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

Figure 5.14 shows the correlation between the ECCS recommended formulas with
the time-temperature curve resulting from the spreadsheet method and the
maximum and average temperatures found from simulations in SAFIR. The
graphs show that the straight lines fit well with the spreadsheet results, and also
with the maximum temperatures from SAFIR. The curves do not fit well with the
average temperature from SAFIR.
As with earlier discussions about the ECCS equations, the limitations on the
temperature range that these equations are valid can be adjusted. Linear
interpolation below 400 °C will give accurate estimations of time-temperature
points, and the upper temperature limit could be extended to 800 °C. Due to the
slow heating found in this simulation, not all three beams have reached this
temperature in the time period simulated. Figure 5.14 a and b, however, justify
this upper limit, and by extending the curves in Figure 5.14 c, the curves will be
close at this temperature also.
The other limitations imposed on this equation regarding the times that this
equation is valid for, and the beam size do not affect the accuracy of the equation
and do not appear necessary.
5.7 COMPARISONS WITH FIRECALC:
5.7.1 Heavily Protected Beam with Three Sided Exposure:
In this section the results from the spreadsheet method is compared with the results
given by the Firecalc programme. The spreadsheet results are used in place of the
results from the SAFIR finite element programme due to the methods of
temperature evaluation made in Firecalc. The data entered into the analysis
programme is very similar to the variables in the formulas in the spreadsheet
method, and the output is in the form of the average temperature.
The output from the Firecalc programme gives the fire temperature, the insulation
surface temperature and the steel temperature, as well as the load bearing capacity.
See Section 2.3.2 for more detail on the analysis procedure of Firecalc.
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