Experimental research on semi-rigid joints used in grid structures and reticulated domes

In order to study the mechanical behavior of semi-rigid Socket joint widely used in space structures,tests on 9 specimens were carried out.3 of the specimens were under bending moments and 6 of the specimens under bending moment and compressive axial force together with different ratio of bending moment to compressive axial force.The results of the specimens under different loading conditions were compared.Furthermore,a simplified model for moment-rotation curves of Socket joints was established.The experimental studies indicate that the Socket joint system has good bending moment capacity and ductility,the initial bending stiffness and critical bending moment of the joint under bending moment and compressive axial force together are higher than that of the joint under bending moment only,the initial bending stiffness of a joint increases when the ratio of bending moment to compressive axial force decreases.So,the load-bearing capacity of the space structures with Socket joint system calculated using the bending stiffness obtained through the specimens under bending moment only is conservative.