Ultimate Strength and Mechanical Behavior of Underwater Pipelines Subjected to External Pressure

Panagiotis Amarianos

Diploma Thesis, February 2014

ABSTRACT

This work investigates the structural behaviour and integrity of underwater pipelines. These pipelines are subjected primarily to external pressure loading, and may fail in the form of collapse because of the phenomenon of buckling propagation. The work is numerical and uses nonlinear finite element simulations in ABAQUS.

In this work, the effects of initial imperfections are examined in terms of the pipeline resistance to external pressure. Imperfections may be mainly in the form of out-of-roundness of the cross-section due to manufacturing or because of external interference. Imperfections may also be in the form of material anisotropy, or the variation of pipe wall thickness. Subsequently, the phenomenon of buckling propagation, and its arrest with the use of appropriate buckle arrestors is examined.

Figure 1: pipe cross-section collapses;
contact between opposite points on the inner pipe wall.

 
Figure 2: buckle propagation develops.

Figure 3: “integral” buckled arrestor stop
buckling propagation.

Figure 4: buckle “crosses over” the arrestor
at an increased level of pressure.