Fatigue analysis of flexible pipes using alternative element types and bend stiffener data
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- Institutt for marin teknikk 
The flexible pipe is a vital part of a floating production system. The lifetime of a flexible riser system is crucial for the Health Safety and Environment (HSE) management. As a result of this, it is very necessary to carry out research on the lifetime of flexible pipe. In this thesis we formalized analysis on flexible pipes, utilizing the finite element analysis software BFLEX 2010, developed by MARINTEK. Chapter 1 describes basic knowledge about flexible pipe and relevant facilities. Chapter 2 gives more information about failure mode of flexible pipe and flexible pipe system. The design criteria and design flow chart is included in this part. Chapter 3 demonstrates the concepts in BFLEX 2010 and its basic principles. For BFLEX 2010, different modeling methods are available for the flexible pipes. In Chapter 4, the basic properties about the flexible pipe which is used in this thesis are introduced. The BFLEX model in this thesis is included in this chapter, too. In Chapter 5, two specified load cases are analyzed by BFLEX 2010 with different bending formulations for tendons. Fatigue damage on tensile armour layers and longitudinal stress in pressure armour is given. The fatigue damage is given in the form of Miner Sum. The comparison between different bending formulations is made. In Chapter 6, Comparison between calculation results and testing data is made. At the same time, correlation study about fatigue damage on tensile armour layer is finished. This thesis focuses on the effect of gap between flexible pipe and bending stiffener, and the influence of the E-modulus of bending stiffener.