Article Advances in Structural Engineering 2016, Vol. 19(5) 746–761 Ó The Author(s) 2016 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1369433215622864 ase.sagepub.com Evaluation on thermal behavior of concrete-filled steel tubular columns based on modified finite difference method Ming-Xiang Xiong 1,2 , Yonghui Wang 2 and JY Richard Liew 2,3 Abstract This article presents a modified finite difference method specific for predicting temperatures in concrete-filled steel tubular composite columns. The modifications were based on existing researches on heat transfer analyses of composite columns by finite difference method. The temperature predictions by the modified method were implemented via MATLAB. Validity was established by comparing the predicted temperatures with test results and those obtained from finite element analyses via ABAQUS. The comparisons showed reasonable predictions by the modified finite difference method. Sensitivity studies were also carried out on the effects of emissivity of fire, thermal contact resistance, thermal property model, and cavity ratio based on the modified method. Through the implementation with MATLAB, it is attractive to calculate fire resistance of the concrete-filled steel tubular columns by combining the modified method with the simple calculation models according to Eurocode 4. Keywords concrete-filled steel tubular column, heat transfer analysis, modified finite difference method, sensitivity study, simple calculation mod- els, thermal resistance Introduction For evaluating fire resistances of concrete, steel, steel–concrete composite members in accordance with Eurocodes, temperature profiles in these mem- bers are required as they give significant influences on such material properties such as strength, elastic modulus, and thermal expansions. For concrete structures, the temperature profiles for slabs, beams, and columns are given in design charts in Eurocode 2 so that they can be directly used for fire-resistant design (EN 1992-1-2:2004, 2004). For steel structures, Eurocode 3 provides a simplified formula to calculate thermal response of both unprotected and protected members (EN 1993-1-2:2005, 2005). The simplified formula is based on section factors of the steel mem- bers and assumption of uniform temperature distri- butions in both steel sections and fire protection materials. Integration in time domain is required and can be implemented in Excel spreadsheets. However, for composite structures, the calculation method for their temperature profiles is not provided by Eurocode 4, although advanced calculation models are briefly introduced (EN 1994-1-2:2005, 2005). The said simplified formula for steel members is not applicable for the composite members since there is temperature gradient existing in the concrete section. It would lead to wrong temperature predictions if uniform temperature distribution is assumed. As a rule of thumb, the concrete section should be discre- tized to cater for the temperature gradient. As a result, both spatial discretization and time integra- tion are required for calculating the temperature pro- files of composite members. Temperature prediction for concrete-filled steel tub- ular (CFST) columns has been introduced by Lie and Chabot (1990a) and Kodur and Lie (1997a). In the research of Lie and Chabot (1990a), the temperature profiles were calculated based on one-dimensional (1D) finite difference method (FDM) for unprotected 1 School of Civil and Transportation Engineering, Guangdong University of Technology, GuangZhou, China 2 Department of Civil Engineering, National University of Singapore, Singapore 3 School of Civil Engineering, Nanjing Tech University, Nanjing, China Corresponding author: Yonghui Wang, Department of Civil Engineering, National University of Singapore, 10 Kent Ridge Crescent, 117576 Singapore. Email: ceexm@nus.edu.sg