Although BS8110 and DD ENV 1992-1-2 begin into practice the design of fire resistance for RC columns is still generally made based on national and international recommendations, most of which are derived from experimental data or simplified calculation methods. Recent results in FEA that considers the material deterioration and corresponding propagation of cracking have proven FEA is capable of providing more accurate predictions for the failure of RC structures.

In the present paper, the fire resistance of RC columns when subjected to a fire is computed using the finite element Method. The analysis considers the influence of the temperature on the material properties and the local failure of material due to tension or compression stress. Other thermal data like density, Poisson's ratio, thermal expansion and diffusivity are analysed in the program. The temperature distribution in the cross- section of the column during a fire is calculated using Hertz's empirical method, which greatly simplify the complex problem. It is then input into the FE programme to do the time-dependent stress analysis. The influence of various parameters on the fire resistance of RC columns is highlighted.

Some important conclusions from the research are presented. The behaviour of rectangular concrete columns when subjected to a fire on its one side has been investigated numerically. The fire resistance of the column at various applied loads has been calculated. The results have shown that the failure of the column when it is subjected to a fire on its one side is caused by the combination of the reduction in material strength due to high temperatures and the compression stresses on the fire exposed side due to axially applied load and the bending induced by the eccentricity due to non-uniform material properties. The studies of influence of parameters on the fire resistance of the column have shown that, increasing concrete cover can increase the fire resistance of the reinforced concrete column.

The non linear finite element program used in the paper can be good to calculate the fire assistance of concrete columns that is adequate for practical purposes. It also can be used in analysis of other structures without the necessity of testing.

1

J.A. Purkiss, "Fire Safety Engineering, Designing of Structures", Butterworth- Heinenmann, Oxford, 1996.

2

K.N. Mustapha, "Parametric Study of The Behaviour of Reinforced Concrete Columns in Fire", PhD Thesis, Aston University, 1994.

3

T.T. Lie, R.J. Irwin, "Method to calculate the fire resistance of reinforced concrete columns with rectangular cross section", ACI Structural Journal, 90(1), 52-60, 1993.

4

Z. Huang, A. Platten, "Nonlinear finite element analysis of planar reinforced concrete members subjected to fires", ACI Structural Journal, 94(3), 272-282, 1997.

5

M.J. Terro, "Numerical modelling of the behaviour of concrete structures in fire", ACI Structural Journal, 95(3/4), 183-193, 1998.

6

J.M. Beck, H. Bizri and B. Bresler, "FIRES-T, a finite element programme for transient thermal analysis (two-dimensional)", Fire Research Group, Department of Civil Engineering, University of California, Berkeley. 1974.

7

K. Hertz, "Sample Temperature Calculations of Fire Exposed Concrete Constructions", Institute of Building Design, Technical University of Denmark, Report No 159, 1981.

8

Z.P. Bazant et al., "Concrete at High Temperatures, Material Properties and Mathematical Models", Longman, Essex, 1995.

9

A.M. Neville, "Properties of Concrete", Longman, Pitman, 1995.

10

J. Witteveen, L. Twilt and F.S.K. Bylaard, "The stability of braced and unbraced frames at elevated temperatures", Second International Colloquium on Column Strength, Liege, 1977.

11

U. Schneider and A. Haksever, "Bestimmung der aquialenten Branddauer von statisch bestimmt gelagerten stahlbetonbalken bei naturlichen Branden", Bericht des Instituts fur Baustoffkunde und Stahlbetonbau der Technischen Universitat Braunschweig, 1976.

12

R.G. Whirley, and B.E. Engelmann, "DYNA3D - A Nonlinear, Explicit, Three- dimensional Finite Element Code for Solid and Structural Mechanics", User Manual, Lawrence Livermore National Laboratory, California, 1993.

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