Vessel Collision Research Articles

Numerical evaluation of novel crashworthy devices for protection of RC piers subjected to vessel impact

The protection of bridge piers crossing navigation channels from the collisions of passing vessels is a critical issue nowadays, as vessel collision upon bridge piers has become one of the major threats to the safety of waterway bridges. This paper aims to develop a novel cost-effective crashworthy device, and to assess the effectiveness of the proposed device for protection of reinforcement concrete (RC) pier columns from vessel impact. The proposed protective device is comprised of a series of steel beams arranged in a frame-type manner with I-shaped cross-sections, where beam segments with reduced cross-sections are used to limit the plastic mechanism within certain structural components. The energy-dissipation capacity of the proposed device and its effectiveness for pier protection are thoroughly assessed by numerical approaches using general-purpose finite-element (FE) programs, where a barge is employed as the impacting vessel. Detailed non-linear FE models of the barge–device–pier system are developed and validated, and a parametric study is then conducted using the validated FE models with consideration of several important design parameters including barge impact velocity and geometric dimensions of the device. The numerical results show that the proposed device can absorb a large portion of impact energy during an impact event, which significantly reduces the magnitudes of impact forces transmitted to a protected RC pier column and attenuates the damage occurred to both the pier column and the impacting barge vessel. It is also found that the plastic deformation of the device can be effectively limited within the section-reduced beam segments whilst the remaining part remains elastic during impact, which would greatly facilitate the restoration of a damaged device after an impact event.

Energy analysis of progressive collapses in a multi-span bridge under vessel impact using centrifuge modelling

Bridges spanning busy coastal or inland waterways are exposed to high risks of accidental vessel collisions. When a multi-span bridge is impacted, progressive collapses may develop within the bridge system, which can be aggravated by a decrease of pile embedment depth due to scour. Yet the system responses of multi-span bridges supported on pile foundations under vessel collisions are not well understood in the literature. Based on two series of advanced centrifuge tests on a three-pier bridge system at normal and scoured conditions, the energy transfer and dissipation in the bridge system during vessel impacts is systematically investigated in this study. During collision, 8–40% of the kinetic energy of the vessel is transferred to the bridge-soil system. The pier that is directly struck by the vessel absorbs 60–80% of the transferred energy. One pier fails when the input energy exceeds its limiting energy dissipation capacity. After failure, the energy redistributes to the adjacent piers, causing progressive collapses. From the energy perspective, mitigation measures for preventing progressive collapses of multi-span bridges should include decreasing the transferred energy, increasing the energy dissipation capacity, minimizing foundation scour, and cutting off the energy transfer path.

Multihazard Performance Assessment of Scoured Bridges Subjected to Barge Collision

Barges offer a safe and cost-effective means for transporting commodities in inland waterway systems. This, however, comes with the risk of barge collision into bridge piers that span navigable waterways. While the vulnerability of such bridges has been investigated in an intact condition under vessel collision, the existing assessment methods fail to capture how scour events that bridge piers often experience during their service life can affect their response to vessel-induced impact loads. To address this gap, three bridge structures were modeled in this study, and a fully loaded barge traveling at 0.5, 1.0, 1.5, 2.0, and 2.5 m/s was allowed to collide into each of them after they underwent various scour scenarios. The scour scenarios under consideration were developed, following the procedure provided in Hydraulic Engineering Circular No. 18, for both 100- and 500-year floods. Based on the obtained results, the impact force, maximum shear, and maximum bending moment that the bridge piers experienced were found to decrease as the scour depth increased, mainly because the bridge piers gained flexibility. On the other hand, the maximum force that the bridge ends witnessed were determined to increase, indicating that the bridge structure can become vulnerable to failure at locations other than bridge piers as the scour depth increases. With an in-depth understanding of the magnitudes and trends of key structural response measures, the outcome of this study provided a rigorous multihazard perspective to improve the safety and performance of bridges built on navigable waterways.

Efficient numerical analyses of RC beams subjected to impact loading using axial-flexure-shear fiber beam model

Similar to wind and seismic loading, impact loading induced by e.g. vessel or vehicle collisions is another type of extreme loading that has become one of the major hazards for the safety of our infrastructural systems such as bridges and buildings. The development of effective strategies which can realistically quantify structural responses under impact loading becomes increasingly important. The widely-used finite-element (FE) simulations using general-purpose FE programs often require excessively high computational cost. This paper therefore aims to develop and implement a computationally efficient axial-flexure-shear fiber beam model based on Timoshenko beam theory with consideration of material non-linearity for the analyses of reinforced concrete (RC) beams under impact loading. The axial, flexural and shear deformation of RC sections during impact are effectively coupled at the fiber and material level. Numerical accuracy of the proposed fiber beam model for non-linear dynamic impact analyses is verified using experimental data from 15 sets of drop-hammer impact tests on scaled RC beams, including flexure-dominant slender beams and shear-dominant deep beams, which demonstrate the great advantage of the proposed fiber beam model over the classical Euler–Bernoulli fiber beam model for applications to impact scenarios where shear deformation of RC members becomes non-negligible.

Design Loads and Pier Responses for Oblique Side Barge Impacts on Bridges

For bridges susceptible to barge collision, design provisions are typically utilized in determining collision scenarios and impact loading. Provisions in the United States require that bridges be designed to withstand two distinct collision events: direct (head-on) and glancing (e.g., oblique side). Head-on impact scenarios are represented using empirically determined static loads, and perpendicular impact loads are applied with magnitudes assumed equal to 50% of head-on impact loads. Subsequent to the formation of these provisions, numerous studies have identified the need to account for dynamic phenomena when designing bridges to resist vessel collision loads. Further, design-oriented computational techniques have been developed to characterize representative vessel–bridge collision scenarios, quantify dynamic barge impact loads, and compute time-varying bridge responses. While previous studies focused on head-on barge–bridge collision, the current study characterizes oblique side barge impact loading and resulting bridge response. Parameters such as barge flotilla configuration, impact angle, and location of impact initiation are investigated across a range of bridge models, leading to the identification of design-relevant oblique side impact scenarios. An alternative to the 50% design approach for oblique side impact scenarios involving the corners of barge bows is then proposed for assessing overall stability. The proposed approach incorporates dynamic phenomena and maintains agreement relative to more detailed analyses.

Long-term increase in mortality of Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary following anthropic activities: Evidence from the stranded dolphin mortality analysis from 2003 to 2017

With the dramatic increase in anthropogenic threats to the Pearl River Estuary (PRE), the population size of the Indo-Pacific humpback dolphins (Sousa chinensis) has significantly decreased over the past decade. To understand the impact and potential risks of intense human activities on these dolphins, factors related to the mortality of humpback dolphins in the PRE were investigated by a detailed examination of 343 dolphin specimens stranded during 2003–2017. There was a significant (p < 0.01) increasing trend for humpback dolphin stranding, reflecting the accelerating rate of the population decline. A large proportion of strandings (35.88%) were neonates. A low recruitment rate implies slow population growth, and hence, limited capacity to resist anthropogenic stress. The most commonly diagnosed causes of death were vessel collision and net entanglement. The concentrations of trace metals, polychlorinated biphenyl (PCB) congeners, dichlorodiphenyltrichloroethane, polycyclic aromatic hydrocarbons, and most of per- and polyfluoroalkyl substances (PFASs) in the dolphin samples were greater than those previously reported in cetaceans globally. Furthermore, Cu, PCB77, PCB169, PCB81, PCB37, and PFASs (excluding PFBA, PFPeA, PFHxA, PFHxDA, and PFODA) were the major pollutants accumulated in neonates. 67% of PCB, 78% of Cu, and 100% of perfluorooctane sulfonate concentrations in the neonates exceeded the threshold for toxicological effects in marine mammals, suggesting that these compounds could be important factors contributing to the low survival rate of calves in this area. This study revealed that vessel transportation, fishing activities, and pollutant bioaccumulation are the three major causes of humpback dolphin mortality in the PRE. These results highlight the need for more efforts to restrict anthropogenic activities, especially vessel traffic, the catching of these marine animals and fishing, and pollutant discharge, in order to prevent vulnerable species from continuous population decline and further extinction.

Forming the area of unacceptable values of the parameters of vessels’ movement for the vessels’ divergence at remote control process

Navigation traffic and the danger of collision are steadily increasing. Features of navigation in narrow corridors (water, air, etc.) require the development of modern methods for assessing the situation of convergence and the choice of maneuvering divergence of vessels. A method is proposed for forming the area of inadmissible values of the parameters of the movement of any vehicles (including marine) with remote control of the process of their divergence. Situations are considered when a collision of sea vessels can be avoided only by changing the speed in case such vessels cannot change course. The proposed method can be generalized to any environment of navigation.

Modeling the potential for vessel collision with southern resident killer whales

Agent-based models can be used to simulate the behavior of animals within a stimulus field. For example, such models are used to estimate the sound exposure of simulated animals ("animats") moving within a computed sound field. This approach has not yet been used to estimate the probability of vessel collision between marine mammals and ships. One reason is the difficulty of defining aversive behavior in response to disturbance. While many animals display aversion, models often use a simplified approach due to insufficient data. Building on the JASCO animal simulation model including noise exposure (JASMINE), a vessel collision framework was developed for southern resident killer whales (SRKWs) using modeled vessel sound fields and AIS data. Animats were programmed to increasingly avoid louder, closer, and additional vessels by changing their heading, speed, and behavioral state based on published data from SRKWs. Animats that remained within a calculated "encounter radius" despite aversive behavior were considered struck by the vessel. Parameters governing aversive behaviors were calibrated by comparing the proportion of animats struck in the simulation with the collision probability for real-world SRKWs. This model provides a starting point to model the risk of vessel collision for SRKW and other species.

Anomaly Detection in Maritime AIS Tracks: A Review of Recent Approaches

The automatic identification system (AIS) was introduced in the maritime domain to increase the safety of sea traffic. AIS messages are transmitted as broadcasts to nearby ships and contain, among others, information about the identification, position, speed, and course of the sending vessels. AIS can thus serve as a tool to avoid collisions and increase onboard situational awareness. In recent years, AIS has been utilized in more and more applications since it enables worldwide surveillance of virtually any larger vessel and has the potential to greatly support vessel traffic services and collision risk assessment. Anomalies in AIS tracks can indicate events that are relevant in terms of safety and also security. With a plethora of accessible AIS data nowadays, there is a growing need for the automatic detection of anomalous AIS data. In this paper, we survey 44 research articles on anomaly detection of maritime AIS tracks. We identify the tackled AIS anomaly types, assess their potential use cases, and closely examine the landscape of recent AIS anomaly research as well as their limitations.

An efficient axial-flexure-shear fiber beam model for dynamic analyses of beam–column framed structural systems under impact loading

Impact loadings induced by collisions from an external impacting object (e.g. a vessel, a vehicle) severely threaten the safety of our infrastructural systems such as bridges and buildings. It is therefore critical to develop effective strategies to quantify the impact loadings and dynamic structural responses so that the safety of structures can be pre-estimated. Although the extensively used finite-element simulations can generally provide realistic predictions of impact forces and dynamic responses of structures subjected to vessel or vehicle collisions, they are often computationally expensive. Therefore, the development of computationally efficient simplified impact models using macro-elements has drawn the attention of many researchers. This paper aims to develop a more general-purpose simplified impact model for dynamic analyses of beam–column framed structural systems under impact loading with consideration of shear effects in beam–column members. The well-known Timoshenko beam theory is adopted to develop a fiber beam model that couples the axial, flexural and shear actions in beam–column members at the fiber and material level. A parametric study is then conducted to thoroughly assess the numerical performance of the proposed simplified impact model using several sets of circular columns with different cross-section diameters and height–diameter ratios under the impact from a barge vessel, the complex finite-element model of which was developed and validated by the author previously. The study indicates that the proposed simplified impact model using the axial–flexure–shear fiber beam model enables a sufficiently accurate prediction of the time-histories of impact forces and dynamic responses of both flexure-dominant high columns and shear-dominant short columns under different impact scenarios.

Challenges and priorities for river cetacean conservation

River cetaceans are particularly vulnerable to anthropogenic impacts due to their constrained ranges in freshwater systems of China, South Asia, and South America. We undertook an exhaustive review of 280 peer-reviewed papers and grey literature reports (1998-2020) to examine the current status of knowledge regarding these cetaceans and their conservation. We aimed to better understand the scale of threats they face, and to identify and propose priority future efforts to better conserve these species. We found that the species have been studied with varying frequency and that most of the research on threats has focused on habitat degradation and fragmentation (43%, mainly driven by dams and extractive activities such as sand mining and deforestation), and fishery interactions (39%, in the form of bycatch and direct take). These threats occur across all species, but more information is needed, primarily on quantifying the population impacts as a basis for designing mitigation measures. Other threats identified include pollution, vessel collisions, traditional use, and poorly managed tourism. Emerging methods such as environmental DNA and unmanned aerial vehicles are described for studying these species. Promising conservation interventions include cetacean-specific protected areas, naturalex situprotection, community-led conservation, and education programmes. However, transnational political will is required for a step change towards broad-scale protection in freshwater environments. In addition, we propose increasing capacity building, developing management plans, working closely with fishing communities, enhancing public awareness, expanding regional collaborations, and diversifying funding.

Analysis of the Obligations and Responsibilities of Anchored Vessels in Vessel Collision Avoidance

Collisions between anchored ships and ships under way at sea often occur. In the handling of collision accidents at sea, anchored vessels are often mistaken for not being liable for collision losses or only bearing a small proportion of liability due to their limited maneuverability. When a vessel under way collides with an anchored vessel, whether the latter has the duty and responsibility to take appropriate actions to avoid the collision is directly related to the determination of the responsibility of the collision between the two vessels. By analyzing international conventions, regulations and local laws and regulations related to ship collision, this paper sorts out the requirements for anchoring ships in avoiding collision, and analyzes the limitations of anchoring ships in avoiding collision by means of navigation simulator. Collision of ships is a kind of tort, and the undertaking of responsibility depends on the degree of the fault. This paper also analyzes the possible faults of anchoring ships, and the reasonable responsibilities to be taken by anchored vessels in a collision by combining the requirements of laws and regulations on the duty of care of anchored vessels, and put forward reasonable measures to be taken in avoiding collision by anchored vessels, in order to provide references to the ship crew, ship manager and owners.

AISChain: Blockchain-Based AIS Data Platform With Dynamic Bloom Filter Tree

Since 2002, hundreds of thousands of vessels have equipped the Automatic Identification System (AIS), which continuously broadcasts its identity and location information for vessel collision avoidance. To utilize these scattered AIS data for further analysis, there are multiple AIS data platforms collecting AIS data from vessels around the world through their satellites and land-based stations. Thus, users can obtain AIS data of vessels from these platforms without dedicated devices. However, existing platforms work in silos, and AIS data is distributed across different platforms, resulting in reduced data availability. In addition, AIS is vulnerable to jamming and spoofing attacks, which can undermine the authenticity of AIS data. In this paper, we propose AISChain, a secure and fast blockchain-based AIS data platform. AISChain adopts consortium blockchain, which only permits those authorized parties (i.e., AIS data providers) to participate in the consensus protocol, and is compatible with current commodity AIS hardware. Since the whole system is co-maintained by multiple authorized parties, AISChain can integrate AIS data resources in a secure way. For avoiding repeated recording of AIS data on the chain, we design the Dynamic Bloom Filter Tree (DBFT) to realize efficient duplication detection in the transaction verification phase. We also propose the dual signature scheme to clarify the AIS data ownership. Moreover, we leverage the geographical location-based blockchain sharding approach to further improve the scalability of AISChain. We implement a prototype of AISChain, and conduct extensive experiments to evaluate the performance of AISChain. Evaluation results show that the search time of DBFT is negligible (4.3 ms) with an extreme low error ratio (0.4%). Meanwhile, AISChain can achieve more than 730 tx/s throughput even when nodes scale to 36. To the best of our knowledge, AISChain is the first work to apply the blockchain technology to secure the AIS data platform.

A Marine GIS-based Alert System to Prevent Vessels Collision with Offshore Platforms

How to effectively use an intelligent aid-to-navigation (AtoN) to prevent ships from accidentally colliding with offshore marine platforms (OMPs) is an important issue for maritime environment. This study proposes a novel collision alert system with three components to process Automatic Identification System (AIS) data in the cloud and broadcast AtoNs to ships in order to avoid collision with OMPs. The first component receives as input fuzzy linguistic variables (vessel size, relative speed, and approach distance) from the AIS data and calculates the radius of the guarding ring. The second component serves a Marine GIS (MGIS), where the system simulates the alert based on a fuzzy guarding ring at one of three levels: green (continuous light), amber (slow flash and alarm), and red (flash and fast alarm). The third component is a warning indicator device, signaling the risk of collision between moving ships and offshore platforms. The MGIS component can also be used on an OMP to alert approaching ships and to warn offshore platform workers and vessel traffic service (VTS) on-duty operators. The ability of the proposed system to protect OMPs from vessel collisions has been verified. Other potential applications include offshore wind turbines, oil rigs, or other working platforms.

Weight of Evidence Approach to Maritime Accident Risk Assessment Based on Bayesian Network Classifier

Probabilistic maritime accident models based on Bayesian Networks are typically built upon the data available in accident records and the data obtained from human experts knowledge on accident. The drawback of such models is that they do not take explicitly into the account the knowledge on non-accidents as would be required in the probabilistic modelling of rare events. Consequently, these models have difficulties with delivering interpretation of influence of risk factors and providing sufficient confidence in the risk assessment scores. In this work, modelling and risk score interpretation, as two aspects of the probabilistic approach to complex maritime system risk assessment, are addressed. First, the maritime accident modelling is posed as a classification problem and the Bayesian network classifier that discriminates between accident and non-accident is developed which assesses state spaces of influence factors as the input features of the classifier. Maritime accident risk are identified as adversely influencing factors that contribute to the accident. Next, the weight of evidence approach to reasoning with Bayesian network classifier is developed for an objective quantitative estimation of the strength of factor influence, and a weighted strength of evidence is introduced. Qualitative interpretation of strength of evidence for individual accident influencing factor, inspired by Bayes factor, is defined. The efficiency of the developed approach is demonstrated within the context of collision of small passenger vessels and the results of collision risk assessments are given for the environmental settings typical in Croatian nautical tourism. According to the results obtained, recommendations for navigation safety during high density traffic have been distilled.

A method for unmanned vessel autonomous collision avoidance based on model predictive control

Aiming at the problem of autonomous collision avoidance of unmanned vessels in the case of multiple vessels encountering at sea, this paper proposes a method for collision avoidance of vessels in open water based on the Mathematical Model Group (MMG) vessel motion mathematical model. This method uses Model Predictive Control (MPC) model algorithm, and considers vessel maneuverability and the International Regulations for Preventing Collision at Sea, 1972 (COLREGs), and uses fuzzy mathematics to analyze the collision risk of vessels during navigation, and then constructs the evaluation function of the collision avoidance algorithm. The vessel's autonomous collision avoidance is realized. The simulation results show that the algorithm can solve the problem of autonomous vessel collision avoidance in the case of multi-vessel encounters in open water, which verifies the effectiveness of the algorithm.

Age structure of stranded Loggerhead Turtles (Caretta caretta) in Turkey

The Mediterranean coast of Turkey includes important nesting beaches and marine habitats for the Loggerhead Turtle (Caretta caretta). We studied the demographic structure of this population by applying the skeletochronological method on stranded individuals. The mean age of stranded turtles was 27.0±3.83 years for females (N=10) and 40.1±14.97 years for males (N=7). The age of first reproduction was 23 years with a curved carapace length (CCL) of 61 cm for females and 21 years with a 67.5 cm CCL for males. The oldest observed female was 34 years old with a 67.8 cm CCL, while the oldest male was 59 years old with a 77.0 cm CCL. Incidental capture in fishing gear (60%) and marine vessel collisions (24%) were determined as the main causes of stranding.

Structural Finite Element Simulation and Evaluation Method for Ship Collision Damage and Residual Strength of the Jacket

Introduction The vessel collision of jacket foundation in an offshore wind farm in the South China Sea happens frequently. Under this circumstance， the accurate assessment of the residual strength after structural damage has become an important technology of the safety of wind farm operation and maintenance. Method Based on the actual jacket structure of a wind farm in the South China Sea and considering the actual ship operation situation in the sea area， this paper used the finite element software ABAQUS to simulate the ship collision damage process of jacket foundation under different combinations of ship mass， initial velocity and collision angle. Result By using the quasi static method， the time interval of the collision forces and the plastic strain contours of the key nodes under different working conditions are concluded. Besides， the relationship between the maximum impact forces and impact factors and typical characteristics of the damage are concluded. Conclusion Based on the analysis， the typical change laws of the residual strength after the ship collision of the jacket are concluded to provide technological support for rapid assessment of the collision damage of related structures in the actual engineering process.

Antofagasta Region in northern Chile, a potential nursing ground for the Southern right whale Eubalaena australis

The Chile-Peru subpopulation (CPe) of the Southern right whale (Eubalaena australis) is classified as Critically Endangered following intense whaling in past centuries. Due to their very low abundance, information on breeding and feeding grounds is also scarce. Unmanned aerial vehicles (UAVs) are increasingly applied in marine mammal research thanks to their low cost and relative ease of use. This case study documents a Southern right whale nursing in Bahía Moreno (23º S), Antofagasta, in northern Chile through high-resolution images taken by UAV of an adult in July 2019 and the same whale with a neonate in August. Combined with earlier data we hypothesize that the Antofagasta Region may be a potential calving and nursing ground for the CPe subpopulation. Given the intense shipping traffic and fishing activities around the Mejillones Peninsula and Antofagasta port, priorly recommended marine spatial planning to help avoid net entanglements and vessel collisions of fin and humpback whales may also contribute to the conservation of the CPe stock.

Modeling Vessel Behaviours by Clustering AIS Data Using Optimized DBSCAN

Today, maritime transportation represents a substantial portion of international trade. Sustainable development of marine transportation requires systematic modeling and surveillance for maritime situational awareness. In this paper, we present an enhanced density-based spatial clustering of applications with noise (DBSCAN) method to model vessel behaviours based on trajectory point data. The proposed methodology enhances the DBSCAN clustering performance by integrating the Mahalanobis distance metric, which considers the correlation between the points representing vessel locations. This research proposes applying the clustering method to historical Automatic Identification System (AIS) data using an algorithm to generate a clustering model of the vessels’ trajectories and a model for detecting vessel trajectory anomalies, such as unexpected stops, deviations from regulated routes, or inconsistent speed. Further, an automatic and data-driven approach is proposed to select the initial parameters for the enhanced DBSCAN approach. Results are presented from two case studies using an openly available Gulf of Mexico AIS dataset as well as a Saint Lawrence Seaway and Great Lakes AIS licensed dataset acquired from ORBCOMM (a maritime AIS data provider). These research findings demonstrate the applicability and scalability of the proposed method for modeling more water regions, contributing to situational awareness, vessel collision prevention, safe navigation, route planning, and detection of vessel behaviour anomalies for auto-vessel development towards the sustainability of marine transportation.