Research On Structural Strength Calculation Method Of Large-scale Transport Ship Subjected To Underwater Explosion

In the construction of the current international naval warships, some large-scale transportships such as rescue ship, replenishment ship, etc are not designed for fighting, but for playingthe key role of guaranteeing the endurance ability and vitality of naval vessels formation onthe sea, and it will be an important part of the future naval equipment construction. Becauseof the main task for these kind of large ship which designing purpose for cargo transportationis supply security, its structure is similar to civilian vessels which structure is generally thedouble shell, and can be said to be " structure strength enhanced" large oil tanker. However, asa member of warship formation, though the large-scale transport’s task characteristic is notdirectly involved in combat, in order to meet the mission requirements, designers shouldconsider certain antiknock intensity for this ship.In view of the particularity of the large transportation ships which is main fortransportation and recharge, the calculation method of longitudinal strength, local strength andresidual strength of large transportation ships under underwater non-contact, near-fieldnon-contact and contact explosion load have been analyzed and summarized based onunderwater explosion shock loading conditions in this paper. The paper aimed at designing aset of strength calculation method that is systematic and standard in this kind of ships’underwater antiknock structures’ design. Thus, in this paper the main works are as follows：Firstly, the destroy characteristics of three kinds’ of underwater explosion load have beensummarized, and the quantized determining criterion which is used to distinguish the threeunderwater explosion load have been put forward. The set method of working condition inthe three underwater explosion have been established, which purpose is that the calculationmodel and loading method are matched the real physical shock condition.Then, based on the section’s characteristics of the large transportation ships, by thetheory of limited strain laminates section, the mathematic method of underwater explosionimpact dynamic bending moment have been established, and the method of sectioncompensation in the plastic stage have been put forward. The calculation method oflongitudinal strength considering the underwater explosion impact dynamic bending momentand section compensation is raised, based on the structures and tasks’ characteristics of the large transportation ships and methods of ultimate strength in Lloyd’sThirdly, the periodic formulae and load form of the interaction between jet and wall arederived based on a lot of previous papers. The plastic response calculation method of shipstructures under underwater near-field explosion shock wave and bubbly jet load are derived.The local damage of large transportation ship under near-field explosion load have beensimulated by ABAQUS with secondary loading.The calculation method of local strengthsafety radius have been raised by the logarithm fitting method and with the use of assessmentrule of ship local strength.Furth, the concept of breach radius and damage radius caused by underwater contactexplosion have been put forward. The application scope of the two methods have beendiscussed because of the two estimation method for the two concepts.The response of typical cabin structures in large transportation ship have been simulatedthrough setting the water field and charge state equation based on ALE algorithm inLS-DYNA program. The residuary strength of large transportation ship structures have beenanalyzed with Lloyd’s rule on the calculation method of damage ship’s residuary strength.