Study on the Towline Tension During the Towing Operation : 1st Report : Behavior in Still Water

Abstract

According to the statistics of the accidents concerning the marine structures, the number of the accidents during the transportation on the sea is the most. It reaches as high as 54.4% out of the total number of accidents. It has been reported that the drift of the marine structures due to the breakage of the tow line covers 13.6% out of this kind of towing accidents. The establishment of the technical standard on the towing operation as a guide principle has been considered to be very difficult, because a great variety of the marine structures and ships have been involved in the towing operation. Therefore, the evaluation of the safety during the towing operation is quite important. The impulsive tension on the towline during the unstable motion can be an important factor leading to the accidents of the towline breakage in the course of towing of the 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 the marine structure such as 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.