Study on Fracture Safty Assessment of Structures

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In order to establish the fracture safety assessment system of structures, such basic researches as 1) study on inspection of ship structures, 2) Baysian reliability analysis for non-periodic inspection, 3) evaluation methods of CTOD for highly strain concentrated structural components, 4) strength assessm ent method of structures by Ultrasonic Testing, 5) study ondistribution of fracture toughness and 6) reliability approach to the defects assessment of structures are carried out.The results of this investigation are summarized as, 1) based on the enquete research data of ship structures, characteristics of the pre-existing cracks are made clear, 3) Baysian reliability analysis is developed for generating appropriate non-periodic structural inspection schedule, 3) estimation method of CTOD value of cracks existing in the structural stress concentration is proposed, 4) Ultrasonic Testing as a tool of NDI is studied and the validity of fracture strength assessment using Ultrasonic Testing is discussed, 5) a new model on the distribution of measured fracture toghness values in weld joints is proposed which can explain the wide scatter of the fracture toghness and 6) the reliability approach is introdued to the crack assessment method where the concept of partial safety factors are adopted to keep reliability level of judgment.These results will play an essetial role in the process of constructing the appropriate method of fracture safety assessment in the near future.