Ship Survivability Research Articles

Probabilistic assessment of damaged survivability of passenger ships in case of grounding or contact

This paper presents a probabilistic framework for the assessment of ship survivability following bottom grounding and side grounding/contact accidents, with specific attention to passenger ships. The proposed framework provides attained subdivision indices for each type of accident. For harmonization reasons and to leverage on the experience of present designers, the proposed approach is consistent with existing SOLAS probabilistic regulations for damaged ship survivability assessment following a collision. In the presented framework, the probability of flooding a (group of) compartment(s), i.e. the so-called “p-factor” associated to each “damage case”, is determined using an automatic, flexible and easily updatable non-zonal approach based on Monte Carlo generation of hull breaches according to the underlying geometrical and probabilistic models of damage. The conditional ship survivability metric is assumed to be provided by the SOLAS “s-factor”. Results from three example applications are reported and discussed. The information provided in the paper are at a level of detail allowing the implementation of the proposed approach. The obtained results indicate the potential practical applicability of the proposed approach, and the benefits of considering different types of damage for a safety-oriented design and for a proper assessment of stability-related risk control options.

함정 재해의 신속 진압을 위한 경로 탐색에 관한 연구

Naval ships could be seriously damaged by enemy attacks in battle. Moreover, this damage could be spread and deteriorated into a secondary accident. Secondary accidents that have adverse effects on naval ship’s survivability, such as fire, flood, smoke extension, and patient occurrence, are defined as casualties. These casualties sharply degrade the survivability of naval ships. Furthermore, naval ships could be burned-out and sunk by casualties in isolated sea. Therefore, damage control and rapid suppression of the casualties in the naval ships is essential. This study was conducted in the establishment of suppression paths according to the characteristics of each casualty so that the developed system can support the rapid suppression in an emergency and even the training situation on a regular state. To establish the suppression paths, the two-dimensional numerical map is designed by converting the three-dimensional features of the naval ships, and the well known algorithms are compared to present the appropriate one for path finding problem on the naval ships. Finally, we devised a specific routing algorithm that fits the characteristics of each casualty in accordance with the Korean Navy’s doctrines and handbooks of casualty suppression.

공기 중 폭발에 의한 함정의 손상반경 간이 계산식 개발

To decide a separation distance of the redundant vital equipment in a naval ship, the damage radius due to an aerial explosion should be estimated. In this research, a simplified formula for the damage radius has been developed by using existing empirical formulae for reflected shock pressure and shock lethality value of equipment. As a numerical example, the damage radius for a typical pump aboard a naval ship has been calculated by the developed formula and compared with the results calculated by Measure of Total Integrated Ship Survivability (MOTISS) which is one of survivability analysis codes verified, validated and accredited by the US Navy. Also, comparison with the results calculated by existing other simplified formulae has been made.

Влияние конструктивной защиты на живучесть корабля

Влияние конструктивной защиты на живучесть корабля

Vessel Financing Fund and the Survival of Local Ship Owners/operators in Rivers State, Nigeria

This study examined the relationship between vessel financing fund and the survival of local ship owners/operators in Rivers State. Vessel financing fund was used as the independent variable as well as the dimension. The variables used in this study to measure the survival of local ship owners/operators in Rivers State (dependent variable) included increase in employment by local ship operators and taxable revenue to government by local ship operators. The study population consisted of 35 indigenous ship operating companies in Rivers State. However, the study sampled 4 staff from each of the companies (140) and validly used 133 of the respondents (95%response rate) for the data analysis. The study used research instrument of questionnaire orientation to elicit information. The study adopted the descriptive and inferential statistical techniques in the assessment of the operational relationship between the variables and tested the six hypotheses with Pearson Product Moment Correlation Coefficient (r). The study found that NIMASA as regulatory authority declines to approve permits for foreign vessels; that shipping companies are not satisfied with the implementation of Nigerian Cabotage Act and NIMASA’s conduct, actions, decisions and policies do not meet the expectations of local ship owners/operators. The study found that there are duplications in vessel registration process with NIMASA. Most vessels that fly Nigerian flags, which is an indication of compliance to the regime still go for Temporary Importation permit with Nigerian Customs Services, which is a clear attestation that no customs duty is paid. From the test of the hypotheses in this study it is evident and conclusive that vessel financing fund has positive and significant relationship with increase in employment of local ship owners/operators and taxable revenue to government by local ship operators in River State. The study therefore, recommends that government should intensify its efforts by ensuring the approval of the proposal on a fiscal incentive programme to encourage indigenous participation in shipping, submitted by NIMASA. This will encourage more investment in shipping, enhance capacity building, lead to improved infrastructural facilities in the existing shipyards and enhance the opportunities of the indigenous operators to lift available cabotage cargoes, especially in the oil and gas industry.

Effect of Vessel Registration Policy on the Survival of Local Ship Owners/Operators in Rivers State, Nigeria

Effect of Vessel Registration Policy on the Survival of Local Ship Owners/Operators in Rivers State, Nigeria

손상통제 함상훈련 시나리오의 효율적 생성에 관한 연구

Damage control is a very important preliminary and primary activity to improve the survivability of naval ships by preventing spread of damage, and various types of onboard damage control training are conducted regularly on naval ships. The scenarios for these trainings should be well organized to improve the training efficiency. However, at present, it takes much time and effort to generate the training scenarios and there is a problem that the procedures and contents of the scenarios vary widely depending on the persons who generate, without the established methods and standards. In this paper, an efficient generation method of damage control onboard training scenarios has been established, especially for flood and fire on naval ships. Also a computer program has been developed based on the established method. The results showed that this method and computer program reduce the time and effort to generate these scenarios, and it is hoped that the method be used as a ROK Navy Standard.

Complementing SOLAS damage ship stability framework with a probabilistic description for the extent of collision damage below the waterline

SOLAS probabilistic damage stability regulations assess the ship safety level through the attained subdivision index, which is a probabilistic measure of ship survivability combining, in principle, the probability of flooding of (groups of) compartments and the corresponding conditional survivability (the s-factor). However, the present SOLAS framework does not embed a probabilistic model for the extent of collision damage below the waterline. A “worst-case approach” is therefore used for the s-factor when there are horizontal subdivision boundaries below the waterline. This leads to a systematic underestimation of the ship survivability in presence of horizontal subdivision boundaries below the waterline, and it prevents an effective assessment of the impact of such boundaries. To make a step forward, the paper presents a probabilistic model for the extent of damage below the waterline, derived from statistical analysis of collision accidents data. From this model, a “u-factor” is defined, and it is described how the “u-factor” could be straightforwardly embedded in the SOLAS framework, in combination with “p-factor”, “r-factor” and “v-factor”, to consistently account for horizontal subdivision boundaries below the waterline, thus avoiding the need for using the “worst-case approach”. An example application is reported to quantitatively assess the effect of the “u-factor”.

Impact of drafts on the damage survivability of cruise ships

Abstract The prevailing probabilistic damage stability concept, as outlined within SOLAS 2009 for passenger ships, calculates the Attained Subdivision Index based upon three loading conditions which combine to form a theoretical draft range for a given vessel. To each of these loading conditions a weighting factor is then applied to account for the probability that a vessel will be operating at or near any of these drafts at the time of collision, should one occur. Currently the weighting factors are applied in a ‘one-size-fits-all’ manner, with the same weightings to be applied in the case of cargo and passenger vessels despite the fact that these ship types are known to have very different tendencies when it comes to the nature of their operation. This in turn, calls into question the suitability of these weightings concerning what degree they, in fact, reflect the operational profile of the vessels covered by the standard. With this in mind, the present paper aims to investigate the suitability and accuracy of the currently assumed draft weighting factors with regards to cruise vessels. This study is conducted using operational loading condition data sourced from 18 cruise ships and spanning up to a period of two years in some cases. On the basis of this data, draft probability distributions are derived and new weighting factors are formed specifically pertaining to cruise ships and the nature of their operation. Finally, an assessment is conducted looking into the impact of the newly derived weighting factors on the magnitude of the Attained Subdivision Index and recommendations are made on how best to implement them.

Simulation-based analysis method for damage survivability of passenger ships

ABSTRACTA new approach for analysing the level of survivability for a passenger ship in the event of a collision damage is presented. Monte Carlo simulation is used for generating a large number of damage cases. The probability distributions for damage extent and location are based on the current SOLAS regulation. Each case is calculated with time-domain flooding simulation, assuming quasi-static motions and calm sea, thus enabling evaluation of the righting lever curve during the flooding process. The ship survivability is analysed based on requirements for a sufficient reserve stability. The proposed method is demonstrated with a large passenger ship design. Based on the detailed investigation of the results, the effects of various design changes are studied. Furthermore, the impact of waves on the flooding process is studied. The presented method for survivability assessment is robust and especially suitable for comparing design variations, or ships with similar main dimensions.

Optimizing anode location in impressed current cathodic protection system to minimize underwater electric field using multiple linear regression analysis and artificial neural network methods

Design of impressed current cathodic protection (ICCP)-anode locations to minimize underwater electric field is important to increase the survivability of naval ships. However, the evaluation of all ICCP-anode location scenarios is time-consuming process even though it is conducted by numerical simulation, especially boundary element method (BEM). To solve this problem, the randomly selected cases of ICCP-anode location in 3, 4 and 5-pair, which were produced by the beta distribution model, were simulated using BEM simulations. Then, the optimized ICCP-anode location scenario from the cases was verified by statistical methods (multiple linear regression and artificial neural network). Predictions of ICCP-anode location and underwater electric field were more correlated with the artificial neural network than the multiple linear regression analysis. Also, the selected ICCP-anode locations were verified by the artificial neural network considering data interactions. Thus, the application of an artificial neural network can be more useful for designing ICCP-anode location that minimizes underwater electric fields.

Application Side Casing on Open Deck RoRo to Improve Ship Stability

RoRo is a vessel that can transport passengers, cargo, container and cars. Open Car Deck is favourite RoRo Vessel in developing countries due to its small GT, small tax and spacious car deck, but it has poor survival of stability. Many accident involve Open Car Deck RoRo which cause fatalities and victim. In order to ensure the safety of the ship, IMO had applied intact stability criteria IS Code 2008 which adapted from Rahola’s Research, but since 2008 IMO improved criteria become probabilistic damage stability SOLAS 2009. The RoRo type Open Car Deck has wide Breadth (B), small Draft (D) and small freeboard. It has difficulties to satisfy the ship’s stability criteria. Side Casings which has been applied in some RoRo have be known reduce freeboard or improve ship’s safety. In this paper investigated the effect side casings to survival of intact dan damage ship’s stability. Calculation has been conducted for four ships without, existing and full side casings. The investigation results shows that defect stability of Open Deck RoRo can be reduce with fitting side casing.

Novel scaling law for estimating propeller tip vortex cavitation noise from model experiment

The tip vortex cavitation (TVC) noise of marine propellers is of interest due to the environmental impacts from commercial ships as well as for the survivability of naval ships. Due to complicated flow and noise field around a marine propeller, a theoretical approach to the estimation of TVC noise is practically unrealizable. Thus, estimation of prototype TVC noise level is realized through extrapolation of the model TVC noise level measured in a cavitation tunnel. In this study, for the prediction of prototype TVC noise level from a model test, a novel scaling law reflecting the physical basis of TVC is derived from the Rayleigh-Plesset equation, the Rankine vortex model, the lifting surface theory, and other physical assumptions. Model and prototype noise data were provided by Samsung Heavy Industries (SHI) for verification. In applying the novel scaling law, similitude of the spectra of nuclei is applied to assume the same nuclei distribution in the tip vortex line of the model and the prototype. It was found that the prototype TVC noise level predicted by the novel scaling law has better agreement with the prototype TVC noise measurement than the prototype TVC noise level predicted by the modified ITTC noise estimation rule.

Impact assessment of wave statistics on ship survivability

This paper presents a brief summary of the work conducted by the MSRC at Strathclyde University in which the effect of operational location on the estimation of a vessel’s survival probability has been investigated and new s-factor formulations proposed. Further work is presented in which updated accident wave statistics have been used in order to assess the impact of vessel specific data on the predicted survivability. A test case on a large container ship has been conducted in order to gauge the effect of the new s-factor formula on the Attained Subdivision Index and thus the vessel safety level with regards to collision damage.

Assessment of Survivability of Surface Combatants after Damage in the Sea Environment

The operating conditions of modern warships, in the natural sea environment, have a significant influence on their survivability in the event that watertight integrity is lost. Up to now, the consideration of sea and weather conditions has been implicitly accounted for in a naval ship's damaged stability assessment. This article outlines a probabilistic approach to assessing a naval ship's damage stability, in which some of the limitations of the currently used damage stability criteria are identified, including the validity of the assumption of moderate sea states at the time of damage. An investigation of the operability of a frigate design found that there is a significant increase in the risk of a ship's loss when changing the operational area from the North Atlantic to the North Pacific. A remarkable additional finding of the study showed that the assumed distribution for the damage penetration has no significant effect on the ship's survivability because of the way modern combatants are designed.

Feasibility study of corner reflector for radar countermeasures and deception for conventional forces

The high-tech large warships are minimal and they are always monitored by opponents, and become primary targets when conflicts occur. The improvement in reducing susceptibility has significant importance because it is difficult for a ship to maintain mission capability and functionality once it is damaged. Ordinary decoys are effective only under the premise that the ship has already been exposed. Traditionally, for naval vessels, techniques related to the radar have been used in military stealth techniques to ensure confidentiality. The corner reflector, on the other hand, can produce rather large radar cross sections. Continued use of deceptive systems such as chaff during operations will help to improve survivability of naval ships. From this viewpoint, corner reflector was considered for making radar countermeasures and deception technology. This paper reviews the current status of corner reflector basis decoys and the technical feasibility of corner reflectors for developing structural decoys.

Shock Response Analysis of Blast Hardened Bulkhead in Partial Chamber Model under Internal Blast

It is necessary to restrict the damage area for the enhancement of ship survivability under the internal blast of a Semi-Armor Piercing (SAP) warhead inside a ship's compartment, and to develop design guidance and performance verification technique of Blast Hardened Bulkhead (BHB) for the protection of its damage diffusion to adjoining compartment and continuous flooding. The objective of this study is to develop shock response analysis technique of BHB under the internal blast using MMALE (Multi-Material Arbitrary Lagrangian Eulerian) formulation and FSI (Fluid-Structure Interaction) analysis technique of LS-DYNA code through the verification of internal blast tests of partial chamber model.

Experimental investigation of the influence of floodwater due to ship grounding on motions and global loads

High profile collision and grounding incidents show that safety standards for ships need improvement to ensure ship survivability and reduce the potential for loss of life. An experimental investigation into the influence of floodwater, and transient flooding on the motions and structural response of a ship hull following a grounding incident is presented. Results show that floodwater can have a significant effect on the magnitude of ship responses; testing of the transient flooding case provides the opportunity to quantify the magnitude of these changes as well as the time to flood by provision of intact and flooded data during a single test. The movement of the floodwater free surface shows some substantial second order sloshing effects close to the ship peak response, but little movement in higher frequency waves. Comparisons to classification design rules indicate that there is scope for further assessment of safety margins, including investigation of global responses in conjunction with any local loading due to the presence of floodwater. Future work will look at improving the modelling of the floodwater free surface and carrying out further transient flooding testing in order to better quantify the effect of a ship grounding incident on the survivability of a vessel.

Damage survivability of cruise ships – Evidence and conjecture

This paper delves into damage stability legislation as it applies to passenger ships. The Concordia accident, like many others before it, has shaken the maritime profession once again with many questions being asked without being able to provide credible answers. Old ships have been designed to lower standards (it is common knowledge that new ships are safer than old ships, with the latter comprising the majority of the population), new standards are holistic and goal-based offering knowledge of the standard these ships are designed to, which is not true for old ships, emergency response is an altogether different science in modern ships and many others. Notwithstanding this state of affairs, there is another more fundamental weakness in the regulations for damage stability, perhaps at the heart of most problems with cruise ships safety, old and new. A critical review into damage stability legislation, as it applies to passenger ships, offers compelling evidence that cruise ship characteristics and behaviour have not been accounted for in the derivation of relevant damage stability rules. As a result, the regulatory instruments for damage stability currently in place do not provide the right measure of damage stability for cruise ships and, even more worryingly, the right guidance for design improvement. This leads to a precarious situation where cruise ships are underrated when it comes to assigning a damage stability standard whilst depriving designers of appropriate legislative instruments to nurture continuous improvement. Documented evidence is being presented and the ensuing results and impact discussed. Recommendations are given for a way forward.

Underwater explosion approximate method research on ship with polymer coating

Battle damage survivability is the prime design criterion of naval ships. Composites and hybrid structures such as polymer coating attract much attention to increase the ship survivability. Aiming to develop the parameter optimization design of the coating and to assess the underwater explosion shock environment and the blast-resistant effect of polymer coating efficiently, an approximate numerical method was performed in this preliminary study. An equivalent continuum model based on the homogenization theory was introduced to simulate the dynamic behavior of the coating. The test data of full-scale underwater explosion tests and the numerical simulation results were investigated. The blast-resistant property of the polymer coating was elaborated. The core strength had an important influence on the ship dynamic response: under low-intensity underwater explosion shock load, “soft” core had greater blast-resistant effect than the other ones, while under high-intensity underwater explosion shock load, “ordinary” core and “hard” core had better blast-resistant effect than the “soft” core.