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

ABSTRACT:
The New Zealand Steel Code consists of few practical design tools other than finding
the time and temperature that a simply supported steel member will fail. Many other
design methods that consistently give accurate estimations of the behaviour of steel
members have been published, and computer programmes developed to assist in the
prediction of the temperature rise of steel when subjected to elevated temperatures
environments.
This report describes the origins of the fire design methods used in the New Zealand
Steel Code, NZS 3404:1997. The New Zealand Steel Code is reviewed and the design
features are compared with the equivalent method found in the Eurocode, ENV 1993-
1-2, which is the most advanced international steel fire code.
The methods of evaluating the temperature rise of protected and unprotected steel
beams are also investigated. Results from the simple formulas included in the New
Zealand Code, and those developed by the European Convention for Constructional
Steelwork, ECCS, are compared with results from the time step ‘spreadsheet’ method
and from the finite element computer programme, SAFIR, for the ISO 834 standard
fire. The comparisons show that the spreadsheet method gives temperatures very close
to the average temperatures calculated by SAFIR for all cross sections and protection
layouts. The equations from ECCS and NZS 3404 give good results for unprotected
steel, and for protected steel the ECCS equations appear to represent the thermal
response of the steel quite accurately while the New Zealand Steel Code has no simple
method of estimating the temperatures for protected steel.
The methods used for comparing the results with the ISO fire are then repeated with
Eurocode Parametric fires, and with results from a real fire test.
Suggested improvements are made for the New Zealand Steel Code, to improve the
concepts and information available to engineers designing for fire safety.
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