Stress analysis of spatial frames with consideration of local flexibility of multiplanar tubular joint

A polyhedral element for a multiplanar tubular joint is suggested. The stiffness matrix of the polyhedron of a flexible joint is formulated based on the local flexibility factor matrix and co-ordinate transformation. An offshore jacket is chosen as a numerical example. The computed results show the great effect of local flexibility of a multiplanar tubular joint on the internal forces, deformation, and stress concentration of the joint. Hence, the consideration of flexibility in the global spatial structural analysis is vital.