IDENTIFICATION OF MODAL PROPERTIES ON LARGE-FLOATING OFFSHORE STRUCTURE MODELS

Abstract

This paper is concerned with experimental modal analysis to estimate the dynamic properties of unit-linked large floating structure models. Floating structure models are consisted of eighth units. Every unit is linked by flat springs. A floating model is anchored by spring-wires on base edges of each unit The vibration tests were carried out by using the impact hummer test and the sweep harmonic excitation method. The vertical acceleration response are measured on upper surfaces of the models by arranging accelerometers on each unit The transfer functions defined by normalized input and output data are analyzed by means of a multi-channel modal analysis software. The modal properties such as natural frequencies and natural modes were estimated by using the curve fitting of frequency response functions. These experimental results were compared with theoretical values obtained by using a two dimentional lumped-mass model with the aid of BEM to consider the fluid-structure interaction.