Analytical and numerical analysis for unbonded flexible risers under axisymmetric loads

Due to the structural complexity, the response of a flexible riser under axisymmetric loads is quite difficult to determine. Based on equilibrium conditions, geometrical relations and constitutive equations, an analytical model that can accurately predict the axisymmetric behavior of flexible risers is deduced in this paper. Since the mutual exclusion between the contact pressure and interlayer gap is considered in this model, the influence of the load direction on the structural behavior can be analyzed. Meanwhile, a detailed finite element analysis for unbonded flexible risers is conducted. Based on the analytical and numerical models, the structural response of a typical flexible riser under tension, torsion, internal and outer pressure has been studied in detail. The results are compared with experimental data obtained from the literature, and good agreement is found. Studies have shown that the proposed analytical and numerical models can provide an insightful reference for analysis and design of flexible risers.