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Fire exposed simply supported wooden I-joist in floor assemblies
SP - Sveriges provnings- och forskningsinstitut, Trätek.
2006 (English)Report (Refereed)
Abstract [en]

A numerical study was conducted with the objective of determining cross-sectional and strength and stiffness properties of I-shaped joists subjected to charring under ISO 834 standard fire exposure. The outcome of this work should be design parameters in terms of Eurocode 5 (EN 1995-1-2) for I-joists in bending where the tension flange is on the fire exposed side of the joist; these are the time of start of charring, charring depths and modification factors for strength. The I-joists are assumed to be integrated in floor assemblies consisting of joists, linings made of gypsum plasterboard or wood-based panels, cavities completely filled with batt-type rock or glass fibre insulation, and a decking. Heat transfer analyses were performed using SAFIR. This software permits us to study the effect of the lining falling off at specified times that are known from full-scale testing or using the criterion of insufficient penetration length of fasteners into unburnt wood. For the determination of the notional charring depth in the flange and the modification factors of the whole cross-section, a computer program CSTFire, written as a Visual Basic macro embedded in Excel, was developed, using the temperature output from the heat transfer calculations and relative strength and stiffness values given by EN 1995-1-2, i.e. compressive strength, tensile strength and moduli of elasticity in compression and tension. The notional charring depth is determined such that the notional residual cross-section of the flange remains rectangular and the section modulus of the I-section is unchanged. The effect of various parameters on the notional charring rate is shown, such as charring phases (i.e. a distinction is made regarding whether the I-section is initially unprotected, protected by a lining, or unprotected after failure of the lining), flange dimensions and depth of cross-section. Modification factors for bending and shear strength are shown as functions of the notional charring depth for different charring phases. In order to simplify these relationships, simple expressions are given for increased user-friendliness and code specification. The effect of the state of stress on the fire-exposed side is demonstrated, however, it remains unclear to what extent bending moment resistance at intermediate supports can be utilized.

Place, publisher, year, edition, pages
2006.
Series
SP Rapport, ISSN 0284-5172 ; 2006:44
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:ri:diva-4738Local ID: 7234ISBN: 91-85533-32-7 (print)OAI: oai:DiVA.org:ri-4738DiVA: diva2:962376
Note
Pris: 360:-SEK. Beställes via BiblioteketBoras@sp.seAvailable from: 2016-09-07 Created: 2016-09-07Bibliographically approved

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SP - Sveriges provnings- och forskningsinstitut, Trätek
Natural Sciences

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CiteExportLink to record
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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
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Output format
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  • text
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