Impact of anti-friction layer on the cross-sectional mechanical properties of unbonded flexible risers

Two models are chosen to simulate anti-friction layer of an eight-layer unbonded flexible riser, one is the helix model which takes actual geometry into consideration, and the other is the simplified cylindrical shell model. Axial and torsional stiffnesses of the unbonded flexible riser under different boundary conditions were predicted by analytical and numerical methods. It is shown that numerical results agree well with theoretical results. Under axial tension, anticlockwise torsion and clockwise torsion (prevented from moving axially), stiffnesses obtained by the two models of anti-friction layer are basically the same. Under axial compression and clockwise torsion (free boundary condition), the cylindrical shell model of anti-friction layer will dramatically increase stiffnesses of the riser. © 2015, Editorial Board of Journal of Huazhong University of Science and Technology. All right reserved.