Comparative Assessment of Ro-Ro Damage Survivability. Limiting Hs in the derived results represents the maximum sea state the damaged vessel can survive repeatedly. The norm that has been adopted in presenting the results of numerical simulations is to provide a capsize region rather than a capsize boundary to correctly reflect the fact that, because of the random nature of all the parameters determining a capsize event, a single boundary curve does not exist. A limiting Hs in the SA calculations is the maximum value of the significant wave height (and hence height of water on deck) in which the vessel fails any one of the relevant criteria. A close observation of Figures 7 to 10 combined with a careful study of Tables A1 to A3 of Appendix A leads to the following noteworthy points: • The agreement between physical model tests and numerical tests is very impressive. With larger ships, in particular, the results between the two are identical. With the smaller size vessels, floodwater sloshing is more pronounced and so should be the damping effect on roll motion. Research to quantify the latter is currently under way. • In general, ships that satisfy SOLAS ’90 criteria “pass” the numerical/physical model tests and by implication will be deemed to be safe according to the “Equivalence” route. This is true for all the ships considered in this sample. There are exceptions, of course, and it has to be appreciated and understood that prescriptive criteria could not possibly represent reality meaningfully in all cases. This result is very encouraging, considering that SOLAS ’90 has been adopted as the new global standard for all existing ferries. It is also somewhat surprising to see that the previously adopted conjecture that vessels constructed to meet SOLAS ’90 standards were capable of avoiding rapid capsize after damage in moderate sea states with a significant wave height of only 1.5 m was a drastic underestimate. Results of ships meeting SOLAS ’90 standards appear to be capable of surviving, on the average, sea states above 3m Hs. In this respect, SOLAS ’90 provides the right platform for future developments. • The critical parameter in achieving compliance with SOLAS ’90 is usually GZmax. • The Stockholm Agreement standard is in general more difficult to satisfy than the numerical/physical model tests specified by the “Equivalence” route. The reason for this derives directly from the fact that the height of water on the vehicle deck postulated by this standard is unrealistic. Its derivation was influenced lar...
Comparative Assessment of Ro-Ro Damage Survivability. [Worst SOLAS Damage] HSEXP HSSIM HSSTO Hs [m] 0 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 SHIPS Figure 8: Comparative Assessment of Ro-Ro Damage Survivability [Midship Damage] HSEXP HSSIM HSSTO Hs [m] 1 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 SHIPS Stockholm Agreement – Past Present & Future (Part I) Page 17 Figure 9a: Worst SOLAS Damage HSPB HSSTO Linear (HSPB) Linear (HSSTO) Hs [m] 2 0 0.05 0.1 0.15 0.2 GZmax [m] 0.25 0.3 Figure 9b: Midship Damage HSPB HSSTO Linear (HSPB) Linear (HSSTO) 5.5 4.5 4 Hs [m] 3.5 1.5 1 0.05 0.15 0.25 0.35 0.45 GZmax [m] 0.55 0.65 Stockholm Agreement – Past Present & Future (Part I) Page 18 Figure 10: Comparison between Stockholm Agreement and Perfomrnace-Based Standards
