RELIABILITY ANALYSIS CONSIDERING ITEMS RELATING TO HUMAN ERROR ON FUNCTIONAL DESIGN APPLICATIONS OF MARINE SYSTEMS. (PART 2). THE UNMEASURABILITY OF SOME EVENTS AND THE RELIABILITY OF ACCIDENT COUNTERMEASURES

The Event Tree Analysis (ETA) method is used to evaluate the reliability of the functional designs of marine systems. Generally, the ETA estimates the incidence probability of an accident by considering the probability of occurrence of each sub-event leading to the accident. The exact estimation of sub-events related to human errors is difficult since they include several unmeasurable factors, and the results could be misleading. In the first part of the paper, a method for the estimation of accident incidence probability using a linguistic function to evaluate the fuzziness of the event probability value. This paper presents a method of reliability analysis considering the measurability of some sub-events such as human error. This process of reliability estimation is based on the degree of belief of the incident event and an additional rule based on a fuzzy measure. As a practical example, the reliability analysis of the fire protection and extinguishing systems during the incidence condition of a ship fire spread are investigated using the proposed method.