GARS2006 S3P2

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Published on November 6, 2007

Author: Jancis

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Risk Analysis of Ship Hull Vibration Using Evidential Reasoning :  Risk Analysis of Ship Hull Vibration Using Evidential Reasoning D. Godaliyadde, J. Wang, G. Phylip-Jones, A.D. Batako School of Engineering, Faculty of Technology and Environment, Liverpool John Moores University Content:  Content Introduction - Necessity of the study - Aim of the research - Objectives Ship Hull Vibration (SHV) - Major causes of SHV - Generic model Methodology - Identification of basic criteria - Rule based technique - Quantification using mapping process - Application of ER to SHV Case Study Conclusion Introduction:  Introduction Motor tanker vessel “Esso Mersey” – The explosion occurred on 4th September 1991, lost 2 lives. Fishing vessel “Elegance” – Fire damage on 30th January 2004 and loss of the vessel on 5th March 2004. Refrigerated cargo vessel “Green Lily” – Total lost on 19th November 1997. Fishing vessel “Jenmar” - Vessel grounded on 19th May 1997. Passenger vessel “Royal Princess” – Major injury to third engineer officer on 4th August 2001. Typical Ship Accidents Caused by Vibration Ship is one of the main modes of transport of passengers and cargo across oceans and waterways, within and between countries, due to its higher capacity, lower cost, lower risk and convenience in loading and unloading. Vibrations in ships need to be taken seriously considering their negative effects on the crew, the cargo and the ship itself. Many of the greatest maritime tragedies have involved vibration. Slide4:  Objectives Aim of the Research This study aims at obtaining risk analysis of ship hull vibration by using evidential reasoning approach. Study of ship vibrations Classification and grading of vibrations Ship hull vibration modelling Methodology Case study Ship Hull Vibration (SHV):  SHV depends on parameters such as … i) Propellers Quality of the shaft system Propeller cavitation Propeller design Rudder ii) Machinery Auxiliary equipment Power generation plant Engine Ship Hull Vibration (SHV) Slide6:  Generic Model of SHV Methodology:  Methodology i) Identification of Basic Criteria There are two types of basic criteria. - Qualitative - Quantitative Qualitative criteria Qualitative criteria are represented by linguistic variables such as very good, good, bad , fair etc. Quantitative criteria Quantitative criteria always represented by a numerical value. eg: Increasing the propeller diameter by 1 m, the vibration can be minimized by 10%. ii) Rule Based Quantitative Data Transformation Technique :  ii) Rule Based Quantitative Data Transformation Technique hn,i Hn (n = 1, …, N) (1) Si(hj) = {(hn,i, γn,j), n = 1, ……, N } (2) and (3) S(hj) = {(Hn, βn,j), n = 1, ……, N } (4) βn,j = γn,j , n = 1, ……, N (5) Si(ei) = {(hj, pj), j = 1, …., Mi} (6) S(ei) = {(Hn, βn,i), n = 1, …., N} (7) Methodology (Continued) iii) Mapping Process:  iii) Mapping Process The mapping process is used to convert qualitative lower level criteria to upper level criteria, as well as quantification of qualitative criteria. eg: Methodology (Continued) Slide10:  iv) Original ER Algorithm (8) (9) (10) (11) (12) {Hn}: {H}: {Hn}: (13) {H}: (14) Methodology (Continued) Slide11:  Case study Step 1: Assessment grades for sub-sub criteria Slide12:  Step 2: Converting quantitative criteria into qualitative criteria H = {Hj, j = 1,…., 4} = {Bad, Normal, Good, Excellent} 1. If rudder clearance to the propeller is 50% (i.e. distance between rudder and propeller is 50% of estimated value of propeller diameter (2.75 m) for generic ship), then it is Excellent (or h4,1 = 50). 2. If rudder clearance to the propeller is 45%, then it is Good (or h3,1 = 45). 3. If rudder clearance to the propeller is 40%, then it is Normal (or h2,1 = 40). 4. If rudder clearance to the propeller is 35%, then it is Bad (or h1,1 = 35). H1 = HClearance = {h1,1, h2,1, h3,1, h4,1} = {35, 40, 45, 50} Case study (Continued) Slide13:  By taking into account the estimated value of rudder clearance (h1 = 36%) of generic ship, since h2,1= 40% h1,1 = 35% and h1,1< h1 < h2,1, h1 can be described as follows: S1 (e1 (Rudder)) = {(h1,1, γ1,1), ( h2,1, γ2,1)} γ1,1 = β1,1 = 0.8 and γ2,1 = β2,1 = 0.2 S (e1 (Rudder)) = {(H1, 0.8), (H2, 0.2)} = {(Bad, 0.8), (Normal, 0.2)} = {(B, 0.8), (N, 0.2)} Case study (Continued) Slide14:  Step 3: Mapping process Mapping from sub-sub criteria (E: Erosion) to sub criteria (R: Rudder) Case study (Continued) Slide15:  Step 4: Use IDS (Intelligent Decision System via Evidential Reasoning) to obtain risk analysis of SHV SSHV = {0.0942, “Very Low”, 0.0712, “Low”, 0.1295, “Average”, 0.2001, “High”, 0.5049, “Very High”} Case study (Continued) Thank you:  Thank you Conclusion The ship hull vibration is a very complicated problem and it is essential to carryout risk estimation in order to take actions to minimize the risk. By using four step methodology, the complicated process is clearly decomposed and simplified very easily without affecting its nature. Evidential Reasoning is capable of producing the risk level of ship hull vibration.

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