Fire resistance of thin-walled tubular T-joints with internal ring stiffeners under post-earthquake fire

Abstract

Abstract The objective of this paper is to computationally investigate the fire resistance of earthquake-damaged thin-walled tubular T-joints stiffened with internal rings at elevated temperatures. An earthquake can cause severe damage to the T-joints, thus may lead to the reduction of fire resistance after that. Additionally, given the needs in improving the performance of T-joints using stiffeners, the behaviors and fire performance of these stiffened T-joints under post-earthquake fire (PEF) is of great interests. A computational model, validated with the existing experimental results, is established to conduct the analysis of the fire resistance behavior of the stiffened tubular T-joints under PEF. Then, by using this model, the stiffening strategies for tubular T-joints using 1 internal ring, 2, and 3 internal rings, are evaluated along with the unstiffened case to investigate their effectiveness in improving the fire resistance capability under PEF. Later, a parametric study is performed for the stiffened T-joints with 3 internal rings under PEF using the validated computational model. 24 finite element models are analyzed under different damage levels, by considering the following key geometric parameters: the diameter ratio (β), the wall thickness ratio (γ) of the T-joint's chord and brace members, the diameter-thickness ratio (α) of the chord member, and the thickness ratio η of ring-stiffener and chord along with the damage variable ( D ˜ ) to account for the level of the T-joint being damaged. The results on different stiffening strategies and the parametric study reveal that the significant influence of the damage variable and the sensitivities of other influencing parameters. The findings from this study provide needed evidence for potential design recommendations for post-earthquake fire resistance of stiffened tubular T-joints.