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  • Predicting the thickness of zero-strength layer in timber beam exposed to parametric fires
    Huč, Sabina, gradbeništvo ; Pečenko, Robert ; Hozjan, Tomaž, gradbeništvo
    In the design of timber structures, the mechanical resistance in fire conditions has to be ensured among others. In the European standards, Eurocodes, the reduced cross-section method is given to ... determine mechanical resistance of timber structural elements in fire conditions. The reduced cross-section method is based on an effective cross-section that is determined by two key parameters, namely the charring depth and the thickness of zero-strength layer where the latter accounts for the reductions of the stiffness and the strength of timber due to elevated temperatures. Although, the thickness of zero-strength layer of 7 mm is only prescribed for the ISO 834 standard fire exposure longer than 20 min in the Eurocodes, the same value is often used for non-standard fire exposures as well, which might not always be correct. Thus, in the present paper the thickness of zero-strength layer is investigated for a timber beam exposed to 44 different parametric fires by means of advanced numerical models and a simple design method. A hygro-thermal model and a mechanical model are applied to determine the temperature field over a timber beam cross-section and the mechanical resistance of the beam during fire exposure, respectively. The simple design method is based on the reduced cross-section method. The obtained results show that the thickness of zero-strength layer varies between 8.4 mm and 30.5 mm, which are substantially higher values than the value of 7 mm suggested in the Eurocodes for the standard fire exposure. The results also indicate that the thickness of zero-strength layer is not a constant value and should be written as a function of the parameters defining a parametric fire curve. Alternatively, the effective cross-section could be simply determined by finding the combined thickness of zero-strength layer and charring depth at temperature of about 90 °C.
    Vir: Engineering structures. - ISSN 0141-0296 (Št. feb., art. 111608, letn. 229, 2021, [11] str.)
    Vrsta gradiva - članek, sestavni del
    Leto - 2021
    Jezik - angleški
    COBISS.SI-ID - 42650371

    Povezava(-e):

    https://doi.org/10.1016/j.engstruct.2020.111608
    Repozitorij Univerze v Ljubljani – RUL
    DOI

vir: Engineering structures. - ISSN 0141-0296 (Št. feb., art. 111608, letn. 229, 2021, [11] str.)
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