Simple method for predicting temperatures in reinforced concrete beams exposed to a standard fire

In performance-based fire safety design, the fire performance of a structure needs to be accurately evaluated, which requires the accurate prediction of temperatures in the structure. While a finite-element or a finite-difference analysis may be carried out for this purpose, structural engineers generally prefer a simpler method. This paper therefore presents a simple, design-oriented method for predicting temperatures in RC beams under a standard fire exposure. Results from finite element heat transfer analysis are first examined to identify the key parameters that determine temperature distributions in RC beams. On the basis of this knowledge, a simple method in the form of handy formulae and diagrams is derived from regression analysis of finite element temperature data, with due consideration of the effects of beam geometry and fire exposure duration. The accuracy of the proposed method is demonstrated by comparing its predictions with temperature data from both finite element analysis and laboratory tests. The proposed method is believed to be attractive to practicing engineers for use in the fire resistance evaluation of RC beams exposed to a standard fire because of its simplicity and accuracy.