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

4.2 RESULTS FOR FOUR SIDED EXPOSURE:
A comparison of three methods of thermal analysis of unprotected steel beams is
made in this section. The results from SAFIR are deemed to be the most accurate
method of analysis due to studies with experimental data showing good correlation
with the results from SAFIR (Gilvery and Dexter, 1997). The results from the
spreadsheet programme have been calculated with a 60 second time step, and the
method and equations used for the estimation of the temperatures are found in
Section 2.1.2. The linear equations found in the New Zealand and Australian
codes and ECCS recommendations are outlined in Section 0 and have been used
with the appropriate H p /A value for four sided exposure.
With four sided exposure to the ISO fire, the steel member generally has a close to
constant temperature over the cross section of the beam. There are only small
temperature variations over the cross section due to the steel geometry and the
temperature profile is symmetrical.
4.2.1 Results from a simulation with the SAFIR programme:
1000
800
Fire
600
Steel temperatures
400
200
0
0 20 40 60 80
time (min)
max temp ave temp min temp fire temp
Figure 4.2: Time temperature curve from a SAFIR simulation showing the variation of temperature
of different elements in the beam for four sided exposure to an ISO fire for the 530UB82.0 beam
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