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    Author(s): Robert H. White
    Date: 2008
    Source: SFPE handbook of fire protection engineering. Quincy, Mass. : National Fire Protection Association ; Bethesda, Md. : Society of Fire Protection Engineers, c2008: pages 4.346-4.366.
    Publication Series: Miscellaneous Publication
    PDF: View PDF  (571 KB)

    Description

    The fire resistance ratings of wood members and assemblies, as of other materials, have traditionally been obtained by testing the assembly in a furnace in accordance with ASTM International (ASTM) Standard E119, International Organization for Standardization (ISO) Standard 834, and similar standards. These ratings are published in listings, such as Underwriters Laboratories Fire Resistance Directory, Gypsum Association's Fire Resistance Design Manual, American Wood Council's Design for Code Acceptance publications, and those in building codes. The ratings listed are limited to the actual assembly tested and normally do not permit modifications such as adding insulation, changing member size, changing interior finish, or increasing the spacing between members. Code interpretation of test results sometimes allows the substitution of larger members, thicker or deeper assemblies, smaller member spacing, and thicker protection layers, without reducing the listed rating. ASTM Standard E20327 provides guidelines on such extension of fire resistance results obtained from the standard ASTM E119 fire test. Three procedures for calculating fire resistance ratings have U.S. building code acceptance: the T.T. Lie and the National Design Specifcation for Wood Construction (NDS) methodologies for calculating fire resistance ratings of exposed wood members and the component additive method (CAM) for protected wood-frame walls, floors, and roofs. The T.T. Lie method is limited to beams and columns. The T.T. Lie methodology and the CAM procedures were developed in Canada and have Canadian code acceptance. In Europe, the Eurocode 5 (EN 1995-1-2 and its corrigendum) on design of timber structures provides calculation methods for the fire design of timber structures. A review of the development of EN 1995-1-2, improvements from the earlier ENV 1995-1-2, and references for the research results used to support its provisions are provided by Konig. Two publications on the overall topic of structural fire design are Structural Fire Protection, edited by T.T. Lie, and Structural Design for Fire Safety, by Andrew H. Buchanan. When attention is given to all details, the fire resistance of a wood member or assembly depends on three items: 1. Performance of its protective membrane (if any). 2. Extent of charring of the structural wood element. 3. Load-carrying capacity of the remaining uncharred portions of the structural wood elements.

    Publication Notes

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    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

    Citation

    White, Robert H. 2008. Analytical methods for determining fire resistance of timber members. SFPE handbook of fire protection engineering. Quincy, MA: National Fire Protection Association, Bethesda, MD: Society of Fire Protection Engineers: 346-366. Chapter 13.

    Keywords

    Char, Douglas fir, plywood, fire testing, laminated wood, testing, veneers, gypsum, wood flammability, flammability, thermal properties, fireproofing agents, fireproofing of wood, timber, wooden beams, fire resistance, gypsum board, fire retardants, fire hazard, ASTM E 119, thermal degradation

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