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

Mandolite by Firepro Safety Ltd
Specific heat, c i = 1100 J/kg K
Thermal conductivity, k i = 0.1 W/m K
Density, ρ i = 362 kg/m 3
Thickness, d i = 0.02 m
5.3.1 Lightly Protected Beams with Four Sided Exposure:
There is a simplified version of the spreadsheet method for steel members with
light insulation. This is covered in Section 2.1.3, and involves neglecting the
insulate heat capacity term in the original formula.
In this section, the results from an analysis with SAFIR are compared with the
results from calculations by the spreadsheet method, both the full equation and the
simplified version. The time temperature curves of these are then compared with
the ECCS, (1985) equations for protected steel beams with light insulation.
For simplification of distinguishing between the results from the two spreadsheet
analyses, the following notation is used:
Spreadsheet 1 – The temperature rise of the member has been calculated with the
full equation, accounting for the effects of the heat capacity of the insulation.
Spreadsheet 2 – The temperature rise of the member has been calculated with the
simplified equation, neglecting the effects of the heat capacity of the insulation.
The insulation is termed light due to its compliance with equation 2.4:
ρ c A > 2ρ
c A
s
s
s
i
i
i
Substituting the appropriate values for each case, and using A i as the perimeter of
the steel multiplied by the thickness of the insulation (20 mm)
530 UB 82.0 beam
H p /A = 178 m -1 , A s = 10500 mm 2 , H p = 1869 mm
7850*600*10500 >2*300*1100*(1869*20)
4.95 x 10 10 > 2.47 x 10 10
92