Study On Force Analysis Of Ship Launching By Pontoon

Ship launching is a technical process to put the ship from the slipway into water after ship construction. It is an important process under the ship construction. As the development of ship industry ,the increase in tonnage of ships and the accident between shipway and ship bottom during the ship launching at home and abroad, the safety of large ships during ship launching has been paid more attention in shipbuilding community. Now a lot of methods of ship launching have been used in the shipyard. For example, Ship longitudinal gravity launching,Ship dock launching,Ship floating dock launching,ship sideways launching,ship end air cell launching,ship launching by pontoon and etc. Ship launching by pontoon which has better security and secrecy is a new ship launch technics among them. Compared with the research of ship longitudinal gravity launching in common used by the shipyard, the analytical research of ship launching by pontoon is relatively laggard.According to the feature of ship launching by pontoon and analysis of two important launching ways, this thesis carries out two simplified elastic foundation coupled beams models to simulate the ship carrying system on the slipway and the ship carrying system on the pontoon. The first model of the ship carrying system on the slipway can predict the distribution of ship-hull's overall longitudinal force and deformation and calculate the strength of carrying system. The second model of ship carrying system on the pontoon can predict the distribution of pontoon's overall longitudinal bending moment, shearing force and launching block's reaction force in longitudinal direction. It also can calculate the longitudinal strength of ship hull.For the two models in this paper listed above, Ship launching with 76000DWT bulk carrier created by Liang Nan Shipyard has been analyzed with nonlinear FEM by MSC/NASTRAN. The design department has used the result of calculation and optimization scheme for the ship into the launching process in this thesis. The result shows that the launching of the 76000 bulk carrier with ship-carrying system is safe and reliable.Furthermore, because of the complex force features during the ship carrying, the paper carries out a simplified elastic foundation coupled beams model to simulate this certain state. Considering the counter-deformation between the ship beam and supporting longitudinal beams. Using the virtual work principle, the paper utilize the deformed energy V and force field U of the system, and obtain the deflection curve y1 of ship hulls girders and deflection curve y2 of supporting longitudinal girders by variational evaluation methods. According to the structural mechanics theory, it can predict the reaction force between ship hulls girders and supporting longitudinal girders, and capacity of the dolly. I have developed a calculation and analysis software. The example's calculation results of is more consistent with the result of non-linear finite element method to calculate. So, it is feasible and convenient for us to analyze the force which act on the ship-hull during ship carrying by energy mothed and provide technical analysis data.