Accession Number : AD0286091

Title :   ANALYSIS OF CRITICAL MOTIONS OF A FLOATING PLATFORM

Descriptive Note : Final rept.

Corporate Author : NAVAL CIVIL ENGINEERING LAB PORT HUENEME CALIF

Personal Author(s) : LEENDERTSE,J.J.

Report Date : 27 AUG 1962

Pagination or Media Count : 33

Abstract : Theoretical calculations and experimental measurements were made to determine the response in heave in the significant frequency range of 3 to 4 seconds of the CUSS 1, an ocean-bottom drilling barge to be used in experimental trials prior to Project MOHOLE. Roll was measured also. Calculations on the basis of a linear response of the barge in heave to a fully developed sea indicated that the amplitude of the response is insignificant at the critical period of 3-1/2 seconds, the caculated natural frequency of the drilling string. A pendulum-type roll pickup was installed on the barge with two heave pickups: One a specially designed horizontally mounted torsionpendulum type sensitive to oscillations in heave of 3 to 4 seconds, and the other a gimbal-mounted conventional accelerometer. The output of both pickups was fed into a specially designed resonance amplifier. Approximately 20 minutes of pertinent barge motion measurements were made during two c uises while the barge drifted. No measurement of water-level variation were made. It was found that in sea , estimated as from 2 to 3 feet in height and with significant periods of 3 to 5 seconds as generated by winds of about 20 knots, the roll of the barge did not exceed three degrees and that its average heave at periods of from 3 to 4 seconds was about 1/4 inch. The spectral density of the heave at a period of 3.4 seconds was about 1/8 inch squared per radians per second. (Author)

Descriptors :   *BARGES, *FLOATS, ANALYSIS, INSTRUMENTATION, MEASUREMENT, MOTION, OCEAN WAVES, ROLL, THEORY

Distribution Statement : APPROVED FOR PUBLIC RELEASE