Compressive and flexural behaviour of concrete filled steel tubes after exposure to standard fire

The previously developed theoretical model had been used to investigate the influence of a number of important parameters on the residual ultimate strength and flexural stiffness of the composite sections and the results of the parametric studies were used to develop formulas for calculating the composite section residual ultimate strength under axial compression or flexural bending and the composite section residual flexural bending stiffness. In these formulas, the ambient temperature compression resistance, bending moment capacity and initial flexural bending stiffness of the composite section should be calculated using an existing design code. In this paper, these formulas are applied to the new test data to assess the suitability of using several different design codes: AIJ-1997, AISC-LRFD-1999, BS5400-1979, DBJ13-51-2003 and EC4-1994.