A Generalized Contact Model for Nonlinear Dynamic Analysis of Floating Offshore Systems

The objective of this work is to present the implementation of a contact model that represents, during a nonlinear dynamic analysis of floating offshore systems, the contact of lines with the platform, as well as the contact involving different lines and, eventually, involving two different platforms in the same model. Traditional contact models consider for instance a generalized scalar element, consisting of two nodes linked by a non-linear gap spring. In this work, the contact model is geometrically defined by volumes that cannot interpenetrate. A penetration stiffness can be defined for each volume; lateral friction can also be considered by this model. An appropriate data structure is used to define the volumes and guarantee the efficiency of the algorithm by an optimized search. The application of the presented contact model is demonstrated by case studies of actual applications for offshore systems: pipelines in S-Lay installation operations, where the contact is complex, specified only in some points of the ramp and stinger; offloading floating hoses that may collide with the hull of the ship, and catlines in lift operations.