A series of model tests was carried out in a towing tank, using a horizontally suspended submerged cable to examine snap loading. A description of the experimental set-up together with the procedures adopted to perform these experiments are presented in the paper. Furthermore, the results obtained, from monitoring the dynamic tension variation, are presented in time and frequency domains together with a description of the dynamic behaviour of the cable.
Due to their flexibility, marine cables are widely used for offshore and subsea engineering. In comparison with the research on cables in air, which is almost as old as civilisation (Irvine, 1981), research on marine cables started much later. Probably the first event to attract attention to the problem was the failure of laying the first trans-Atlantic cable in 1857 when among others Lord Kelvin (1857) and Airy (1858) considered its analysis. However, it was only several decades ago that research on marine cables became progressive and systematic as the increasing offshore activities required a good understanding of their statics and dynamics. Due to fluid drag the dynamics of marine cables are quite different from the cable dynamics in air. In air the geometric configuration is the only source of non-linearity, assuming that the strain-tension relation is linear, and most cables respond to applied loads through a combination of stretching and line deformation. The natural frequencies for cable dynamics in air are dominated by the ratio of the elastic stiffness to the catenary stiffness. However, when the cable moves in water, there is another source of non-linearity due to fluid drag, and the cable dynamics becomes more under the influence of the elastic stiffness unless the cable vibrates very slowly, as the drag forces the cable to respond more by stretching and less by line deformation.
