The structural fire endurance of prestressed concrete is affected mainly by
the method of framing—simply supported and unrestrained, continuous, or
restrained against thermal expansion.
For simply supported and unre-
114strained members, the cover to the reinforcement and the load intensity govern the fire endurance.
For continuous beams and slabs, the
amount and location of negative and
positive moment reinforcement determine how much moment redistribution
will occur, which in turn determines
the fire endurance. 5.
For restrained members, structural
fire endurance is affected only by the
member's ability to withstand the restraining forces, and this is seldom a
problem.
The fire endurance of restrained
floors or roofs is generally governed by
the criteria for temperature rise of the
top surface.
Within the past few years, we have
made great strides in developing data
for use in rational methods of designing
for fire resistance. I am optimistic that
within a few years structural engineers
will have the data necessary to design
concrete structures for any required degree of fire resistance.