The traditional way of assessing the operational risk of passenger ships is based on the concept of susceptibility and vulnerability to an accident. Such an approach is mainly used to study the possible risk in given operational scenarios, adopting simplified quasi-static methods to assess the vulnerability of the vessel and using empirical definitions for the damage breach modelling. These methods are not employing first-principles methods for the risk evaluation and are not suitable for the development of onboard real-time risk assessment. To this end, developments in the EU-founded project FLARE led to a multi-level risk assessment framework based on first principle methods, that can be applied as a basis for an onboard risk assessment in real-time. The framework for real-time assessment is based on the development of databases for damage locations and dimensions and survivability. Here, the development of a suitable database of damages is discussed, concerning the employment of direct crash simulations with the software SHARP, aiming at developing a database of collisions suitable for a general operational scenario. The resulting database can be used as a data source for the development of a surrogate model for fast application in real time. This paper addresses the application of the process to a reference cruise vessel.

Real-time assessment of flooding risk associated with the collision between two ships, requires a fast estimation of damage dimensions and associated survivability. The state-of-the-art frameworks for risk assessment on passenger ships do not consider a direct evaluation of damages through crash simulations but refer to probabilistic considerations, modelling damage characteristics according to statutory marginal distributions of damage breaches too old to be any longer relevant. In any case, such an approach is not possible for the real-time risk assessment process developed in project FLARE, aimed at promoting the employment of first-principles tools for risk evaluation. In this spirit, the present work investigates the possibility of developing a database-oriented damage breach model, which employs direct crash analyses with the super-element code SHARP. However, the sole usage of crash simulations is not suitable for real-time applications. Therefore, starting from the collision simulation database, surrogate models have to be derived for real-time application. In this specific case, three different strategies have been used for the models creation namely: multiple linear regressions, neural networks and decision trees. Here, the strategy to build the database and application on a reference passenger ship is described, highlighting the differences in accuracy and calculation time between the proposed surrogate models.

Flooding risk identification is a task always treated within a very narrow scope between the life-cycle of a passenger ship. Therefore, different approaches and methods are available for design, operational or onboard applications. Furthermore, the models employed and proposed solutions use simplified methods based on empirical or probabilistic concepts. One of the aims of the EC-founded project FLARE was to promote the use of first principle methods throughout the whole vessel life-cycle, from the design phase up to the onboard risk management. To this end, this work presents the challenges and potential applicability of a real-time flooding risk evaluation methodology for ship-to-ship collisions, based on first-principles calculations. The possibility to perform direct calculations for survivability allows us to define a multi-level approach to flooding risk, separating Level-1 predictions, purely based on semi-empirical models and databases, from Level-2 predictions based on the concept of Potential Loss of Life (PLL). Here, besides a description of the multi-level risk assessment based on PLL, the different tasks of design and operational phases are addressed. Such issues are then linked to the real-time flooding risk evaluation for onboard applications, potentially working for different hazard types but conceptualised for the case of ship-to-ship collisions. The developed method applied to an arbitrary set of models, shows that the approach and tools employed for creating the framework are suitable for a real-time calculation of flooding risk.

The in-force probabilistic framework for passenger ship survivability assessment covers collision hazards. The framework primarily pertains to a static approach. Nonetheless, more complex dynamic analyses usually employ the same damage definitions, adding besides the breach characteristics, the environmental condition selection or, more precisely, the irregular wave environment necessary to simulate the damage scenarios. The traditional dynamic approaches to survivability consider only the significant wave height sampled from statistical formulations, with the wave period deriving from a constant steepness assumption. However, wave height and period influence ship dynamics in waves differently, especially concerning survivability after damage. Therefore, aiming at a direct assessment of ship survivability and the probability of loss of lives determination in realistic operational scenarios, it is essential to properly study the influence of combined variations of wave height and periods and their occurrence. The present study proposes a methodology for dynamic simulations in site-specific conditions derived from the Global Wave Statistics. The study documents the process in two critical collision damages for a reference passenger ship, using wave height and period combinations typical of the main sea areas of interest for passenger ships and performing a sensitivity analysis on the simulations needed to evaluate survivability. This enhanced analysis allows identifying the limiting environmental conditions for the critical damage cases, including the effect of heading variations, determining the ship's survivability to specific damage in an operational area.

Theory and application of damage stability followed over the years two dissociated paths: static assessments and dynamic simulations. The first approach, being easy to apply and understand, has been preferred by ship designers and regulators; the second, more advanced and first-principle oriented, has been mainly reserved for research or high-level consultancy, especially for passenger ships. Nowadays, the availability of numerical flooding simulation tools across the scientific community and calculation power in the industry allows for a possible definitive transition of damage stability assessment towards direct numerical analyses. However, research should softly drive designers towards more advanced processes via a suitable didascalic calculation framework. The multi-level approach pursued in project FLARE is an example of such a transition from static to dynamic damage stability assessment. The present work initially carefully reviews the probabilistic concept of damage stability, critically comparing the prescriptive statistical methods with direct ones and providing insights and guidance on how researchers and designers can reconcile with the original implicit assumption of the probabilistic approach. Secondly, the development of the multi-level framework highlights incongruences concerning modelling of damages between static and dynamic assessments, disfavouring the comprehension of dynamic results to designers. Two detailed examples highlight the differences in dynamic simulation results between different damage breach modelling, leading to completely different flooding paths for the same damage case. Finally, the paper indicates how a compromise between academic approach and application could help designers to start their transition towards direct numerical damage stability analyses.

The damaged stability assessment for a passenger ship is a process requiring the simulation of multiple damage scenarios. Nevertheless, the stochastic nature of the damage stability framework requires the analysis of a statistically significant number of cases. On the other hand, the probability density functions used to estimate the possible damage dimensions and locations along the ship generate many scenarios that are not critical for the ship's survivability, especially for large passenger ships. It is standard to apply empirical rules to restrict the number of damage scenarios, such as critical damages is only above two compartments, considering that damage stability regulations currently in force ensure survivability levels beyond this extent of breaches. However, a rigorous approach is lacking. To this end, in the present work, it is proposed to use more scientific-based methods to identify critical damages. This paper presents three original approaches developed in the context of a multi-level damage stability assessment. The first method relies on preliminary static calculations, the second on the energy absorbed by the ship during an impact, and the third on a purely dynamic approach. Here, the methods are critically compared on two sample passenger ships for collision damages, showing their respective advantages and disadvantages.

A more contemporary damaged stability assessment of a passenger ship can be addressed with a non-zonal approach, assessing multiple damage types and environmental conditions and employing dynamic analysis for ship survivability. This direct method necessitates the generation and simulation of many damage scenarios. However, the probabilistic models for damage characteristics describe many damages that are not critical for ship survivability. To restrict the number of damage scenarios, hence calculation time, designers currently apply empirical rules, such as critical damages are only above two compartments, considering that damage stability regulations currently in force to ensure survivability levels beyond this damage extent. However, a rigorous approach is lacking. The present work explores the use of more scientific methods as damage filters. The first method uses preliminary static calculations. The second uses the energy absorbed by the ship during an impact, and the third is suitable for a purely dynamic approach. The paper critically compares the three methodologies on two sample passenger ships for collision damages, showing their respective advantages and disadvantages.

Development of damage stability as a scientific subject, specifically in damage ship hydrodynamics and, generally, flooding risk assessment, has evolved primarily by inquisitive academics with support by people with vision and passion towards maritime safety enhancement from industry and Government, the latter in the wake of serious accidents. Notwithstanding this, the subject has seen remarkable development in a short period of time in terms of understanding process, and developing methods and tools for practical implementation of such developments. The stage has now been reached where large-scale EC and industry-funded projects are bringing all requisite knowledge and experience together towards implementation by end users with the view to institutionalizing such developments. The paper critically traces and presents key developments starting from basic concepts to a complete framework for performing numerical simulations of ship survivability in operational conditions in the seaway, leading to flooding risk assessment with application potential for new and existing ships with focus on the design phase but with operation potential in ship operation, the latter involving emergencies.

Modern optimisation methodologies have revolutionised the engineering sector and pave the way for innovation. In ship design, this has been spearheaded by the introduction of the Holistic Design approach that allows more attributes and performances of the end product to be assessed accurately and concurrently even at the early design phase. In this respect, the authors present herein a methodology based on the optimisation of the functionalities that the general arrangement needs to provide (in this case; adjacency, noise and evacuation flow). The methodology allows for a large optimisation space, several objectives and intrinsic control by the user at all the stages. By re-arranging the location of the spaces onboard, in relation to their position on the hull as well as between themselves, significant improvements can be achieved. More functional objectives can be incorporated through modularity and penalty functions, keeping the overall process simple and flexible to adapt to fluid early design requirements.