Local buckling and plastic collapse of corroded pipes has been r/investigated, for cost-effective and safe design of pipelines and risers. The analytical equations derived by the author in 1998 are newly extended to account for the effect of yield anisotropy. This study is motivated by the need to design high strength pipe whose yield stress in hoop direction is higher than that in longitudinal direction. The derived analytical equations are compared with finite element results. Two sets of design equations are derived for corroded pipes with yield anisotropy:

  1. Elastic-plastic buckling of pipes under external pressure, axial force and bending;

  2. Plastic collapse of pipes under internal pressure, axial force and bending.

The derived analytical equations agreed well with results of finite element analysis and may be used in strength assessment of corroded pipelines and risers.


Local buckling and collapse strength of metallic pipes has been an important subject for the design of pipelines, risers and TLP tendons, as well as piping, pressure vessels, tubular structures in offshore and civil engineering. Elastic-plastic buckling of pipes under external pressure was solved by Timoshenko as described in his book "Theory of Elastic Stability" (Timoshenko and Gere, 1961). Recent years, non-linear finite element analysis can be used as an accurate tool to predict buckling/collapse capacity of pipes under external pressure, bending and axial force. The finite element model has been validated against laboratory tests and applied to derive design equations. The review of the historic work and the latest research results on this topic may be found from Murphey and Langner (1985), Ellinas et al. (1986), Gresnigt (1986) and a series ofjoumal papers by Bai et al (1993, 1994, 1995, 1997, 1998). Their equations agreed well with their finite element analysis and laboratory tests.

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