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

thicker beams have not yet reached 650 °C where the curves generally tend to
deviate more from each other. Even with this reasoning however, the lighter beam
does have a larger spread between the spreadsheet and SAFIR results at 500 °C
than the other two heavier beams studied in this report. The temperature reaches
500 °C after 45 minutes from the SAFIR simulation for the lightest beam, while
the spreadsheet gives a time of 41 minutes. This is longer than the difference in
times for the two other beams analysed here which both had a time difference of
2.5 minutes between the two simulations.
5.2.3 Comparison with the ECCS equation:
The formula recommended by ECCS for protected steel is:
40( 140)
d
t = T −
i
A
l
5.1
ki
H
p
where T l = the limiting temperature of the steel (°C)
k i = the thermal conductivity of the insulation (W/m K)
d i = the thickness of the insulation (m)
0.77
This equation is valid for the temperature range of 400 °C to 600 °C, for section
factors between 10 and 300 m -1 , for times between 30 and 240 minutes and for
ratios of insulation thickness to thermal conductivity from 0.10 to 0.30 m 2 °C/W.
The section factors forfoursided exposure for the beams are 178 m -1 for 530 UB
82, 241m -1 for 310 UB 40.4 and 334 m -1 for 180 UB 16.1 beams, so the lightest
beam is out of the size range recommended. The insulation thickness to
0.02
conductivity ratio is = 0. 105 so this fits within the required range.
0.19
Equation 5.1 is intended for light protection, for which the properties of the
insulation must meet the following criteria, from equation 2.4:
ρ c A > 2ρ
c A
s
s
s
i
i
i
For Fendolite, where the properties are as given in Section 5.2, the equality for the
530 UB 82.0 beam becomes:
88