Abstract: A compliant offshore structure in which stabilization against excessive sway is provided by a resilient pile assemblies. A series of drive piles extend into the ocean floor beneath the base of the structure. Drive piles extend upward to a position proximate a pile attachment location on the structure a spaced distance above the ocean floor. The upper end of each drive pile is secured to the structure at the pile attachment location by a resilient coupling. The resilient coupling permits the structure to move upward and downward a slight distance relative to the substantially rigid drive pile. This accommodates sway of the structure. The resilient coupling biases the structure back to a vertical orientation in response to sway of the structure. In a preferred embodiment the pile attachment location is situated proximate the base of the offshore structure.

Abstract: A complaint offshore platform in which the primary restoring force to lateral displacement is established by flex piles driven into the seafloor and fixedly secured to the platform legs a preselected distance above the seafloor. The platform includes a substantially rigid space-frame structure extending from the ocean bottom to a position above the ocean surface. A drilling and production deck is secured atop the space-frame structure. Shear piles extend through the base of the space-frame structure to prevent lateral displacement of the base while permitting the space-frame structure to pivot about its base. As the platform sways about its base in response to environmental forces, the flex piles establish a vertical couple at the location at which they are attached to the space frame structure. This couple resists movement of the platform away from a vertical orientation. In the preferred embodiment, the flex piles are secured to the platform at or near one-half the total height of the space-frame structure.