عنوان مقاله [English]
As an innovative type of composite construction, concrete-filled double skin steel tube (CDFST) has the potential to be used as columns in high-rise buildings. CFDST columns consist of two concentrically-arranged inner and outer steel skins with the annulus between the skins filled with concrete. Of prime features of CFDST columns is the interaction between steel tubes and concrete core. The confinement of the steel tubes on the concrete core benefits the interaction along the interfaces. However, when the interface interaction of steel tubes and concrete core vanish, the deformation starts to loom large. The deformation rate of the columns is increased under fire exposure. The current study aims to investigate the effect of interaction of concrete core and inner steel tube on the fire resistance of CFDST columns considering steel links (longitudinal stiffeners) embedded inside the concrete core welded to exterior surface of the inner tube. Finite element models for CFDST columns were developed using ABAQUS package in this study. A sequentially-coupled thermal-stress analysis procedure is conducted to evaluate the effects of inner steel tube- concrete interaction on the fire performance of these columns. The uses of stiffeners in the CFDST columns increase the fire resistance of the columns effectively. The specimens with stiffeners embedded in the exterior surface of the inner tubes exhibited excellent fire resistance. It can be attributed to the fact that interaction of stiffeners, inner tube and concrete core provides adequate bond and friction at the interface surfaces, contributing to the composite action improving strength during the process of
fire exposure. This implies that the interaction of concrete and steel components increases the fire performance of these columns significantly, a striking conclusion, which requires strategies to retain such performance. The conclusions, drawn from this study, can in turn, lead to the suggestion of some guidelines for the design of CFDST columns.