Wave control fuction and friction damping of a pile-supported floating body

J. Ocean Eng. Technol. 1997;11(1):65-73.

School of Ocean Eng Pukyong National Univ.

말뚝계류식 부유체의 파랑제어 기능과 마찰감에 관한 연구

김헌태

Keywords: Pile-Supported Floating Body, Floating Structure, Offshore Structure, Friction Damping, Coulomb Friction, Equivalent Damping Coefficient

핵심용어: 말뚝계류식 부유체, 부유식 구조물, 해양구조물, 마찰감쇠, 쿨롬마찰, 등가감쇄함수

Abstract

The floating body discussed in this study is a 2-D rectangular floating unit supported by four vertical piles at its corners. Structures of this type are frequently seen as floating piers for the crafts in a small harbour. The movement in some modes of motion of such a flating body is fully or partially restrincted by the piles. The authors(Kim et al. 1994) carried out a series of model tests on its wave control function, its motion and the loads on piles. The experimental results showed that a certain degree of intial constriction force which clamps the floating unit in the horizontal direction can effectively reduce the body motion and wave energy without increasing mooring forces. This may be due to the friction forces occuring between the piles and the rollers installed in the mooring equipments on the floating unit. In this paper, we develop a numerical model for the prediction of wave transformation and floating body motions, where the friction force is idealized as the Coulomb friction and linearized into a damping force using the equivalent damping cofficient. This linearization is verified by comparing the results of motions between the linear and nonlinear analysis of the ezuations of motion. We further compare the caculation results by the linear model with the experimental results and discuss the effect of the friction force or the constriction force on body motions and wave energy dissipation.