Experimental study of semi-rigid joint systems subjected to bending with and without axial force

Socket joints and bolt-ball joints are typical semi-rigid joint systems widely used in spatial structures. In this paper, tests on fifteen joints are carried out to study their mechanical behavior. Three socket joint systems are subjected to bending moment and shear force, and another seven socket joint systems and five bolt-ball joint systems are subjected to bending moment, shear force and axial compressive force. The main characteristics of the moment–rotation relationship for the connections under different loading schemes are summarized and discussed. The results indicate that: (i) both socket and bolt-ball joint systems have good bending stiffness; (ii) the axial compressive force increases the initial bending stiffness of the joints; (iii) the axial compressive force has different effects on the bending moment capacity of different joints; and (iv) the yield process of moment–rotation curves of the joints is shortened due to the action of the axial compressive force.

► Tests of fifteen joints are carried out under different loading schemes.
► Socket and bolt-ball joint systems have good bending stiffness.
► Axial compressive force increases the initial bending stiffness of the joints.
► Axial force has different effects on the moment capacity of different joints.
► The yield process of moment–rotation curves is shorten by the axial force.