On the axial-torsional structural behaviour of flexible pipes, umbilicals and marine cables

Abstract

An analytical model for predicting the axial-torsional structural behaviour of flexible pipes, umbilicals and marine cables is presented. The analytical model is based on the interaction between the component layers of a generic flexible structure. The flexible structure is analysed as a combination of helical and cylindrical components placed in arbitrary order. A governing equation for the flexible structure is derived, the solution of which provides the axial-torsional load-displacement relationship. The model also provides additional information, such as the construction of individual component layers, interfacial contact pressures and interlayer gap amplitudes. Results are presented for a typical marine cable, an umbilical and a flexible pipe. Tensile tests have been carried out on the marine cable and the umbilical and good agreement between theory and experiment is demonstrated.