Assessment of alternative approaches for the representation of torque and twist in pipeline and riser analysis

This paper addresses the problem of evaluating the elastic deformations and motions of flowlines and cables where bending and torsional effects are present. For such problems where large deflections and finite rotations of sections may occur, it is important that the kinematics are properly developed and consistent with the constitutive relation between torque and twist of the flowline. Two alternative techniques are compared, one based on an extension to the classical theory of elastic rods and the other on a more established method that uses convected coordinate systems that translate and rotate with the centreline of the pipe. Both are implemented within a finite element framework and applied to a series of elementary problems for the purposes of evaluating the respective methods.