Abstract：In recent years, the elliptical concrete-filled steel tube (CFST) structure has attracted the attentions of architects and structural engineers gradually. Compared with the traditional circular and square CFST columns, the elliptical CFST columns have streamline appearance and can provide higher torsion rigidity, so they have wide application prospect in high-rise and large-span building structures. Previous researchers have investigated the post-fire bond behaviour of circular and square CFSTs experimentally and theoretically, but no relevant research has been reported on the post-fire bond behaviour of elliptical CFST. Spring elements are used to simulate the slip between the steel tube and concrete, and finite element analysis (FEA) model is developed to analyse the post-fire bond behaviour of elliptical CFSTs. For comparison, the FEA models of circular and square CFSTs with the same interface contact area as that of the elliptical CFST are established as well. The temperature distribution, postfire bond stress-slip relationship and bond strength of the three types of CFSTs are analysed according to the FEA models. Finally, based on the established FEA model, parametric study on the post-fire bond strength of elliptical CFSTs is conducted. The investigated parameters include: target temperature (20 ℃, 600 ℃ and 800 ℃) , high temperature duration time (30 min, 90 min, 120 min and 180 min), concrete strength (30 MPa, 40 MPa, 50 MPa, 60 MPa), section perimeter (388 mm, 484 mm, 630 mm, 727 mm) and aspect ratio (1.25, 1.50, 2.00, 2.25). It can be found that the influences of concrete strength and section perimeter on the bond strength of elliptical CFST after fire are significant, while the influence of other parameters is relatively minor.
