Work

An empirical methodology for bend stiffener sizing

Year: 2025

Type: article

Abstract: A flexible riser hanging from an offshore platform may experience excessive curvatures at the hang-off zone due to the stiffness discontinuity between the riser and its attachment point. To mitigate this issue, a bend stiffener is typically installed to gradually increase the bending stiffness of the riser's upper section, thereby limiting curvature. Previous studies have modeled the bend stiffener, often with a conical profile, as a cantilever beam. The structural analysis of this beam results in a second-order nonlinear differential equation with variable coefficients. While an explicit analytical solution for this equation is not available, a numerical solution can be obtained using advanced mathematical algorithms, which can be implemented through software tools like Matlab. This paper introduces an empirical procedure for designing a bend stiffener. The riser's hang-off section, including the bend stiffener, is modeled as a cantilever beam. A key assumption is made that at a certain distance from the tip of the bend stiffener, the bending moment of the riser approaches zero. At this ``zero-moment'' point, the axial tension force and rotation angle of the riser are assumed to be known from global dynamic analysis. The procedure begins by determining the length of the riser section between the zero-moment point and the tip of the bend stiffener. With this length known, the shear force, tension force, and bending moment at the tip of the bend stiffener can be calculated based on the equilibrium of the riser section. The second part of the procedure involves estimating the dimensions of the bend stiffener, particularly the length and outer diameter of its conical section. To simply the process and avoid relying on advanced mathematical methods, the bend stiffener is treated as a series of short segments, each modeled as a cantilever beam with a constant cross-section. Starting from the tip of the bend stiffener, the length and outer diameter of each successive segment are estimated iteratively using equilibrium, deformation equations, and material mechanics. The proposed bend stiffener sizing is compared with numerical solutions from previous studies and validated using finite element analysis. This empirical procedure offers a practical tool for the preliminary sizing of bend stiffeners.

Source: Applied Ocean Research

DOI: 10.1016/j.apor.2025.104518

Authors: Rui Zhen, Chen Shi, Xingxian Bao

Institutions: Harbin Institute of Technology, China University of Petroleum, East China

Language: English

Topic: Offshore Engineering and Technologies

Subfield: Ocean Engineering

Field: Engineering

Domain: Physical Sciences

SDG: Industry, innovation and infrastructure

Open Access status: gold

Estimated APC paid: $2,950