Keywords: structure analysis, finite element, loading condition optimization, simulation.

The floating dock in this paper is used to transport hull sections built in a shipyard from one bank to another. Airbags are used to move the ship section on to the dock, step by step. During this course, by adjusting the dock's ballast tanks' water in real time according to the length of the hull section on the dock, the dock's floating condition can be controlled so that the hull section can be moved smoothly and safely onto the dock. But it is difficult to undertake the structural analysis for a floating dock in real-time as a result of the complex interaction between the hull section and the dock, as well as some other factors, for example the tide. Usually we can do this for some selected positions with static FE analyses. However this is not complete or in real-time which makes the calculation results inaccurate so that the floating dock designed in this way may not satisfy the safety requirements. Therefore, the simulation method to study the floating dock's transporting progress is of practically significance.

The floating dock is designed as a eudipleural structure, which is mainly composed of three parts: the main body under the deck (ballast tanks), the operations control room above the deck, and the winch room located in the after part of the dock. The dock's ballast system includes 27 eudipleural ballast tanks. The adjusting water is controlled by the water control valves of the ballast water system located in the operations control room.

The simulation calculation has two crucial questions to answer. One is how to obtain the real-time adjusting results of every ballast tank of the dock in real-time. The other is the FE simulation to calculate the floating dock for every time step during the working process. In this paper, water adjustment of every ballast tank of the dock is calculated in real-time by applying "Powell" and "SUMT" optimization methods [1]. Then a frame structure of the floating dock working process is constructed with a parameterized design language (APDL) command flow method [2] in the ANSYS environment and a total of 31 loading steps are applied to the whole process of simulating the dock. Finally the FE structure model's strain and stress state under every loading step and the structure's analysis results for any required node of the dock related to the time course can be made out.

This paper presents a study of working process simulation for a floating dock based on real-time floating condition optimization calculations and a FE analysis. In this way, the floating dock's working properties of both stress and strain during the working process can be predicted and controlled. This improves the dock's design and ensures that the dock can be operated more safely according to the simulation results. Meanwhile, it proves that FE simulation for complicated large-scale engineering structures is feasible and practical.

1

H.W. Tang and X.Zh. Qin, 2001. Practical Optimization Methods, Dalian University of Technology Press, Dalian, 144-145, 156-158. (in Chinese)

2

Bo Yi Inditing Room, 2004. APDL Parametric Finite Element Analysis Technique and Applied Instances, Press of Water Resources and Electric Power, Beijing. (in Chinese)

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