Calculation method for design of reinforced concrete columns under fire conditions

The determination of the fire resistance of concrete columns is essentially based on tabulated data containing the dimensions of the cross section and values of the concrete cover However, more scientific approaches such as analytical formulations should be proposed to consulting engineers for a quick and efficient design. A large number of experimental results have been examined; they have been performed at the Universities of Ghent and Liege in Belgium at the Technical University of Braunschweig, and at the Fire Research Station in Ottawa, Canada. A computer code SAFIR, developed at the University of Liege for the simulation of the structural behavior under fire conditions, has been used for the analysis of the experimental results and for the progressive development of the formulation. The design formula has been obtained in three steps. The first step consists of determining the plastic crushing load of the column at elevated temperature on the basis of numerical simulations. The second step is the determination of the buckling coefficient for centrically loaded columns. The third step is the development of a nonlinear amplification term for eccentrical loads. The formula has been calibrated to take into consideration the particular effects of the concrete cover and the additional amplification appearing for the high values of the slenderness ratio.