SFPE Engineering Guide on Fire Exposures to Structural Elements

Appendix A: Theoretical Examination of Methods

As can be seen in Figure A. 1, predictions of burning rate vary markedly among the different methods. Some of the methods assume stoichiometric or ventilation-limited burning, while others account for fuel-controlled burning.


Figure A.1: Comparison of Burning Rate Predictions

RESULTS BY HARMATHY FOR WOOD CRIBS



From Equation 20 similar results can be derived:


or


RESULTS BY BULLEN AND THOMAS FOR POOL FIRES


The pool fire results are explained by the stoichiometry and thermal feedback.

The locus of


s and both are larger for liquids compared to wood.

CIB DATA

In the CIB experiments the fuel is placed over the entire floor; therefore, A F ? A.

Here the theory gives


From Equation 26, for

for which agrees with the trends in Figure A.2.


Figure A.2: Wood Crib and Liquid Pool Fires

EUROCODE

The Eurocode prescribes



Here t* is essentially Q w *?2

or only

This specification must assume a ventilation-limited fire and ignores the other variables.

LIE

Only a ventilation-limited fire is assumed.

Lie gives .

The theoretical development gives


For temperature, T = f(F, t) and C, a constant which takes into account the properties of the bounding materials of the enclosure.


This represents kpc since k ~ p.

MAGNUSSON, THELANDERSSON, AND PETERSSON

Magnusson, Thelandersson, and Petersson compute a result for temperature based on a similar theory. They augment it with a rate of rise for developing fire and a prescribed cooling phase. They use only the ventilation-controlled...

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