Significant characteristics of three-dimensional flexible riser analysis

The development of a full three-dimensional solution for general flexible pipeline and riser configurations is outlined. The procedure is based on a hybrid beam-column finite element which can model the gross motions and generalized section forces of a range of slender structures from mooring lines to rigid pipelines in arbitrary three-dimensional configurations. Special emphasis is given to characteristics of the problem that are significant with respect to floating production systems based on flexible pipelines. These include the use of a pre-processor program based on simple cable equations for locating the initial configuration, variable-step static and dynamic solution schemes, seabed contact algorithms and the modelling of finite three-dimensional rigid body rotations. The utility and ease of use of the overall approach is demonstrated by application to a selection of examples drawn from field experiences with the system. These examples are designed to illustrate significant characteristics governing the design and analysis of flexible pipeline installations.