Numerical simulation of double bottom structures under stranding

Abstract

This thesis compares the resistance with damage of various types of double bottom structures in a stranding event. The four double bottom structures from (Naar, Kujala et al. 2002) are used as analysis model. Explicit finite element program, ABAQUS/Explicit is used to carry out the simulation. The material failure is modeled using forming limit diagram. The structure is penetrated by a conical indenter with a rounded tip. The indenter is forced laterally into the structures at different positions. The purpose is to compare penetration with fracture, resistance force, energy absorption, deformation and collapse mode for the different structures. Those four structures are: a conventional double bottom, a structure where outer shell is stiffened with hat-profiles, a structure where sandwich panel is used as outer shell and a structure stiffened exclusively with hat-profiles. The result shows that the use of forming limit diagram damage criterion produces likely similar rupture initiation points between (Naar, Kujala et al. 2002). This suggests that the technique is possible for material damage modeling in a standing event. In addition, the use of hat-profiles is found to be useful for increasing the passive safety of ship in stranding event.