Exact yield hyper-surface for thin pipes

A yield hyper-surface for pipe sections subjected to combinations of normal forces, internal and external pressure, twisting moments, biaxial bending moments and biaxial shearing forces is developed. The formulation is based on the fully plastic capacity of the pipe as determined by the maximum dist orsional energy density yield criterion. The solution is obtained by maximi zing a lower bound analysis and yields a yield hyper-surface that is exact within the limitations of the formulation. The developments are expressed a s universal nondimensional relationships suitable for limit states design o f elevated pipes, submerged pipes, offshore platforms and structural tubula r steel members. Previously established interaction relations for bending m oments, axial forces and internal pressure are recovered as a special case of the general solution. The merits of using the yield hyper-surface to cha racterize generalized plastic hinge behavior in elasto-plastic pipe stress analysis are presented. (C) 2001 Elsevier Science Ltd. All rights reserved.