Study on fire resistance of circular hollow section (CHS) T-joint stiffened with internal rings

This paper aims to study the fire resistant performance of circular hollow section (CHS) T-joint stiffened with internal rings under axial compression at elevated temperatures. Experimental study and finite element analysis are combined to carry out the investigation. Two full-scale tubular joints, one is un-stiffened and the other is stiffened with ring-stiffeners, are designed and tested. A constant axial loading is applied at brace end of the joints firstly, and then the joints are heated in accordance with ISO 834 standard heating curve uniformly in an electric heating furnace until failure. It is found that the internal rings enhance the fire resistant performance of CHS T-joint by decreasing the temperature of chord efficiently and prolonging the fire-resistant time. Sequentially, the corresponding finite element models of the two joints are built on basis of the experiments by employing sequentially coupled thermal-stress method. By comparing with the experimental data including temperatures of chord and brace and displacements of crown, saddle and brace end, the finite element models are verified to be accurate and reliable. And then numerical analysis is conducted to investigate the reinforcing efficiency of ring-stiffeners and impact of geometrical parameters (β and γ) on the fire resistant performance of the stiffened joints by adopting the verified modeling method. It is summarized that the failure mode converts with geometrical dimensions of ring-stiffener and geometrical parameters of tubular joint changing.

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