The Berthing of a Large Tanker to a Jetty

For the design of fenders and dolphins it is essential to have available an adequate method to describe the berthing manoeuvre of a large tanker to a jetty. Such a method should result in a prediction of maximum load in the dolphins, departing from a certain dolphin elasticity and lateral speed of approach of the tanker. The calculation method generally used up till now is based on the assumption that the kinetic energy of the tanker when it touches the fenders has to be absorbed by the fenders. In fact, this approach is based on an equation of motion with a constant added mass coefficient and zero damping. The choice of the added mass coefficient has always been a problem due to a lack of data, especially where the added mass in shallow water is concerned. In this paper, data are presented on the added mass and damping of large tankers in shallow water. These data were obtained from experiments (forced oscillation tests). From these data it appeared that it is not justified to use a constant (time-independent) added mass and damping coefficient. Therefore it is suggested to use the equations of motion according to W.E. Cummings, which employ impulse response functions. Data on these functions are presented for large tankers for different keel clearances, which can be used for practical applications. An example is given how to use the data for the prediction of maximum fender loads and the results of the calculations are compared with measurements, obtained from model tests.

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