Quasi-Static Flooding Analysis Method of a Damaged Ship Considering Oil Spill and Cargo Load

When a ship is damaged at sea, it is important to predict its behavior as well as whether it is to sink or not. If the ship comes to an equilibrium, the equilibrium position and time should be estimated; otherwise, the time to sink should be estimated. Furthermore, flooding analysis should be carried out not only during the design stage of the ship for preventive reasons, but also after an accident for a better investigation of its causes. In addition, flooding analysis methods that can provide predictions in case of an accident are of particular importance, as there is no time for the required calculations in an emergency. For this purpose, a quasi-static flooding analysis method for the damaged ship in the time domain is proposed in this study. There are a number of studies in which the equilibrium position and time were estimated by flooding analysis. However, most of them have not considered the air pressure effect in fully flooded compartments, and the method of determining the fluid volume in these compartments was not accurate. In the present study, the virtual vent and accumulator method are used to calculate the reference pressure in the fully flooded compartments, and the compartment shape is considered by using polyhedral integration. Also, spilled oil and solid cargo items from the damaged ship are taken into account for realistic flooding analysis. Finally, the damage stability criteria were checked not only in the final state, but also during the entire time of the flooding, as the intermediate states can be more hazardous than the final state. To validate the feasibility of the proposed method, it was applied to a naval ship, which is considerably more stringent for damage stability. As a result, we checked the availability of this study.

ON THE STABILITY OF FAST FERRY IN DAMAGE SCENARIOS

The ro-ro ships are characterized by a large garage compartment extending from stern to bow. Damage conditions, heavy weather and large floodable spaces could create serious accidents, with the loss of life and goods at sea, both for conventional ferries and fast ferries. The occurred accidents showed the need of a more accurate approach to the damaged ship stability in waves, also in head sea and following sea conditions, because of the great movements of water on the car deck. With this aim a tool for analysing the ship response in wave with damaged compartments has been developed and applied on a typical fast ferry. The ship dynamic is simulated in time domain, including non-linear effects, taking into account critical scenarios on the damaged ship. The applications regard ship grounding, assuming head sea, modelled by regular wave. In addition to that, also the particularly critical condition of a transversal wind heeling moment has been applied to compute non symmetrical behaviour. Moreover the stability problems arising from the presence of trapped water in the garage compartment are investigated assuming the same environmental scenarios.

An Advanced Salvage Method for Damaged Ship Structures

An advanced salvage method is proposed for damaged ships to ensure a short-term decision-making process for a safe ocean towage to the repair yard. The residual longitudinal strength must be greater than the sum of the still water and the maximum vertical wave bending moment. The ultimate bending moment is determined numerically for a container vessel by using an incremental iterative approach (Smith method) and wave-induced loads are predicted by means of hydrodynamic analyses. Successful applicability of the advanced salvage method is demonstrated for a damaged container vessel, which was towed from La Libertad, Ecuador, via Panama to the repair yard in Zhoushan, China, in restricted environmental conditions.

Captive Model Tests for Assessing Maneuverability of a Damaged Surface Combatant with Initial Heel Angle

The present study is about the application of a four-degree-of-freedom (4DOF) maneuvering mathematical model based on Abkowitz’s model for assessing damaged ship maneuverability with initial asymmetry. A scaled model of the Office of Naval Research Tumblehome hull with a damaged compartment was used as the test model. Based on the survivability regulations for naval vessels, the damaged compartment was designed and located near the bow, such that it had an initial heel and trim. Static and dynamic captive model tests were performed on the damaged ship model to determine the maneuvering coefficients for the maneuvering mathematical model. Maneuvering simulations were carried out with the captive model test data and 4DOF maneuvering mathematical model. The advance speed in the maneuver reduced more in the damaged condition than in the intact condition, and maneuverability was severely degraded during starboard turning.

Review of Ultimate Strength Assessment of Ageing and Damaged Ship Structures

The objective of this work is to provide an overview of the ultimate strength assessment of ageing and damaged ship structures in the last decades. Particular attention is paid to the ultimate strength of plates, stiffened panels, box girders, and entire ship hull structures subjected to corrosion degradation, fatigue cracking, and mechanical damage caused by accidental loading or impact. A discussion on the effect of the cyclic load on the plate rigidity, re-yielding, and ultimate load capacity on the ship hull girder is also part of the present study. Finally, some conclusions and discussions about potential future work are provided, identifying that more studies about the impact of corrosion degradation on the structural behaviour of the stiffened panels and the overall hull girders are needed. Studies related to the dynamic collapse behaviour of corroded and damaged ship structures under time-variant load also requires additional attention.