超设计基准地震作用下核电厂常规岛主厂房连续倒塌破坏机制及抗震裕度评估

There is a first class seismic item named electric power house located at the side of the Conventional Island Building gable near the Nuclear Island side. The various loadings connecting nuclear islands and conventional island pipes are put on the gables of Conventional Island Building. A progressive collapse of the conventional island will directly threaten the safety of the nuclear island, which may lead to a leak of nuclear. Therefore, progressive collapse resistant capacity of conventional island should be strictly controlled. Taking conventional island building for nuclear power plant as an object and considering synthetically lateral incremental collapse failure mechanism and the vertical progressive collapse failure mechanism of conventional island building under the input of over design base earthquake. The methods combination of shaking table model test, field measurement and numerical simulation will be utilized in this project to investigate the problems including how to select the severest adequate real strong earthquake ground motion for seismic analysis and design of conventional island building for nuclear power plant and the ground motion characteristics of in the near-field ground motions in the field of conventional island building; the damage mechanism of progressive collapse and the relationship of robustness against progressive collapse for conventional island building, quantitatively revealing the interrelationship between the robustness against progressive collapse and the structural ductility, collapse rate, loading bearing capacity, structural dynamic parameters, and so on; a method for calculating the seismic margin of conventional island will be proposed; getting command of the damage mechanism of progressive collapse based on energy dissipation capacity of joints with shape memory alloy, coming up with the design rule improving the reliability and robustness of conventional island structures; time-variant characteristics and relationship of physical parameters and modal parameters of conventional island building, revealing the real varying relationship between time-variant characteristics and the damage mechanism of progressive collapse, and in the end, an assessment method of the structural capacity against progressive collapse for conventional island building would be proposed for technical assistance to seismic assessment and safe operation of Chinese nuclear power plant.

常规岛主厂房结构靠近核岛端山墙一侧建有抗震I类物项电气厂房，承受各种连接核岛与常规岛管道的荷载。如果常规岛发生连续倒塌将直接威胁核岛的安全，进而可能引发核泄漏，应严格控制常规岛主厂房结构的抗倒塌能力。本项目以核电厂常规岛为研究对象，综合考虑常规岛在超设计基准强震作用下侧向和竖向失效模式，采用振动台模型试验、现场实测和数值模拟相结合的方法，深入研究其最不利输入地震动特点及其确定方法；基于MIDA静力非线性数值方法的不同倒塌模式下常规岛倒塌破坏机理及基于新型形状记忆合金节点耗能的倒塌破坏模式控制方法；定量地揭示其抗倒塌能力与结构延性、倒塌率、承载力储备以及结构动力参数等指标之间的相互关系，提出其抗震裕度计算方法；研究常规岛物理及模态参数时变特征及其关系，揭示在超设计基准强地震作用下常规岛主厂房参数时变规律及其连续倒塌破坏机理，最终为核电厂抗震评估和安全运行提供技术支撑。

在我国双碳目标背景下，核能势必成为实现“碳中和”的有效能源之一，但我国地震环境复杂，核电的安全运行值得关注。常规岛主厂房属于Ⅲ类抗震物项，抗震设防属于重点设防类，又由于其紧邻核岛布置，还应进行极限安全地震SL-2作用下的抗倾覆验算。近些年以福岛地震为代表的超设计基准事件频发，在超设计基准地震等极端偶然荷载作用下结构的竖向重要构件依旧存在受损破坏，进而发生竖向连续倒塌威胁核电厂安全运行的可能。这对在役核电厂的安全运行构成威胁，日本的福岛和柏崎刈羽两个核电厂遭遇超设计基准地震引发了核电厂运行安全事故。本项目在此背景下，开展了如下研究工作：（1）梳理了国内外抗连续倒塌设计规范及核电厂常规岛主厂房超设计基准荷载，并总结和述评了中国国内钢结构抗连续倒塌研究现状；（2）选取中国强震台网中心地震记录数据库中120条近断层强地震记录，采用时频分析方法研究地震动强度参数的时变特性和衰减规律，分析了不同地震动强度参数的适用性，给出了常规岛主厂房的最不利设计地震动；（3）基于节点位移响应、承载力系数法确定了常规岛主厂房和核岛侧山墙结构的构件重要性排序，选出前四种作为最危险构件进行拆除构件研究了抗连续倒塌性能，抗倒塌过程中弯矩等内力主要向失效柱上方的梁构件传递，塑性铰的发展方向符合变形协调准则，梁机制和悬链线机制的抗力来源与大小根据结构布置的不同而有一定的区别，最后确定了最不利倒塌模式；（4）进行了自复位边节点、型钢异型节点抗连续倒塌性能试验，提出了包括3D打印技术在内的几种抗连续倒塌能力的提升措施，并对加固后钢筋混凝土柱、剪力墙等构件的力学性能和抗震性能进行了系统地试验和数值模拟研究，给出了最优最经济的提升措施；（5）在役核电厂常规岛主厂房的健康监测及抗震裕度评估，对某在役核电厂进行现场振动监测试验，得到结构的动力特性。结合震害预测状态矩阵，建立基于基频参数变化区间所确定的常规岛主厂房损伤状态矩阵。研究成果是提高核电厂常规岛主厂房抗连续倒塌设计水平和开展在役核电厂延寿或者评估其抗震裕度的重要依据。