EXTREME BENDING AND TORSIONAL RESPONSES OF FLEXIBLE PIPELINES

The paper concentrates on evaluating the elastic motions of flexible flowlines where bending and torsional effects significantly contribute to the response. Examples include flexible riser systems in extreme offset positions, shallow water systems subjected to large vessel motions and flexible jumper hose configurations bent into three-dimensional hoop-like curved shapes. For all such cases, it is very import ant that the kinematics are properly developed and understood so as to ensure the accurate computation of the distribution of bending and torsion along the flowline. A consistent formulation of the kinematics, within the context of a convected co-ordinate system of axes, is developed with a particular emphasis on the torsional components. Second order strain terms and their equivalent finite element forms are derived with respect to arbitrarily large translations and rotations of sections and coupled bending and torsional behaviour. The overall mixed finite element static and dynamic solution scheme also incorporates penalty parameters on both the torque and axial forces in order to enhance the accuracy and robustness of the computations. A number of numerical examples are presented in order to validate the approach.