Experimental study on residual performance of welded hollow spherical joints subjected to axial compression after a fire

To study the residual performance of the welded hollow spherical joint after exposure to high temperatures. A total of 12 welded hollow spherical joint specimens are heated to six different preselected temperatures and subsequently air-cooled and water-cooled to the ambient temperature. Axial compressive tests are thereafter performed until the joints are damaged. The displacement characteristics, strain development, failure modes, stiffness, ductility, and load bearing capacity of specimens are investigated. The results show that the mechanical properties of spherical joints are considerably affected by the temperatures and cooling methods. Under the air-cooling condition, both the stiffness and compressive load of spherical joints decrease with an increase in the exposed temperature, and the ductility increases considerably. Under the water-cooling condition, the stiffness and ductility of spherical joints decrease with the increase in exposed temperature. The yield and ultimate loads decrease when the temperature is up to 500 °C and then gradually increase when the temperature exceeds 500 °C.