A unified method for calculating temperatures of CFST members with various cross-section shapes and concrete types exposed to fire

Concrete-filled steel tubular (CFST) columns have been widely used in practice. Due to the direct exposure of the steel tube to fire, CFST columns may experience severe mechanical performance damage under fire conditions. High temperatures are the fundamental factor affecting fire-exposed members, and understanding the temperature distribution and evolution within the cross-sections of these members is crucial for researching their fire resistance. Finite element analysis, mathematical processing, and numerical calculations are used in this paper to establish a unified calculation method for the strength reduction ratio of the core concrete, which considers multiple cross-sections (circular, square, and rectangle), various materials (ordinary performance concrete, high performance concrete, and recycle aggregate concrete), and arbitrary strength reduction curves. And the equivalent temperature of the concrete core could be obtained by combining with the inverse function of the corresponding reduction curves, based on the calculation results of this method. Error analysis indicates that the proposed methods exhibit good accuracy.