Interaction Formula for Reinforced Concrete Columns in Fire Conditions

This paper presents a simple and rational interaction formula - the Rankine method for predicting the fire resistance of reinforced concrete (RC) columns under fire conditions. Conventionally, the Rankine method has been applied to RC columns and frames subjected to increasing loads but maintained at ambient temperature. Based on a theoretical approach, the Rankine method is extended to RC columns subjected to fire conditions by taking the temperature effects on steel reinforcement and concrete material into consideration. The accuracy of the method is verified through four sets of experimental test results comprising 76 columns. The method yields reasonably accurate predictions for the fire resistance of RC columns. In addition, the paper includes two worked examples to illustrate the flexible use of such a formula for either predicting the load-bearing capacity or the fire exposure time of an RC column subjected to the standard ISO 834 fire curve.