Background to New Edition of API Bulletin 2U- Stability Design of Cylindrical Shells

Abstract

API Bulletin 2U has recently been revised. New formulations for local buckling of ring-stiffened and ring-and stringerstiffened cylindrical shells, when subjected to both longitudinal and circumferential hoop stresses, have been developed. The new formulations are in line with classical buckling equations and are compatible with the test data. The definition of plasticity reduction factor has been revised to make it more consistent throughout the document. It has been found that the presence of vertical stringer, especially when spaced closely, play an important role in modifying the distribution of stresses in rings and shells due to applied external pressure and axial loading. New formulations have been developed to determine stresses in the shell at rings and midway between ring spacing for ring stiffened and ring and stringer stiffened shells when subjected to external pressure and axial load. Sample computations have been added to the bulletin to help and illustrate to the user the sensitivity of various parameters affecting design decisions.