This paper describes a full scale testing and finite element investigation of the wrinkling behavior of corroded pipe. It is applicable to corroded pipe subjected to multi-axial loading such as longitudinal bending, internal pressure, and axial compression. The finite element procedure incorporates the non-linear material behavior of the pipe steel by the use of a multilinear kinematic hardening plasticity model. Corrosion is simulated numerically by a reduced wall thickness section. Simulated pipe structural behavior is critically compared to a full scale test. During the testing program, a full scale, 48-inch diameter section of the Trans-Alaska pipeline is subjected to multi-axial loading. Corrosion in the pipe is physically simulated using a reduced wall thickness section of the pipe. Deflections, curvature, and loading are measured for comparison to the finite element simulations. The results indicate a good correlation between the numerical model and full scale test in predicting the, deflection, curvature, and moment capacity of the pipe at wrinkling.
The integriity analysis of degraded pipe is attracting an increasing amount of attention from pipeline operators faced with making a repair/replace/ignore decision with regard to maintenance and operation of aging pipelines. While pressure based guidelines exists which allow pipeline operators to define the operational margins of safety against rupture (Battelle, 1989), reliable procedures for the prediction of wrinkling in degraded pipes subjected to combined loading are virtually non-existent. After nearly 20 years of service, some areas of the Trans- Alaska Pipeline have sustained normal settlement and/or corrosion inherent to aging pipelines. The settled areas can be identified reliably using a "smart pig" which measures curvature of the pipeline based on changes in pig orientation. A smart pig can also be used to measure changes in pipe wall thickness, and hence, identify areas with external corrosion without prior excavation of the pipe.
