Avaliação de modelos analíticos para previsão da relação momento-curvatura de risers flexíveis

Abstract

Deepwater oil exploration is an activity of substantial economic importance to the country. Due to the environmental and operational conditions involved, its feasibility depends on the study and development of specialized technologies, such as flexible risers. Flexible risers are essential tubular structures for offshore oil exploration, responsible for transporting fluids between subsea systems and floating production units. These structures are characterized by low bending stiffness and a multilayered configuration composed of metallic and polymeric layers, which provides a high capacity to accommodate large relative displacements and to withstand elevated axial stresses and pressures. However, under operational conditions, flexible risers exhibit complex bending behavior, described by a nonlinear and hysteretic moment–curvature relationship. An accurate representation of this relationship is fundamental for realistic structural analyses, particularly in fatigue assessments and under extreme dynamic loading conditions. Despite its relevance, the determination of the moment–curvature relationship faces practical limitations in experimental programs and entails high computational costs in numerical approaches based on the Finite Element Method. In this context, analytical models emerge as interesting alternatives for application in global analyses, although they strongly depend on the adopted simplifying assumptions. Therefore, this work aims to assess the performance of analytical models proposed in the literature for predicting the moment–curvature relationship of flexible risers under different loading conditions. Axisymmetric models are implemented and verified to compute the contact pressures between layers for bending models. Subsequently, bending models are implemented and validated through comparison with available experimental results, enabling a discussion of the impact of the adopted hypotheses. Finally, a categorization of the implemented models is presented according to the main aspects involved in predicting the moment–curvature relationship of flexible risers.