Flexible Riser Bending Hysteresis Influence on Bend Stiffener Response

The bending stiffness response is an important parameter in the lifetime assessment of unbounded flexible risers. Its behavior is governed by interlayer friction mechanisms leading to a non-linear moment x curvature relationship that is highly dependent on the internal pressure. In order to investigate its influence on the critical bend stiffener hang-off region response, a detailed finite element analysis is carried out using a specialized tool for a short segment length of a selected 2.5″ ID riser cross section. Different internal pressures are numerically analyzed and the resulting local hysteretic bending response is then adjusted and directly incorporated into a global dynamic analysis tool that uses an equivalent elasto-plastic formulation with a hardening parameter that controls the behavior of the slippage mechanism. A fully coupled irregular wave dynamic analysis is then carried out and the flexible riser curvature distribution response in the bend stiffener region compared for different bending hysteresis models adopted.