STUDY ON THE MOTION RESPONSE TO WAVES OF A BUOYANT TOWER CAPABLE TO VERTICALLY SLIDE

• Published in: PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN Vol. 17; pp. 187 - 192
• Main Authors: SEKITA, Kinji, SUZUKI, Tomoya, NOMOTO, Yukio, TANIGUTI, Naoyuki
• Format: Journal Article
• Language: English
• Published: Japan Society of Civil Engineers 2001
• Subjects: Buoyant tower; dynamic analysis; nonlinear wave damping; wave; wind and current
• ISSN: 0912-7348; 1884-8265
• DOI: 10.2208/prooe.17.187

An articulated buoyant tower developed more than fifteen years ago for offshore oil and gas development has often been used for marine communication tower in Japan. Owing to a set of universal joints at bottom and abuoyant tank attached to intermediate part of the tower, the tower rotates small against rough waves; however it isaffected to the tidal changes, thus the height of a navigation light on the top of the tower from sea surface varies. So we designed the new buoyant tower having a slide beneath the joints, which permits amount of vertical movementso as to keep the height almost constant. Therefore we conducted the time domain analysis for the pitching and heaving motion of the vertical movable tower to the waves, currents and winds. In this study, we intended to make clear the both effect of the nonlinear drag damping which caused by the relative velocity between tower and water particle and the natural periods to the response. The paper describes the nonlinear effects of the damping caused by the wave and current to the response characteristics for the towers installed at the three kinds of water depth, along with the changes of the natural period in accordance with the draft and inclination of the tower.