Alternative analytical and finite element models for unbonded flexible pipes under axisymmetric loads

Lu, Hailong; Vaz, Murilo Augusto; Caire, Marcelo

doi:10.1016/j.oceaneng.2021.108766

Cited by 13 publications

(4 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The development of numerical models of unbonded flexible risers containing detailed geometric properties to simulate the nonlinear hysteresis characteristics of the structure is the current direction of development [ 122 , 123 , 124 , 125 ]. The advantages of this include simulating the nonlinear contact and friction characteristics between adjacent layers and calculating the structural response characteristics of the unbonded flexible risers under the action of complex coupling loads.…”

Section: Development Of Cross-sectional Properties Of An Unbonded Fle...mentioning

confidence: 99%

Review of the Development of an Unbonded Flexible Riser: New Material, Types of Layers, and Cross-Sectional Mechanical Properties

Liu,

Qu,

Chen

et al. 2024

Materials

View full text Add to dashboard Cite

Unbonded flexible risers consist of several helical and cylindrical layers, which can undergo large bending deformation and can be installed in different configurations to adapt to harsh marine environments; thus, they can be applied to transport oil and gas resources from ultra-deep waters (UDW). Due to their special geometric characteristics, they can ensure sufficient axial tensile stiffness while having small bending stiffness, which can undergo large deflection bending deformation. In recent years, the development of unbonded flexible risers has been moving in an intelligent, integrated direction. This paper presents a review of unbonded flexible risers. Firstly, the form and properties of each interlayer of an unbonded flexible riser are introduced, as well as the corresponding performance and configuration characteristics. In recent years, the development of unbonded flexible risers has been evolving, and the development of machine learning on unbonded flexible risers is discussed. Finally, with emphasis on exploring the design characteristics and working principles, three new types of unbonded flexible risers, an integrated production bundle, an unbonded flexible riser with an anti-H2S layer, and an unbonded flexible riser with a composite armor layer, are presented. The research results show that: (1) the analytical methods of cross-sectional properties of unbonded flexible risers are solved based on ideal assumptions, and the computational accuracy needs to be improved. (2) Numerical methods have evolved from equivalent simplified models to models that account for detailed geometric properties. (3) Compared with ordinary steel risers, the unbonded flexible riser is more suitable for deep-sea resource development, and the structure of each layer can be designed according to the requirements of the actual environment.

show abstract

Section: Development Of Cross-sectional Properties Of An Unbonded Fle...mentioning

confidence: 99%

Review of the Development of an Unbonded Flexible Riser: New Material, Types of Layers, and Cross-Sectional Mechanical Properties

Liu,

Qu,

Chen

et al. 2024

Materials

View full text Add to dashboard Cite

show abstract

“…On the contrary, the standard solving algorithm has a higher solving efficiency; however, the calculation is not easy to converge while considering the geometric and material nonlinearities as well as the nonlinearities of interlayer and intralayer mutual contact. With the improvement of computer computational performance, more and more scholars began to consider the establishment of numerical models containing the detailed geometric characteristics of unbonded flexible risers [20,[27][28][29][30][31][32][33][34]. Among them, Ren et al [35][36][37] numerically simulated the unbonded flexible riser model using its actual geometry, including the S-type carcass layer and the Z-type pressure armor layer.…”

Section: Tensile Armor Layermentioning

confidence: 99%

Nonlinear Slippage of Tensile Armor Layers of Unbonded Flexible Riser Subjected to Irregular Loads

Liu,

Qu,

Liu

et al. 2024

JMSE

View full text Add to dashboard Cite

The unbonded flexible riser has been increasingly applied in the ocean engineering industry to transport oil and gas resources from the seabed to offshore platforms. The slippage of helical layers, especially the tensile armor layers of unbonded flexible risers, contribute to the nonlinear hysteresis phenomenon, which is a research hotspot and difficulty. In this paper, on the basis of a typical eight-layer unbonded flexible riser model, the nonlinear slippage of a tensile armor layer and the corresponding nonlinear behavior of an unbonded flexible riser subjected to irregular external loads are studied by numerical modeling with detailed cross-sectional properties of the helical layers, and are verified through a theoretical method considering the coupled effect of the external loads on the unbonded flexible riser. Firstly, the balance equation of each layer considering the effect of external loads is established based on functional principles, and the overall theoretical model of the unbonded flexible riser is set up in consideration of the contact between adjacent layers. Secondly, the numerical modeling of each separate layer within the unbonded flexible riser, including the actual geometry of the carcass and pressure armor layer, is established, and solid elements are applied to all the interlayers, thus simulating the nonlinear contact and friction between and within interlayers. Finally, after verification through test data, the behavior of the unbonded flexible riser under the cyclic axial force, torsion, bending moment, and irregular external and internal pressure is studied. The results show that the tensile armor layer can slip under irregular loads. Additionally, some suggestions related to the analysis of unbonded flexible risers under irregular loads are drawn in the end.

show abstract

“…Their model incorporated nonlinear periodic boundary conditions for both axisymmetric and constant curvature bending loads. Lu et al [29,30] derived alternative analytical and finite element models of unbonded flexible pipes under various loading conditions, focusing on the thermal loads and expansion coefficients. Fang et al [31] implemented the RUC-based finite element model in the Abaqus simulation package to efficiently predict the bending behaviors of submarine power cables, demonstrating the model's robustness and computational efficiency for studying cables under bending conditions.…”

Section: Introductionmentioning

confidence: 99%

Reference Power Cable Models for Floating Offshore Wind Applications

Janocha,

Ong,

Lee

et al. 2024

Sustainability

View full text Add to dashboard Cite

The present study aims to address the knowledge gaps in dynamic power cable designs suitable for large floating wind turbines and to develop three baseline power cable designs. The study includes a detailed database of structural and mechanical properties for three reference cable models rated at 33 kV, 66 kV, and 132 kV to be readily used in global dynamic response simulations. Structural properties are obtained from finite element method (FEM) models of respective cable cross-sections built in UFLEX v2.8.9—a non-linear stress analysis program. Extensive mesh sensitivity studies are performed to ensure the accuracy of the predicted structural properties. The cable’s structural design is investigated using global response simulations of an OC3 5MW reference wind turbine coupled with the dynamic power cable in a lazy wave configuration. The feasibility of the present reference cable in floating offshore wind applications is assessed through a simplified analysis of cable fatigue life and structural integrity analysis of the cable in extreme environmental conditions. The analysis results suggest that the dynamic power cable does not significantly affect the response characteristics of the floating wind turbine in the analyzed lazy wave configuration. Furthermore, a simplified fatigue analysis demonstrates that the proposed cable design can sustain representative environmental loading scenarios and shows favorable dynamic performance in a lazy wave configuration.

show abstract

Alternative analytical and finite element models for unbonded flexible pipes under axisymmetric loads

Cited by 13 publications

References 20 publications

Review of the Development of an Unbonded Flexible Riser: New Material, Types of Layers, and Cross-Sectional Mechanical Properties

Review of the Development of an Unbonded Flexible Riser: New Material, Types of Layers, and Cross-Sectional Mechanical Properties

Nonlinear Slippage of Tensile Armor Layers of Unbonded Flexible Riser Subjected to Irregular Loads

Reference Power Cable Models for Floating Offshore Wind Applications

Contact Info

Product

Resources

About