FIRE DESIGN OF STEEL MEMBERS - Civil and Natural Resources ...

=
H
p
A
(m -1 )
7.85
The constants k 0 to k 6 are determined from tests to fit the data. For a particular
insulation, the constants are determined by iterations to fit the available data, and
then interpolation between the results can be made using the formula above with
the constants substituted in. The regression analysis method can be used to
interpolate between theoretical data points with information found from computer
simulations, or from results from standard fire tests. Bennetts et al (1986) give
further information and examples. The fit of the regression lines to experimental
results do not fit with as little error as theoretical results due to the approximate
nature of the theory of the regression analysis and the variability of the material
over the cross section and between tests.
Limitations and conditions on the use of the regression analysis are also covered in
NZS 3404, detailing the tests applicable to use, and the limitations of the results.
Eurocode 3 uses a spreadsheet time step formula for predicting the temperature of
the protected steel. This equation is similar to the protected steel equation used in
this report and stated in Section 2.1.3, except that it includes a term to account for
the increase in fire temperature during the time step and adds one third of the heat
capacity of the insulation to the steel, rather than one half as is in equation 2.3.
The formula is as follows:
∆T
s
ki
=
dics
p
s
H
p
A
( T − T )
f s
∆t
− e
1+
φ
3
φ
10
−1∆T
f
3.12a
c H
i
ρi
p
where φ =
d
i
3.12b
cs
ρ
s A
3.1.6 Determination of PSA from a single test:
PSA is the period of structural adequacy of an element. This can be determined
from the results of a single standard fire test provided that conditions a) – d) in
Section 3.1.5 are met as well as:
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