Vessel – Fender Dynamic Interaction  JIER Marine Fenders

Vessel – Fender Dynamic Interaction

 

Vessel – Fender Dynamic Interaction

In order to achieve more appropriately designed marine fender Systems, an understanding of the vessel-fender dynamic interaction is essential. The dynamic analysis can describe more accurately the fender’s energy absorption characteristics and operational Performance requirements.

There are several approaches which consider the total energy of a berthing ship to be absorbed by the fender/pier system in addition to the magnitude of the fender reaction force generated. A simple and commonly used approach is the energy method; Accurate predictions using this method involve knowledge of hydrodynamic coefficients and system stiffnesses for the total system. Empirical values are commonly used in this method. System damping has been ignored in this approach. Alternate Statistical approaches consider information obtained from model measurements to determine the design energy value of the berthing impact and fender energy absorption; With the design risk selected, the design value of the energy to be absorbed by the fender system can be determined.

The disadvantage of this method is in obtaining the necessary Statistical information for problem Solution. Kim proposes an approximate and simpler method. The idea is based on the use of time average of the kinetic energy of the berthing ship during the time interval of fender compression.

This method is applicable only to the ship in calm water and berthing broadside. The time domain solutions of forces and motions have been developed by van Oortmerssen and Fontijn. Both of these methods use Impulse Response Function techniques. It is easy to adopt different external forces and some other factors in the time domain method. The procedure presented herein is based upon a simplified convolution integral for added mass and damping calculations, which eliminates the disadvantage of the expensive calculation in the above time domain solutions. Although the mathematical problem is formulated herein in sway, yaw, surge and roll motions, only the lateral motion results are presented here. The hydrodynamic coefficients, as functions of frequency, can be determined theoretically using two-dimensional strip theory or three-dimensional source distribution method. In order to verify the current technique with Fontijn’s results, the same hydrodynamic coefficients are used herein.