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distance between the center of gravity of the struck and striking ships. As collision starts the force
increases until the side shell plate fails. Then force decreases rapidly, then increase again until failure
of inner hull plate. Fig. 4 shows the collision forces of subject VLCC are higher than those of original
VLCC, It reveals higher collision force is needed for new VLCC than the original VLCC.
As shown in Fig. 5, the absorbed energy of subject VLCC is higher than those of original VLCC. That
is, the side structure of subject VLCC absorbs more energy than the original VLCC because softer
structure absorbs more energy in collision.

5w
450 n

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
Penetration (rn)

Figure 4: Collision Force Variation with Penetration Figure 5: Comparison of Absorbed Energy

6 CONCLUSIONS
In this research, it can be found that the longitudinal structural members of the new VLCC have
increased scantlings in comparison with the design of original VLCC. According to the results of 3-D
cargo tank F.E. analyses, the transverse structural members of subject VLCC are reinforced.
By the result of fatigue assessment in longitudinal stiffeners and hopper knuckle connections, it can be
found that the new VLCC has sufficient fatigue life. And it has been found that transverse stress is the
dominant factor to cause the fatigue cracks for hopper knuckle connections.
In this paper, energy absorption capacity, damage mechanism and structural behavior according to the
design modification for VLCC are studied. As the result of the evaluation of collision strength, the
scantlings of both the new and original VLCCs are sufficient to endure the corresponding collision
loads. In other words, the new VLCC as well as original VLCC is “safe” against oil leakage in the
suggested scenario. And it shows the side structure of the new VLCC has a better collision capacity.
Through this research, the newly designed VLCC is found to have enough strength with regard to
yielding criteria, structural stability, fatigue strength and collision capacity.
References

Chang- Hwan Jang, Jae-Hyung Park and Joo-Ho Heo (1999). Comparison of Collision Capacity for
VLCC according to Design Modification. Proceedings of the Annual Autumn Meeting. SNAK,
445-448.
DNV( 1999). Direct Strength Calculations. Rules for Classification of Ships.
DNV( 1998). Fatigue Assessment of Ship Structures. Classification Notes No.30.7.
Jae-Hyung Park, Joo-Ho Heo, Young-Man Lee and Yeong-Soo Bae (1999). A Development of New
VLCC for Productivity. Proceedings ofthe Annual Spring Meeting. SNAK, 435-438.
M. Wagner(1998). Fatigue Strength of Structural Members with In-Plane Notches. IIW.
MSC(1996). DYTRAN User’s Manual Version 3.0.