it might be useful to begin by reviewing briefly, the standard fire test
methods for materials and constructions
used in the United States and Canada
(ASTM E-119). Specimens of floors,
roofs, beams, columns, and walls, having dimensions exceeding certain specified minimum values, are subjected to
a standard fire while supporting their
design loads. For example, floor or roof
specimens must be representative of the
construction they simulate and the area
exposed to fire must be at least 180 sq
ft, with neither dimension less than 12
ft.
Throughout the fire test, the specimen must support gravity loads equivalent to the maximum permissible load
applied in the building which the specimen represents. The underside of a
floor or roof is exposed to a "standard"
fire. The fire is standard by virtue of
the fact that the temperature of the fire
(measured 12 in. from the specimen)
is specified in terms of a time-temperature curve (see Fig. 1). The fire endurance of a specimen is defined as the
elapsed time during a fire test until an
end point is reached.
Prior to 1969 the end point criteria
(ASTM E-119) for floors and roofs
were:
1. The specimen must support its design load (structural end point).
2. Flames or gases hot enough to ignite cotton waste must not pass through
the specimen (flame passage end
point).
3. Unexposed surface temperature
must not rise more than 250 F average,
or 325 F maximum at any point (heat
transmission end point).