A METHOD FOR COMPUTING FLOAT PLATFORM MOTIONS IN WAVES

A new procedure is presented for the prediction of the longitudinal motions, in regular head seas, of ocean platforms supported by slender vertical floats. Experimental information describing the hydrodynamic forces acting on the floats is used to solve the equations of motion for harmonic oscillation in heave, surge, and pitch. These hydrodynamic forces are obtained from tests conducted on a single isolated float. They are expressed as two separable parts, one due to the disturbance imposed by the waves acting as though the vehicle were completely restrained and one due to the motion of the vehicle as though there were no wave disturbance. When the measured motions of a free four-float vehicle are compared with the motions as computed under the new procedure, reasonably good agreement is found. The approach should be useful in design development and in structural load evaluation not only for multifloat vehicles but for other types of marine structures as well.