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Auto-Extinction of Engineered Timber as a Design Methodology

https://research.thinkwood.com/en/permalink/catalogue1676
Year of Publication
2016
Topic
Fire
Material
CLT (Cross-Laminated Timber)
Author
Bartlett, Alastair
Hadden, Rory
Bisby, Luke
Lane, Barbara
Year of Publication
2016
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Fire
Keywords
Extinction
Fire Propagation Apparatus
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 3934-3941
Summary
Engineered timber products such as cross-laminated timber (CLT) are gaining popularity with designers due to attractive aesthetic, sustainability, and constructability credentials. The fire behaviour of such materials is a key requirement for buildings formed predominantly of exposed, structural timber elements. Whilst design guidance focuses on the residual structural capacity of timber elements exposed to a ‘standard fire’, the fundamental characteristics of CLT’s performance in fire, such as ignition, flame spread, delamination, and extinction are not currently considered. This paper focuses on the issues relating to increased fuel load due to a combustible building material itself. Whilst an increasingly common protection solution to this conundrum is to fully encapsulate the timber elements, there is limited supporting test data on this approach. Through understanding these concepts from a fundamental, scientific perspective, the behaviour can be properly understood, and, rather than limiting design, can be incorporated into design to satisfy suitable performance criteria. In this paper therefore, the concept of auto-extinction – a phenomenon by which a timber sample will cease flaming when the net heat flux to the sample drops below a critical value – is explored experimentally and related to firepoint theory. A series of c.100 small scale tests in a Fire Propagation Apparatus (FPA) have been carried out to quantify the conditions under which flaming extinction occurs. Critical mass loss rate at extinction is shown to occur at a mass flux of 3.5g/m2s or a temperature gradient of 28K/mm at the charline. External heat flux and airflow were not found to affect the critical mass loss rate at the range tested. This approach is then compared with a compartment fire with multiple exposed timber surfaces. With further testing and refinement, this method may be applied in design, enabling architects’ visions of exposed, structural timber to be safely realised.
Online Access
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Resource Link
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