Yu, M. and Wang, T. and Huang, W. and Ye, J. (2019) Fire resistance of concrete-filled steel tube columns with preload:Part II: Numerical and analytical investigation. Composite Structures, 223. ISSN 0263-8223
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Abstract
Cast-in-situ concrete-filled steel tube (CFST) structures are inevitably subjected to preload that are developed in the steel tube during the construction process. These preloads may have detrimental effects on the overall performance of a CFST component, such as a CFST column, especially when the column is subjected to elevated temperature. However, existing design methods of CFST exclude the impacts of preload in fire resistance design. In this paper, a three-dimensional finite element model for predicting fire resistance of CFST with preload is developed and validated by experimental tests. The model is then used to predict fire resistance time of CFST columns with different slenderness, load and preload ratios. The results show that preload of the steel tube have little influence on the fire resistance of short CFST columns, while the influence of preload on the fire resistance can be significant when the slenderness ratio is greater. Further increase of the slenderness ratio exceeding a certain range, however, reduces the effect of preload. It can be generally concluded that fire resistance of slender CFST columns decreases with increase of preload ratios and the effect of preload on fire resistance of CFST columns is more prominent when the load ratio is greater. In addition, formulas for calculating fire resistance of cast-in-situ concrete-filled steel tubes (CFST) with preload are proposed. This paper is a companion paper of Yu et al. (submitted for publication).