Fragility Analysis of Main Aftershock by Nuclear Power Plant SSC Coupling System Model Considering SSI Effect
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摘要: 核电厂体系的地震易损性分析能够反映耦合的结构、系统和部件(SSC)在不同地震强度下的失效概率,土-结构相互作用(SSI)和主余震作用是地震易损性分析中2个非常重要的因素。本文建立了AP1000核电厂SSC耦合体系模型,选用典型软岩石地基作为场地条件,根据AP1000设计谱选取主余震记录,采用增量动力分析(IDA)方法对耦合体系模型进行考虑SSI效应的地震易损性分析。经计算分析可知,主余震作用对结构和设备的破坏可能大于单一主震的作用效应。考虑SSI效应普遍增大了SSC主余震易损性的条件失效概率。由典型SSC抗震性能结果可知,耦合体系的失效模式为屏蔽厂房混凝土首先开裂,随后蒸汽发生器管道屈服,最后主蒸汽管道进入屈服。考虑SSI效应时,破坏状态基本完好与一般破坏之间的极限状态下屏蔽厂房、蒸汽发生器、管道的高置信度低失效概率(HCLPF)值分别为0.48g、0.68g和0.92g。由本文研究可知,在核电厂易损性评估过程中,SSI效应和主余震作用的影响不容忽视。
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关键词:
- AP1000核电厂SSC耦合模型 /
- 土-结构相互作用(SSI) /
- 主余震作用 /
- 地震易损性分析
Abstract: Seismic fragility analysis of NPP systems can reflect the failure probability of coupled structures, systems and components (SSCs) under different earthquake intensities, in which the soil-structure interaction (SSI) and the main aftershock effect are two very important factors. In this paper, the AP1000 NPP SSC coupled system model is established; the typical soft rock foundation is selected as the site condition; the main aftershock records are selected according to the AP1000 design spectrum; and the coupled model is analyzed for seismic fragility considering the SSI effect using the IDA calculation method. It is calculated and analyzed that the damage to the structure and equipment from the main aftershock effect may be greater than the effect of a single mainshock. Considering the SSI effect generally increases the conditional failure probability of SSCs under main aftershocks. From the typical SSC seismic performance results, the failure mode of the coupled system is that the concrete of the shield building cracks first, followed by the yielding of the steam generator piping, and finally the main steam piping enters yielding. Considering SSI effect, the values of high confidence low failure probability (HCLPF) of the three in the limit state between basically intact failure state and general failure state are 0.48g, 0.68g and 0.92g respectively. The research results indicate that the effects of the SSI and the main aftershock should not be neglected in the fragility assessment of nuclear power plants. -
图 1 AP1000核电厂剖面图[15]
SG—蒸汽发生器;Pipe—主蒸汽管道;ASB—屏蔽厂房;SCV—安全壳;CIS—内部结构
Figure 1. Section View of AP1000 Nuclear Power Plant
表 1 软岩石场地土层参数
Table 1. Parameters of Soft Rock Site Soil Layer
层号 土层类型 厚度/m 剪切波速Vs/(m·s−1) 密度/(kg·m−3) 1 砂土-1 3.048 640.09 2082.42 2 砂土-1 3.048 655.33 2082.42 3 砂土-2 3.048 670.57 2082.42 4 砂土-2 3.048 685.81 2082.42 5 砂土-2 3.048 701.05 2082.42 6 软岩-1 3.048 1303.03 2082.42 7 软岩-1 3.048 1316.73 2082.42 8 软岩-1 3.048 1330.45 2162.51 9 软岩-1 3.048 1344.16 2162.51 10 软岩-1 3.048 1357.89 2162.51 11 软岩-1 3.048 1371.61 2162.51 12 软岩-1 3.048 1383.80 2162.51 13 软岩-2 3.048 1402.09 2162.51 14 软岩-2 3.048 1426.47 2162.51 15 软岩-2 3.048 1447.81 2162.51 16 软岩-2 3.048 1463.05 2162.51 表 2 地震动序列信息
Table 2. Main Aftershock Motion Sequence
序号 地震动事件 台站 编号 震级 Vs-30/(m·s−1) 1 Chi-Chi TCU059 1498 7.62 272.67 2378 5.90 2 Northridge Csataic-Old 963 6.69 450.28 1652 6.05 3 Northridge Jensen Filter Plant 983 6.69 525.79 1704 5.28 4 Northridge LA-Baldwin HilDS 985 6.69 297.07 1706 5.28 5 Northridge LA-Century City 998 6.69 277.98 1707 5.28 6 Northridge LA-Century City 990 6.69 365.22 1708 5.28 7 Northridge LA-Hollywood 995 6.69 316.46 1660 6.05 8 Northridge Newhall-
Fire Sts1044 6.69 269.14 1721 5.28 9 Northridge Santa Monica 1077 6.69 336.20 1730 5.28 10 Northridge Tarzana-
Ceder Hill1087 6.69 257.21 1739 5.28 表 3 耦合体系模型频率与振型信息
Table 3. Frequency and Vibration Mode of Coupled System Model
模态序号 频率/Hz 振型 1 3.51 屏蔽厂房X方向一阶水平位移 3 3.89 屏蔽厂房Y方向一阶水平位移 4 4.82 蒸汽发生器X方向一阶水平位移 7 6.14 安全壳X方向一阶水平位移 12 7.18 安全壳Y方向一阶水平位移 13 7.66 蒸汽发生器Y方向一阶水平位移 16 8.17 蒸汽发生器Z方向一阶竖直位移 21 12.25 内部结构X方向一阶水平位移 22 13.03 内部结构Y方向一阶水平位移 表 4 典型SSC破坏状态及指标划分
Table 4. Classification of Typical SSC Damage States
名称 破坏状态 描述 破坏指标范围 屏蔽厂房底部单元横向相对位移 DS0 结构无开裂 <0.647 mm DS1 混凝土开裂 0.647~4.151 mm DS2 内部钢筋屈服 4.151~14.993 mm 蒸汽发生器最大应力 DS0 内部管道
弹性变形<259 MPa DS1 内部管道屈服 259~668 MPa DS2 内部管道破裂 >668 MPa 主蒸汽管道最大应力 DS0 管道弹性变形 <300 MPa DS1 管道屈服 300~465 MPa DS2 管道破裂 >465 MPa DS0—基本完好;DS1—一般破坏;DS2—严重破坏 表 5 典型SSC易损性曲线参数
Table 5. Parameters of Fragility Curves for Typical SSC
SSC名称 极限状态 不考虑SSI 考虑SSI βU Am βR Am βR 屏蔽厂房 LS1 1.56g 0.27 1.24g 0.33 0.25 LS2 4.61g 0.27 3.90g 0.33 0.25 蒸汽发生器 LS1 2.51g 0.34 2.01g 0.37 0.40 LS2 6.94g 0.34 4.97g 0.37 0.40 主蒸汽管道 LS1 2.92g 0.35 2.31g 0.40 0.40 LS2 4.63g 0.35 3.54g 0.40 0.40 -
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