Bend stiffeners for flexible pipes: A comparative study between Attachment and Pipe in Pipe modeling

Resumo

This paper presents a comparative analysis between two modeling methodologies for bend stiffeners applied to subsea flexible pipes: the Attachment model and the Pipe in Pipe model. The main motivation lies in the need to ensure the structural integrity of pipelines during installation operations in offshore environments, especially in deep and ultra deep waters, where dynamic loads are significant. A top riser deployment scenario was simulated under different environmental conditions and top angle presets of 1º, 3º, and 5º. The analysis focused on maximum top tension, top angle, shear force and bending moment of the stiffener, line curvature below the stiffener, and simulation runtime. Results show that both approaches yield similar global performance for top tension and angle, while the Pipe in Pipe model offers greater freedom of movement for the riser and shorter simulation times (on average 22% faster). However, this approach requires more detailed input data, especially regarding the definition of contact stiffness, which can cause convergence problems. It is possible to conclude that Attachment is preferable for early design stages or when frequent adjustments are needed, whereas Pipe in Pipe is recommended for consolidated projects demanding greater accuracy in representing stresses and relative motions.