Parametric study on axially loaded square hollow section T-joints at elevated temperature

Abstract

The paper presents the numerical study of tubular square T-joints under fire conditions. The sequentially coupled thermal-displacement numerical model was proposed to examine the performance of square hollow section (SHS) joints. The developed finite element (FE) model was validated against available experimental test results and applied to study the influence of dimensionless parameters on the strength of SHS tubular T-joints at elevated temperatures. These parameters include brace-to-chord width ratio β, chord-width-to-thickness ratio γ, chord-to-brace thickness ratio τ and loading ratio nF. The obtained results show that the critical temperature of T-joints is mostly influenced by the loading ratio nF and β parameter. Different methods to obtain the joint resistance are presented. The strength of the joint obtained based on EN 1993-1-8 was compared with FE analysis, which showed that the decrease in the joint resistance in brace axial compression follows the curve of Young's modulus reduction factors. Finally, the strength of the joint was calculated based on the component method, with a temperature increase specified for each individual component. This method gave higher results in joint strength, when the non-uniform temperature distribution within the joint was taken into account.