Analysis of anchor drop and drag over the pipeline

• Main Author: Lai, Kah Yip
• Other Authors: Ong Lin Seng
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Mechanical engineering::Mechanics and dynamics
• Online Access: http://hdl.handle.net/10356/17180
• Institution: Nanyang Technological University

The present work examines the denting response of a pipeline subjected to quasi-static anchor loading, imposed by a triangular block with patch profile. Using Simulation module of ANSYS Workbench V11.0, a parametric study is conducted and denting force-displacement results are obtained for various pipe’s thickness, lengths, internal pressures, indenter widths and orientations. The finite element modeling consists of a quarter-model which is constructed using SOLID186 elements. Initial frictionless contacts are considered for the pipe-indenter and pipe-soil interfaces using contact pair elements. Boundary conditions are set to simulate a fixed end pipeline lying on a rigid seabed. Displacement loading using time steps is employed to determine the response of the pipe under indentation. A successful replicate model of previous work is obtained to ensure a good level of accuracy in simulation runs. It was found that when the pipe wall thickness is increased, the pipe has more resistance to indentation and required more denting force to cause non-linear deformations. Similarly, when the internal pressure of a pipe is increased, the pipe becomes stiffer. With an increase in pressure, the localized denting length increases as well. The plots of yield force for various length to diameter ratios also show that a shorter pipe will require a larger force to cause structural deformations. For the effect of indenter width, it is found that the force required for a pipe to deform non-linearly increased when a wider indenter is used. Ovalisation results are tabulated to investigate the extent of deformation for various widths and thickness. Lastly, the denting behaviours show that a transversely loaded indenter required more denting force for structural deformation as compared to a longitudinally loaded indenter. These results are based on a simplified model and do not include all aspects of pipeline indentation. However, the parameters tested will give an insight into the possibility of failure of pipe during an anchor-loaded impact. Future work recommendations for improvements to the FEM model are made.