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

f
f
y
y
( T )
(20)
= 1.0
0 < T < 215 °C 3.3a
905 − T
= 215 < T < 905 °C 3.3b
690
The ECCS recommended variation of yield stress with temperature follows the
formulas given below in equation 3.4 a-b:
f
f
y
f
f
y
( T)
T
= 1.0 +
0 < T < 600 °C 3.4a
(20)
y
( T )
= 108
(20)
y
767 ln( T )
1750
( 1−
T )
1000
T − 440
600 < T < 1000 °C 3.4b
The Eurocode again uses values in a table to show the variation of the yield stress
with temperature. The difference between that given by NZS 3404 and the
Eurocode are small and beyond the scope of this project to determine which, if
either, is most accurate. Figure 3.2 shows the variation of the proportion of yield
stress with temperature.
1.2
Yield Stress ratio
1
0.8
0.6
0.4
0.2
ECCS
Eurocode 3
NZS 3404
0
0 200 400 600 800 1000 1200
Temperature ( o C)
NZS 3404 Eurocode ECCS
Figure 3.2: Variation of the yield stress of steel with temperature as given by various sources
The New Zealand Steel Code equations tend towards zero at a lower temperature
than the other equations in Figure 3.2, for the proportion of strength remaining in
steel at elevated temperatures. The ECCS equations propose a more severe loss of
strength of steel than those recommended by CTICM, but also introduce a factor to
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