Calculation of the Hydrostatic and Structural Integrity of Docking Sequences

Abstract

The conditions of competition within ship yards are changing. The current market situation requires a new orientation of the Pella Sietas ship yard with flexible solutions for new ship types. Complex, heavy and ice-going ships show one way for future designs. In view of all the technical difficulties involved in such challenging projects, the first question must be how to handle these heavy constructions with the yards building facilities available. The Pella Sietas yard is using a floating platform for newbuildings. The question arises whether or not this platform is still capable and suited for this kind of ship types. The docking procedure is a complex multi-body interaction that copes with hydrostatic and structural challenges. The docking operation is regulated by the sequence of flooding and emptying ballast water tanks of the dock. At any time of this dynamic operation the hydrostatic stable equilibrium of ship and dock must be ensured. When the ship becomes afloat the keel block system transfers the ships weight on the structure of the dock. It must be ensured that the resulting tensions and deformations do not exceed the maximum permissible values. This paper describes a fast calculation method that determines the mentioned hydrostatic as well as the structural investigations during the docking procedures. The method implies a numerical progressive flooding simulation that calculates the hydrostatics of ship and dock under consideration of their interaction by dock blocks together with the ballasting sequence in the time domain. Furthermore it calculates the block forces distribution by applying the deformation method. In the calculation process ship and dock are modeled as Timoshenko beams and the dock blocks as non-linear spring elements. Moreover the shear force and bending moment distributions of ship and dock are calculated and the deflection lines are presented. Therefore, the described method enables the ship yard to evaluate quickly the possibility of building new types of ships on the existing building platform and allows evaluating which modifications are useful to enlarge the capacity of the platform even further. It provides a useful tool to minimize local and global stresses and deformations of the interacting bodies during the whole docking procedure by fast optimization of the block system arrangement and the ballasting sequences. As a result the described method could expand the range of flexibility of a given floating dock structure. In addition, the whole hydrostatic and structural integrity of docking sequences can be computed faster and more accurate even at a very early project stage.