Fire resistance of collar-plate-reinforced multi-planar tubular KK-joints: experimental and numerical study for the design formulation

In the present paper, the fire resistance of two-planar tubular KK-joints reinforced with collar plates is studied and formulated. After establishing a finite element (FE) model and its verification against the results of experimental tests, a total of 1440 numerical simulations were performed on 360 FE models of collar-plate-stiffened two-planar tubular KK-joints at four different temperatures (20, 400, 550, and 700°C). The studied joints were analysed under the axial loading and the reinforcing effect of the collar plate was investigated. Results showed that the resistance enhancement coefficient (Rs) increases by increasing the γ, θ, and τ; while it decreases by increasing the β. Results of the parametric investigation were utilised to establish new design equations to determine the bearing capacity of collar-plate-stiffened two-planar tubular KK-joints under the brace axial loads at fire condition