This paper is concerned with the theoretical calculation of the temperature of steel columns or beams when they are exposed to the flame with the fire temperature curve to test their resistivity to the fire. These steel columns and beams are usually protected by some heat insulation plates, and they are heated from all sides in a fire testing furnace. In this case, the heat quantity which streams into the core penetrating the insulation plate can be obtained by solving the fundamental equation of heat conduction. The temperature of the steel in the core is available using this heat quantity.

To make the calculation simple, an approximate heating curve of rectangular form is used instead of the standard heating curve. The discrepancy caused by this approximation is discussed. A proposal to estimate the influence of free water content in the insulation plate is made, too.

From these theoretical considerations, some important points for the performance of experiment are pointed out, especially how to carry out the fire resistance test using models.

Finally, the comparison of experimental result with the calculated one for two cases is made, and it is concluded that this calculation method is useful for the theoretical backing of the fire test.

* Manuscript received on April 25, 1963