A SIMPLE AND RATIONAL APPROACH FOR FIRE RESISTANCE PREDICTION OF RC COLUMNS

Fire resistance of reinforced concrete (RC) columns, which is traditionally determined by expensive furnace tests, presents a formidable problem to structural engineers. There is a need for simple calculation methods that are based on sound engineering principles instead of solely relying on tabulated test data. In this paper, the Rankine approach is presented. The premise is that RC columns in fire can fail under two modes: crushing for stocky columns and buckling for slender columns. For columns in the intermediate range, these two modes will interact with each other, causing a reduction in the load capacity of real columns. The Rankine approach assumes a linear interactive relationship between the two failure modes. The method can also be applied to steel and composite columns. The formulation is presented for both axially- and eccentrically-loaded columns. Four case studies comprising 76 tested RC columns are compiled and compared with Rankine predictions. Satisfactory agreement is obtained