Many offshore structures are fabricated with tubular members. The connections between the different tubular members are denoted tubular joints. A tubular joint is made up of a chord (element of largest diameter) and one or more braces.

The classification of a joint is not solely determined by the geometry, but also by the axial loads in the members. For example, if the axial force in one brace in an X-joint is much less than the other, the joint would be classified as a T-joint.

Although real structures are composed of multiplanar joints, the treatment of simple planar joints can be used if the members are within $\pm 15^\circ$.
The nominal axial and bending stresses are multiplied by the appropriate Stress Concentration Factor (SCF) to obtain the stress at the crown and saddle of the chord and brace^{1}.
The resulting stresses can be combined to find the resulting stresses along the perimeter of the chord-brace intersection as described in DNV RP-C203 ^{2}. Once the Hot Spot Stresses (HSS) are calculated, a fatigue calculation can be performed.

The equations used for the determination of the tubular joint SCF ^{3} ^{4} are based on the equations developed by Efthymiou ^{5}. A comprehensive comparison of tubular joint SCF parameteric equations can be found in "Stress Concentration Factors for Simple Tubular Joints, Assessment of Existing and Development of New Parametric Formulae"^{6}.

Since the equations are rather tedious to calculate, we have provided a calculator for T and Y joints, X joints, K joints, KT joints

If you need to calculate the SCF's for more complicated joints, such as grouted joints, ring stiffened joints, or configurations not covered by these equations, contact us for a finite element solution.