Research on fire resistance design of welded hollow spherical joints under axial tension

In this paper, the numerical simulation analysis of the fire resistance behaviour of WHSJs under tension is carried out based on the existing experimental research. The numerical simulation analysis shows that the high-stress area of the stiffened joint is located in the middle part of the stiffener during the initial heating stage. When the joint is heated to about 1000 s, the stress reaches the maximum. As the temperature rises, the maximum stress decreases, and the high-stress area shifts to the intersection of the sphere-steel tube. When the failure state is reached, the joint is rapidly elongated, and the maximum stress continues to decrease. The load ratio, sphere thickness, and stiffener are the main factors affecting the fire resistance behaviour of the tensioned joints, and the diameter of sphere and steel tube has some impact on the fire resistance behaviour of the joints. With the increase of the load ratio and stiffener inner diameter, the critical temperature of the joint decreases approximately linearly. The critical temperature increases approximately linearly with the improvement of the sphere thickness. The increase in sphere diameter, steel tube thickness, and steel strength has little influence on the fire resistance behaviour of the joint. The critical temperature calculated by the code is much higher than the critical temperature obtained by the test, and the critical temperature recommended under different load ratios by the code is relatively conservative. Based on the parameter analysis, the design method for the fire resistance behaviour of the axial tensile WHSJs was proposed. • The numerical simulation analysis of the fire resistance behaviour of WHSJs under tension is carried out based on the existing experiment. • The temperature at the failure point of WHSJs is used as the criterion for the critical temperature. • The design method for the fire resistance behaviour of the axial tensile WHSJs was proposed.