Effects of Highly Ductile Steel on the Crashworthiness of Hull Structures in Ship to Ship Collision

Abstract

In order to preliminary investigate effect of HDS (Highly Ductile Steel) on the crashworthiness of struck ship, a series of large scale 3-dimensional ship-ship collision analysis are carried out using the non-linear finite element code LS-DYNA. A very large crude oil carrier (VLCC) is assumed to collide with midship region of another double hull (D/H) VLCC in right angle (90 deg.). Two collision points for the struck VLCC are assumed. One is between Swash Bulkhead (S.BHD) and Oil Tight Bulkhead (OT.BHD), the other is just on S.BHD. Damage extent and total absorbed energy until oil cargo tank ruptures in the case of HDS are compared with those in the case of conventional material. Critical colliding speed (VB,cr) is also compared. Effects of HDS on absorbed energy and VB,cr are discussed in detail. It can be found energy absorption by inner shell (IS) rupture with using HDS is about 2–3 times larger than that with using conventional It is also estimated that IS rupture does not take place when a striking ship collides in less than 8kt in the case of using HDS although a critical striking velocity in the case of conventional bow is about 4–5kt.

An analytical method to assess the structural responses of ship side structures by raked bow under oblique collision scenarios

“…where, L is the height of the deformed side plating, 1 L is the length of the left side of the deformed side plating, 2 L is the length of the right side of the deformed side plating, line DC represents the displacement of the striking ship,  is the collision angle between the striking ship and the struck ship, 1  is the instantaneous rotation angle of the left side in the longitudinal direction, 2…”

“…In addition, some new design methods for improving ship safety have also been proposed, such as the accidental limit state (ALS) design method. According to statistical data, the striking angles of ship collisions are normally distributed 1 and oblique collision scenarios are more frequent. A ship collision is a dynamic nonlinear process, and a large amount of kinetic energy is absorbed by the hull structure within a short period of time, which may cause the hull structure to exceed the elastic deformation and to enter into the plastic deformation, or possibly tear and rupture.…”