ABSTRACT
A series of tests were carried out on conventional welded CHS YT-joints with gaps with a pulsing axial compression applied to the diagonal brace. Two sets of boundary conditions were used in the test, one with only one redundant restraint to the chord member, and the other with three additional restraints.
It was found that incremental collapse occurred as much as 18% below the static strength of the joint, depending upon the number of constraints, and that the ultimate strength of the joint was largely unaffected by the number of constraints. The collapse mode consisted of plastic indentation of the wall of the through member in a combination of lateral and rotational modes. The results obtained from these experiments have a bearing on the choice of ultimate strength criteria to be employed in the design of structures with variable repeated loads.
