1,720,988 research outputs found
STPA Based Approach for a Resilience Assessment at an Early Design Stage of a Cruise Ship
No full textSeveral definitions and approaches have been proposed to study resilience in different fields like materials, ecology, psychology and infrastructures. A general definition, applicable also to human-made or engineered systems, describes resilience as the ability to maintain capability in case of disruption.
Thanks to its systemic, top-down approach, STAMP (System-Theoretic Accident Model and Processes) has been already identified in literature as a very effective and “conductive” reference when reasoning about the possible need of resilience of a complex system. The STAMP-based tool named STPA (System Theoretic Process Analysis) establishes the following steps: identify system accidents, hazards; draw functional control structure; identify unsafe control actions (UCAs); identify accident scenarios; formulate decisions and recommendations. It focuses on what actually is in the hands of the system designer and operator i.e. the possibility to take action on hazards that can be eliminated or controlled.
In this paper an approach to design resilience into a cruise vessel will be proposed. An application case will be developed considering the specific hazard of dead ship condition i.e. of energy black-out on board. In case of navigation close to the shore and in heavy weather condition, this situation can rapidly evolve into a loss. The ship energy production and delivery system, both for the propulsion and for the hotel services, will be considered. Running the procedure up to the level of UCAs enables the identification of the possible disruptive events capable to degrade the operational performance of the system. Starting from this point, suggestions will be discussed for a selected UCA, able to prevent or mitigate it. A metric for ship resilience will be proposed as well with the aim to allow comparisons among different design solutions
The influence of ship stability in waves on naval vessel operational profiles
No full textEnsuring a widely safe operational profile of naval vessels is one of the leading aspects of the design process. With reference to weather conditions, this kind of vessels often cannot avoid heavy situations to guarantee the continuity and the effectiveness of service. For this reason, an applied research investigation aimed to define guidance in operations is deemed as a worthwhile activity. In particular, the performance in waves under the perspective of intact stability has been considered in this work. The IMO second-generation intact stability criteria have been identified as a suitable tool for these investigations: as a result, there is evidence that operational guidance can be developed for a set of representative naval vessels, following the relevant guidelines. Outcomes have been represented by means of comprehensive polar diagrams addressing the intact stability failures modes. Bearing in mind the actual operational profile, results have been analysed and discussed considering how ship and operating decisions in a seaway condition may affect the performance in terms of ship stability
HUMAN FACTOR AND AUTOMATION: A STPA APPRACH TO ENHANCE SHIP SAFETY
No full textShips complexity is continuously increasing and lots of action controls, traditionally carried out by crew members, are now managed and executed by the on-board automation systems. The relation among humans and automation system shall be studied with specific attention to their mutual interface and interaction issues, in order to better pursue safety. The STAMP (System-Theoretic Accident Model and Processes)-based tool named STPA (System Theoretic Process Analysis) consists the following steps: identify system hazards; draw functional control structure; identify unsafe control actions (UCAs); identify accident scenarios; formulate decisions and recommendations. In this paper an approach to model the relations among human operator and automation, based on STPA, will be proposed. An application case will be developed considering a large passenger ship and the specific hazard of dead ship condition (energy black-out). In case of navigation close to the shore and heavy weather condition, this situation can rapidly evolve into a ship loss
APPLICATION OF CAST to COSTA CONCORDIA ACCIDENT
No full textCAST (Causal Analysis based on Systems Theory) is used to rationally elicit the cause of Costa Concordia accident
Intact Stability Assessment of RO-RO Pax Vessel in the Framework of Second Generation Intact Stability Criteria with a Specific Focus on the Operational Profile
No full textOne year later the finalization of Second Generation Intact Stability
criteria (SGISc), there is still the need to validate the robustness and consistency of
these criteria as indicated by IMO. Not compliance with a stability criterion cannot
be always fixed acting only on the vessel design; also operative considerations are
needed in order to reduce the risk level during the navigation. After an introduction
to SGISc and rule framework for passenger ships, an application will be carried out.
A Ro-Ro pax ferry has been selected as subject of this investigation. Vulnerability
levels (i.e. Level 1 and Level 2) are applied in order to assess the compliance of a
modern representative Ro-Ro ferry. Moreover, a study about how the environmental
conditions may affect the results is undertaken considering different scenario, such
as the geographical area or the maximum encountered wave height
An insight about roll damping within the second generation intact stability criteria
No full textDespite the recognized complexity to estimate the damping influence on ship roll motion, some efficient semi-empirical methodologies have been developed along the years to this purpose. CFD methods, in principle the most appropriate tools to predict roll damping, are not a favorite option in preliminary design at present due to their implications in terms of complexity and computational time. In this paper, an integration of the semi-empirical Ikeda’s simplified method has been formulated with modification of the bilge keels and lift components, following a contribution found in the literature and relevant for Ro–Ro ships. Moreover, with focus on damping evaluation, the second generation intact stability criteria (SGISc) have been investigated: the second-level vulnerability criteria for dead ship condition and parametric roll have been applied to a Ro–Ro passenger ship. Both the consolidated and the new proposed roll damping prediction methods have been implemented in order to appreciate their effects on the final outcome
Parametric Formulation of the Floodable Length Curve: Application Case to Offshore Patrol Vessels
No full textThe residual buoyancy of vessels after damage has a fundamental role in their survivability and it is implemented through adequate ship internal subdivision. Traditionally the number and the position of transverse watertight bulkheads are selected for most ships early in the design phase by means of the “floodable length curve” coupled with the concept of “margin line”. However, for naval vessels, it is more and more common during the acquisition process to explore a wide domain of feasible ships, identified with the assistance of automated processes and assessed also in terms of capabilities, among which is survivability. The generation and the comparison of a considerable number of different ship configurations is very time consuming. Therefore recourse to a parametric expression of the floodable length curve is considered to be a very efficient approach and would thus enable characterisation of the ship, in terms of survivability performance. In this paper such an approach is presented, using an offshore patrol vessel (OPV) as the case study
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