- Compliant offshore platforms are designed to allow controlled movement of the platform as an alternative to near-rigid resistance to wind, wave and current loading by fixed platform designs. The equations of motion, valid for both single and multi-articulated towers, are derived using a Lagrange equation approach. The resulting equations are then used to study the sensitivity of a tri-articulated tower to select design parameters. A tension-restrained articulated platform (TRAP) proposed by the offshore industry for use in 914 m (3000 ft) of water is used for comparison in the sensitivity studies. Dimensionless parameters are developed and used to identify the roles of several key variables in altering the natral periods of tower vibration in order to avoid regions of significant environmental excitation. 1991.