Ship Damage Research Articles

Performance characterisation for risk assessment of striking ship impacts based on struck ship damaged volume

Ship collision accidents are rare events but pose huge threat to human lives, assets, and the environment. Many researchers have sought for effective models that compute ship stochastic response during collisions by considering the variability of ship collision scenario parameters. However, the existing models were limited by the capability of the collision computational models and did not completely capture collision scenario, and material and geometric uncertainties. In this paper, a novel framework to performance characterisation of ships in collision involving a variety of striking ships is developed, by characterising the structural consequences with efficient response models. A double-hull oil carrier is chosen as the struck ship to demonstrate the applicability of the proposed framework. Response surface techniques are employed to generate the most probable input design sets which are used to sample an automated finite element tool to compute the chosen structural consequences. The resulting predictor-response relationships are fitted with suitable surrogate models to probabilistically characterise the struck ship damage under collisions. As demonstrated in this paper, such models are extremely useful to reduce the computational complexity in obtaining probabilistic design measures for ship structures. The proposed probabilistic approach is also combined with available collision frequency models from literature to demonstrate the risk tolerance computations.

An experimental study of hull girder loads on an intact and damaged naval ship

The study reported in this paper is focused on experimental investigation of the hull girder loads on an intact and damaged naval ship DTMB 5415 at zero speed. The experimental campaign was carried out in head and beam regular waves at the University of Strathclyde. The effect of the use of moorings in the model experimental setup was investigated in the context of loads assessment, and the moorings are shown to influence the measured hull girder loads at some wave frequencies compared to the free drift case. Therefore the tests in beam seas are performed with free drifting model while the moored model setup was adopted for head seas. The results for ship motions are compared with those from a previous campaign giving an insight into repeatability and uncertainty of measurements. The roll decay of the ship in both intact and damaged conditions is analysed and the linear and quadratic extinction coefficients for the model and the ship scale are reported and detailed discussion on intact-versus-damaged ship roll damping behaviour is given. The results for the hull girder loads are presented for intact and damaged ship. An investigation of the nonlinear effects due to wave height variation in the range wave height to wave length from 1/50 to 1/22 on the shear force and bending moment values was carried out for a range of wave lengths to ship length ratios from 0.8 to 1.4. The results of the extensive campaign are compared against similar experimental studies forming a benchmark data for validation of numerical methods.

Investigation on the Structural Damage of a Double-Hull Ship, Part I – Ship Collision

Marine structure is designed to be able to resist various load conditions during its operational period. However, in design process, analysis of accidental loads, such collision and grounding, has not been included for both merchant ship and navy vessel. These loads are spontaneous and several remarkable casualties may occur after collision and grounding taking place. The aim of this paper is to investigate structural damage on the target ship during collision and grounding considering on failure process and damage extent. This work is divided into two parts which in the Part I, ship collision is discussed, and the Part II deals with interaction of ship structure with sea bottom in grounding. In the Part I - Ship Collision, condition of the side structure is observed, including the inner hull after impact which is considered as the key to determine safety condition of ship cargo. A passenger ship is modelled in this work and designated as the struck ship which will be struck by the striking ship in collision process. Resistance capability of the double-hull structure against side collision is evaluated. Virtual experiment is conducted by nonlinear finite element method in order to calculate several dynamic collision scenarios which are built based on physical parameter, namely target location. Based on calculation results, damage on the side hull is found to be highly influenced by relative height between two ships prior collision. Crashworthiness criteria are summarized and result tendency indicates that in the mentioned location, the striking ship produces larger tearing on the lower part of the struck ship. Contribution of each collision scenario on the resultant force is presented in later part in order to observe structural behaviour of each determined location in encountering side collision.

Investigation on the Structural Damage of a Double-Hull Ship, Part II – Grounding Impact

Possibility of marine and offshore structures to experience accidental loads has been seriously considered up to this day. Remarkable casualties on related aspects are rising demand to ensure ship safety which in this subject is observed on marine structure. Ship is an example of marine structure that may be subjected to accidental loads during its operation. The aim of this paper is to investigate damage extent of the target ship under different accidental loads, namely collision and grounding with considerations to failure process and deformation contours. This work is divided into two parts which in the Part I, ship collision is discussed, and the Part II deals with interaction of ship structure with sea bottom in grounding. In Part II - Grounding impact, evaluating tearing damage on the bottom structure is essential in estimating environmental casualties caused by oil leakage. A chemical tanker is modelled to be the target ship in a series of grounding scenarios. Condition of the structural damage and tendency of the internal energy, crushing force and structural acceleration are observed. Prediction of the tearing opening and location of the initial failure in further grounding process are also presented in this paper. Virtual experiment is conducted by nonlinear finite element method in order to calculate the defined grounding scenarios which are built based on the target location on the bottom structure. Based on calculation results, condition of the double-hull structure after grounding is found to be highly influenced by arrangement of the longitudinal members which is evidenced by the fact that these members provide higher resistance than the transverse part. Finally, influence of the indenter's position on structural responses in grounding is summarized.

Total resistance prediction of an intact and damaged tanker with flooded tanks in calm water

This paper presents the prediction of the total resistance of an intact and damaged ship model using the computational fluid dynamics (CFD) technique. The study is performed on the model of a tanker with a large hole in the bottom of the hull. The damage is based on statistical data on ship grounding accidents and the chosen hole size and location in the midship area represents its plausible size and location due to grounding. Reynolds-Averaged Navier-Stokes (RANS) equations with the volume of fluid (VOF) surface capturing technique are employed to solve the flow around the steadily advancing model of a damaged ship in calm water. The experiments, both on an intact and a damaged ship model that were carried out in the towing tank of the Brodarski Institute in Zagreb, Croatia, are used to evaluate the results. The numerical results are in a good agreement with the experimentally obtained results. The significant average increase of 27% in total resistance due to the altered flow around the hole and inside the flooded tanks can be observed for the analysed case. The study shows that the proposed CFD model and settings provide a good prediction of the total resistance together with the flow both around the damaged hull and inside the flooded tanks of the damaged tanker.

Comparing rock shape models in grounding damage modelling

Groundings are among the most common and destructive maritime accidents. Sea bottom shape influences greatly what kind of damage the ship structure suffers and whether this leads to loss of water tightness.Sormunen et al. [21] presented and statistically compared rock models used in grounding damage analysis with detailed bottom shape data from two Finnish harbour fairways. The results were promising in terms of statistical fit especially for the binormal rock model, which also showed a wide range of flexibility in representing different types of sea bottom shapes. However, this measure does not explicitly tell if the model rock in grounding damage analysis results in similar damage size as real rocks cause. To test this, this paper develops a framework for studying, testing and evaluating rock models in terms of resulting grounding damage. FEM is used to analyse and compare grounding damage of rock models to the actual rock using otherwise identical grounding scenarios. Analysis is performed for four different real rocks with each rock being modelled with four different analytical rock models as well.The results show that rock models with good statistical fit did not necessarily result in similar grounding energy compared to results using the real rock. Differences in energy are caused especially by the rougher surface of the real rocks. For the similarity in rock area and the damaged ship structure element volume the results are much better, especially for the binormal model. As such another criteria for evaluating rock models for grounding damage analysis is needed. The results show that the damaged material volume is strongly linearly dependent on the rock area- and volume metrics. A similar linear dependency exists between the damaged volume and the energy dissipated in grounding. Knowledge of these relationships can be used towards estimating grounding damage of ships in future investigations, but rock surface unevenness should be evaluated as well.

Study of VLCC tanker ship damage stability during off-shore operation

Today, for the carriage of crude oil on sea are used larger tanker ships, especially from VLCC class. The operation of this type of ships requires in many cases special conditions, mainly related to water depth in the terminal area and enough maneuvering space for entrance and departure. Because, many ports from all over the world don't have capacity to operate this type of ships inside, in designed oil terminal, have chosen for development of outside terminals, off-shore oil terminals. In case of this type of terminals, the problems of water depth and manoeuvring space are fixed, but other kind of situations appears, regarding the safety in operation and environment factors impact on ship during mooring at oil transfer buoy. In the present paper we intend to show a study made using simulation techniques about VLCC class tanker ship in case of a damage condition resulted after a possible collision with another ship during loading operation at an off-shore terminal. From the beginning, we take in consideration that the ship intact stability, during all loading possible situations, has to be high enough, so that in case of some damage with flooding of different compartments due to hypothetical dimension water hole, the ship stability in the final stage of flooding to correspond to the requirements for damage stability and, also, to complementary requirements for damage ship stability.

Compartment level progressive collapse strength as a method for analysing damaged steel box girders

It is vital to be able to rapidly assess damaged ship structures. This ensures the safety of personnel and facilitation of the most effective repair or recovery. Interframe progressive collapse analysis has been used as a method for rapid assessment for vessels but its suitability for application to damaged vessels has been questioned, due to the limited failure modes assessed and modelling assumptions required when implementing the method. To reduce the cost and increase the effectiveness of the recovery of a damaged vessel, it will be important to more accurately assess the structure by determining the correct failure mode. This paper presents a study on the use of progressive collapse analysis to model damaged box girders which assesses the structure across multiple frame boundaries. The study shows that while progressive collapse analysis can be applied in the assessment of damaged box girders, implementing the newly proposed assessment allows greater accuracy in the calculation of the collapse strength through capture of the true mode of failure. This new method will allow the effects of the damage on surrounding structure to be captured which can influence the deflection shapes that will lead to collapse of the structure.

URANS simulations for a flooded ship in calm water and regular beam waves

CFD simulations are conducted for zero-speed damaged passenger ship SSRC in calm water and waves with 6DOF motions including flooding procedure in calm water, roll decay in calm water and motions in regular beam waves for various wavelengths. The simulations model the 6DOF soft spring experimental mount, the one- and two-room flooding compartment configurations, including both intact and damaged conditions. For flooding and roll decay, simulations show ability to predict the trend of increases in roll period and damping due to flooding, as reported in ITTC. The damping magnitudes were often under-predicted with large errors while the roll period and compartment water height were well predicted. Two-room compartment simulation showed three times larger damping than one-room compartment cases whereas the roll period was similar for both conditions. For wave cases, all motions show primarily 1st order responses, except for parametric roll condition which shows large ½ harmonic responses for the intact ship. The 2nd order responses are small for both damaged and intact ship. The larger roll period and damping for the damaged ship shift the peak of responses to smaller wave frequency and reduce the amplitude of responses. The average error is often large for 1st order intact ship pitch and damaged ship surge and pitch. The errors are larger for most ½ and 2nd order responses. Large errors could be partially due to the complex mounting system in the experiment. Overall, current CFD results show better predictions than those reported for potential flow solvers even though the computational cost is larger.

Stability Investigation Damaged Ships

There are many areas in which naval vessels could improve safety standards, although naval vessels are not necessarily regarded as less secure than the civil vessels. Although the navies never have considered water on deck a problem, it seems that this problem has a critical value in the ship damage stability analysis. As an example, this damage should be investigated if the ship has a low freeboard. For this research various studies and calculations have been carried out on several designed test vessels. It is possible to decide which criteria to use in terms of damages for each type of vessel, for example a landing ship faces more risk having grounding or raking on its bottom. This technical paper concludes with a method that helps and supports the naval architect in the analysis of damage stability. In this way, the naval engineer is able to determine which of the existing criteria fits best with the requirements of the ships function by following these few principles.

THE ANALYSIS OF EFFECTIVE ENERGY OF SHIP’S BERTHING TO THE QUAY

The berthing of ship to the quay is last stage of navigation process. An ideal manoeuvre would be consisted in a total loss of speed at the moment the ship makes contact with the quay. In practice, the ship has some speed, which caused the impact of ship in the quay. The accident can be happened when kinetic energy overdone the admissible value during contact the ship-quay. In results, the damage of ship’s hull or port structure can occur. The fenders improve the safety of berthing operations by partially absorbing the kinetic energy of ship. The fenders parameters should be properly selected relative to existing condition during ship’s berthing. It depends on effective energy of berthing ship. There are used some method to calculate of its value. One of them is based on phenomena of ship turning relative to point of first contact to the quay. Then the part of ship’s kinetic energy is altered to work of turn, and in result, energy of ship impact is decreased. This part can be determined by coefficient of eccentricy. Its value mainly depends on radius of ship’s turning, which is equal of distance between point of ship, gravity and point of first contact with quay. Simplified method of calculation the eccentricy coefficient based on ships angle of approaching to the quay. But such estimated value is weighted some discrepancy. The paper presents the analysis of methods of calculation the kinetic energy during first impact in the quay. Especially, the geometrical shape of ship’s hull is considered to achieve the accuracy value of ship’s impact energy during the berthing to the quay. The application of elaborated method permits to optimize the parameters of fender system.

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."

Effects of hull damage on global loads acting on a trimaran ship

This paper focuses on the calculation of global loads on a trimaran in intact and damage conditions. Validated numerical methods, including strip theory and panel method, are used to predict still water static and wave-induced dynamic loads acting on the intact and damaged ship in the frequency domain. The analysis is carried out using ShipX (VERES) and MAESTRO-Wave codes. Comparison of the results shows a good agreement, particularly in vertical loads. The results demonstrate that an imposed damage changes not only the distribution of global still water static loads, but also that of the global wave-induced dynamic loads. It is also observed that in some cases the loads acting on the undamaged cross sections increase considerably compared to the intact condition. This is due to the change in the distribution of loads acting on the ship under damage condition.

Shock-Resistance Research of Ship Structural Subjected to Underwater Explosion

A finite element model ships, for example design test condition of the underwater explosion, selection of explosive package quantity is 1000KG TNT, the explosive location along the direction of the ship with the bow, midship and stern, the angle of attack in three exploded cross section have 90 degrees, 60 degrees, 45 degrees, 30 degrees and 0 degrees. According to the current standard to calculate the ship damage radius, critical radius and safety radius of specific values under the effect of underwater explosion, interpolation calculation and draw the envelope. Analysis shows that the vitality of ships and shock-resistance is not only related to the explosive distance, also related to the attack position.

Risk Evaluation of Drifting Ship by Tsunami

Drifting ship due to tsunami inundation flow may cause additional damage in harbor area. Many drifting ships were found in the 2011 Great East Japan earthquake tsunami and these caused various problems (damage of ships themselves, striking other structures and obstacle for restoration). In this sense, it is very important for disaster prevention to predict the drifting motion of a large ship by tsunami current. This study aims to simulate the drifting motion of ships by the 2011 Tohoku earthquake tsunami in Kesennuma harbor, Miyagi Prefecture. First, we simulated the hydrodynamic features of the 2011 tsunami by numerical simulation. Secondly, we analyzed the drifting motion of large ships using the result of tsunami numerical simulation. In the analysis, several test cases were conducted by changing parameter and initial position of the ship. Then we verified the results of the ship drifting simulation by comparing with actual grounding position of ships. Throughout the comparisons and verifications, we found the grounding position by the simulation was generally consistent with actual position of ships. Although it is necessary to verify the drifting route of ships, the results suggest that this model is beneficial for future disaster prevention.

Experimental assessment of intact and damaged ship motions in head, beam and quartering seas

This paper presents an extensive study on the experimental prediction of motions for the well-known 5415 frigate hull in intact and damaged conditions. The experimental campaign is conducted for two geosim models, 1/100 and 1/51 scale, at zero speed in head, beam and quartering seas. All experimental results for 1/51 model are presented as 1st and 2nd order RAO, commenting on physical reasons for second order response occurrences. The results show the changes in motion responses when a ship hull is in damaged condition, they highlight the model scale effects and demonstrate the comparisons between the tests in which the model may freely drift and those in which the mean position of the model is restrained. For damaged ship in free drift tests the damage opening orientation is varied and its effect on RAO and free drift velocity is commented.

Performance assessment of damaged ship hulls

In this paper, a probabilistic framework for performance assessment of ship hulls under sudden damage accounting for different operational conditions is presented. Grounding and collision accidents are considered as sudden damage scenarios. The combined effects of sudden damage and progressive deterioration due to corrosion are investigated. The performance of ship hull is quantified in terms of ship reliability and robustness. The longitudinal bending moment failure is considered as the limit state. The longitudinal bending moment capacities of the intact and damaged ship hulls are assessed using an optimization-based version of incremental curvature method. The wave-induced loads for different ship speeds, headings and sea states are identified based on hydrodynamic analysis and the ship performance under different operational conditions is investigated. The approach is illustrated on an oil tanker. Under different operational conditions the reliability index associated with the intact and damaged ship hull and the robustness index associated with damage scenarios are presented in polar plots. In addition, aging effects on ship reliability are investigated.

GOALDS—Goal Based Damage Ship Stability and safety standards

The new probabilistic damaged stability regulations for dry cargo and passenger ships (SOLAS 2009), which entered into force on January 1, 2009, represent a major step forward in achieving an improved safety standard through the rationalisation and harmonization of damaged stability requirements. There are, however, serious concerns regarding the adopted formulation for the calculation of the survival probability of passenger ships, particularly for ROPAX and large cruise vessels. The present paper outlines the objectives, the methodology of work and main results of the EU-funded FP7 project GOALDS (Goal Based Damaged Stability, 2009–2012), which aims to address the above shortcomings by state-of-the-art scientific methods and by formulating a rational, goal-based regulatory framework, properly accounting for the damage stability properties of passenger ships and the risk of people onboard.

Study on Collision Damage Behavior of Ship

Ship collision is a kind of dangerous accident which may result in serious damage of struck hull structure during shipping process. The damage of ship depends on the relative rigidity of striking ship and the capabilities of crash resistance of ship structures. The rigidity of bow is always considered as higher than that of side, so the structure of bow is regarded as rigid body. But this method is so conservative that the result of numerical simulation may be wrong when the rigidity of side of one ship is higher than that of bow of another ship. The process of collision of two ships is simulated, in which the structures of two ships are all defined as elastic body. The behavior of side is studied and some useful results are found.

Numerical study of damage ship hydrodynamics

A RANS based CFD solver with VOF modeling of free surface is employed to investigate the effects of sloshing and flooding on damage ship hydrodynamics. The numerical study includes three research works, i.e. the simulations of forced roll motion of an intact ship, sloshing of water in tank and forced roll motion of a damage ship. The computed roll moments in the tank and at opening were compared. The coefficient of roll damping was obtained and validated against model test data. The results show that the impact of sloshing on damage ship hydrodynamics is frequency dependent. It becomes significant near natural roll frequency of the tank. The phase differences between hydrodynamic and hydrostatic components are increasing with frequency. The flooding at opening of a damage ship tends to alleviate the sloshing impact.