5. Use of the developed R–D diagrams
The R–D diagrams and corresponding R–D formulations developed here can be used as a first estimate of the residual ultimate longitudinal strength performance of container ships immediately after a grounding accident has occurred when the location and amount of grounding damage is approximately known. The R–D diagrams can also be used to determine the acceptance criteria for grounding strength performance. For example, IMO (2000) specifies requirements that the ultimate longitudinal strength of all newly built ships be no smaller than 90% of the strength performance.
Fig. 10 presents a graphic expression of the determination of residual ultimate longitudinal strength based on the GDI value according to the IMO guideline (90% of the original ultimate moment capacity). Table 3 shows the GDI upper limit for each of the four container ships based on obtained R–D diagrams as illustrated in Table 2. For example, the grounding damage amount of a 13,000TEU container ship should not exceed a GDI value of 0.3650 in hogging conditions.