Research On Security Assessment System Of Pontoon During Ship Launching Based On NAPA

There are many ship launching methods, it can be divided into three types: berth launching, dock launching and pontoon launching according to launching facility,.The force of pontoon from launching ship is transmitted by blocks. launching ship, blocks, pontoon and sea water consist of a mutual constraint system.if the reaction force of one block is too great, it's easy the deformation of this region is beyond limits, the safety of pontoon structure is in risk, whether the process of pontoon during ship launching is safe must through a series of calculation could we known.The calculation of blocks'reaction force is a key link in the pontoon system calculation. There are a great many traditional calculation methods, but more or less exist there lilitations, difficult to guarantee accuracy.Through comprehensively analyze the entire pontoon system, consider the effects of all factors such as the launching ship is uncertain, the block's layout scheme is uncertain, etc..Simplify the whole system as one-dimension theoretical computational model, simulate launching ship as non-uniform beam,blocks as uniaxial compression spring and pontoon as uniform beam, use ship design software NAPA as platform, exploit a set of integral block's reaction force and floating condition parametric calculating program with NAPA BASIC language, achieve parametric calculation of block's reaction force and floating condition. Mainly consist of: 1) element fixed-end shearing force and bending moment calculation module; 2) known conditions input module; 3) assembled stiffness matrix formation module; 4) Elastic support disposal module; 5) Gaussian elimination method solution module; 6) deflection calculation module of launching ship and pontoon; 7) blocks'reaction force calculation module; 8) floating condition and stability calculation module; 9) output module. Then establish pontoon parametric geometric model considering deflection, load the reaction force, make full use of the inner functional module to conduct pontoon hydrostatics calculation, to form shearing force and bending moment curve quickly etc..At the same time, use one bulk carrier as case verification, then refer to the mandatory rule of the people's Republic of China, compare the main date in the calculating result with standard requirement, check whether meet requirement, there by test whether the entire pontoon system is safe and reliable, establish a set of integral safety assessment system of pontoon during ship launching.