blir mest omtalade. Efter händelsen sker ett omfattande utredningsarbete för att förelägga hur det som inte fick hända kunde ske. Utredningen beskriver även räddningstjänstens val av metod och taktik för att kunna nyttja detta för framtida insatser. Vad som däremot lätt glöms bort är de insatser då räddningstjänstens arbete får god effekt och resulterar i att olyckans skada begränsas.

    Detta examensarbete kommer beröra just dessa händelser av brand i bostad, då räddningstjänstens arbete får den effekt som eftersträvas, det vill säga arbetet har lett till en lyckad insats. Arbetet kommer därefter belysa vilka faktorer som legat till grund för att insatsen blivit lyckad, så kallade framgångsfaktorer.

    Syftet med arbetet är att identifiera framgångsfaktorer vid lyckade insatser för brand i bostad. Framgångsfaktorerna ska ligga till grund för att skapa ett utvecklingsunderlag berörande metod- och taktikval inom räddningstjänsten. För att göra detta krävs en tydlig definition av innebörden av en lyckad insats. Utifrån syftet har följande frågeställningar formulerats: Vad innebär att en insats är lyckad? Vad innebär framgångsfaktorer för operativa insatser vid brand i bostad? Vilka framgångsfaktorer kan identifieras inom de utvalda insatserna och hur kan de identifieras, finns det gemensamma? Hur kan framgångsfaktorer nyttjas?

    Metoderna som tillämpats är kvalitativa intervjuer och granskning av bland annat händelserapporter från utvalda insatser av brand i bostad. Ansvarigt befäl för samtliga händelser tillfrågades att delta som respondenter till intervjustudien. Intervjufrågorna är framtagna med avsikt att besvara rapportens tre frågeställningar. Arbetet ger ett resultat som beskriver följande framgångsfaktorer för brand i bostad:

    • Riktig och tillräcklig information i ett tidigt skede
    • Ett snabbt motiverat agerande för att direkt slå ner branden
    • Yttre faktorer som räddningstjänsten inte kan påverka:
    • Agerande av utomstående innan räddningsinsatsen påbörjats
    • Byggnadens utformning
    • Brandens placering
    • Delegera ansvar och uppgifter
    • Ett tydligt definierat mål som samtliga eftersträvar
    • Utbildning och kunskap, tidigare erfarenheter, nya metoder
    • Tillgängliga resurser
    • Ha god kvalitet vid omhändertagande av de drabbade, såväl på plats som efteråt
    • Samverkan mellan berörda aktörer
      • Ha en helhetssyn över situationen och samtliga aktörers behov
      • Ha förståelse för olika aktörers perspektiv av situationen
      • Ha ett gemensamt språk mellan aktörer för att undvika missförstånd
      • Dela information mellan inblandade aktörer för att undvika dubbelarbete

    Slutligen belyser arbetet hur räddningstjänstens kunskapsutbyte ser ut i dagsläget.

  • 257.
    Sobótka, Maciej
    et al.
    Faculty of Civil Engineering, Wrocław University of Science and Technology.
    Pachnicz, Michał
    Faculty of Civil Engineering, Wrocław University of Science and Technology.
    Rajczakowska, Magdalena
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Induced Crack Network Evolution in Geomaterials: µct Examination and Mathematical Morphology Based Analysis2018Inngår i: Proceedings of China-Europe Conference on Geotechnical Engineering, Cham: Springer, 2018, Vol. 1, s. 216-219Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fracture parameters of the rock material are known to change due to applied loading, having effect on, e.g. the rock permeability coefficient which can be estimated based on the geometrical descriptors of the crack space. In this paper, a method of crack network evolution analysis is proposed for the rock samples subjected to uniaxial compression. Fracture development is investigated using ex-situ time-lapse micro-computed tomography (µCT). The sets of images are acquired for each specimen at three damage levels: before loading, at approximately 50% of compressive strength and, finally, after reaching micro-dilatancy threshold (or compressive strength). The reconstructed and segmented 3D crack network is examined at each loading stage. The analysis consists of image processing and determination of the selected morphological parameters, i.e. volume fraction of the crack, spatial distribution of the fracture aperture, tortuosity as well as the structure model index (SMI).

  • 258.
    Song, Shoutan
    et al.
    Southeast University, Nanjing.
    Yang, Dong
    Southeast University, Nanjing.
    Tu, Yongming
    Southeast University, Nanjing.
    Sas, Gabriel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Analysis of the shear strength of joints in segmental prestressed concrete bridges2016Inngår i: 19th IABSE Congress Strockholm 21-23 September 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment / [ed] Lennart Elfgren, Johan Jonsson, Mats Karlsson, Lahja Rydberg-Forssbeck and Britt Sigfrid, CH - 8093 Zürich, Switzerland, 2016, s. 573-579Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Joints in segmental prestressed concrete bridge (SPCB) are weak links and shear failures are likely to take place under loads. Determining the shear strength is an important part in the design of a SPCB. The shear strength in the joint relates closely to the joint form (as dry joints, epoxy joints, flat joints and keyed joints). The strength can be divided into three main parts: (1) The strength of the dry plane connection, known mainly as concrete surface friction; (2) The strength of the epoxy plane connection; and (3) The strength of the shear key root. This paper analyzes the failure mechanism and shear strength of these three parts .It also considers the influences of the shear key size and the seam height to shear strength, and establishes calculation formulas of the joint section strength in a united form. This provides a guide for the joint design in precast segmental bridges

  • 259.
    Stavridou, Nafsika
    et al.
    Department of Civil Engineering, School of Engineering, University of Birmingham, Birmingham, UK .
    Koltsakis, Efthymios
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Baniotopoulos, Charalampos
    Department of Civil Engineering, School of Engineering, University of Birmingham, Birmingham, UK .
    Structural analysis and optimal design of steel lattice wind turbine towers2019Inngår i: Proceedings of the Institution of Civil Engineers: Structures and buildings, ISSN 0965-0911, E-ISSN 1751-7702, Vol. 172, nr 8, s. 564-579Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wind energy has shown its dominance among the means of sustainable energy production by the accelerating rise in total installed capacity and increase in size of wind energy structures. Taking into consideration the fact that the supporting structure of onshore wind power generators constitutes approximately one-third of the initial construction cost, structural optimisation of the tower is considered crucial towards the minimisation of capital expenditure during construction. Contemporary energy needs employ the construction of constantly taller and more powerful wind power converters, whose robust design in parallel with compression of initial capital expenditure cannot be neglected. The dominant structural configuration for onshore wind power generators is the tapered steel tower, but lattice towers using enhanced special cross-sections can be a rather promising solution towards economy of material use. The present paper addresses the structural performance and optimisation of tubular and lattice steel wind turbine towers, examining alternative configuration solutions for a given height and rotor characteristics. The finite-element software Abaqus has been used for the implementation of the structural models and an algorithm has been elaborated in Mathematica software in order to allow for optimisation of the use of the cross-section in the case of lattice towers.

  • 260.
    Stenlund, Anders
    et al.
    Trafikverket.
    Nilsson, Martin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Railway Bridge Research: A Survey 2005 Sustainable Bridges SB-D1.42005Rapport (Fagfellevurdert)
    Abstract [en]

    An overview is reported of current research regarding railway bridges. Research themes and active institutes and organisations are listed. The work has been carried out during 2004/2005 in the project “Sustainable Bridges –Assessment for Future Traffic Demands and Longer Lives”, an Integrated Research Projectwithin the Sixth Framework Programme of the European Commission. Most of the material has been obtained from the web but personal knowledge and direct communication with some of the institutes/organisations has also been used. An overview like this can never be complete and we apologize for all unintended omissions. Research is going on all over the world. The most studied subjects are:

    • Assessment

    • Structural behaviour and monitoring

    • Repair and strengthening

    • Dynamic effects and vibration

    • Life cycle analysis

  • 261.
    Tole, Ilda
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Habermehl-Cwirzen, Karin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Cwirzen, Andrzej
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Mechanochemical activation of natural clay minerals: an alternative to produce sustainable cementitious binders – review2019Inngår i: Mineralogy and Petrology, ISSN 0930-0708, E-ISSN 1438-1168, Vol. 113, nr 4, s. 449-462Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mechanochemical activation can be defined as a process able to induce structural disorder through intensive grinding. In certain conditions, it may increase the chemical reactivity of the processed material. The process is extensively utilized in extractive metallurgy, synthesis of nanocomposites or pharmacology. It is also considered an environmentally friendly alternative to activate kaolinitic clay avoiding high calcination temperature. This paper aims to give a comprehensive overview of the process, its evolution, process parameters and applications. The paper focuses on the mechanochemical treatment of natural clay minerals, aiming at their transformation into cementitious or pozzolanic materials. It provides a summarized review of the theories related to the mechanochemistry and discusses commonly used models. The paper also analyzes various key factors and parameters controlling the mechanochemical activation process. The optimization and control of the several factors, as the filling ratio, the grinding media, the velocity, the time of grinding, etc., can promote developments and new research opportunities on different fields of application. Examples of applications, with a special focus on mechanochemically activated clay minerals and their use as cementitious binders, are listed as well.

  • 262.
    Tole, Ilda
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Habermehl-Cwirzen, Karin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Rajczakowska, Magdalena
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Cwirzen, Andrzej
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Activation of a Raw Clay by Mechanochemical Process: Effects of Various Parameters on the Process Efficiency and Cementitious Properties2018Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 11, nr 10, artikkel-id 1860Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The efficiency of the mechanochemical activation (MCA) is influenced by various process parameters as well as by the properties of the treated material. The main objective of this research was to optimize the MCA process, gaining enhancement of the chemical reactivity of a Swedish raw clay, which is going to be used as an alkali-activated cementitious binder. The effects of the amount of water, the filling ratio, the rotation speed, and the grinding duration on the amorphization degree were evaluated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Generally, wet and dry processes showed an extensive amorphization of both kaolinite and muscovite minerals present in the studied clay. On the contrary, quartz was amorphized mainly by the wet grinding process. The efficiency of both dry and wet grinding processes was enhanced by the increased number of grinding media versus the amount of the activated material. However, longer processing times caused significant agglomeration while a higher rotational speed enhanced the amorphization. Preliminary tests have shown that alkali activation of the processed clays produced hardened samples. Furthermore, the increased amorphization corresponded to the increased compressive strength values.

  • 263.
    Tran, Anh Tuan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Lateral-torsional buckling resistance of cold-formed high strength steel rectangular hollow beams2016Inngår i: Insights and Innovations in Structural Engineering, Mechanics and Computation / [ed] Alphose Zingoni, Boca Raton: CRC Press, 2016, s. 1051-1055Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Hollow sections have been widely used for steel structures. Applications of High Strength Steel (HSS) on cold-formed hollow sections lead to thinner and lighter structures. This paper presents numerical investigations on the lateral-torsional buckling resistance of the cold-formed high strength steel rectangular hollow beam. Results from finite element analysis using Abaqus software are compared to calculations accroding to Eurocode 3. First, buckling analyses are carried out to investigate buckling behaviors of the rectangular hollow beams. In this step, elastic critical moments have been investigated and compared to calculations according to SN003. Buckling shapes have been also obtained in this step. Secondly, nonlinear analyses using Riks method have been performed. Buckling resistances of the beams with various thicknesses, various high strength materials S460, S650 and S960 have been compared to calculations according to EC 3. Further investigations on geometric imperfection sensitive have been carried out with different amplitudes L/1000, L/750, L/500 and L/250.

  • 264.
    Tran, Anh Tuan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Resistance of cold-formed high strength steel sections: Effect of cold-formed angle2019Doktoravhandling, med artikler (Annet vitenskapelig)
  • 265.
    Tran, Anh Tuan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Bernspång, Lars
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Veljkovic, Milan
    Delft University of Technology, The Netherlands.
    Rebelo, Carlos
    University of Coimbra, Portugal.
    Simões da Silva, Luís
    University of Coimbra, Portugal.
    Influence of cold-formed angle on high strength steel material properties2018Inngår i: Advanced steel construction, ISSN 1816-112XArtikkel i tidsskrift (Fagfellevurdert)
  • 266.
    Tran, Anh Tuan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Bernspång, Lars
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Veljkovic, Milan
    Delft University of Technology, The Netherlands.
    Rebelo, Carlos
    University of Coimbra, Portugal.
    Simões da Silva, Luís
    University of Coimbra, Portugal.
    Resistance of cold-formed high strength steel angles2019Inngår i: Advanced steel construction, ISSN 1816-112X, Vol. 15, nr 3, s. 242-251Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes a study of the behaviour of cold-formed high strength steel angles. Thirty-six specimens with different cold-formed angles (90°, 100°, 120°, 140°, 160°, and 170°) and different thicknesses (4 mm and 6 mm) were considered. The initial geometric imperfections of the specimens were determined using the 3D laser scanning method. The magnitudes of these geometric imperfections for torsional and torsional-flexural buckling and flexural buckling analyses were proposed. The commercial finite element analysis (FEA) programme ABAQUS with shell elements S4R was used for finite element analyses. Different material strengths in corner and flat parts along with different proof stresses (0.2%, 0.01%, and 0.006%) were considered in the numerical models. The experimental and FEA results showed good agreement. Influence of cold-formed angle on non-dimensional slenderness and reduction factor curves of the 4 mm thick columns with 90° and 120° cold-formed angles was analysed.

  • 267.
    Tran, Anh Tuan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Veljkovic, Milan
    Delft University of Technology.
    Rebelo, Carlos
    University of Coimbra, 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.
    Resistance of cold-formed high strength steel circular and polygonal sections: Part 2: Numerical investigations2016Inngår i: Journal of constructional steel research, ISSN 0143-974X, E-ISSN 1873-5983, Vol. 125, s. 227-238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper is the second part of the study on the cold-formed high strength steel circular and polygonal sections intended to be used in tubular wind towers. Results from 32 numerical finite element analysis (FEA) models were compared with and calibrated against results of the tests on 32 corresponding specimens. The FEA results agreed well with the experimental results in terms of resistances and load-displacement curves. Further investigations on the numerical models were performed. Yield stress used in the FEA significantly affected the resistances of the numerical models. Using 0.2% proof stress leaded to higher resistance than the experimental results. Corners significantly influenced buckling behaviour in the polygonal section models. Analyses of an oval opening in the tubular specimens showed that peak stresses around the opening were considerably higher in the polygonal section models than in the circular section models. Finally, investigation of sensitivity to geometrical imperfections indicated that failure modes of numerical models with geometrical imperfections according to EC3 significantly differed from those of tested specimens and numerical models with geometrical imperfections obtained from the 3D scans.

  • 268.
    Trane, Joakim
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    En studie i automatiska brandlarmsystem hos Norrbottens läns sjukhus2019Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Automatiska brandlarmsystem spelar ofta en central roll i byggnaders brandskydd. Systemen fyller en viktig funktion då de utformas för att detektera brand i ett tidigt skede och därefter aktivera nödvändiga åtgärder för att minimera konsekvenser av en brand. Dessa åtgärder kan exempelvis vara att aktivera utrymningslarm eller styrning av ventilationssystem. Sjukhus är ofta komplexa byggnader med många olika verksamheter under ett och samma tak och det ställs därför höga krav på att brandlarmanläggningar skall fungera som avsett.

    Det nämns i Sverige såväl som internationellt i Europa att det är väldigt få automatlarm från brandlarmanläggningar där det faktiskt utbrutit en brand, jämfört med antal larm då det inte utbrutit en brand. Det är ingen ovanlighet att andelen brandtillbud är så låg som 5%. Inträffade bränder på Norrbottens läns sjukhus består inte bara av olyckor och tekniska fel utan orsakas även av individers illvilja och desperata handlingar. Hur fungerar då brandlarmanläggningarna på Norrbotten läns fem sjukhus, och hur uppfattas dem av personal och räddningstjänster?

    De automatiska brandlarmsystemen på Norrbottens läns fem sjukhus undersöktes genom en förstudie, dokumentgranskning och till sist en kvalitativ intervjustudie med driftpersonal, räddningstjänster och besiktningspersonal. Primärt fokus var att undersöka om sjukhusens brandlarm ger likvärdigt skydd eller om någon anläggning utmärker sig mer än de andra på något sätt. Syftet var även att undersöka sjukhusets egen personals och kommunernas räddningstjänsters uppfattning om brandlarmen. Det finns omfattande regelverk som styr vilka typer av verksamheter som kräver ett automatiskt brandlarm, hur dessa skall dimensioners, underhållas och besiktigas. I SBF 110 – Regler för brandlarm finns bestämmelser att revisionsbesiktningar skall utföras. Dokumentgranskningen bestod av sammanställning och jämförelser mellan protokoll från revisionsbesiktningar för de olika åren på respektive sjukhus. Även insatsstatistik för respektive kommun undersöktes.

    Insatsstatistik och besiktningsprotokoll från de olika sjukhusen skiljde sig något men vid närmare granskning kunde ett samband mellan de båda ses för de enskilda sjukhusen. Dessa samband tillsammans med framkomna åsikter vid intervjustudien visade att åtgärdsarbete och underhåll sköts bättre på ett par sjukhus än andra. Även räddningstjänsters och besiktningsmäns uppfattning styrkte, oberoende av varandra, dessa mönster. Med dessa åsikter tillsammans med teorier och resultat från tidigare studier om brandlarm kunde slutsatser dras.

    Besiktningspersonal menade att vissa verksamheter vidtar åtgärder och arbetar för en säkrare anläggning medan andra upplevs som att de inte tar åt sig eller vill göra förbättringar i samma utsträckning. Räddningstjänsterna skiljde sig även åt i sin uppfattning där en menade att sjukhuset är stort och inte är ett problemområde rent larmmässigt, och att ett visst antal falsklarm måste förväntas och accepteras av en sådan stor verksamhet. En annan räddningstjänst menade att sjukhuset är en av de verksamheter som genererar flest larm i kommunen och hoppas på en förbättring. Sjukhusens egen personal, i form av driftpersonal, anläggningsskötare och driftchef, var generellt nöjda med sina anläggningar och upplevde inga större problem.

    Sammanfattning

    II

    Efter en sammantagen bedömning av insamlat och tillhandahållet material anses Gällivare sjukhus vara det sjukhus som har mest arbete att göra runt sitt brandlarm för att nå upp till en likvärdig nivå som de bäst presterande sjukhusen. Bidragande orsaker till detta har varit den jämförelsevis höga falsklarmstatistiken och låga åtgärdsstatistiken. Besiktningspersonalens åsikter som oberoende part speglade denna statistik och var på så vis ett bra komplement som styrkte dessa observationer. Kiruna sjukhus tillsammans med Kalix och Piteå bedöms som de sjukhus som ligger i framkant med sitt arbete och har det tillsynes bäst fungerande arbetet runt brandlarmanläggningarna. Detta med utgångspunkt i den höga åtgärdsstatistiken och lägre antalet automatlarm som genererats från dessa sjukhus. Räddningstjänsterna i dessa tre kommuner har goda uttalanden och reflektioner angående sjukhusen. Även besiktningspersonal uppgav sig ha goda erfarenheter från dessa sjukhus.

  • 269.
    Täljsten, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. Fundació CTM Centre Tecnològic, Metallic and Ceramic Materials Department, Manresa, Spain.
    FRP Strengthening of structures-bridging gaps in academic research and industry-25-years' experience creating innovation2018Inngår i: MATEC Web of Conferences: International Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR 2018) / [ed] M.G. Alexander; H. Beushausen; F. Dehn; P. Moyo, EDP Sciences, 2018, Vol. 199, artikkel-id 01003Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents experience how academic research and industrial needs can be bridged together, focusing on external bonding with FRP:s. The paper is based on personal experience from research at university level where the results was brought to the industry and then further developed. The work spans from theory that was incorporated in design manuals to practical instruction how to install FRP:s on site. The author discusses the research from the end of the 80ties until today and how this research successfully was implemented in the construction industry. At the end a process for innovation is presented, based on the finding from research and implementation. The overall work can be divided into five phases; research, development, demonstration, implementation and finally innovation. 

  • 270.
    Täljsten, Björn
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Sas, Gabriel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Kompositförstärkning av betong2016Bok (Annet vitenskapelig)
  • 271.
    Täljsten, Björn
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Sas, Gabriel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Bagge, Niklas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. WSP.
    Nilimaa, Jonny
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Popescu, Cosmin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Carolin, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser. Trafikverket.
    Häggström, Jens
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. Trafikverket.
    Bridges tested to failure in Sweden2018Inngår i: IABSE Conference 2018 – Engineering the Past, to Meet the Needs of the FutureJune 25-27 2018, Copenhagen, Denmark, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Five bridges of different types have been tested to failure and the results have been compared to analyses of the load-carrying capacity using standard code models and advanced numerical methods. The results may help to make accurate assessments of similar existing bridges. There it is necessary to know the real behaviour, weak points, and to be able to model the load-carrying capacity in a correct way.The five bridges were: (1) a strengthened one span concrete road bridge - Stora Höga ; (2) a one span concrete rail trough bridge loaded in fatigue – Lautajokk; (3) a two span strengthened concrete trough railway bridge - Övik; (4) a one span railway steel truss bridge -Åby; and (5) a five span prestressed concrete road bridge - Kiruna. The unique results in the paper are the experiences of the real failure types, the robustness/weakness of the bridges, and the accuracy and shortcomings/potentials of different codes and models for safety assessment of existing structures

  • 272.
    Täljsten, Björn
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Carolin, Anders
    Trafikverket.
    Pedersen, Henning
    COWI, Lyngby, Denmark.
    Repair and Strengthening of Railway Bridges - Guideline SB-STR: Sustainable Bridges, SB-D6.12007Rapport (Fagfellevurdert)
    Abstract [en]

    Not all bridges need to be strengthened. More refined calculation models or following up through monitoring may show that strengthening is obsolete. Nevertheless, if it is found that strengthening is necessary, then it would be advantageous if the owner, designer and contractor are given guidance. This report presents a structured way to address strengthening needs and suitable strengthening systems connected to that need.The purpose with this report (guideline) is to give the railway owners (and also the designer and contractors) guidance for repair and strengthening of railway bridges. The proposed method of working with this guideline is new and innovative, taking the standpoint in the bridge component that needs to be strengthened, i.e. flexure, shear etc. and from that level suggesting a strengthening method. The method itself is connected to what here has been denoted a graphical index. For each bridge type and/or structural element, a sketch is presented and locations for different common strengthening problems are highlighted. To the problem, a method description and a case study are then connected which clearly explain how the strengthening problem can be solved. In the guideline focus has foremost been placed on new repair and strengthening methods that have been investigated in the work within work package 6 in the Sustainable Bridges project. However, an extended summary of commonly used strengthening methods for concrete, metallic and masonry arch bridges is also presented – but not to the same extend as for FRP bonding and external prestressing. It is suggested that the report is used as a living document and has also been written as such. That means that it should be easy and possible to upgrade the method of working with new strengthening methods and systems, it should also be possible to add for example design suggestions and more detailed work descriptions if needed. The method of working is very suitable to incorporate in a database which then easily could be upgraded over time. However, this has not been possible to accomplish within the current project. The guideline contains a main report showing the structure to follow. In the appendices are the method descriptions and cases studies appended.

  • 273.
    Täljsten, Björn
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Enochsson, Ola
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser. Bodens kommun, Sverige.
    Puurula, Arto
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser. Savonia University of applied Sciences, Kuopia, Finland.
    Nordin, Håkan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Holm, Göran
    Swedish Geotechnical Institute, Lindköping, Sweden.
    Bengtsson, Per Evert
    Swedish Geotechnical Institute, Lindköping, Sweden.
    Bennitz, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Carolin, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser. Trafikverket, Luleå, sweden.
    Field Tests: Örnsköldsviks Bridge – Full Scale Testing; Vitmossen -  Strengthening of the Subsoil; Frövi Bridge – Strengthening & Monitoring: Sustainable Bridges Background document 6.32007Rapport (Fagfellevurdert)
    Abstract [en]

    The report contains three parts:

    - Strengthening of the Örnsköldsviks Bridge with Near Surface Mounted CFRP Rods

    - Strengthening of the Sub-soil at Vitmossen, Avesta, Sweden

    - Strengthening of the Frövi Bridge with CFRP Rods and Tubes

  • 274.
    Täljsten, Björn
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Helmerich, Rosemarie
    BAM, Bundesanstalt für Materialprüfung, Berlin, Germany.
    Naumes, Johannes
    RWTH, Aachen, Germany.
    Al-Emrani, Mohammad
    Chalmers University of Technology, Göteborg, sweden.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. Skanska Sverige.
    Carolin, Anders
    Trafikverket.
    Method statement guideline: Workmanship and Quality Control of CFRP-strengthened structures: Sustainable Bridges Background document 6.42007Rapport (Fagfellevurdert)
    Abstract [en]

    This method statement guideline has the purpose of serving the designer and users of Fibre Reinforced Polymer (FRP) strengthening systems regarding the installation procedure. It discusses the Workmanship and Quality Control regarding FRP strengthened concrete and metallic structures The guideline shall be seen as a general recommendation document and special applications might need additional guidance.

  • 275.
    Täljsten, Björn
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Holm, Göran
    Swedish Geotechnical Institute, Lindköping, Sweden.
    Bengtsson, Per Evert
    Swedish Geotechnical Institute, Lindköping, Sweden.
    Arntsen, Bård
    Norut Northern Research Institute, Narvik, Norway.
    Helmerich, Rosemarie
    BAM, Bundesanstalt für Materialprüfung, Berlin, Germany.
    Al-Emrani, Mohammad
    Chalmers University of Technology, Göteborg, sweden.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. Skanska Sverige.
    Nordin, Håkan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Gebrimichael, Yonas
    City University, London, UK.
    Boyle, William J. O.
    City University, London, UK.
    Melbourne, Clive
    USalford, Manchester, UK.
    Tomor, Adriann
    Salford University of Technology, UK.
    Repair and Strengthening of Railway Bridges. Literature and Research Report: Sustainable Bridges Background document 6.22007Rapport (Fagfellevurdert)
    Abstract [en]

    The following eight sub-deliverables are presented, with the responsible partners given at the end of each subdeliverable:

    D6.2.1 Strengthening Methods for the Subsoil, SGI

    D6.2.2 Combined CFRP Strengthening and Cathodic Protection, Norut

    D6.2.3 Automated Thermography Systems for Quality Control of the Bond Behaviour for Typical CFRP Systems, BAM

    D6.2.4 Strengthening Metallic Structures using Advanced Composites, Chalmers

    D6.2.5 Strengthening of Concrete Structures with the use of Mineral Based Composites, Ltu

    D6.2.6 Strengthening of Structures with External Prestressing, Ltu

    D6.2.7 Integrated Sensor Systems for FRP repair and Strengthening, City

    D6.2.8 Repair and Strengthening of Masonry Arch Bridges, SAL

  • 276.
    Udell, Lukas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Brandskydd under byggtid för massivträhus- Finns det en problematik?2018Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
  • 277.
    Varedian, Mattias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Collin, Peter
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A new improved type of friction connection: An experimental study2017Inngår i: IABSE Conference, Vancouver 2017: Engineering the Future, Zürich, Switzerland: IABSE -International Association for Bridges and Structural Engineering , 2017, s. 214-221Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Indenters in the slip planes of a bolted lap joint increase its load bearing capacity. In an experimental study, conducted at the Luleå University of Technology, Sweden, a part of the European R&D project PROLIFE, RFCS 2015-00025, indenters between two plates a) were loaded in compression and b) shear loaded in a lap joint. The load to press a 2.5 mm diameter stainless steel indenter 2.3 mm into the plates was 11 kN and the effective friction of the joint was improved. In a reference test with two shear planes and plain as rolled plates, no indenters and an M30 bolt pre-loaded to 320 kN, the joint slip resistance force was 54.5 kN and the effective friction coefficient μeff=0.09. For an identical arrangement but with 29 indenters per shear plane, the slip resistance was close to 250 kN and μeff was increased to 0.40, at the current Eurocode acceptable joint slip of 0.15 mm.

  • 278.
    Vehmas, Tapio
    et al.
    VTT Technical Research Centre of Finland Ltd., Espoo.
    Anna, Kronlof
    VTT Expert Services Oy, Espoo.
    Cwirzen, Andrzej
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Effect of Additional Surfaces on Ordinary Portland Cement Early-Age Hydration2017Inngår i: Materials Sciences and Applications, ISSN 2153-117X, E-ISSN 2153-1188, Vol. 8, nr 12, artikkel-id 80241Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Early-age hydration of Ordinary Portland Cement (OPC) was studied in the presence of two additional surfaces. Additional surfaces are known to accelerate the early-age hydration of OPC. Autocatalytic reaction modelling was used to determine acceleration mechanism of additional surfaces. Heat development of the hydration was measured with semi-adiabatic calorimetry and the results were modelled with an autocatalytic reaction. Autocatalytic reaction modelling was able to determine number of initially active nucleation sites in early-age hydration. OPC hydration followed autocatalytic reaction principles throughout induction period and accelerating period. Both of the added surfaces, limestone filler and calcium-silicate-hydrate (C-S-H) coated limestone filler accelerated the early-age hydration. According to autocatalytic modelling, the C-S-H coated filler increased the number of initially active nucleation sites. Pristine limestone filler accelerated the early-age hydration by providing the additional nucleation sites throughout the early-age hydration. The difference was explained with common theories of nucleation and crystal growth. Autocatalytic model and measured calorimeter curve started to significantly deviate at the inflection point, where the reaction mode changed. The reaction mode change depended on the average particle distance. Early-age hydration, modelled as autocatalytic reaction was able to improve understanding of OPC early-age hydration and quantify the number of initially active nucleation sites. Understanding and quantifying the acceleration mechanisms in early-age hydration will aid larger utilization of supplementary cementitious materials where understanding the early-age strength development is crucial

  • 279.
    Vehmas, Tapio
    et al.
    VTT Technical Research Centre of Finland, Espoo .
    Anna, Krönlof
    VTT Technical Research Centre of Finland, Espoo.
    Cwirzen, Andrzej
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Calcium chloride acceleration in ordinary Portland cement2018Inngår i: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 70, nr 16, s. 856-863Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Early-age hydration of ordinary Portland cement is now acknowledged to originate from nucleation and crystal growth of calcium–silicate–hydrates. The acceleration mechanism of water-soluble inorganic substances, such as calcium chloride, is still unclear. In the present study, the acceleration mechanism was approached in two independent ways. First, the acceleration effect of filler materials (limestone and quartz powder) and calcium chloride (CaCl2) were studied experimentally with a conduction calorimeter. Second, the calcium chloride effect was studied with thermodynamic modelling. The experimental test results showed that the filler materials accelerated the acceleration period of ordinary Portland cement hydration, whereas calcium chloride accelerated hydration throughout the 24 h measuring period. A synergistic effect was observed with fillers and calcium chloride. Thermodynamic modelling indicated that calcium chloride provides a supersaturation with respect to pure calcium–silicate–hydrate. It was concluded that the supersaturation provides a qualitative explanation for both calcium chloride-induced acceleration and the synergistic effect observed with fillers

  • 280.
    Veljkovic, Milan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Activity: University Education for Future Industrial Needs2007Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 281.
    Veljkovic, Milan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Aktivitet: Advanced Steel Construction : an International Journal2005Annet (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    The International Journal of Advanced Steel Construction provides a platform for the publication and rapid dissemination of original and up-to-date research and technological developments in steel construction, design and analysis. Scope of research papers published in this journal includes but is not limited to theoretical and experimental research on elements, assemblages, systems, material, design philosophy and codification, standards, fabrication, projects of innovative nature and computer techniques. The journal is specifically tailored to channel the exchange of technological know-how between researchers and practitioners. Contributions from all aspects related to the recent developments of advanced steel construction are welcome.

  • 282.
    Veljkovic, Milan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Aktivitet: COST Action C25, Sustainability of Constructions: Integrated Approach to Life-time Structural Engineering2006Annet (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Navn: Member of Management Committee, Chairman of WG2: Life cycle functional performance

  • 283.
    Veljkovic, Milan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Aktivitet: COST Action C26,Urban Habitat Constructions under Catastrophic Events2006Annet (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Navn: Managment Committee member

  • 284.
    Veljkovic, Milan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Aktivitet: Journal of Constructional Steel Research2008Annet (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    The Journal of Constructional Steel Research provides an international forum for the presentation and discussion of the latest developments in structural steel research and their applications. It is aimed not only at researchers but also at those likely to be most affected by research results, i.e. designers and fabricators. Original papers of a high standard dealing with all aspects of steel research including theoretical and experimental research on elements, assemblages, connection and material properties are considered for publication. Those presenting research findings in a form suitable for practical use are especially welcome.

  • 285.
    Veljkovic, Milan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Project: Economic and Durable Design of Composite Bridges with Integral Abutments2007Annet (Annet (populærvitenskap, debatt, mm))
  • 286.
    Veljkovic, Milan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Project: High-strength steel tower for wind turbines2007Annet (Annet (populærvitenskap, debatt, mm))
  • 287.
    Vestman, Victor
    et al.
    Ramböll, Luleå.
    Collin, Peter
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Häggström, Jens
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Improvement of fatigue resistance through box-action for I-girder composite bridges2016Inngår i: IABSE CONGRESS, STOCKHOLM, 2016: Challenges in Design and Construction of an Innovativeand Sustainable Built Environment / [ed] ennart Elfgren, Johan Jonsson, Mats Karlsson, Lahja Rydberg-Forssbeck and Britt Sigfrid, CH - 8093 Zürich, Switzerland, 2016, s. 1988-1994Konferansepaper (Fagfellevurdert)
    Abstract [en]

    When strengthening existing I-girder composite bridges one idea is to make the cross section act like a box section, by adding a horizontal truss between the bottom flanges. This means that eccentric loads produce a torque that is transferred by shear forces around the section. The magnitude of the effects coming from introducing such a framework between girders is addressed in this article. The fatigue resistance will be improved by the reduced stress ranges and increased amount of tolerated load cycles and extend the lifetime of the details, and by so the lifetime for the bridge.

  • 288.
    Vikström, Matilda
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Edlund, Desirée
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Byggnadstekniska lösningar för brandskydd på radhusvindar2018Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
  • 289.
    Wang, Chao
    et al.
    Southeast University, Nanjing.
    Wang, Zhilan
    Southeast University, Nanjing.
    Zhang, Jiwen
    Southeast University, Nanjing.
    Tu, Yong-Ming
    Southeast University, Nanjing.
    Grip, Niklas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Ohlsson, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    FEM based research on the dynamic response of a concrete railway arch bridge2016Inngår i: IABSE CONGRESS, STOCKHOLM, 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment / [ed] Elfgren, Lennart; Jonsson, Johan; Karlsson, Mats; Rydberg-Forssbeck, Lahja; Sigfid, Britt2016, CH - 8093 Zürich, Switzerland, 2016, s. 2472-2479Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The dynamic response of a concrete railway arch bridge is studied through a case study of the bridge over Kalix River, situated at Långforsen on the railway line between Kalix and Morjärv in northern Sweden. A simplified beam-element model, a spatial grillage-beam model and a refined shell-element model were built to analyze the bridge structure. A methodology was applied where measured static and dynamic responses were used to update finite element models of Långforsen Bridge. A multi-response objective function was presented, and the finite element method was proved feasible by comparison of predicted and measured response. In the paper comparative analyses were made of the time history displacement of three finite element models under three measured load cases. A standard train model from EUROCODE, HSLM-A 1, was applied and the dynamic responses under different speeds were studied. The results showed that a refined shell element model could accurately analyze dynamic responses of the concrete railway arch bridge in a better way than beam element and spatial grillage models. The dynamic analysis based on this type of shell model can give an optimized suggestion for the railway operation as well as for the design of high-speed railway bridges.

  • 290.
    Wang, Chao
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. South East University, Nanjing, China.
    Zhang, JIwen
    South East University, Nanjing, China.
    Tu, Yongming
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. South East University, Nanjing, China.
    Sabourova, Natalia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Grip, Niklas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Fatigue Assessment of Reinforced Concrete Railway Bridge based on a Coupled Dynamic System2020Inngår i: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper proposes a fatigue damage assessment methodology of a reinforced concrete bridge based on a train bridge coupled dynamic analysis system. This coupling system is composed of a vehicle a ballasted track and a bridge structure to realize a coupled vibration analysis during train passages. This methodology adopts the Palmgren Miner rule to linearly accumulate fatigue damage, and accomplishes fatigue assessment based on recommended SN relationships for reinforced concrete from various criteria. In this paper, the dynamic performances of a bridge structure are analyzed with two different vehicle models, a moving load model (and a moving spring mass damper model). Calculated dynamic stresses areused to evaluate the fatigue damage of critical positions in a reinforced concrete bridge. A case study is carried out of a railway arch bridge with a span of 89 m, Långforsen Bridge. It runs over Kalix River on the railway between Kalix and Morjärv in northern Sweden The fatigue assessment is made by combining the presented methodology with measurements. Furthermore, the effects of train speed and axle load on fatigue damage are investigated. The results indicate that good estimations of the fatigue damage assessment are made for four measured cases based on a train-bridge coupled dynamic analysis. For low speeds and light loads no difference could be seen in the cumulative fatigue damage for the two vehicle models. But high speeds and/or heavy load ssignificantly affect the fatigue damage.

  • 291.
    Wennberg, Filip
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Förekomst och hantering av psykisk ohälsa och stress inom räddningstjänsten i Norrbotten: En enkät- och intervjustudie2018Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
  • 292.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Boundary Conditions in Fire Protection Engineering2016Inngår i: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, s. 45-64Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

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

  • 293.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Fire Exposure of Structures According to Standards2016Inngår i: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, s. 185-193Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

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

  • 294.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Heat Transfer by Convection2016Inngår i: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, s. 89-105Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

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

  • 295.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Heat Transfer by Radiation2016Inngår i: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, s. 65-87Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

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

  • 296.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Introduction2016Inngår i: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, s. 1-16Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

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

  • 297.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Measurements of Temperature and Heat Flux2016Inngår i: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, s. 133-151Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

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

  • 298.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Numerical Methods2016Inngår i: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, s. 107-124Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

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

  • 299.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Post-Flashover Compartment Fires: One-Zone Models2016Inngår i: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, s. 153-174Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

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

  • 300.
    Wickström, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Pre-flashover Compartment Fires: Two-Zone Models2016Inngår i: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, s. 175-183Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

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

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