Numerical Assessment of the Fire Resistance of Tubular Steel Columns Filled with Concrete Tiago A. C. Pires 1 , João Paulo C. Rodrigues 1 *, José Jéferson Rêgo Silva 2 1 Faculty of Sciences and Technology of the University of Coimbra, Dept. of Civil Engineering, Portugal, 2 Federal University of Pernambuco, Dept. of Civil Engineering, Brazil, * Tel.: +351.239.797245; Fax: +351.239.797242; E-mail: jpaulocr@dec.uc.pt. Abstract. Nowadays concrete filled steel hollow (CFSH) columns are largely used in construction due to the structural and architectural advantages such as high load bearing capacity and aesthetic appearance. This paper presents a three- dimensional nonlinear finite element model to predict the behavior of CFSH col- umns in fire and its more relevant parameters. The model was validated in com- parison with results of fire resistance tests on CFSH columns with restrained thermal elongation. The model shows a good agreement between the numerical and experimental results being able to assess the fire performance of the columns. Keywords: fire, resistance, concrete, steel, hollow, columns, restraining. 1 Introduction Nowadays concrete filled steel hollow (CFSH) columns are largely used in construction due to the structural and architectural advantages such as high load bearing capacity and cool appearance. For predicting the performance of these structures in fire is common for engineers the uses of computational or analytical methods to assess it and consequently cover a wide range of situations in a faster way and with less cost. In case of the CFSH columns some researchers presented in the recent past models to predict the thermo-mechanical behavior of these col- umns in fire (Lie 1994, Ding and Wang 2008, Schaumann et al. 2009, Hong and Varma 2009, Espinos et al. 2010). However validation of the models was not investigated considering the re- straining to thermal elongation of the column on fire experimental tests. The be- havior of these columns when inserted in a building structure is different from those when isolated. Restraints on column thermal elongation, provoked by the building surrounding structure, plays a key role on columns stability, since differ- ent forms of interaction between the heated column and the cold adjacent structure occur. When the column is heated, it is observed an increase of the restraining forces due to the restraining to thermal elongation provided by the building sur-