The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Dracos Vassalos - One of the best experts on this subject based on the ideXlab platform.
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Intact Stability of passenger ships: safety issue or design concern? Neither!
2019Co-Authors: Dracos Vassalos, Georgios Atzampos, Donald Paterson, Jakub Cichowicz, Kristian Bertheussen Karolius, Evangelos Boulougouris, Dimitrios KonovessisAbstract:Stability has been a primary focus of the maritime industry and of immense interest to the IMO from the outset. Despite several attempts to resolve Stability-related issues, the problem of Stability remains one that has yet to be resolved. Reasons for this, range from the complexity of the problem itself to misconceptions in its very nature, particularly concerning intact or compromised conditions of the ship in question. Emphasis in this paper is placed on the latter. More specifically, whilst intact Stability of ships is an extremely interesting scientific problem, to what extent is it a determining factor in the design and operation of passenger ships? Currently, intact Stability and Damage Stability share the same stage from a regulatory perspective and, consequently, they have equal impact on design and operation-related decisions, an example of which is the use of combined intact and Damage Stability GM limit curves (e.g. IACS Rec 110 Rev1). However, in line with goal-based regulations and standards, design and operational decisions should be risk-informed in which case, matters relating to Damage Stability are of higher concern, simply by virtue of the fact that Damage Stability is by far the greater risk contributor. In fact, for passenger ships (>500GT), the level of risk associated with intact Stability is indiscernible in contrast to that of Damage Stability. More importantly, in the operational loading conditions of such vessels, Damage Stability is a more dominant constraint. Hence, such ships can be designed on the basis of Damage Stability considerations alone. This paper delves in this direction by drawing on the current regulation-making process for risk estimation as adopted by IMO as well as current design and operational practice. Findings from European research and related studies are provided in order to substantiate the argument that intact Stability for passenger ships is neither a safety issue nor a design concern.
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Damage Stability of passenger ships – notions and truths
Contemporary Ideas on Ship Stability, 2019Co-Authors: Dracos VassalosAbstract:A painstaking evolutionary development on Damage Stability of ships is giving way to unprecedented scientific and technological developments that has raised understanding on the subject as well as the capability to respond to the most demanding societal expectations on the safety of human life and to do so cost-effectively. Within less than half a century, Damage Stability calculations catapulted from one scenario per newbuilding (QE II, mid-1960s over a few months) to tens of thousands of scenarios (modern cruise liners in 2010s in a few weeks). Given the steepness of the learning curve and the pace of developments, it is understandable that certain notions were accepted as truths without due rigor and, as such, continue to shape contemporary thinking and developments. This paper draws attention to various issues that are emerging as knowledge grows and proposes a way forward for establishing a stronger foundation to safety assurance in the maritime sector and for future developments on the subject.
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Defining rational Damage Stability requirements
Contemporary Ideas on Ship Stability, 2019Co-Authors: Nikolaos Tsakalakis, Dimitrios Konovessis, Dracos VassalosAbstract:The major benefit of switching from the deterministic frameworks for Damage Stability of the past to the current performance-based state of the art is the ability to have a measurement of the level of survivability of any given design. The required level of survivability is probably the key parameter in any probabilistic framework, in essence answering the question “how safe is safe enough?”. To this end, survivability analysis results on representative cruise and Ro-Pax ships can be related to design and operational parameters with a view to define and quantify the relationships between Damage survivability characteristics following a collision and time available for evacuation with potential outcomes in terms of people potentially at risk. For this paper, established numerical methods for the measurement of performance-based survivability have been utilised and used as benchmark against available analytical methods in an attempt to define a rational requirement for the level of survivability.
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Damage Stability Making Sense
Contemporary Ideas on Ship Stability, 2019Co-Authors: George Mermiris, Dracos VassalosAbstract:Although aviation, nuclear, processing, etc. industries have long ago adopted and established preventative frameworks and procedures to safeguard against unwanted outcomes of daily operations, the maritime industry still places the emphasis on the mitigation of consequences following an accident. Despite the widely expressed opinion that prevention is the way forward, curing occupies a central position not only in every day practice but in the underlying regulatory framework as well. Contrary to this approach, the work presented here aims to create the necessary momentum towards rationalisation of the fundamental choices made during the design process, thus attracting attention to areas where prevention strategies can find fertile ground and be fruitful and cost-effective. The methodology addresses the occurrence of a collision event and the crashworthiness capacity of a ship as prerequisites for its survivability assessment, with promising results to encourage further development.
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Designing for Damage Stability beyond design level
2016Co-Authors: Dracos Vassalos, Donald Paterson, Evangelos Boulougouris, Markku KanervaAbstract:This paper describes the background and provides the rationale and the framework to embrace all feasible measures (passive/design and active/operational – normal and emergencies) for improving the Damage survivability of RoRo Passenger ships. The ideas elaborated in the paper is an attempt to elucidate and assess the impact on options for new and existing ships of increasing the required subdivision index R, the former in response to the higher Damage Stability standards recom- mended following the conclusion of the EMSA III project and the latter in case IMO decided to apply higher Damage Stability requirements retrospectively, particularly in the aftermath of an accident. Such a framework would provide the motivation for instigating and estab- lishing novel Damage Stability enhancing paradigms in line with IMO Circular 1455 on equivalents, for alter- native compliance. This, in turn, would enable the industry to focus on all credible measures for Damage Stability enhancement in case of a flooding accident. This represents a step change both in the mind-set of naval architects and in safety legislation but the impact will be immense and mostly positive. This paper paves the way in this direction by providing the background and rationale for such a framework and by introducing an alternative system for Damage Stability enhancement that involves injecting highly expandable foam in the compartment(s) undergoing flooding during the intimal post-accident flooding phase thus enhancing Damage Stability and survivability of RoPax vessels well beyond the design levels in the most cost-effective way currently available. This is a mind-set changing innovation that is likely to revolutionise design and operation of most ship types and RoPax, in particular. A number of applications are considered in the paper for a range of ship sizes with impressive results that will challenge the cur- rent established practice.
Apostolos Papanikolaou - One of the best experts on this subject based on the ideXlab platform.
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Advanced Damage Stability assessment for surface combatants
Ocean Engineering, 2016Co-Authors: Evangelos Boulougouris, Stuart Winnie, Apostolos PapanikolaouAbstract:Abstract One of the major contributors to the survivability of a surface combatant is her reduced vulnerability to weapon effects and as such the ship׳s Damage Stability characteristics determine a ship׳s ability to resist the consequences of possible flooding, namely to not capsize and/or sink. There are serious concerns about the limitations of the current semi-empirical deterministic criteria in which a combatant׳s Damage Stability is assessed upon. This paper details a comparison between the current approach and a newly presented probabilistic approach with the aim of determining which will result in a more accurate way of estimating the level of survivability of a particular design. A study is also presented in which the maximum Damage length used in the naval ship assessment is increased to merchant ship standards of 0.24 L bp .
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Damage Stability requirements for passenger ships : collision risk based cost benefit assessment
2015Co-Authors: Rainer Hamann, Apostolos Papanikolaou, Odd Olufsen, Henning Luhmann, Eleftheria Eliopoulou, Dracos VassalosAbstract:Currently built passenger ships have to comply with SOLAS 2009 probabilistic Damage Stability requirements. There are, however, serious concerns regarding the sufficiency of these requirements with respect to the Required Subdivision Index R, which should properly account for the risk of People On Board (POB) and ship’s inherent survivability in case of loss of her watertight integrity. In recent years extensive research on determining the appropriate level of R using risk-based methods has been carried out. The urgency of the matter was reinforced by the quite recent Costa Concordia (2012) accident, even though this accident was not related to a collision event. This paper outlines the objectives, the methodology of work and first results of the ongoing studies funded by EMSA (EMSA III project) focusing on risk-based Damage Stability requirements for passenger ships. In compliance with IMO Formal Safety Assessment process a collision risk model is further developed based on the results of EU GOALDS project and a new required index shall be suggested by means of cost-benefit assessment. The updated collision risk model uses information from the most recent analysis of casualty reports of databases considering the period 1990 to 2012
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Comparative study of Damage Stability regulations and their impact on the design and safety of modern ROPAX ships
2013Co-Authors: George Zaraphonitis, Apostolos Papanikolaou, Christina Roussou, Aphroditi KanelopoulouAbstract:The present paper summarizes the results of an investigation on the survivability of ROPAX ships in Damaged condition following a collision accident. A small size ROPAX design has been selected and a series of design modifications have been elaborated, to study their effect on the ship’s survivability, expressed by the Attained Subdivision Index, as well as on its lifetime economic performance, using three different Damage Stability formulations (SOLAS 2009, GOALDS and SLF 55), all based on the probabilistic concept. The ultimate goal of this study is to investigate the feasibility of raising the current regulatory requirements on the ship’s survivability, while keeping the economic impact of the corresponding design modifications within acceptable limits.
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on the development of the new harmonised Damage Stability regulations for dry cargo and passenger ships
Reliability Engineering & System Safety, 2008Co-Authors: Apostolos Papanikolaou, Eleftheria EliopoulouAbstract:Abstract This paper outlines the methodological background and presents a summary of the main results of a series of undertaken international, IMO-led studies, on the harmonisation of the new probabilistic, risk-based regulations with the currently in-force regulatory provisions for assessing the Damage Stability of dry cargo and passenger ships. It reviews the historical development of the new regulations, to be applied to all new buildings on January 1, 2009, and the anticipated impact of the new rules on the design and indirect operation of various subcategories of dry cargo and passenger ships. It identifies certain loopholes in the existing regulations that appear cured by the new ones, though certain compromises adopted in the development of the new regulations, particularly those related to large passenger ships’ survivability, have left some open issues to be addressed in the near future.
Stefan Krüger - One of the best experts on this subject based on the ideXlab platform.
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A Monte Carlo Based Simulation Method for Damage Stability Problems
Volume 3: Structures Safety and Reliability, 2019Co-Authors: Stefan Krüger, Hendrik DankowskiAbstract:Abstract To cope with future developments of the SOLAS 2009 B1, Damage Stability investigations must become a central part of the initial design phase. If Damage Stability calculations are performed in the classical way, they are very time consuming with respect to both modelling and computational time. To overcome this problem, Damage Stability can be treated as a stochastic process, where the probability of a Damage case and the survivability of that particular Damage case need to be determined. This task can be solved by direct numerical simulations based on the Monte Carlo principle. If statistical Damage distributions are once known, the Monte Carlo simulation delivers a population of Damages which can be automatically related to certain Damage cases. These Damage cases can then be investigated with respect to their survivability. Applying this principle to SOLAS 2009 Damage Stability calculations leads to a number of implementation problems which must be solved to guarantee that the MC simulation delivers exactly the same results as the manual, zone based Damaged Stability calculation. If these problems are solved, the MC based Damage Stability calculations can be used during the initial design phase until the Damage Stability approval. The proposed method reduces the computational effort drastically which supports the initial design phase of the ship’s compartmentation. The method further leads to higher attained indices and consequently to a safer and more efficient design.
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Progressive Flooding Assessment of the Intermediate Damage Cases as an Extension of a Monte-Carlo based Damage Stability Method
2013Co-Authors: Hendrik Dankowski, Stefan KrügerAbstract:The computation of intermediate flooding stages for current Damage Stability rules is a very complex and time consuming task for the design engineer and usually only performed manually for certain critical cases and stages. A progressive flooding method is presented in this paper, which computes the flux between the compartments based on the Bernoulli equation. Large and partly flooded openings are taken into account as well as optional air compression and flooding through completely filled rooms. The method is validated with the standard benchmark model test recommended by the ITTC. Especially for multi-compartment Damage combinations, the correct treatment of possible critical intermediate stages of flooding is unclear and only briefly described in the current SOLAS 2009 regulations. The method presented here uses a typical Damage opening based on the generated Damage cubes by a Monte Carlo simulation to perform a direct progressive flooding assessment for each critical intermediate case. This method has the advantage to remove the limitation of typical three to four discrete intermediate stages of flooding, that are usually assumed. Instead, it allows to investigate each intermediate Damage case in the time domain to gain a more detailed view on the severity of the flooding process and the vulnerability of the ship with regard to flooding of the watertight integrity after Damage. The generation of the Damage cases and the required openings is completely automated by chopping the section based hydrostatic model of the hull and the compartments with an appropriate Damage cube. A robust and fast algorithm taking into account complex compartment geometries including negative sub-spaces will be presented. The combination of flooding calculations with a Monte Carlo method extends the classical Damage Stability calculations to the time domain, which allows a more accurate estimation of the overall safety level of a ship to withstand Damage.
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On the safety level of the SOLAS 2009 Damage Stability rules for RoPax vessels
Marine Systems & Ocean Technology, 2011Co-Authors: Hendrik Dankowski, Stefan KrügerAbstract:The new probabilistic Damage Stability rules in SOLAS 2009 and their impact on the safety of the ship subdivision design have been widely discussed. Especially the safety level of RoPax designs are considered for further investigations. This paper describes a methodology to compare the safety provided by different Damage Stability regulations for a certain ship design. The determination of the Damage cases probabilities are based on a Monte Carlo simulation for the Damage distributions. The Damage cube itself is modeled by distribution functions retrieved from statistics based on the HARDER project. This gives a very elegant, fast and direct approach of Damage calculations. Together with the calculation of the survivability of all Damage cases, this allows to identify and compare the safety level indices of different Damage Stability standards. The method has been used in the “EMSA Study on Damage Stability of ROPAX vessels”. The theory of the simulation methodology and some extracts of the results of the EMSA study will be presented in the following. It has been shown in the study that for the investigated RoPax designs the new SOLAS 2009 rules are less stringent than the old, deterministic rules according to the Stockholm agreement. This means that especially the old water-on-deck requirement results in more se-vere designs and that the required index of the new Damage rules is too low for the investigated RoPax vessel designs.
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On the safety level of the SOLAS 2009 Damage Stability rules for RoPax vessels
Marine Systems & Ocean Technology, 2011Co-Authors: Hendrik Dankowski, Stefan KrügerAbstract:The new probabilistic Damage Stability rules in SOLAS 2009 and their impact on the safety of the ship subdivision design have been widely discussed. Especially the safety level of RoPax designs are considered for further investigations.
Hendrik Dankowski - One of the best experts on this subject based on the ideXlab platform.
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A Monte Carlo Based Simulation Method for Damage Stability Problems
Volume 3: Structures Safety and Reliability, 2019Co-Authors: Stefan Krüger, Hendrik DankowskiAbstract:Abstract To cope with future developments of the SOLAS 2009 B1, Damage Stability investigations must become a central part of the initial design phase. If Damage Stability calculations are performed in the classical way, they are very time consuming with respect to both modelling and computational time. To overcome this problem, Damage Stability can be treated as a stochastic process, where the probability of a Damage case and the survivability of that particular Damage case need to be determined. This task can be solved by direct numerical simulations based on the Monte Carlo principle. If statistical Damage distributions are once known, the Monte Carlo simulation delivers a population of Damages which can be automatically related to certain Damage cases. These Damage cases can then be investigated with respect to their survivability. Applying this principle to SOLAS 2009 Damage Stability calculations leads to a number of implementation problems which must be solved to guarantee that the MC simulation delivers exactly the same results as the manual, zone based Damaged Stability calculation. If these problems are solved, the MC based Damage Stability calculations can be used during the initial design phase until the Damage Stability approval. The proposed method reduces the computational effort drastically which supports the initial design phase of the ship’s compartmentation. The method further leads to higher attained indices and consequently to a safer and more efficient design.
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An Experimental Study on Progressive and Dynamic Damage Stability Scenarios
Volume 8A: Ocean Engineering, 2014Co-Authors: Oliver Lorkowski, Hendrik Dankowski, Florian KluweAbstract:Current Damage Stability rules for ships are based on the evaluation of a ship’s residual Stability in the final flooding stage. The consideration of the dynamic propagation of water within the inner subdivision as well as intermediate flooding stages and their influence on the resulting Stability is very limited in the current Damage Stability regulations. The investigation of accidents like the one of the Estonia or the European Gateway reveals that intermediate stages of flooding and the dynamic flooding sequence result in significant fluid shifting moments which have a major influence on the timedependent Stability of Damaged ships. Consequently, the critical intermediate stages should be considered when evaluating designs with large cargo decks like RoRo vessels, RoPax vessels and car carriers. Also the safety of large passenger ships with respect to Damage Stability is affected by the aforementioned effects. In this context a new numerical flooding simulation tool has been developed which allows an evaluation of a ship’s timedependent Damage Stability including all intermediate stages of flooding. The simulation model is based on a quasi-static approach in the time domain with a hydraulic model for the fluxes to ease the computation and allow for fast and efficient evaluation within the early design stage of the vessel. This allows studying multiple Damage scenarios within a short period. For the further validation of this numerical simulation method a series of model tests has been particularly set up to analyse the time-dependent Damage Stability of a floating body. The test-body has been designed specifically to reflect the most typical internal subdivision layouts of ships affected by the effects mentioned above. The experimental study covers a static model test series as well a dynamic one. The static model test series has been set up with the aim to analyse the progressive flooding of selected compartments in calm water. Within the dynamic model test series, the model is excited by a roll motion oscillator to evaluate the influence of the ship motion on the water propagation and the associated Damage Stability. The model tests presented in this paper comprise side leaks in typical compartments which are used for a basic validation of the simulation toll and the measurement devices. Particular attention has been drawn on Damage scenarios with critical intermediate flooding stages in consequence of restricted water propagation.The presented results enable a further validation of the numerical flooding simulation and give an insight view on the chosen experimental setup.
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Progressive Flooding Assessment of the Intermediate Damage Cases as an Extension of a Monte-Carlo based Damage Stability Method
2013Co-Authors: Hendrik Dankowski, Stefan KrügerAbstract:The computation of intermediate flooding stages for current Damage Stability rules is a very complex and time consuming task for the design engineer and usually only performed manually for certain critical cases and stages. A progressive flooding method is presented in this paper, which computes the flux between the compartments based on the Bernoulli equation. Large and partly flooded openings are taken into account as well as optional air compression and flooding through completely filled rooms. The method is validated with the standard benchmark model test recommended by the ITTC. Especially for multi-compartment Damage combinations, the correct treatment of possible critical intermediate stages of flooding is unclear and only briefly described in the current SOLAS 2009 regulations. The method presented here uses a typical Damage opening based on the generated Damage cubes by a Monte Carlo simulation to perform a direct progressive flooding assessment for each critical intermediate case. This method has the advantage to remove the limitation of typical three to four discrete intermediate stages of flooding, that are usually assumed. Instead, it allows to investigate each intermediate Damage case in the time domain to gain a more detailed view on the severity of the flooding process and the vulnerability of the ship with regard to flooding of the watertight integrity after Damage. The generation of the Damage cases and the required openings is completely automated by chopping the section based hydrostatic model of the hull and the compartments with an appropriate Damage cube. A robust and fast algorithm taking into account complex compartment geometries including negative sub-spaces will be presented. The combination of flooding calculations with a Monte Carlo method extends the classical Damage Stability calculations to the time domain, which allows a more accurate estimation of the overall safety level of a ship to withstand Damage.
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On the safety level of the SOLAS 2009 Damage Stability rules for RoPax vessels
Marine Systems & Ocean Technology, 2011Co-Authors: Hendrik Dankowski, Stefan KrügerAbstract:The new probabilistic Damage Stability rules in SOLAS 2009 and their impact on the safety of the ship subdivision design have been widely discussed. Especially the safety level of RoPax designs are considered for further investigations. This paper describes a methodology to compare the safety provided by different Damage Stability regulations for a certain ship design. The determination of the Damage cases probabilities are based on a Monte Carlo simulation for the Damage distributions. The Damage cube itself is modeled by distribution functions retrieved from statistics based on the HARDER project. This gives a very elegant, fast and direct approach of Damage calculations. Together with the calculation of the survivability of all Damage cases, this allows to identify and compare the safety level indices of different Damage Stability standards. The method has been used in the “EMSA Study on Damage Stability of ROPAX vessels”. The theory of the simulation methodology and some extracts of the results of the EMSA study will be presented in the following. It has been shown in the study that for the investigated RoPax designs the new SOLAS 2009 rules are less stringent than the old, deterministic rules according to the Stockholm agreement. This means that especially the old water-on-deck requirement results in more se-vere designs and that the required index of the new Damage rules is too low for the investigated RoPax vessel designs.
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On the safety level of the SOLAS 2009 Damage Stability rules for RoPax vessels
Marine Systems & Ocean Technology, 2011Co-Authors: Hendrik Dankowski, Stefan KrügerAbstract:The new probabilistic Damage Stability rules in SOLAS 2009 and their impact on the safety of the ship subdivision design have been widely discussed. Especially the safety level of RoPax designs are considered for further investigations.
Eleftheria Eliopoulou - One of the best experts on this subject based on the ideXlab platform.
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Damage Stability requirements for passenger ships : collision risk based cost benefit assessment
2015Co-Authors: Rainer Hamann, Apostolos Papanikolaou, Odd Olufsen, Henning Luhmann, Eleftheria Eliopoulou, Dracos VassalosAbstract:Currently built passenger ships have to comply with SOLAS 2009 probabilistic Damage Stability requirements. There are, however, serious concerns regarding the sufficiency of these requirements with respect to the Required Subdivision Index R, which should properly account for the risk of People On Board (POB) and ship’s inherent survivability in case of loss of her watertight integrity. In recent years extensive research on determining the appropriate level of R using risk-based methods has been carried out. The urgency of the matter was reinforced by the quite recent Costa Concordia (2012) accident, even though this accident was not related to a collision event. This paper outlines the objectives, the methodology of work and first results of the ongoing studies funded by EMSA (EMSA III project) focusing on risk-based Damage Stability requirements for passenger ships. In compliance with IMO Formal Safety Assessment process a collision risk model is further developed based on the results of EU GOALDS project and a new required index shall be suggested by means of cost-benefit assessment. The updated collision risk model uses information from the most recent analysis of casualty reports of databases considering the period 1990 to 2012
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on the development of the new harmonised Damage Stability regulations for dry cargo and passenger ships
Reliability Engineering & System Safety, 2008Co-Authors: Apostolos Papanikolaou, Eleftheria EliopoulouAbstract:Abstract This paper outlines the methodological background and presents a summary of the main results of a series of undertaken international, IMO-led studies, on the harmonisation of the new probabilistic, risk-based regulations with the currently in-force regulatory provisions for assessing the Damage Stability of dry cargo and passenger ships. It reviews the historical development of the new regulations, to be applied to all new buildings on January 1, 2009, and the anticipated impact of the new rules on the design and indirect operation of various subcategories of dry cargo and passenger ships. It identifies certain loopholes in the existing regulations that appear cured by the new ones, though certain compromises adopted in the development of the new regulations, particularly those related to large passenger ships’ survivability, have left some open issues to be addressed in the near future.
