RMS research interests were often motivated by specific offshore structural concepts. These concepts vary greatly with the properties of the oil/gas field to be developed – most particularly with its water depth. Applications have included oil drilling and production facilities in water depths ranging from 50 meters to more than 2 km. The trend however is ever deeper: exploratory drilling has been performed, from ships, at depths exceeding 3 km. Resulting structural concepts range from familiar rigid piled steel frames ("jackets"), to massive "gravity-based" concrete structures, and more recently to novel, tethered floating structures like TLP's, Spars, and production ships.
Technical challenges for these offshore structures include a number of nonlinear mechanisms. The hydrodynamic forces on these structures are complex nonlinear transformations of the random wave elevation history and current speed. The structure itself may also behave in nonlinear ways, especially under extreme conditions that challenge the safety of the facility. Examples include the restoring forces of the mooring lines under large deformations, and the material and geometric nonlinearities of the jacket braces under severe wave or seismic conditions. The complex fluid-structure interactions of large-body structures in high, nonlinear waves are imperfectly understood and under continuing development; large laboratory tests of proposed designs are common. Our contributions have included procedures for the analysis of model test and, more recently, field data from such structures. These procedures can be used to suggest important combinations of wave and current parameters for use in designing these (expensive) wave tank experiments.