Study on Fracture Safty Assessment of Structures

为建立结构断裂安全评价体系，开展了1)船舶结构检验研究、2)非定期检验贝叶斯可靠度分析、3)高应变集中结构构件CTOD评价方法、4)超声检测结构强度评价方法、5)断裂韧性分布研究、6)结构缺陷评价可靠性方法等基础研究。研究结果如下：1)基于船舶结构的遗留研究数据，明确了现有裂缝的特征；3)发展了贝叶斯可靠度分析，生成了合适的非周期性结构检查计划；3)提出了结构应力集中存在裂缝的CTOD值估计方法；(4)研究了超声检测作为无损检测的工具，探讨了超声检测对断裂强度评估的有效性；(5)提出了焊缝断裂韧性测量值分布的新模型，解释了断裂韧性的广泛离散性；(6)在裂纹评估方法中引入了可靠性方法，采用部分安全系数的概念，保持了判断的可靠性水平。这些结果将在今后合理构建裂缝安全评价方法的过程中发挥重要作用。

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.