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

elasticity with temperatures as given by NZS 3404, Eurocode 3, and from ECCS,
(Bennetts et al 1986).
1.2
Modulus of Elasticity ratio
1
0.8
0.6
0.4
0.2
0
ECCS
Eurocode 3
NZS 3404
0 200 400 600 800 1000 1200 1400
Temperature ( o C)
NZS 3404 Eurocode 3 ECCS
Figure 3.1: Variation of the Modulus of Elasticity with temperature as given by various sources.
The formula published by ECCS is given below in equation 3.2 but has been
replaced by the data points recommended by the Eurocode, EC3.
E( T )
−12
4
−9
3
−7
2
−5
= 1−17.2x10
T + 11.8x10
T − 34.5x10
T + 15.9x10
T 3.2
E(20)
The temperature for which the modulus of elasticity reduces to zero is at a very
low temperature of 625 °C for this ECCS equation, which is much lower than the
zero strength. Comparing this limiting temperature with that of more recent
studies suggests that this correlation is outdated. Recent studies such as that by
Poh (1996), show that steel retains proportions of strength for temperatures up to
1000 °C.
Variation of Yield Stress with Temperature:
The following formula, equation 3.2 a-b, is given in the New Zealand and
Australian codes for the variation of yield stress with temperature. These
relationships are based on a regression analysis of data found from elevated
temperature tensile tests performed in Australia and Great Britain, Proe et al,
(1986). The variation of yield stress with temperature is generally considered
independent of the steel grade, so one formula is valid for all grades of steel
(Purkiss, 1996)
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