Practical calculation method for residual mid-span deflection of CFST columns after exposure to the ISO-834 standard fire

Based on the nonlinear finite element procedure NFEACFST, influences of parameters on residual mid-span deflection of CFST columns (concrete-filled steel tubular columns) with circular sections after exposure to the ISO-834 standard fire are analyzed. The parameters include temperature ascending time ratio, fire load ratio, load eccentricity ratio, cross-sectional dimension, steel ratio, material strength, slenderness ratio, type and thickness of fireproof paint. It is found that time ratio, fire load ratio, load eccentricity ratio, cross-sectional dimension, slenderness ratio, type and thickness of fire-proof coating are of importance. A simplified calculation formula of residual mid-span deflection after exposure to the ISO-834 standard fire is suggested based on systematic parameter analysis. Furthermore, validity is provided by the results of examination. The formula accords with the influent principals of the main parameters, and provides references for the uses of CFST columns in engineering practices.