Influence of Nonlinear Mechanical Contact on Hang-Off Location in Flexible Risers’ Structural Response Available to Purchase

The safe design of flexible pipe on top near its support, in even more challenging deepwater loading conditions, requires more advanced studies to contribute to a better understanding of the influence of nonlinearities on the riser structural response in time-domain numerical computational analysis. The flexible structural non-linear dynamic analysis took into account risers terminated on spider deck passing through I-tube structure which applies lateral movement restriction represented by annulus area of contact elements. Axial movement is free although limited by a minimum slack in the riser guide until the bend stiffener conical interface. This work presents the main outputs of a sensitivity study of the flexible riser dynamic analyses installed in semi-submersibles. Amongst the main benefits of the project are comparisons between a simplified pontoon configuration model x sophisticated spider deck configuration model. The study presents the relevant differences and the level of conservatism inherent to each analyzed configuration models. Critical analysis of the flexible riser response was carried out given critical loading cases and compared among distinct riser specifications in terms of moment and force transmissions from the working point of the bend stiffener to the I-tube support at the bell mouth elevation providing us more realistic interpretation relevant to design reliability of the platform I-tube structure. In addition, the present work aims to study the influence of nonlinearities in the bending moment cumulative distribution and in the damage calculation derived from the dynamic analysis riser response in the top region under extreme far loading conditions.