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

To determine the performance of a steel member, analysis can be made of a single
member, or of the structure as a whole, or more complex member arrangement
with the use of a finite element computer package. This section details the design
method of evaluating single members according to Eurocode 3. This analysis
method may be used for single, simply supported members exposed to elevated
temperatures.
General:
As stated earlier for global analysis, the load bearing function of a steel member
shall also be assumed to be adequate if:
E
fi, d
≤ R
fi,
d , t
The design resistance
R
fi d , t
,
at time t shall be determined for the temperature
distribution in the cross section by modifying the design resistance for normal
temperature design to take account of the mechanical properties of steel at elevated
temperatures. The design force may be axial force, bending moment or shear force
either separately or in combination.
Tension members:
For tension members with uniform temperature distribution across the cross
section, the design resistance N f is given by:
N
f
Af
yk
y,
T
= 7.4
where A is the area of the cross section, f y is the yield strength at time t = 0, and k y,t
is the reduction factor for yield strength at temperature, T.
If there is a non-uniform temperature distribution, the design resistance N f may be
determined from:
N
f
i =1, n
Ai
k
y,
T , i
= f
7.5
y
Where A i is the elemental area of the cross section, k y,T,i is the reduction factor for
yield strength at temperature T of the element.
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