Theoretical and finite element methods for cross-section design of deep-sea flexible pipelines

Glass fiber-reinforced flexible pipes (FGRFP) have emerged as a new solution for offshore oil and gas transportation due to their high strength, light weight, and excellent corrosion resistance. Given the complex loading conditions in the marine environment, it is essential to design the cross-sectional structure of the pipeline and perform a mechanical performance analysis. First, the thickness of the reinforcement layer in FGRFP is designed based on macromechanical theory. A theoretical model is then developed based on composite laminated plate theory to describe the nonlinear behavior of the material. By analyzing the stress distribution of FGRFP under design conditions, the fiber winding (FW) angles are optimized. The accuracy of this model is then validated using finite element method (FEM). Results indicate that, compared to single-angle winding, a multi-angle fiber winding (FW) structure provides a more uniform radial stress distribution in the reinforcement layer, significantly enhancing the load-bearing capacity of FGRFP. Under complex loading conditions, with a pipe wall thickness of 18 mm and a winding angle of [ ± 5 0 12 ∘ / ± 5 5 6 ∘ ] , the design meets the required performance standards and achieves high overall performance. These findings provide valuable insights for the production of FGRFP. • A new theoretical model for FGRFP was developed based on composite laminated plate theory. • A multi-angle fiber winding structure was designed, improving stress distribution in FGRFP. • FEM validation showed the model’s accuracy and its applicability under complex conditions.