Structural fire resistances of reinforced concrete interior/edge/corner columns

All the existing fire test standards have the obvious weaknesses which the test column was subjected to a concentric load and 4-side heating. The fire endurance of such an experiment conceivably represents the fire rating of an interior column, but it has been used in assessing fire ratings of edge and corner columns in the same structural system. This paper utilized analytic empirical equations to calculate the failure loads of RC columns subjected to 1-, 2-, 3-, or 4-side heating. The calculated results show that the fire endurances of 2- and 3-side heating of rectangular concrete columns are somewhat shorter than that of a 4-side heating. Conceivably, a provision stated in the ACI 216R-89, “Columns larger than 12 in. (305 mm) diameter or 12 in. (305 mm) square are designed for 3 hr and 4 hr fire resistance classifications in most building codes in America.” deserves a further discussion.