Numerical study of hybrid tubular K-joints with circular braces and square chord in stainless steel

This paper introduces a finite-element analysis (FEA) on hybrid tubular K-joints with circular braces and square chord in stainless steel. The finite-element models (FEMs) were established by using the shell element S4R for circular braces, square chord and welds. The FEMs were validated by comparing the failure modes, failure strengths and joint deformation curves obtained from the experiments and FEA. A parametric study was carried out on 162 FEMs to evaluate the influences of brace diameter/chord width ratio ((beta = d1/b(0)), brace/chord thickness ratio (tau = t(1)/t(0)), chord width/thickness ratio (2 gamma = b(0)/t(0)), overlap ratio (0 = (q/p) x 100%) of overlapped tubular K-joints and eccentricity (e) of gapped tubular K-joints. The numerical results show that the joint strengths of overlapped tubular K-joints increased with the increment of the beta, tau and O-v, values, as well as the decrement of the 2 gamma value, while the joint strengths of gapped tubular K-joints increased with the increment of the beta and tau values, as well as the decrement of the 2 gamma and e values. The comparison of the failure strengths with design strengths demonstrates that the design formulae of CIDECT and Australian/New Zealand Standard (AS/NZS) are generally unconservative, whereas the design strengths determined by Eurocode (EC3) and Chinese Code are relatively close to the failure strengths for overlapped tubular K-joints. The design formulae of AS/NZS are generally unconservative, whereas the design formulae of CIDECT, EC3 and Chinese Code are generally conservative for gapped tubular K-joints. The design equations are proposed by introducing the correction factors that considered the influences of geometrical parameters of beta, tau, 2 gamma and O-v, which were validated to be accurate for hybrid tubular K-joints in stainless steel.