engleski

Accounting for the nonlinearities of tank supports in structural assessment of the vessels equipped with independent tanks

Many vessels nowadays are equipped with independent tanks either for the purpose of LNG/LPG transportation or for the use of LNG/LPG as a fuel. The particularity of the independent tanks is that they are not rigidly connected to the hull structure but are supported by an important number of dedicated supports. During the operations, and depending on the wave conditions, these supports can temporarily loose contact or the tank can slide over them. These effects have an important influence on the structural response, especially close to the contact region, and need to be accounted for consistently in the structural analysis. The problem of contact is fundamentally nonlinear and cannot be treated using a linear structural solver. Commercial software (Nastran, Abaqus …) provide a general solution to contact problems, but the computational time becomes prohibitive for practical applications of long simulations in waves. The method developed in the present work uses a set of pre-calculated linear responses and combines them in an iterative procedure in order to assess the nonlinearities of the contacts behavior. The method is validated by comparisons with the expensive Nastran simulations and it is shown that the CPU time is incomparably lower for the same accuracy. In addition the new method appears to be much more stable than the one implemented in Nastran. The efficiency of the proposed procedure is first validated on simplified cases and is finally applied to the practical case of real vessel.

Independent tanks ; Contact problem ; Hydro-structure interactions

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