تحلیل عددی رفتار سازه های پر شده با بتن، ستون های بتن آرمه فولادی Numerical Analysis on Structural Behaviors of Concrete Filled Steel Tube Reinforced Concrete (CFSTRC) Columns Subjected To 3-side Fire

1. Introduction Concrete filled steel tube reinforced concrete (CFSTRC) consists of inner concrete filled steel tube (CFST) and outer reinforced concrete (RC), as shown in Fig. 1. This kind of structure combines all the advantages of CFST and RC perfectly, so it has a high load bearing capacity, good anti-seismic performance, excellent fireproof property and convenient workability. As a result, CFSTRC columns have been widely applied to high-rise and super high-rise buildings (Hong and Tao, 2005). Along with its extensive application, the fire resistance capacity of CFSTRC columns are drawing attentions from an increasing number of researchers. For the column in the building structure, the columns are usually in non-uniform fire due to the heat absorption of the wall and the surrounding structure, such as the single side, adjacent sides, opposite sides, and the three surfaces. The reduction in the surface of the fire affected the overall temperature of the column section and the degree of damage of the material to some extent, which is beneficial to the improvement of the fire resistance of the structure. On the other hand, under the condition of single axial symmetry, which is subjected to single-sided fire and three-sided fire, the structure produces asymmetric temperature deformation and additional eccentricity, which may reduce the fire resistance of the structure. Thus, the mechanism and fire resistance of the columns exposed to non-uniform fire differ from columns under uniform fire, thereby necessitating the understanding of fire resistance for columns under non-uniform fire to generate the corresponding fire resistance design method for the columns. A lot of research has been performed on the fire resistance of columns under non-uniform fire (Guo and Shi, 2003; Wu et al., 2007; Li, 2003; Lv et al.; 2012; Lv et al., 2013; Yang et al., 2010). Xu and Liu (2013) and Feng et al. (2008) conducted experimental investigations on CFSTRC columns subjected to four-side uniform fire. However, little research has been executed on the fire behavior of CFSTRC columns exposed to nonuniform fire. The present study depicts the typical threesided fire as the foundation for determining the working mechanism of CFSTRC columns when was subjected to a non-uniform fire.