This paper presents a numerical method for damage evaluation of steel structures under fire conditions based on degraded material property values. As the measure of structural damage to fire, a damage index is proposed which indicates how much a structure loses its material strength when exposed to fire. The index is formulated with the ratio of a volume-weighted average of material strength at elevated temperatures to that of the strength at room temperature. To investigate the feasibility of proposed damage index, fire testing and the corresponding structural fire analysis of steel–concrete composite beams are performed using a design fire load. The fire is modeled using a standard fire curve proposed in American Society for Testing and Materials E119. A regular real-scale composite beam and the beam protected by a fire-resistant material layer, the latter of which is typical of structural members used in nuclear power plant buildings in Korea, are considered for the fire damage evaluation. The damage state of the composite beams is evaluated using the fire damage index at each time the fire progresses, and it is compared with the value of the post-fire damage index of the beams. By the use of the proposed damage index, the effect of fire-resistant materials on structural integrity is quantified, and it is investigated whether the damage state of each beam at the end of the fire load satisfies the design performance of composite beams used for nuclear power plant structures.

本文提出了一种基于退化材料性能值的火灾条件下钢结构损伤评估的数值方法。作为对火灾造成的结构破坏的一种度量，提出了一种破坏指数，该指数指示结构在暴露于火中时会失去多少材料强度。该指数由高温下材料强度的体积加权平均值与室温下强度的体积加权平均值之比得出。为了研究建议的损伤指数的可行性，使用设计火荷载进行了钢混凝土组合梁的火灾测试和相应的结构火灾分析。使用美国试验和材料学会E119中提出的标准着火曲线对火进行建模。规则的真实比例复合梁，并由耐火材料层保护，后者是韩国核电站建筑物中使用的典型结构构件，可用于火灾损失评估。使用每次火灾进行时的火灾破坏指数来评估复合梁的破坏状态，并将其与梁的火灾后破坏指数进行比较。通过使用提出的损伤指数，量化了耐火材料对结构完整性的影响，并研究了在火荷载结束时每根梁的损伤状态是否满足用于核的复合梁的设计性能。发电厂的结构。使用每次火灾进行时的火灾破坏指数来评估复合梁的破坏状态，并将其与梁的火灾后破坏指数进行比较。通过使用提出的损伤指数，量化了耐火材料对结构完整性的影响，并研究了在火荷载结束时每根梁的损伤状态是否满足用于核的复合梁的设计性能。发电厂的结构。使用每次火灾进行时的火灾破坏指数来评估复合梁的破坏状态，并将其与梁的火灾后破坏指数进行比较。通过使用提出的损伤指数，量化了耐火材料对结构完整性的影响，并研究了在火荷载结束时每根梁的损伤状态是否满足用于核的复合梁的设计性能。发电厂的结构。