The seaway trade market has expanded in the last years and container ship dimensions are constantly increasing for higher cargo capacity. In the early design stage, main dimensions are usually determined based on an existing ship database from which regression formulas are derived. In the present paper, a database of 260 non-sister container ships built from 1979 to 2022, representing 20% of the world fleet, has been considered to derive and compare different types of regressions. Simple regressions have been developed and compared with equivalent formulations available in literature, proving better approximations of the trends. The study has been further extended by multivariable regressions and forest tree algorithms, which allow the use of more than one independent variable and provide a better fitting compared to simple regressions. Forest tree regressions return the highest values of fitting coefficients, but the technique is not of easy application due to the absence of mathematical expressions. The main contribution is the updated set of simple and multivariable regression formulas which have a higher goodness of fit than previous works and can be easily employed by designers in the early design stage and in multi-attribute design procedures.

Survivability of damaged ships, especially ro-ro/passenger (ropax) vessels, is of paramount interest. Nowadays, time-domain simulation of flooding and motions of damaged ships are more frequently performed to obtain a more realistic overview of the actual survivability in case of a flooding accident. An international benchmark study on simulation of flooding and motions of damaged ropax vessels was conducted within the EU Horizon 2020 project FLARE, using new dedicated model tests as a reference. The test cases include transient flooding in both calm water and in irregular beam seas, as well as gradual flooding and capsizing in beam seas. The studied damage case is a two-compartment collision damage, and the studied intact metacentric height values were lower than the statutory requirements to achieve also capsize cases. Numerical results were carefully compared against measurement data from the model tests. In transient flooding cases the capsize conditions were generally detected well by most codes. However, much variation was observed in the internal flooding and capsize mechanisms. For gradual flooding in beam seas, the results for capsize rate and time-to-capsize were characterized by significant variability among the codes. Results indicate that more research is needed to further improve the time-domain flooding simulation methods to correctly capture both transient flooding phenomena and motions of damaged ship in high waves.