Study on Fracture Safty Assessment of Structures

为建立结构断裂安全评估体系，开展了以下基础性研究工作：1)船舶结构检测研究；2)非周期检测贝叶斯可靠性分析；3)高应变集中结构构件CTOD评估方法；4)结构超声强度评估方法；5)断裂韧度分布研究；6)结构缺陷可靠性评估方法。研究成果概括为：1)基于已有的船体结构研究数据，明确了已有裂纹的特征；3)开展了贝叶斯可靠性分析，以生成合理的非周期结构检测计划；3)提出了结构应力集中裂纹CTOD值的估算方法，4)研究了作为无损检测工具的超声检测方法，讨论了超声检测用于断裂强度评估的有效性，5)提出了一种新的焊接接头断裂韧度测量值分布模型，该模型可以解释断裂韧性的广泛分散性，6)在裂纹评估方法中引入了部分安全系数的概念来保持判断的可靠性水平，这些结果将在不久的将来建立合适的断裂安全评估方法的过程中起到重要的作用。

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.