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

1.6.4 Methods of steel protection:
There are many passive fire protection means available to reduce the temperature rise
of steel members when exposed to elevated temperatures. The fire resistance of these
are often calculated using heat transfer principles and properties of the protection but
these should be backed up with test results to determine the actual behaviour of the
product in place
Some common forms of protection for steel, and methods to increase the fire resistance
of steel members are listed below. The methods used in this report are the spray on
and board protection.
Spray-on Insulative Protection:
This method of protecting steel is usually the cheapest form of passive fire protection
for steel members. These materials are usually cement based with some form of glass
or cellulosic fibrous reinforcing to hold the material together, (Buchanan, 1999). The
disadvantages of spray on materials are that the application is wet and messy and the
finish is not architecturally attractive. However this is not usually a problem for
structural members that are hidden with suspended ceilings and partitions. The other
important aspect of this insulation is the ‘stickability’ of the material, or how well the
material stays in contact with the steel member at normal and elevated temperatures.
If the insulation falls off the steel it obviously no longer is protecting the steel so the
cohesion and adhesion of spray on protection must be thoroughly tested.
Board Systems:
Most board systems that are used to increase the fire resistance of steel members are
made out of calcium silicate or gypsum plaster. Calcium silicate boards are made of
an inert material and the board can remain in place for the duration of the fire.
Gypsum plaster board has good insulating properties, and its resistance to elevated
temperatures is improved with the high moisture content present in the board, which
must be evaporated at 100 °C before the board further increases in temperature. This
gives a time delay when the board reaches 100 °C, but reduces the available strength in
the board after the water has evaporated.
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