Slack phenomena in tethers of submerged floating tunnels under hydrodynamic loads

The tethers of submerged floating tunnels (SFT) might undergo slack in some serve sea states. It is one of the possible hazard conditions SFT confronted. This paper investigates the slack phenomena in SFT tethers under hydrodynamic loads. A bilinear stiffness model is used to simulate SFT tethers. Results show that the tether will go slack under a large wave height and snap force happens. The occurrence of the current makes the tethers downstream prone to slack. Then a procedure for preliminary slack prediction is introduced. Slack criterion and an analytical solution of SFT pre-slacking response is derived for the prediction. The procedure provides a practical method for selection of the design values of SFT structure configurations.