Abstract
The connection of a flexible riser to the floating production system is identified as a critical area with respect to extreme deformation and fatigue damage. Bend stiffeners are designed to provide a gradual stiffness transition at the riser–vessel interface, protecting the riser against overbending and from the accumulation of fatigue damage. Thus, they are of vital importance to deep-water oil and gas production systems. A methodology for the bend-stiffener taper design is firstly outlined in this paper. The exact expression of the angle at the tip of the bend stiffener required for the design is derived. Then, a mathematical formulation and the numerical solution procedure for the geometrical and material non-linear analysis of the riser-stiffener system are developed. The governing differential equations are obtained from geometrical compatibility, equilibrium of forces and moments, and non-linear material constitutive relations. An analytical approach to predict the bending moment versus curvature relation for each cross-section is presented assuming that the bend-stiffener material is non-linear symmetric, while for asymmetric materials the constitutive relation is calculated numerically. A numerical solution procedure is implemented in MATLAB code to solve the boundary value problem. Furthermore, the flexible pipe structure exhibits an approximately bi-linear hysteretic bending moment against curvature relation. The effect of the bending stiffness bi-linear behaviour on the bend-stiffener response is evaluated for the non-linear material case. A case study is carried out and the results show the potential influence of the material non-linearity on the stiffener response and the need to incorporate the effect of non-linear bending of the pipe in bend-stiffener analyses.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call