Static Strength of Axially Loaded Tubular K-Joints. I: Behavior

Abstract

This paper reports the results of an extensive finite-element study into the static behavior of axially loaded tubular K-joints. The emphasis of the study was on the effects of the geometric parameters and the overlap amount on the behavior of overlap joints. The results of some K-joints with small gaps were also included for comparative purposes. The study reveals new insight into how the behavior of axially loaded overlap K-joints varies across the practical range of geometric parameters. Certain overlap geometries were seen to be 100% efficient, with the joints reaching the brace member squash load capacity. Other failure modes of chord bending, brace local buckling, and in particular, combined chord bending and brace local buckling were evident. Examination of the load-deformation characteristics for the sharp falls in the postpeak load—reflecting sudden joint failures, which have been a suggested cause for concern in the past—has revealed that relatively few overlap geometries exhibit such behavior. The ultimate capacity results, and their significance in the light of available design guidance, are examined in a companion paper.