Analysis of accidental iceberg impacts with membrane tank LNG carriers

Abstract

The probability of ship-iceberg impacts are increasing due to increasing production and due to more transportation routes near arctic areas. The first part of this thesis is an introduction to Liquefied Natural Gas (LNG) and the LNG carriers, particularly LNG carriers with membrane type cargo containment system.

Some theory regarding the principles of Non Linear Finite Element Analysis (NLFEA) and ship-iceberg collision is briefly described.

A detailed finite element model of the cargo tank is created. For Finite Element Modelling MSC Patran is used. Choice of element and element size is described. Boundary conditions are introduced to compensate for the non-analysed part of the structure. Two different iceberg models are included and the explicit NLFEA solver LS-DYNA is used for the integrated analysis. Seven different collision points are checked for the two different iceberg models.

Deformation of the inner hull is explored and checked against design criteria. Figures and graphs are included to illustrate this. Accelerations, velocity and deflection is found for some critical nodes in inner and outer hull and checked for critical values.