Yong Bai - Deepwater Flexible Risers and Pipelines

In this chapter, an easy theoretical method for estimating the tensile stiffness of the unbonded flexible pipe is verified by numerical simulations. Secant modulus is employed in order to carry out the plastic behavior of the material, and this theoretical model is suitable for high loading conditions, which can provide relatively accurate tensile strength for pipeline engineers. The following conclusions could be drawn.

When considering both pressure and tensile armor layers in the pipe’s profile, the external pressure will not have very big impact on its tensile capacity as the radial stiffness of the pressure armor are large enough to resist the radial deformation induced by external pressure.

MSFP is only suitable for shallow water application. Adding a certain profile of pressure armor into MSFP leads to a significant increase in terms of resistance capacity (about eight times). In order to avoid material waste, the profile of the pressure armor could be adjusted according to the water depth, and this can make MSFP exploitable for deeper water depth.

Tangent modulus should be used for next works in order to obtain more accurate results. The contribution of the interlocked carcass should also be taken into account in future works, to verify whether its radial stiffness leads to a remarkable increasing tensile capacity of the pipe.

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