Plastic Interaction Relations for Pipe Sections

Abstract

General interaction relations for pipe sections subjected to combinations of normal forces, internal or external pressure, twisting moments, biaxial bending moments, and biaxial shearing forces are developed. The derivations are based on the fully plastic capacity of the pipe as determined by the maximum distortional energy density yield criterion. Close form interaction relations are obtained for general load combinations and an accurate approximation is proposed. Previously established interaction relations for bending moments, axial forces and internal pressure are recovered as a special case of the general solution. The developments are expressed as universal nondimensional relationships suitable for limit states design. Consideration is given to the limits of applicability of the interaction relations and a systematic design procedure is proposed based on the interaction relations obtained and their limits of applicability. The relations are applicable in the design of elevated pipes, submerged pipes, supports of offshore platforms, and tubular structural steel members.