STUDY ON THE TOWLINE TENSION DURING THE TOWING OPERATION - 1ST REPORT: BEHAVIOUR IN STILL WATER

According to the statistics of accidents concerning marine structures, 54.4% occur during transportation by sea. It has been reported that the drift of marine structures due to the breakage of the tow line is 13.6%. Establishment of a technical standard for towing operations has been considered to be very difficult, because a great variety of marine structures and ships have been involved in the towing operation. Therefore, the evaluation of safety during the towing operation is important. The impulsive tension on the towline during the unstable motion can be an important factor leading to towline breakage in the course of towing of marine structures. The towline tension during the unstable motion in still water is discussed in this paper as a first step to investigate the towline tension in the case of general single towing, using two representative models of a marine structure such as a barge and semi-submersible. The hydrodynamic force on the towline due to the current and the deformation of the towline have also been investigated both theoretically using the Imaginary Reaction Method and experimentally.