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

From Figure 4.5 a-c, the formula range for the ECCS formula, Equation 4.2, can be
extended to at least 700 °C as an upper limit. This could even be extended to 800
°C as this temperature is within the same accuracy as in the recommended range.
Below 400 °C, a linear interpolation method could be recommended as this will
give temperatures close to the spreadsheet curve. The temperature range suggested
by for the New Zealand code equations appears valid, with an upper temperature
limit of 850 °C, and linear interpolation for temperatures below 500 °C.
Although the temperature gradients differ markedly between the two simulation
types, this only occurs due to the minimum temperature being much lower in the
SAFIR 2 simulations from the effects of the concrete slab. The maximum timetemperature
curves in both simulations are the same, meaning that the maximum
temperatures are not affected by the presence of a concrete slab on the top flange.
This is intuitively correct, because the maximum temperatures in the SAFIR 2
simulations are found in the bottom flange and web which are exposed to the fire
and not in contact with the slab.
Although the cooling effects do cool the top flange and the top of the web, the
temperature is quite constant throughout the rest of the cross section giving the
same maximum temperatures in SAFIR 1 and SAFIR 2. The effects of conduction
do not change the temperature across the section below the top of the web.
These maximum temperatures are also the same as the maximum temperatures
found in the four sided ISO 834 fire exposure to unprotected steel, as seen in
Section 4.2.1. When the curves are plotted on the same graph, the curves are
exactly the same as seen in Figure 4.mm below. Although it is hard to distinguish,
there are three curves plotted in Figure 4.10, showing the maximum temperatures
found in four sided exposure, three sided without a slab (SAFIR 1) and three sided
with a slab (SAFIR 2). The maximum temperatures found in the bottom flange
and web of the beam is therefore independent of the presence of a slab, and if the
maximum temperature over the cross section is required to be found, then from
Sections 4.2.1 and 0, the spreadsheet method gives an accurate answer with the
least difficulty.
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