During deep-water pipeline installation, the pipe is subjected to high external pressure, which may trigger structural instability is the form of collapse, with catastrophic effects. Pipe resistance of against this instability is a major issue for safeguarding offshore pipeline integrity. In the present paper, the collapse resistance of steel pipes fabricated by the JCO-E pipe manufacturing process are examined. The paper describes a combined experimental, numerical and analytical work on the collapse of a 30-inch-diameter X60 JCO-E pipe. The pipe is subjected to full-scale external pressure testing that determined its collapse (ultimate) and propagation pressure. The pipe, prior to collapse, has been subjected to heat treatment at a level that represents the coating process. Prior to collapse testing, initial ovality measurements have been obtained along the pipe. Furthermore, strip specimens have been extracted from the pipe, before and after heat treatment, and the corresponding material properties have been obtained from uniaxial testing. Numerical calculations are also performed using a full-scale three-dimensional finite element model that simulates the collapse test procedure, using the real material properties from the strip specimens. The experimental data and the numerical results on collapse pressure of the pipe are compared with the predictions of the DNV-ST-F101 formula, and the value of fabrication factor ?fab is discussed.
Collapse testing and analysis of JCO-E steel pipes
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