The fire resistance of internally ring-stiffened multi-planar tubular TT-joints was studied and formulated in the present paper. TT-joints were examined under axial loading. After developing a finite element (FE) model and its verification against the experimental data, a total of 324 numerical analyses were performed on 81 FE models of internally ring-stiffened multi-planar TT-joints at four different temperatures (20, 400, 550, and 700 °C) subjected to axial loading. The reinforcing effect of internal rings was investigated. Results showed that the resistance enhancement coefficient (Rs) increases by increasing the γ; while it decreases by increasing the β. Results of the parametric investigation were utilized to establish a new set of design equations to determine the bearing capacity of internally ring-stiffened multi-tubular TT-joints subjected to brace axial loads at fire-induced elevated temperatures.