Experimental and numerical study on fire resistance of circular tubular T-joints

• Experimental tests on tubular T-joints with internal rings in fire conditions are conducted.
• Failure process of T-joints with and without reinforcement in fire condition is discussed.
• Finite element simulation of tubular T-joints in fire condition is carried out.
• Effect of some parameters on fire resistance of tubular T-joints is investigated.

This paper focuses on experimental investigation and preliminary numerical parametric study on fire resistance of CHS T-joints under axial compression. In experimental test, three CHS T-joints subjected to axial load are heated in accordance with predefined heating curves in electric heating furnace. The failure mode of the specimens at elevated temperature is found from experimental observation to be plastic failure of chord face around the brace/chord intersection. The experimental phenomena and displacement–temperature curves show that the T-joints fail suddenly after temperature exceeds certain value. Additionally, the temperature–time and displacement–temperature curves of specimens obtained from experimental measurements are used to verify the accuracy of finite element models presented in this study. In preliminary numerical parametric study, the finite element models are built using finite element software ABAQUS. Sequentially coupled thermal–stress analysis is used to conduct numerical simulation. The comparison between experimental and numerical results shows that the proposed finite element models can simulate the fire test successfully and are reliable to carry out a preliminary numerical parametric study to investigate the influence of several principal dimensionless parameters on fire resistance of CHS T-joint, such as α, β, γ, and loading ratio n. For the CHS T-joints with different values of β and n, the reaction force caused by constraint at chord ends is also studied. It has been found that the behavior of CHS T-joint at elevated temperature is significantly affected by the geometrical parameters and loading ratio n. Additionally, the reaction force cannot be neglected if the chord ends are fully constrained.