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  • 1.
    Just, Alar
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Nurk, Jane Liise
    Tallinn University of Technology, Estonia.
    Mäger, Katrin Nele
    Tallinn University of Technology, Estonia.
    Improved fire design model for cross-laminated timber and glulam2022Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Adhesives state the essential prerequisite for manufacturing large timber construction elements from rigidly bonded solid wood boards of growth and processing bound limited dimensions. In the first two decades after the invention of glulam up to the 1930s, adhesives based on natural organic substances like blood and proteins were used. Such adhesives can have high dry strength but are weak when applying water or temperature. These adhesives were then replaced by synthetic ones, firstly in the early 1930s by (phenol )-resorcinol-formaldehyde (RF/PRF) adhesives and then by urea-formaldehyde (UF) adhesives. Numerous tests have shown that the boiling water resistant duroplastic RF/PRF adhesives are very stable at high temperatures up to/beyond the charring of wood (Dorn and Egner, 1967; Klippel 2014). Contrary hereto, the UF adhesives later classified in Europe as type II adhesives have significantly reduced water resistance (e.g. Raknes (1997) and are less temperature stable and fire resistant, although the latter was not communicated sufficiently. The RF-, PRF- and UF- adhesives were exclusively used up until the 1980s when the presently existing timber standards for “cold” and fire design were being developed. From the 1980s onwards, adhesives with various chemical compositions have been added to the market. Firstly the duroplastic melamine-urea-formaldehyde and pure melamine formaldehyde (MUF/MF) adhesives, followed in the mid-90s by the moisture-hardening one-component polyurethane (1C-PUR) adhesives, then followed by the emulsion-polymer isocyanate (EPI) adhesives. In order to speed up curing times, being of utmost high economic importance, significant amounts of polyvinyl acetate (PVAc) have been added to the hardeners of MUF adhesives with drawbacks on temperature stability. Each of the developed adhesives has its advantages and disadvantages regarding strength, water and/or temperature resistance, application robustness and price. According to EN 1995-1-2:2004, chapter 3.5, the behaviour of a bond line in fire may not be considered explicitly if the bond line is made of phenol-formaldehyde and aminoplastic, Type I adhesives, according to EN 301. Regarding the general principle that adhesives shall produce joints of such strength that the integrity of the bond is maintained in the assigned fire resistance period, a footnote hints at the point that some adhesives show softening considerably below the charring temperature of wood.

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  • 2.
    Mäger, Katrin Nele
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad, Träbyggande och boende. Tallinn University of Technology, Estonia.
    Brandon, Daniel
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad, Träbyggande och boende.
    Just, Alar
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad, Träbyggande och boende. Tallinn University of Technology, Estonia.
    Determination of the effective material properties for the thermal simulations2016Ingår i: Proceedings of the International Network on Timber Engineering Research 2016 (INTER 2016), 2016, s. 397-400Konferensbidrag (Övrigt vetenskapligt)
  • 3.
    Mäger, Katrin Nele
    et al.
    Tallinn University of Technology, Estonia.
    Just, Alar
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Wikner, Alfred (Medarbetare/bidragsgivare)
    Masonite Beams, Sweden.
    Improved fire design model for walls and floors with I-joists2022Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Wooden I-joists, being factory-made ultra-light and highly optimised products, are typically used as the load-bearing elements in timber frame assemblies (TFA), which consist of a combination of material layers – sheeting boards (claddings) and cavities which may be partially or completely filled with insulation. The materials used in conjunction with a timber member in a TFA affect the heating of the timber member. The joists consist of flanges (made of sawn wood, LVL or glulam) and a web (made of a wood - based board). Fire resistance of such wooden structural products is a complex matter. However, the current European design standard for timber structures in fire – Eurocode 5 Part 1-2 (2004) provides no guidance for I-joists. The fire resistance of wooden I-joists has been previously investigated by König (2006) and Schmid et al. (2011), who developed calculation models to analyse the load-bearing capacity of wooden I-joists exposed to fire for floors. There have been significant changes in the variety and types of materials used in conjunction with I-joists. Therefore, the application of these models is limited nowadays. Additionally, they focus on the reduced properties method. Only the effective cross-section method will be included in the revised Eurocode 5 Part 1-2. This report describes the unified model for wooden I-joists in both wall and floor assemblies which follows the philosophy of the effective cross-section method. Additionally, it should be used with all types of cavity insulation and fire protection systems. The unified I-joists model aims to be introduced to the new revised Eurocode 5 Part 1-2. Two phenomena have to be considered according to the ECSM: charring and mechanical resistance. It is assumed that the charring of wood is a material characteristic which is not dependent on the orientation of the structure (wall or floor). The charring of the flanges is primarily dependent on the cladding material and thickness. After the failure of the claddings, the charring is influenced by cavity insulation. Gypsum plasterboards as cladding and stone and glass wool as cavity insulation have been tested and analysed. A large number of thermal simulations have been analysed to investigate the influence of various factors (e.g. flange size, cavity insulation material, protective boards) on the charring behaviour of the fire-exposed flange and the web. The combination of different materials and the slender nature of I-joists makes their fire resistance a complicated issue. The thin web is very sensitive to elevated temperatures and charring. Additionally, adhesives used in finger joints in the flanges and the joint between the flanges and the web influences the load-bearing capacity. The loss of strength and stiffness were seen in wood at elevated temperatures is considered in the ECSM by a zero-strength layer. The zero-strength layer (ZSL) is an additional reduction of the cross-section to compensate for the decrease in strength and stiffness properties. The development of the expressions to calculate the ZSL depths for compression elements is discussed in this paper.

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  • 4.
    Olofsson, Robert
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Just, Alar
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Mäger, Katrin Nele
    Tallinn University of Technology, Estonia.
    Sterley, Magdalena
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Wikner, Alfred (Medarbetare/bidragsgivare)
    Masonite Beams, Sweden.
    Loaded fire tests with I-joists2022Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The aim of the tests was to evaluate the potential reduction of the moment capacity of I-joists caused by bondline integrity of the finger joints. Each I-joist was made with 11 different adhesives in the finger joints in tension flange. All the adhesives were from Firenwood selection. Finger joints in tension may show a lower load-bearing capacity in the fire situation depending of the bond line integrity in fire. I-joists were loaded in bending with the tension flange being closer to the fire. I-joists were protected with gypsum plasterboard during the entire fire test. Cavities of the test assembly were filled with stone wool.

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  • 5.
    Olofsson, Robert
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Mäger, Katrin Nele
    Tallinn University of Technology, Estonia.
    Just, Alar
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Persson, Tommy (Medarbetare/bidragsgivare)
    Masonite Beams, Sweden.
    Wikner, Alfred (Medarbetare/bidragsgivare)
    Masonite Beams, Sweden.
    Large-scale fire tests of engineered wood systems2022Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report presents the four large-scale fire tests performed within the FIRENWOOD project. The aim of the tests was to verify the improved fire design models for the I-joists and crosslaminated timber. The results of the loaded floor test with cross-laminated timber were also compared with results from an unloaded model-scale test with similar lamella thicknesses and adhesive. The aim of the compartment fire test was to study the behaviour of I-joists in physically based fire compared to the behaviour in standard fire. The second aim was to compare the fire behaviour of the compartment made of timber frame assemblies with I-joists and the previously performed similar compartments made with CLT. All large-scale tests reported here were performed with engineered wood structures using adhesive No.9

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