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The dynamic response of ships following grounding and collision accidents may be influenced by structural topology as well as operational and environmental conditions. Traditionally, the consequences of such events may be assessed by crude empirical methods or laborious experiments. Computational methods offer a useful alternative in terms of accurately capturing crushing mechanisms also accounting the influence of surrounding water. This paper presents a benchmark study that compares the structural dynamic response by explicit nonlinear FEA approaches and the semi-numerical super-element method. Simulations for typical accident scenarios involving passenger ships confirm that implementing the influence of hydrodynamic restoring forces in way of contact may be useful for either collision or grounding. Yet, for grounding scenarios, the damaged area resulting from analytical simulations appears to be sensitive to the failure strain values adopted to model the rupture of the ship bottom floors.

openaire: EC/H2020/730888/EU//RESET Safety assurance of autonomous ships is one of the major long-term challenges faced by the maritime world. Applying systemic hazard analysis methods at this early stage will guide the design and operation of safe autonomous ships. This paper proposes an initial hierarchical ship systems structure that could be the basis for a systemic hazard analysis of autonomous ship systems and operations. The approach is based on the systems theory and the principle of hierarchy and has been developed via the combination of models used in past research projects and requirements of the STCW convention. For enabling the operation of autonomous ships, the ship crew functions are either replaced by ship technical systems or assigned to the Shore-Based Control Centre (SCC).

The increasing system complexity due to technological advances in recent decades requires the implementation of Model-Based System Engineering (MBSE) languages. While MBSE languages can support in creating detailed and precise system descriptions, requirements, functions, and component interactions, the development of several modelling languages has formed a challenge for system engineers to select a suitable modelling language for complex operations. Since the implementation of MBSE modelling languages is extensive and requires high resources, system engineers need to select the most suitable one for their project. Furthermore, the prepared system models are utilized by different end-users such as system engineers, operators, and marketing professionals. As a result, it is necessary to integrate the perception of end-users in the modelling language selection process. Hence, a decision-making support framework needs to be developed, which will incorporate the opinions of end-users in the selection process. Correspondingly, this study proposes a Multi-Criteria Decision-Making framework aimed to select the most appropriate and practical modelling language. The framework integrates the end-user’s perception in the selection process using the Technology Acceptance Model and reckons the MBSE language features as comparison criteria. To analyze the data collected from the end-users, integration of Multinomial Process Tree modelling and Bayesian inference is developed. The applicability of the proposed model was tested in a ship pilotage operation case study. The results show that the framework can support system engineers during the initial selection process of the MBSE modelling language.

Maritime characteristics make the progress of automatic operations in ships slow, especially compared to other means of transportation. This caused a great progressive deal of attention for Autonomy Degree (AD) of ships by research centers where the aims are to create a well-structured roadmap through the phased functional maturation approach to autonomous operation. Application of Maritime Autonomous Surface Ship (MASS) requires industries and authorities to think about the trustworthiness of autonomous operation regardless of crew availability on board the ship. Accordingly, this paper aims to prognose the health state of the conventional ships, assuming that it gets through higher ADs. To this end, a comprehensive and structured Hierarchal Bayesian Inference (HBI)-based reliability framework using a machine learning application is proposed. A machinery plant operated in a merchant ship is selected as a case study to indicate the advantages of the developed methodology. Correspondingly, the given main engine in this study can operate for 3, 17, and 47 weeks without human intervention if the ship approaches the autonomy degree of four, three, and two, respectively. Given the deterioration ratio defined in this study, the acceptable transitions from different ADs are specified. The aggregated framework of this study can aid the researchers in gaining online knowledge on safe operational time and Remaining Useful Lifetime (RUL) of the conventional ship while the system is being left unattended with different degrees of autonomy.

Ship performance in level ice involves problems such as attainable speed and maneuverability under different ice thickness. As the alternative to analytical methods, numerical simulation models have been proposed in recent years to improve the accuracy and to analyze more complex operations. However, current numerical models use quite diverse approaches to model the icebreaking components, and focus on rather different aspects, while the choices need more justification. The primary aim of this paper is to propose a framework for the development of effective and efficient numerical models to simulate ship performance in level ice, based on state-of-the-art knowledge of ship-ice interaction. This covers a discussion of modelling purposes and a hierarchical decomposition of the problem, followed by a strategy and two methods which could be applied to improve accuracy and credibility, as well as methodology of validation. Following the proposed framework, a numerical model is proposed as a prototype model, which simulates ship performance in level ice, and can be developed further in future. The numerical simulation results are compared with full-scale measurement results of a ship on the Baltic Sea, indicating reasonable estimation of ship turning. This implies the validity of the model as a prototype of the proposed framework.

Maritime activity in the Arctic is on the increase, driven by multiple factors including the development of Arctic natural resources, climate change, regulatory changes, improved technology and operations, national and international policies, infrastructure developments, fuel prices, and the global economy. This article aims to identify and analyze such change drivers and to discuss how these might influence the future of three specific segments of Arctic shipping: destination-Arctic shipping (operation between Arctic and non-Arctic locations), trans-Arctic shipping (operation between non-Arctic locations through Arctic waters), and Arctic cruising. The study finds that each considered segment of Arctic shipping is subject to a unique set of significant change drivers.

Substantial progress has been made in the last decades to computationally model the structural response of marine structures subjected to collision and grounding accidents. The finite element method stands out as the most reliable and robust technique within other tools for this purpose. However, there are still some complex physical aspects arduous to be modeled numerically. This work presents an experimental technique to reproduce the mechanical response and collapse mode of marine structures subjected to collision and grounding events by using miniature models built by additive manufacturing. This experimental technique relies on structural scaling and thickness distortion formulations. A raking test on a large-scale ship bottom was replicated in a 1:30 reduced scale to validate this technique. The miniature ship bottom structure was additively manufactured from stainless steel 316L considering all structural details. Flat dog-bone samples with different thicknesses were also built in the same way for mechanical characterization of the material via tensile tests and microscopy analysis of material fractures. Tensile tests showed a good consistency in stress-strain curves with a small, but noteworthy, influence of plate thickness and a large dispersion in rupture elongations. The fractured sections revealed various void formations around non-sintered metal powder. In spite of that, the structural response obtained from miniature test showed a good correspondence with the large-scale reference test when both are brought to the same dimensional scale.

openaire: EC/H2020/723526/EU//SEDNA Maritime activity in the Arctic is on the increase, driven by the extraction of Arcticnatural resources, trans-Arctic shipping, and Arctic tourism. To manage related risks to humans and the polar environment, in January 2017 the International Maritime Organization (IMO) enforced the international code for ships operating in polar waters (Polar Code). The code is fundamentally goal-based, allowing designers to deviate from established prescriptive rules, facilitating design optimization and innovation. However, for designers to be able to implement goal-based regulations, they need relevant and validated design tools. Toward this end, we discuss new insights of relevance on two related topics, namely (a) the assessment of ice loading on ships, and (b) risk assessment in Arctic shipping.

openaire: EC/H2020/730888/EU//RESET Ship collision attracts prevalent attention due to its high occurrence frequency and severe potential conse-quence. It is therefore of pressing importance to prevent ship collision at sea for safe maritime transporta-tion. Non-linear Velocity Obstacle (NL-VO) algorithm has received increasing attention in maritime colli-sion avoidance by taking the dynamics of ship action during the encounter process into consideration. How-ever, one precondition of NL-VO algorithm is that the trajectory of target ship needs to be known in ad-vance, which makes the application of this algorithm limited in the historical ship collision risk analysis ra-ther than the in real-time collision avoidance. Although the generalized velocity obstacle algorithm over-comes this limitation using the trajectory prediction module, the trajectory uncertainty of the target ship is not discussed leading to the possible inaccurate collision risk assessment. Therefore, this paper presents a real-time collision risk assessment method based on an improved NL-VO algorithm by including the uncer-tainty analysis of the target ship’s predicted trajectory. The proposed method consists of two main modules: trajectory uncertainty module assumes that the increase in the radius of the circular restricted area is con-sistent with the Wiener process; collision risk assessment module utilizes the non-linear velocity obstacle algorithm combined with the dynamic circular restricted area to evaluate the potential collisions. Several encounter scenarios in a specific port channel are designed to demonstrate the feasibility of using this pro-posed method to assess ship collision risk in real-time. The result shows that this improved NL-VO algo-rithm can timely identify a ship that is in danger of colliding with the own ship and know when the collision will occur, which contributes to reducing ship collision occurrence probability.

openaire: EC/H2020/730888/EU//RESET As autonomous ships are currently developed, modern technologies are implemented into ship systems for enabling autonomous operations. Tight coupling in safety-critical systems created new challenges for the engineers and operators. Designing, operating and analyzing these complex systems requires a deep understanding about the system composition, requirements and expected behavior or functionality. The increasing complexity of the systems requires the implementation of modern model-based approaches. Instead of large texts, these new modelling techniques aim to present detailed system information with simplified models. This paper compares system modelling techniques known as System Modelling Language (SysML) and Object Process Methodology (OPM). These methods are used to model a Dynamic Positioning system (DP-system). Results show that the SysML is more suitable than OPM for modelling the autonomous ship systems due to its ability to present detailed system information in a simple and coherent way.

The concept of autonomous merchant ships is quite recent. The increasing interest in autonomous vessels is nowadays calling for smart technologies that are supposed to replace the human actions on board. This involves troublesome issues related to ship safety. In the future, decision-making processes that are conventionally performed by human beings on board ship will be moved ashore to the control centre and maybe even completely replaced by computers and smart technologies. This paper proposes a method suitable for oceangoing ships, providing an autonomous routine for the avoidance of two dangerous phenomena involving excessive motions of the ship, e.g. the synchronous roll and the parametric resonance, both taking place in rough seas. The method is two-fold, since it pertains to the process of route planning and route monitoring and it encompasses two submethods (A and B). Submethod A is used to define a set of operational scenarios to be avoided due to excessive accelerations, with the use of a numerical ship motion model. This is applied at the route-planning stage. Submethod B is developed to monitor ship motions and to detect large roll motion for a ship in the seaway. It also raises alerts at two levels, first when the large roll motions are expected to develop (leaving ample time for remotely located operators to react), second when the large roll motions are developing (leaving a short time window for action taken on board the ship). The main sources of uncertainty are defined and the solutions to address those are proposed. Finally, the method is applied on simulated time histories of ship motion, which is a container ship traversing the Pacific Ocean. The obtained results are promising; however, further work is required with respect to various manoeuvers performed by a ship in the seaway.

Selection of suitable ice class for ships operation is an important but not simple task. The increased exploitation of the Polar waters, both seasonal periods and geographical areas, as well as the introduction of new international design standards such as Polar Code, reduces the relevancy of using existing experience as basis for the selection, and new methods and knowledge have to be developed. This paper will analyse what can be the limiting ice thickness for ships navigating in the Russian Arctic and designed according to the Finnish-Swedish ice class rules. The permanent deformations of ice-strengthened shell structures for various ice classes is determined using MT Uikku as the typical size of a vessel navigating in ice. The ice load in various conditions is determined using the ARCDEV data from the winter 1998 as the basic database. By comparing the measured load in various ice conditions with the serviceability limit state of the structures, the limiting ice thickness for various ice classes is determined. The database for maximum loads includes 3-weeks ice load measurements during April 1998 on the Kara Sea mainly by icebreaker assistance. Gumbel 1 distribution is fitted on the measured 20 min maximum values and the data is divided into various classes using ship speed, ice thickness and ice concentration as the main parameters. Results encouragingly show that present designs are safer than assumed in the Polar Code suggesting that assisted operation in Arctic conditions is feasible in rougher conditions than indicated in the Polar Code. Keywords: Loads, Serviceability, Limit ice thickness, Polar code

Full-scale measurements on polar research vessels present an opportunity to advance the state-of-the-art in ship design through high-quality long-term measurements of environmental conditions and s...

Overload response of the stiffening frames in ship side structure due to ice loading is an important design consideration for ships operating in ice infested waters. By overload, we mean loads that are larger than assumed by the rules. Therefore, the response of ice strengthened grillage frames is investigated under a range of idealized rectangular pressure patches and by assuming different boundary conditions for the structural units. A flat, representative grillage of an ice-strengthened ship is considered and analysed using non-linear Finite Element Method. The response of the grillage frames is compared with the isolated frame response. Two frame types are considered: flatbars and L-frames. Finite element simulations revealed that patch length has strong effect on the frame deformation mode. The key characteristic that differentiates the response under shorter and longer patches is the longitudinal membrane stretching of the shell plating. Longer patches tend to suppress this deformation mode that leads to similar frame behaviour observed in isolated frame analysis. It is further shown that overload capacity of grillage frames reduces with increasing patch length to levels observed in isolated frame analysis. Analysis of plastic strain development in the frames and plating revealed that plastic strain localized faster in frames, but shell plating is more sensitive to patch height variations. This renders frames more susceptible to fracture than plating. Finally, the local failure mechanisms of the L-frames tend to diminish the load sharing capability and so negatively affects the overload behaviour.

Unmanned merchant vessels' prototypes are expected to come into operation within a few years. This revolutionary shift in the shipping industry is feared to negatively impact the safety of maritime transportation. Therefore, in order to support future designers of remotely operated merchant vessels system, we applied System-Theoretic Process Analysis (STPA), identifying the most likely safety control structure of the analysed system and investigating it. The aim was to suggest potential ways of increasing the system's safety and to assess the effectiveness of such measures. Results indicate that the implementation of remotely-controlled merchant vessels and, in a wider sense, unmanned ships, and ensuring their safety shall consist of executing various controls on regulatory, organisational and technical plains. Potential effectiveness is evaluated and some recommendations are given on how to ensure the safety of such systems.

Transportation in ice-prone waters is a timely topic because of the pursuit of natural resources and sea routes. S.A. Agulhas II voyaged in Antarctic waters during the austral summer of 2013–14. Th...

For the design and transit simulation of ice-going ships, a number of methods have been proposed for the prediction of ship resistance and transit speed in various ice conditions. In this paper, selected methods for ship performance in level ice, ridged ice and channel ice are evaluated based on full-scale measurement data of two ships. Uncertainties are identified and evaluated for a better understanding of the deviations in the results. Ice thickness in full-scale data was measured using multiple methods to minimize the uncertainty. The thickness of level ice was measured by a stereo camera system. The ridge profile was identified through measurement with an electromagnetic device. Visual observation was conducted for the description of encountered ice conditions. For a better estimation of ship net thrust through propulsive data, the net thrust model is revised in this paper to take the effect of power and propeller pitch into consideration. The results show that for transit simulation, the selected methods for level ice give acceptable prediction of ship speed with certain underestimation. For ridged ice, the method seems to underestimate the speed, especially when a ship needs to conduct ramming operation. Data acquisition is the most problematic for the investigation of channel ice. The uncertainties due to the modelling of sub-processes and ice properties lead to certain scatter in applying these methods for speed prediction. Possible improvements are given as the conclusion of this work.

Ship operation and ice loading in floe ice fields have received considerable interest during recent years. There have been several numerical simulators developed by different institutes which can simulate ship navigation through floe ice fields and estimate ship performance and local ice loads. However, public data obtained from full-scale measurement covering comprehensively ship performance and ice loads under various ice thicknesses, concentrations and floe sizes are rare. The 2018/19 Antarctic voyage of the Polar Supply and Research Vessel (PSRV) S.A. Agulhas II gathered considerable data of the ship in floe ice fields under various thicknesses, concentrations, and floe sizes. The aim of this paper is to carry out statistical analysis to seek suitable probability distributions which adequately fit the measured ice load and therefore suitable to be used as parent distributions for long-term estimation. For this aim, three categories of probability distributions, namely standard distributions, truncated distributions and mixture distributions are tested. It is found that truncated distributions can fit the load data better than standard distributions bounded at the threshold. In addition, mixture distributions are shown to have promising features, which fit the data well and are able to separate distribution components. Subsequentially, the well-performed distributions are used as parent distributions to make long-term load estimations. The estimation results demonstrate that long-term estimations are sensitive to the selection of parent distribution, which addresses the importance of finding correct distribution to model short-term ice loads. The data of ten selected cases will be published for the use of other researchers.

Funding Information: The model tests have been funded by the South-eastern Finland–Russia CBC 2014–2020 program via the project Future Potential of Inland Waterways (INFUTURE). The authors would like to thank Jarkko Toivola for the valuable discussions on the practical situation of ships in narrow ice channel. Publisher Copyright: © 2021 The Authors

openaire: EC/H2020/814753-2/EU//FLARE This paper presents a big data analytics method for the evaluation of ship-ship collision risk in real operational conditions. The approach makes use of big data from Automatic Identification System (AIS) and nowcast data corresponding to time-dependent traffic situations and hydro-meteorological conditions respectively. An Avoidance Behavior-based Collision Detection Model (ABCD-M) is introduced to identify potential collision scenarios and Collision Risk Indices (CRIs) are quantified when evasive actions are taken for each detected collision scenario in various voyages. The method is applied on Ro-Pax ships operating over 13 months of the ice-free period in the Gulf of Finland. Results indicate that collision risk estimates may be extremely diverse among voyages, and in 97.5% of potential collision scenarios the evasive actions are triggered only when risk is at 45% or more of its maximum value. The overall CRI for ships operating over the given area tends to be lower for adverse hydro-meteorological conditions. It is therefore concluded that the proposed method may assist with the (1) identification of critical scenarios in various voyages not currently accounted for by existing accident databases, (2) definition of commonly agreed risk criteria to set off alarms, (3) the estimation of risk profile over the life cycle of fleet operations.

This work presents a revision of the structural similarity technique developed for the experimental modeling of marine structures subjected to collision, grounding or similar catastrophic events via miniature models with drastic scale reduction. This revision involved basically the inclusion of combined collapse modes to predict the mechanical behavior of structural members and the redefinition of the flow stress range. The revised technique was validated through numerical simulations of the miniature modeling of nine large-scale marine structures’ experiments found in literature and here presented in the form of nine study cases. Each study case evaluates the accumulated effects of scale reduction, thickness distortion and material distortion in the miniature model as part of the similarity technique. In general, a reasonable-to-good correspondence was observed between the force and absorbed energy responses obtained from reference large-scale structures and their miniature models once brought to the same dimensional scale. Discrepancies between structural responses were quantified by evaluating the normalized root mean square error. By these means, most of the study cases presented errors below 12.5% in terms of force response and below 4.5% in terms of absorbed energy response. On the other hand, lower agreement was encountered when reproducing experiments strongly ruled by progressive buckling or crack initiation/propagation together with severe reduction scales. In these cases, better results are achieved when implementing a more accurate material failure model or by moderating the reduction scale.

Structures used in Arctic regions must comply with ice-induced loading without failure, asset loss, or loss of life. Current structural design regulations, particularly for ships, rely primarily on...

This article investigates how the-organization of the shipbuilding process influences production efficiency-by creating a model of the shipbuilding process utilizing a Bayesian network. In this model, the variables are determined by factors having an impact on production efficiency. Causal dependencies between these variables create the network. Three different configurations of organization are included, namely, line organization, project organization, and a hybrid organization. All model probabilities for reaching the targeted production efficiency are elicited from experts. Based on the results, project organization has the highest probability of achieving the desired efficiency. The higher probability is mainly because, in project organization, clear responsibilities lead to target-oriented problem solving and decision making. The model demonstrates that organization has impact on production efficiency. The model can also be used for further developing the cruise shipbuilding process.

A method for estimating ship's resistance caused by sea ice ridge keels is revised and used as a part of a method for predicting performance of ships in ridged ice conditions. The resistance method is based on a continuum plasticity model of ridge rubble and is simple to compute. The performance prediction method combines deterministic simulations of ship motion with probabilistic modelling of ridged ice fields. Performance estimates given by the model are distribution of attainable mean speeds for given ice conditions and probability of the ship being able to operate independently. A comprehensive sensitivity analysis was performed to gain insight into the model and identify possible problematic parameters. The sensitivity analysis covered both the ice conditions and modelling assumptions. Two data-sets were used to test the simulation method. One set included the depth profile of sea ice, machinery data and the speed of a ship operating in ridged ice. The resistance method was able to predict the mean speed over 3km well. The second data-set consisted of a history of ship's speeds and positions from AIS data and ice conditions estimated by a numerical ice model HELMI, developed in the Finnish Meteorological Institute. Observed mean speeds were mostly well within the distributions of mean speeds simulated by the transit simulation model. Predictions of independent operation were also promising.

To achieve increasing emission requirements, the cruise ship industry is working to develop higher efficiency ships. Cruise ships are different from other ship types in their relatively higher consumption of electrical power, steam and hot water. Several novel high-efficiency system concepts are possible for on-board electrical power generation and other utility services, each with differing impacts and first costs. Low-emission concepts novel to the cruise ship industry include combinations of exhaust gas heat recovery, heat pumps, steam turbines and organic Rankine cycles (ORCs). Yet, evaluation of these concepts is difficult given the different operating modes of cruises, and overall efficiency is dependent on the dynamic operational sequences. In this paper, we compare alternative energy efficiency concepts for cruise ships through simulation studies of the ship operations when equipped with different novel power generation systems. We find that the dual pressure steam systems and ORC offer the greatest potential for energy efficiency improvements in the cruise ship industry. We also find that relatively conventional technologies enable cruise ships to comply with planned upcoming higher ship energy efficiency requirements.

Ice management enables offshore and marine activities in Arctic waters in the presence of sea ice or icebergs. The presence of ice introduces additional risks to the activities. This paper discusses the risks in the light of novel risk perspectives, emphasizing uncertainties arising from potentially weak background knowledge in ice management operations. An ice management system is defined and a generic risk picture of an ice management operation is created. Risk theory is connected to the results using discussion and a conceptual example. Ice management operations are complex socio-technical systems requiring expertise in various fields. Available data is scarce and uncertainties are high. Still, the main activities need to trust in the ice management system to operate safely. The risks in ice management operations culminate in decision making and physical ice management. These need to be better understood to manage the operational risks.

According to International Maritime Organization (IMO), the Baltic Sea Area has some of the densest maritime traffic in the world. The Baltic Sea was designated a Particularly Sensitive Sea Area (PSSA) at IMO Marine Environment Protection Committee's 53 rd session in July 2005. The Mandatory Ship Reporting System in the Gulf of Finland Traffic Area (GOFREP) was established by IMO in 2003 and has been in operation since 2004. The objective of this study in progress is 1) to outline the hierarchical structure of the maritime navigation safety management system from European to ship onboard level and 2) to apply the Systems-Theoretic Process Analysis (STPA) to identify system level hazards and potentially unsafe ship speed and maneuvering control actions with respect to IMO Collision Regulations (COLREGs) Rules on ship safe speed, ship safe separation distances and the Traffic Separation Schemes requirements with the aim of evaluating the effective hazard control options to enable efficient updating of ship level situational awareness and the enforcement of safety constraints in real time.

The prototypes of unmanned merchant vessels are expected to come into service within the coming years. The main line of argument supporting their introduction pertains to the increase in navigational safety, which is expected to be achieved by reducing the frequency of human-related accidents on board ships, by removing the crews. On the other hand, the response of unmanned ship to potential accidents is still uncertain. With enthusiasm on one side and apprehension on the other, the literature lacks an objective study on the effect of unmanned ships on safety of maritime transportation. This paper constitutes an attempt to bridge the aforementioned gap by applying a framework based on what-if analysis to a hundred maritime accident reports. The aim of the analysis is to assess whether the accident would have happened if the ship had been unmanned, and once the accident had happened - would its consequences have been different. The results obtained reveal that the occurrence of navigational accidents (e.g. collision, grounding) can be expected to decrease with the development of unmanned ship. However the extent of consequences resulting particularly from non-navigational accidents (e.g. fire, ship loss due to structural failure) can be expected to be much larger for the unmanned ships when compared to the conventional ones.

Autonomous vessels have become a topic of high interest for the maritime transport industry. Recent progress in the development of technologies enabling autonomous systems has fostered the idea that autonomous vessels will soon be a reality. However, before the first autonomous vessel can be released into her actual context of operation, it is necessary to ensure that it is safe. This is a major challenge as the experience of autonomous ships is very limited. This study highlights the need for elaborating a systemic and systematic hazard analysis since the earliest design phase of an autonomous vessel. In particular, it proposes a process for elaborating an initial hazard analysis and management that provides coherent, transparent and traceable safety input information for the design of an autonomous vessel. The process is applied to analyse the hazards of two autonomous vessel concepts for urban transport in the city of Turku, Finland.

In the last few years, additive manufacture techniques — also known as 3d printing — are gaining more applications in the maritime sector including the production of functional large ship components in compliance with demanded operational and quality standards. By contrast, 3d printing miniature models of marine structures with the aim to reproduce structural responses brings along a higher degree of complexity. On the one hand, miniature thin-walled structures entails different manufacturing challenges when compared with large-size ship components. On the other hand, modeling structural events that comprise extreme reduction scales (around 1:100), material deformation and fracture at high loading rates, among other aspects, require purpose-designed scaling laws to handle all these effects adequately. The aim of this work is to present a wide panorama in the development of miniature 3d printed marine structures aiming to model experimentally ship collision and grounding events in reduced scale. Some preliminary experimental tests in miniature marine structures are also presented.

In this paper a three dimensional ice material model is developed, with several key factors affecting ice behavior are considered. This material model is based on viscoelastic theory, comprising elastic, delayed elastic and viscous components. Strain rate effect on the ice behavior is embedded in the viscous term, and the time dependent characteristic is reflected by the delayed elastic term. The viscous term is based on the improvement of Glen’s law, which is originally related to temperature variation. The pressure hardening and pressure softening phenomena are included through improving this relation. This model also takes into account the sensitivity of porosity induced mainly by air bubbles and brine volume. The proposed ice material model is programed by Fortran and implemented in LS-Dyna. The accuracy of the proposed ice material model is verified through simulations of tri-axial and uniaxial compressive experiments, comparing the predicted ice strength with experimental results.

This paper investigates the influence of the strain rate and element size on the fracture of steel plates presented in marine structures undergoing grounding when modeled by the finite element method. Three different experimental tests (tensile, tearing and perforation tests), performed at different velocities, are used in the study. These tests are conceived to cover diverse rupture modes related mainly to crack initiation and propagation. Plastic strain- and stress state-based failure criteria were calibrated from these experiments. Sensitivity to strain rate and mesh size were also evaluated. A ship grounding event was reproduced experimentally in 1:100 reduced scale. This experiment was FE modeled to evaluate the performance of the aforementioned failure criteria. The results verified the significant influence of the strain rate and stress state on the failure strain. In addition, it is shown that the sole use of tensile tests is not enough to properly characterize the material failure observed in the structural collapse mode of the miniature ship bottom structure. This collapse is shown to be a combination of stretching and tearing of structural members.

openaire: EC/H2020/730888/EU//RESET Considerable advances have been made in the last decades to computationally model the structural response of marine structures subjected to collisions and grounding events. Within existing numerical tools, finite element method stands out as one of the most complete, reliable and robust technique. However, there are still some complex aspects difficult to model numerically such as the effect of ship cargo, surrounding water, harsh environment conditions, pre-damaged structures, explosion, etc. The aim of this work is to present the ongoing development of a novel tool to reproduce experimentally the structural collapse of marine structures in reduced scale. The main potential applicability of this novel technique is to replicate complex ship accident scenarios. This tool combines principles of structural similarity, experimental mechanics and miniature metallic marine structures made of rolled steel sheet and additive manufacture. The structural response of some crushing experiments in real-scale marine structures are reproduced in miniature to validate the technique.

openaire: EC/H2020/730888/EU//RESET With the global warming and a large amount of sea ice melting, the available Arctic Sea Route has greatly enhanced the value of Arctic shipping. Ship operations under icebreaker assistance have become an essential way to facilitate the safe navigation of merchant vessels sailing through the Arctic Sea Route in ice-covered waters, but they can also put the crew and the ship in danger caused by a possible collision between the assisted ship and the icebreaker. In this paper, a dedicated Human and Organizational Factors (HoFs) model of ship collision accidents between an assisted ship and an icebreaker is developed and analyzed with the aim to identify and classify collision risk factors. First, a modified model of the Human Factors Analysis and Classification System (HFACS) for collision accidents between a ship and an icebreaker in ice-covered waters is proposed, which helps to analyze ship collision reports. Then, a Fault Tree Analysis (FTA) model is utilized to analyze the fundamental collision risk factors according to the statistical analysis of accident reports and expert judgments based on the HFACS-SIBCI model. Finally, qualitative analysis is carried out to analyze collision risk factors under icebreaker assistance, where Risk Control Options (RCOs) are formulated. An important guidance for the risk control of ship collisions during icebreaker assistance in ice-covered waters is provided for lawmakers and shipping companies.

Maritime accidents have the potential to cause significant financial loss, injury, and damage to the environment. One approach to investigating maritime safety is to focus on near misses, that is, situations which did not lead to an accident but where an accident was narrowly avoided. Based on the principles of the traffic conflict technique, which ranks traffic encounters through a conflict severity hierarchy, this paper proposes a novel model for screening maritime traffic data for near miss ship-ship encounters, particularly for open sea and coastal restricted sea areas. Compared to previous methods, the proposed method has a greater specificity, leaving fewer possible near miss cases to be assessed by navigational experts in a contextualised traffic setting. This is achieved by including the effect of ship size through a ship domain, and by better accounting for the criticality of the encounter direction through the Minimum Distance To Collision concept compared to earlier proposed models. The factors included in the model and their relation are based on expert judgments and using knowledge from previous studies. Model parameters are derived from AIS data points from a reference encounter situation dataset. The developed model has been applied to traffic data from the Northern Baltic Sea. The model is subjected to a number of validity tests, the results of which suggest that the model is adequate for ranking and prioritizing encounters for further assessment in an expert judgment phase to identify near misses. Thus, it establishes a method to enable subsequent research into the validity of near miss information to make statements of maritime safety in relation to collision accidents.

Most of the risk models for ship-grounding accidents do not fully utilize available evidence, since it is based on accident statistics and expert opinions. The major issue with such kinds of models is their limitation in supporting the process of risk-management with respect to grounding accidents, since they do not reflect the reality to the extent required. This paper presents an evidence-based and expert-supported approach to structure a model assessing the probability of ship-grounding accidents, to make it more suitable for risk-management purposes. The approach focuses on using evidential data of ship-grounding accidents extracted from the actual accident and incident reports as well as the judgement elicited from the experts regarding the links and probabilities not supported by the reports. The developed probabilistic model gathers, in a causal fashion, the evidential contributing factors in ship-grounding accidents. The outcome of the model is the probability of a ship-grounding accident given the prior and posterior probabilities of the contributing factors. Moreover, the uncertainties associated with the elements of the model are clearly communicated to the end-user adopting a concept of strength-of-knowledge. The model can be used to suggest proper risk-control-measures to mitigate the risk. By running uncertainty and sensitivity analyses of the model, the areas that need more research for making educated decisions are defined. The model suggests the high-level critical parameters that need proper control measures are complexity of waterways, traffic situations encountered, and off-coursed ships. The critical area that calls for more investigation is the onboard presence of a sea-pilot.

Groundings are among the most common and serious maritime accidents. The shape of the sea bottom is one of the important factors that determine the extent of grounding damage on ships, including loss of watertightness. This paper presents a four-step methodology for mathematically analyzing sea bottom shapes, where individual peaks are identified and isolated from larger datasets. To these individual peaks mathematical models are fitted and the goodness of the fit is evaluated. The aim is to develop mathematical rock models that can be used in grounding damage analysis. The method is applied to bottom topography data from the two busiest tanker harbors in Finland. As potential mathematical rock models common assumptions found in literature as well as new suggestions are used. It was observed that rocks vary in shape and size locally as well as between different geographical areas. This highlights the need to have rock models that are flexible enough to model a wide range of sizes and shapes so that the local conditions can be taken into account. This includes modeling asymmetrical shapes, which is not taken into account in the current models. The analysis results suggest using a binormal function to describe the bottom shape: This model gives overall better goodness-of-fit test results than the cone and polynomial models. In the data the binormal model can model well the also the bottom shapes where the polynomial and conical models had a good fit in statistical terms. Although the paper discusses data from the Gulf of Finland, the framework for analyzing bottom shapes is expected to be applicable to other sea areas as well. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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.

Maritime piloting, the process of navigating ships safely in congested waters, is an area of maritime operations where emerging technologies may be used to develop and implement more robust navigation safety systems. This is supported by the commercial potential of remote piloting as a substitute for pilotage exemptions, today granted to experienced captains. This paper introduces a novel configuration for remote piloting operations in intelligent fairways. Results are supported by methodological and empirical research with the aim to enhance our understanding of merging the role of a pilot in autonomous fairway infrastructures. It is demonstrated that under controlled conditions remote piloting may be a safe option in selected fairways. However, upscaling will require greater understanding of risks associated with the implementation of emerging technologies , fairway features and environmental phenomena.

Undoubtedly, the main advantage of the additive manufacture technology is to allow building miniature structural parts with a large degree of complexity such as to replicate structural details of real-scale marine structures. This work presents a new technique for reproducing the structural response of large-scale thin-walled metallic structures when subjected to crushing loadings by using scaled-down additive manufactured models. This technique couples scaling laws for strain rate sensitive materials and a thickness distortion technique based on the structural collapse mode. In order to validate this coupled technique, the structural response of a large-scale crushing test of a web girder structure was experimentally replicated by using a 1/40 scale reduction model. The results and conclusions summarize the prospects and limitations of additive manufacturing of miniature complex marine structures for structural purposes and crashworthiness verification.

openaire: EC/H2020/730888/EU//RESET The lack of situational awareness is a major cause of ship collisions. Thus, enhancing the situational awareness of the stand-on ship is a key for navigational safety, where the intention estimation of the give-way ship is crucial. According to COLREGs, the stand-on ship is not allowed to take evasive actions until the give-way ship does not take proper actions timely. The stage that needs the stand-on ship to take actions plays as the second protective layer for the ship, which is named as ‘Stand-on Ship as Second Line of Defense’ (SLoD). A method to estimate the intention of the give-way ship and to trigger SLoD is proposed in this article. Four modules of the proposed method include: “data pre-processing” collects all traffic information and determines the ships' obligations; “action identification” pinpoints the turning points; “action uncertainty” generates a bounded reachable velocity considering the give-way ship's maneuverability; “conflict assessment” judges potential collision by using non-linear velocity obstacle algorithm. Several typical encounter scenarios are simulated to demonstrate the feasibility of the proposed method. The results show that intention estimation of the give-way ship improves the situational awareness of the stand-on ship, which can support the stand-on ship to make collision avoidance decisions.

Marine vessels and offshore structures functioning in Earth's frigid zones require ice management to continue their routine operations. Icebreakers are the most influential vessel in assisting marine operations in Polar Regions. The present study is set to analyze the clearance area of level ice using Azimuthing propeller jet in bollard condition, by means of full-scale and model scale experiments. Moreover channel widening and heeling test is performed to analyze the escorting ability of an icebreaker with only using propeller jets. Scope of the current investigation can be incorporated in designing new icebreakers and maintaining desired channel width based on propeller jets effect. Propeller jets can be used to break level ice, when the ship is stationary or moving, where the amount and capacity of breaking or clearing the ice are based on the thrust of the propeller, angle between the propeller jet axis and free surface, and thickness of the ice as well as propeller running time. This paper presents a comparison between full-scale experiments data (carry out in the Gulf of Bothnia, March 2017) and model scale trials performed in Aker Arctic testing facility on the level ice sheet. These experiments were based on image data from external camera and propeller flow parameters, where the area, as well as coordinate calculation, were within 3% of the accuracy from the acquired images. Full-scale ice thicknesses utilized in the experiments were selected and confirmed from surveillance videos. Model-scale images were corrected using Hugin software while ImageJ was used to calculate ice clearance parameters. Propeller thrust and area analysis show 10-22 % of the variation in the results of the model and full-scale experiments for 16 mm thick model ice. 16 mm thick model ice results are much closer to full-scale trials than 25 mm thick model ice. Test results at 30° and 90° pod angles could be extrapolated to design a prototype vessel. Channel widening shows worthy outcome, with the use of Azipods at a speed of 8 kn channel width of 36 m can be attain by positioning the stern Azipods at 30° puller configuration. Changing the pod inclination by 30% will increase the channel width to 20%. In the widening of new level ice channel, 30° pod angle is the most suitable.

As the initiatives to develop and implement autonomous merchant vessels into the global shipping industry are gaining momentum, their safety remains in the spotlight. It is argued that every effort shall be taken to ensure that the safety of maritime transportation is not reduced in the process, but the question of how to achieve it remains open. Meanwhile, the systemic approach is more widely being used to analyse innovative systems’ safety. We therefore apply a System-Theoretic Process Analysis to develop a model suitable for safety analysis and design recommendations’ elaboration for future autonomous vessels. Furthermore, we introduce a method of evaluating and communicating uncertainties pertaining to the method. The results indicate that the system-theoretic safety analysis’ outcome can be affected by manageable uncertainties despite the fact that the system in question is yet to be implemented.