Application of formal safety assessment for ship hull vibration modelling

This research has evaluated the rules, guidelines and regulations related to ship vibrations. A historical failure data analysis is carried out to identify associated components, equipment and the areas of defects related to ship vibration problems. Ship Hull Vibration (SHV) is recognised as a major problem onboard ships and the propulsion system is identified as the major contributor to SHV. The current status of ship vibrations is reviewed and possible sources which create SHV are recognised. The major problems identified in this research are associated with risk modelling under circumstances where high levels of uncertainty exist. Following the identification of research needs, this PhD thesis has developed several analytical models for the application of Formal Safety Assessment (FSA). Such mode quently demonstrated by their corresponding case sti vith regard to application of FSA for SHV modelling. Firstly, in this research a generic SHV model is constructed for the purpose of risk estimation based on the identified hazards. The hazards include the SHV effects induced by ship design criteria, failure of components, and different patterns associated with the ship propulsion system (propeller system and machinery) as the major contributors to SHV. Then risk estimation bn is carried out utilising Evidential Reasoning (ER) and a fuzzy rule base.Secondly, ship selection (decision making) is investigated to to select the best ship design based on the risk estimation results of SHV. The risk estimation is carried out using ER, a fuzzy rule base and continuous fuzzy sets. The best ship design is selected by taking into account an ER-based utility ranking approach. Thirdly, combining discrete fuzzy sets and an Analytical Hierarchy Process (AHP) risk estimation is conducted in terms of four risk parameters to select the major causes of component failure and then SHV

Formal Safety Assessment of a Marine Seismic Survey Vessel Operation, Incorporating Risk Matrix and Fault Tree Analysis

In maritime safety research, risk is assessed usually within the framework of formal safety assessment (FSA), which provides a formal and systematic methodology to improve the safety of lives, assets, and the environment. A bespoke application of FSA to mitigate accidents in marine seismic surveying is put forward in this paper, with the aim of improving the safety of seismic vessel operations, within the context of developing an economically viable strategy. The work herein takes a close look at the hazards in North Sea offshore seismic surveying, in order to identify critical risk factors, leading to marine seismic survey accidents. The risk factors leading to undesirable events are analysed both qualitatively and quantitatively. A risk matrix is introduced to screen the identified undesirable events. Further to the screening, Fault Tree Analysis (FTA) is presented to investigate and analyse the most critical risks of seismic survey operation, taking into account the lack of historical data. The obtained results show that man overboard (MOB) event is a major risk factor in marine seismic survey operation; lack of training on safe work practice, slippery deck as a result of rain, snow or water splash, sea state affecting human judgement, and poor communication are identified as the critical risk contributors to the MOB event. Consequently, the risk control options are focused on the critical risk contributors for decision-making. Lastly, suggestions for the introduction and development of the FSA methodology are highlighted for safer marine and offshore operations in general

A Subjective Cost-Benefit Analysis Approach for Selecting Ship Propulsion Systems

A ship propulsion system is the major contributor to the occurrence of Ship Hull Vibration (SHV), which can easily lead to marine tragedies. Wrongly selecting ship propulsion systems will also significantly increase ship owners' operational costs. Based on a hierarchical structure for modelling propulsion systems, a subjective novel cost-benefit criteria analysis approach is developed to select the most economical propulsion system with the consideration of vibration characteristics. The weights of all the criteria are estimated by utilising an Analytical Hierarchy Process (AHP) technique. All the quantitative criteria in the hierarchy are converted into the qualitative criteria by proposing a novel approach. Membership Functions (MFs) of continuous fuzzy sets are employed to estimate the fuzzy performance ratings of all the criteria. By taking into account fuzzy performance ratings of all the criteria, a fuzzy Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) decision matrix is constructed. Finally, the most economical propulsion system, with consideration of vibration characteristics, is selected using the fuzzy TOPSIS method. The results of this paper reveal that the fuzzy TOPSIS is suitable for propulsion system selection.</jats:p

A Subjective Multiple Criteria Decision-Making Approach for Modeling Ship Hull Vibration

AbstractThis article presents a subjective, novel approach to deal with multiple criterion ship design decision making on the basis of interval data. In this novel approach, quantitative interval- and single-valued criteria are modeled and transformed into qualitative criteria by using membership functions of continuous fuzzy sets. Mapping is provided to transform criteria onto a common utility space. All the interval-valued qualitative criteria are transformed by proposing a new algorithm to represent them with a single value for each linguistic term. Normalization is carried out for all the transformed criteria. By combining all the normalized data, an evidential reasoning algorithm is applied to synthesize the generic ship design criteria. Finally, an ER-based utility ranking approach is used to select the ship with the best design criteria on the basis of the risk estimation results of ship hull vibration. The results of this research reveal that the developed approach is suitable for dealing with a ship selection problem based on the risk estimation results of ship hull vibration.</jats:p

Abstract Risk Analysis of Ship Hull Vibration Using Evidential Reasoning

A subjective approach incorporating Evidential Reasoning (ER) algorithm is developed in order to achieve the risk analysis of Ship Hull Vibration (SHV). A hierarchical process is developed using the available data of the issue, then the qualitative and quantitative criteria are applied as one of the steps to obtain risk analysis. The quantitative criteria are converted to the qualitative ones by applying a rule based quantitative data transformation technique to make use of the ER and quantified qualitative assessments, which is employing the mapping process to determine an aggregated value for each alternative. The risk analysis of SHV is produced graphically by using the IDS (Intelligent Decision System) software. The results of this research reveal that the ER is applicable to obtain risk analysis of SHV

A Subjective Risk-Estimation Approach for Modeling Ship Hull Vibration

A subjective novel approach incorporating an evidential reasoning (ER) algorithm is developed to achieve the risk estimation of ship hull vibration (SHV). A hierarchical structure for SHV modeling (hazard identification model) is constructed using a combined qualitative and quantitative approach. The quantitative criteria are converted to the qualitative criteria by applying a rule-based quantitative data transformation technique to make use of ER. A mapping process is formulated to convert and quantify the qualitative criteria. Intelligent Decision System (IDS) software is used for synthesis in the hierarchical structure and to produce the risk-estimation results graphically. The results of this paper reveal that the ER is capable of producing the risk estimation of SHV.</jats:p