Flexible floating anti-collision systems (FFASs) have been proved to be an effective method to prevent the possible collision between the uncontrolled vessels and marine structures. At the same time, the dynamic responses of the system under harsh waves are essential for the design and assessment of the FFAS. In the present study, a wave basin experiment was performed to investigate the wave-induced dynamic responses of a FFAS, which was consisted of five horizontal floating buoys both connecting and mooring with flexible lines. Extensive measurements were carried out to quantify the motion responses of the central and adjacent buoys with different wave heights and wave periods. The results shows that the sway and roll motion are significantly enhanced around the natural periods, which would greatly threaten the offshore and onshore mooring lines. Due to the coupling effect of the motion components, the surge difference between the adjacent buoys also got a peak value around the sway natural period, which directly threaten the block lines.
To reduce the possible collisions between the navigation vessels and the offshore structures, e.g. the sea-crossing bridges, wharf, platform, offshore wind turbines, etc. (Gershunov, 1986; Storheim and Amdahl, 2014; Storheim et al., 2015), different kinds of methods were proposed to protect the vessels and structures (Peterson and Pedersen, 1981; Storheim and Amdahl, 2014). Owing to the existence of specific design considerations, such as complex structure arrangement, poor foundation, deep water condition and significant change of water level, the flexible floating anti-collision system (FFAS) consisting of multiple connecting interchangeable floating units is proven as an effective and favorable method to prevent the possible vessel collisions (Oda and Nagai, 1976). Moreover, the multi-bodies structure has many remarkable advantages, e.g. simple transportation, relocation potential, relatively short duration of installation, flexibility for future extensions and lower construction cost. However, as an independent mooring multiple structures, the reliability of the FFAS under harsh sea conditions should be noticeable in the design and application of the FFAS. Therefore, it is necessary to investigate the motion responses including the motion magnitude and the relative motion of the floating buoys.