Comparison with the test results shows that the proposed model can well capture the column mid-height deflection at ambient and elevated temperatures. It has been validated with a large set of data including 47 specimens tested at ambient temperature and 68 specimens under fire conditions. The proposed model has a wide range of applicability for both normal strength concrete and high strength concrete with a compressive strength ranging from 24.1 MPa to 97.2 MPa. mid-height deflection) of columns under fire conditions and determine the fire endurance under any heating curve. Moreover, it can trace structural response (i.e. The proposed model can be used to determine load–deflection curves and predict peak loads of RC columns at ambient temperature. It incorporates heat transfer analysis, different strain components at high temperature and slenderness effect. The model transforms the cross-sectional capacity to actual column (structural) capacity by introducing a stability term. In view of limited studies on modelling of high strength concrete (HSC) columns under fire conditions, this paper develops a simple yet universally applicable model to analyse the behaviour of HSC columns under ambient and fire conditions. 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. The third step is the development of a nonlinear amplification term for eccentrical loads. The second step is the determination of the buckling coefficient for centrically loaded columns. The first step consists of determining the plastic crushing load of the column at elevated temperature on the basis of numerical simulations. The design formula has been obtained in three steps. A computer code SAFIR, developed at the University of Liège 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. A large number of experimental results have been examined they have been performed at the Universities of Ghent and Liège in Belgium, at the Technical University of Braunschweig, and at the Fire Research Station in Ottawa, Canada. However, more scientific approaches such as analytical formulations should be proposed to consulting engineers for a quick and efficient design. 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.
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