Fire Resistance of Unprotected Steel Columns

Fire resistance of unprotected steel columns is examined by standard fire test and numerical analyses based on a 1,000 D F (538 D C) critical temperature for failure. It is shown that fire resistance time varies with the shape factor of column weight divided by the heated perimeter, and two simple equations for calculating the fire resistance times of unprotected steel columns are established. A practical example shows that large columns used in high-rise buildings can have fire resistance times of up to one hr. The more conservative of the two equations is recommended for use in building standards.