A photograph of the experimental test-rig is shown in Fig. 1(a). It consists of a 6.2 m 5.2 m 0.4 m floating raft,
constructed by 16 I-shaped steel beams, which are bolted together. It is supported on a flexible hull structure by 18 BE-400
type resilient isolators mounted on 18 steel pillars. The 7 m 6 m 0.7 m flexible hull structure is made from steel plates
which are welded together and supported by 26 pneumatic isolators. The details of the test-rig are given in Table 1.
From modal testing, it was found that there were 25 modes below 150 Hz [17]. A Bruel and Kjaer (B&K) type 3628 shaker,
positioned at the center of the floating raft as shown in Fig. 1(b), was used as a primary vibration source to excite the raft and
simulate a primary uncontrolled vibration source. Note that this is an intermediate stage of experimentation. In the next
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