A Method for the Prediction of Design Space for a Bend Stiffener Cone

Bend stiffeners are commonly used to protect flexible flow-lines and dynamic risers from over-bending, especially in the areas where they interface with fixed or floating structures. Sizing of bend stiffeners and confirmation of their feasibility is an important step in the design of the complete riser system. The objective of this paper is to develop a method for the prediction of the design space for the bend stiffener cone, which is defined in terms of its length and diameter at the base. The analysis method is based on the analytical formulation for an elastic cone consisting of the main pipe and the hollow bend stiffener. A “marching” technique is developed which is based on combining linear solutions for several conical segments. The analysis method requires a small number of segments, and is efficient in dealing with large deflections. It is shown that even a linear solution alone for the bend stiffener cone provides good accuracy for moderate deviation angles. Criteria for setting the design space boundaries for the bend stiffener cone are discussed. The selection of load cases from the tension-angle curve is discussed and its effect on the shape of the design space is demonstrated. The method is illustrated by developing a design space for the bend stiffener of a typical flexible riser connected to the turret of an FPSO.