The effect of sea conditions on the connecting forces in a pusher-barge system

The popularity of using pusher-barge systems is growing all the time world-wide. At the same time the size of systems is getting larger and transport routes have been changed from sheltered waters to oceans. The main purpose of the present study is to describe the phenomenon of two floating bodies connected together at sea. Particularly the forces acting in the connection are concerned. The connection, a transversal shaft between the bodies, allows the relative motion in one degree of freedom. This paper describes an experimental study on sea loading of a coupling in pusher-barge systems. A series of model tests with barge and pusher models were carried out in the tank of Maritime Research Institute of Finland. The models were connected with a transversal shaft. The shaft was equipped load sensors and the three-dimensional forces of the connection were measured. The absolute motions of the barge and the relative motion between the pusher and the barge were measured, too. The influences of the barge size and wave direction on sea load were investigated. Also the irregular wave height was varied from moderate to extreme conditions. Finally, by means of the model results a short-term response predictions were made and the most probable extreme values of forces were derived.