中文摘要：

低温和厚度增大是钢材断裂韧性变差的重要因素，随着我国钢结构厚板的广泛应用和低温寒冷地区建筑业的快速发展，钢结构脆性破坏问题会越来越突出。现行规范中指导钢材选材的冲击功指标无法对断裂破坏做出准确的评定，因此引入基于断裂力学缺陷评估方法的断裂韧性指标非常必要。本文在钢结构厚板低温断裂韧性试验结果的基础上提出了一种钢结构厚板断裂韧性的分级评定方法，为选材方法的讨论奠定了基础。

英文摘要：

Low temperature and large plate thickness are important factors for toughness deterioration of structural steels. With a large number of applications of structural steel thick plate and the rapid development of construction industry in cold regions, brittle fractures of steel structures become more and more prominent. The impact toughness index adopted by the current design codes can＇ t make accurate evaluations about fracture failures, so the introduction of fracture toughness index used in fracture mechanics becomes very necessary. A fracture toughness classification method of thick steel plate is put forward in this paper following the results of fracture toughness tests at low temperature. This paper provides basis for material selection discussions in the succeeding paper.