Physical model tests on a very large floating breakwater

A new concept of floating breakwater (FB) is experimentally and numerically investigated, specifically a very large structure, made in ferrocement, designed to resist to severe wave conditions. Compared to traditional FBs, the new concept of structure has much larger geometrical dimensions (of order 10 times). The mooring system is a critical issue and, in general, a different design is necessary. Two types of spread moorings and a tethered one are analyzed and compared, with the aim of giving precious information to the designer. Results are relative to: (i) the structure efficiency in attenuating the incident waves, that is excellent for waves of period up to 10 s; (ii) the maximum and average loads along the mooring lines and on the anchor (investigated for waves of height up to 6 m). It was found that the mooring has a strong influence on the structure efficiency, and the effects of the different rigidity and compliancy of the analyzed mooring systems are discussed, with reference to snapping events, proposing possible measures to reduce the mooring loads under extreme wave conditions.