Post-fire residual strength of steel tubular T-joint with concrete-filled chord

The post-fire behavior of steel tubular T-joints with a concrete-filled chord (CFC) was experimentally and numerically investigated. The results reveal that the residual strength has no obvious decrease after lower than or equal to 400℃ fire exposure, but as the fire temperature increases, it is significantly linear decreased. Meanwhile, the average residual strength of the T-joints is increased by at least three times after infilling concrete. This is mainly because the in-filled concrete can prevent the T-joints areas from indenting, and the T-joints’ failure mode changes from buckling to bending failure of the chord. Thus the mechanical properties of these steel and concrete joints are fully developed. However, the influence of concrete strength on the residual strength is very limited. Moreover, the post-fire residual strength of T-joints with CFC decreases more than that of T-joints without CFC as the damage of concrete in fire is irreparable.