Axial force–bending moment interaction in a jointing system part I: (Experimental study)

• We represented a test procedure that enables realistic testing of a space structure jointing system.
• The main objective was the experimental study of the effects of compressive axial force on the moment-rotation behaviour.
• Experimental results showe that the compressive axial force increases the initial slope of the moment-rotation curve.
• Axial force gives rise to softening of the joint behaviour and it decreases the ultimate moment capacity of the joint.

In a space structure, each connection can be subjected to different ratios of axial force to bending moment. In this paper, a test procedure was presented that enables realistic testing of a steel space structure jointing system by applying different combinations of axial forces and bending moments to the connection. The main objective of the test programme was the experimental study of the effects of compressive axial force on the moment–rotation characteristic of a joint. A suitable test set-up was designed and constructed to achieve a reasonable simulation of real connection behaviour. From the experimental results, it has been found that the compressive axial force has three important effects on the moment–rotation characteristics. It increases the initial slope of the moment–rotation curve with the reduction in the stiffness occurring more slowly to begin with but increasing more rapidly afterwards. It decreases the ultimate moment capacity of the connection. It also gives rise to softening of the connection behaviour.