A Probabilistic Approach to Wood Charring Rate
VTT WORKING PAPERS 31
70
60
50
40
30
20
10
0
Gamma
Lognormal
probability density
charring depth l (mm)
ESPOO 2005
0
20
40
60
80
0.0
time (min)
0.5
1.0
1.5
2.0
charring rate (m m /m in)
A Probabilistic Approach to
Wood Charring Rate
Jukka Hietaniemi
VTT Building and Transport
ISBN 951–38–6583–5 (URL: http://www.vtt.fi/inf/pdf/)
ISSN 1459–7683 (URL: http://www.vtt.fi/inf/pdf/)
Copyright © VTT 2005
JULKAISIJA – UTGIVARE – PUBLISHER
VTT, Vuorimiehentie 5, PL 2000, 02044 VTT puh. vaihde 020 722 111, faksi 020 722 4374
VTT, Bergsmansvägen 5, PB 2000, 02044 VTT tel. växel 020 722 111, fax 020 722 4374
VTT Technical Research Centre of Finland, Vuorimiehentie 5, P.O.Box 2000, FI–02044 VTT, Finland phone internat. +358 20 722 111, fax +358 20 722 4374
VTT Rakennus- ja yhdyskuntatekniikka, Kivimiehentie 4, PL 1803, 02044 VTT puh. vaihde 020 722 111, faksi 020 722 4815
VTT Bygg och transport, Stenkarlsvägen 4, PB 1803, 02044 VTT tel. växel 020 722 111, fax 020 722 4815
VTT Building and Transport, Kivimiehentie 4, P.O.Box 1803, FI–02044 VTT, Finland phone internat. +358 20 722 111, fax +358 20 722 4815
Technical editing Maini Manninen
Published by
Series title, number and report code of publication
VTT Working Papers 31
VTT–WORK–31
Author(s)
Hietaniemi, Jukka
Title
A Probabilistic Approach to Wood Charring Rate
Abstract
This report presents a probabilistic model for wood charring rate and an application of the model to assess fire resistance of a wooden load-bearing beam. The model is an empical one, based on quantification of the dependence of the wood charring rate on the principal physical factors governing the charring process. These factors include the influence of the heat flux exposing the wood surface, the wood density and moisture content as well as the ambient oxygen concentration. The application introduces a novel approach to assess the endurance
70
60
50
40
30
20
10
0
Gamma
Lognormal
probability density
charring depth l (mm)
ESPOO 2005
0
20
40
60
80
0.0
time (min)
0.5
1.0
1.5
2.0
charring rate (m m /m in)
A Probabilistic Approach to
Wood Charring Rate
Jukka Hietaniemi
VTT Building and Transport
ISBN 951–38–6583–5 (URL: http://www.vtt.fi/inf/pdf/)
ISSN 1459–7683 (URL: http://www.vtt.fi/inf/pdf/)
Copyright © VTT 2005
JULKAISIJA – UTGIVARE – PUBLISHER
VTT, Vuorimiehentie 5, PL 2000, 02044 VTT puh. vaihde 020 722 111, faksi 020 722 4374
VTT, Bergsmansvägen 5, PB 2000, 02044 VTT tel. växel 020 722 111, fax 020 722 4374
VTT Technical Research Centre of Finland, Vuorimiehentie 5, P.O.Box 2000, FI–02044 VTT, Finland phone internat. +358 20 722 111, fax +358 20 722 4374
VTT Rakennus- ja yhdyskuntatekniikka, Kivimiehentie 4, PL 1803, 02044 VTT puh. vaihde 020 722 111, faksi 020 722 4815
VTT Bygg och transport, Stenkarlsvägen 4, PB 1803, 02044 VTT tel. växel 020 722 111, fax 020 722 4815
VTT Building and Transport, Kivimiehentie 4, P.O.Box 1803, FI–02044 VTT, Finland phone internat. +358 20 722 111, fax +358 20 722 4815
Technical editing Maini Manninen
Published by
Series title, number and report code of publication
VTT Working Papers 31
VTT–WORK–31
Author(s)
Hietaniemi, Jukka
Title
A Probabilistic Approach to Wood Charring Rate
Abstract
This report presents a probabilistic model for wood charring rate and an application of the model to assess fire resistance of a wooden load-bearing beam. The model is an empical one, based on quantification of the dependence of the wood charring rate on the principal physical factors governing the charring process. These factors include the influence of the heat flux exposing the wood surface, the wood density and moisture content as well as the ambient oxygen concentration. The application introduces a novel approach to assess the endurance
References: Babrauskas, V. 2004. Wood Char Depth: Interpretation in Fire Investigations. referred to 13th April 2005) Bevington, P de Souza Costa, F. & Sandberg, D. 2004. Mathematical Model of a Smoldering Log. Dunlap, F. The Specific Heat of Wood. 1912. Washington DC. US Department of Agriculture, Bulletin No Fang, J. B. 1982. Fire Endurance Test of Selected Residential Floor Constructions. National Bureau of Standards, Gaithersburg MD, USA. (NBSIR 82 2488). Fredlund, B. 1988. A Model for Heat Transfer and Mass Transfer in Timber Structures During Fire (Report LUTVDG/(TVBB-1003)). 254 p. Hietaniemi, J., Korhonen, T., Joyeux, D. & Ayme, N. 2004. Risk-based Fire Safety Engineering Approach to Obtain Balanced Structural Fire Resistance Requirements Hietaniemi, J. & Korhonen, T. 2004a. A case study of performance of load-bearing wooden structures in natural fire Engineering, WCTE 2004, Volume II, Lahti, June 14–17, 2004. Helsinki: RIL, VTT, Wood Focus Protection, Faculty of Wood Sciences and Technology. 2004. 9 p. Hietaniemi, J., Hostikka, S. & Korhonen, T. 2004. Probabilistic Fire Simulation. In: Almand, K Holm, C. & Loikkanen, P. 1981. Joint Investigation of Vertical Furnaces in Nordic Countries Hostikka, S. & Keski-Rahkonen, O. 2003. Probabilistic simulation of fire scenarios. Hostikka, S., Keski-Rahkonen, O. & Korhonen, T. 2003. Probabilistic Fire Simulator. load-bearing wooden constructions). Licentiate of Technology Thesis, Helsinki University of Technology, 1979 Koch, P. 1969. Specific Heat of Oven-dry Spruce Pine Wood and Bark. Wood Science, Vol Korhonen, T., Hietaniemi, J., Baroudi, D. & Kokkala, M. 2002. Time-Dependent EventTree Method for Fire Risk Analysis: Tentative Results. 7th International Symposium of Fire Safety Science McGrattan, K. B. (Ed.). 2004a. Fire Dynamics Simulator (Version 4): User 's Guide. 104 p. (NIST Special Publication 1019). McGrattan, K. B. (Ed.). 2004b. Fire Dynamics Simulator (Version 4): Technical Reference Guide Technology. 51 p. (NISTIR 6783, 2002 Ed.). McGrattan, K. B., Forney, G. P., Floyd, J. E., Hostikka, S. & Prasad, K. 2002b. Fire Dynamics Simulator (Version 3) – User 's Guide Institute of Standards and Technology. 81 p. (NISTIR 6784, 2002 Ed.). Mikkola, E. 1988. Unpublished time-series data on charring of several wood product under constant heating in the cone calorimeter. Mikkola, E. 1989. Puupinnan syttyminen (Ignition of wooden surface). Espoo: VTT Tiedotteita 1057 Mikkola, E. 1990. Charring of wood. Espoo: VTT Tutkimuksia 689. ISBN 951-383711-4. 40 p. Njankouo, J. M., Dotreppe, J.-C. & Franssen, J.-M. 2004. Experimental study of the charring rate of tropical hardwoods Nurbakhsh, S. 1989. Thermal decomposition of charring materials. PhD dissertation. Ohnemiller, T. J., Kashiwagi, T. & Werner, K. 1987. Wood gasification at fire level heat fluxes Oksanen, T. 2005. Privite communication. Parker, W. J. 1985. Development of a Model for the Heat Release Rate of Wood. Gaithersburg, MD: National Bureau of Standards. 108 p. (NBSIR 85-3163). Perälä, J. & Reuna, R. 1990. Lumen vesiarvon alueellinen ja ajallinen vaihtelu Suomessa (Regional and temporal variation of snow water value in Finland) Quintiere, J.G. & Harkleroad, M.T. 1985. New Concepts for Measuring Flame Spread Properties, Fire Safety: Science and Engineering, ASTM STP882, T.Z Schaffer, E. L. 1967. Charring rate of selected woods – transverse to grain. Madison,