Stress and Strain Concentration Factors of Completely Overlapped Tubular K(N) Joints

Abstract

A full-scale uniplanar completely overlapped tubular K(N) joint specimen is tested to determine the hot spot strains at the joint intersections for the verification of the finite-element (FE) model. The test results reveal that the maximum strain concentration occurs on the through brace saddle near the lap brace. On the chord, the strain distributions perpendicular to the weld toes are linear but on the through brace and the lap brace, they are nonlinear. Based on the FE analysis results, the effects of through brace and lap brace geometric parameters on the joint stress concentration factors (SCF) are found most crucial. The use of the existing Y-joint formulas has considerably underestimated and overestimated the SCF on the through brace saddle near the chord and the lap brace, respectively. At a relatively large gap size, the SCF values at the joint intersection of the through brace and the lap brace are close to that of the Y joint.