1. 上海核工程研究设计院 www.snerdi.com.cn
Assessment of Base-isolated CAP1400
Nuclear Island Design
Yang Jie, Li Shaoping, Yuan Fang
Shanghai Nuclear Engineering & Research Institute
上海核工程研究设计院

2. Outline 01 Introduction 02 SI Design of CAP1400 03 Shaking Table Test
2018/11/19
Outline 01
Introduction 02
SI Design of CAP1400 03
Shaking Table Test 04
Conclusions

3. 1. Introduction
Seismic Isolation
Seismic isolation (SI) is a widely used strategy of earthquake- resistant design in civil engineering applications.
To position a horizontal flexible layer of isolation units between the structure and the foundation.
The dynamic response of the structure is modified.

4. 1. Introduction
Why SI
SI direct benefit: shift of the frequency and so significant reduction of the acceleration
And its consequences:
reinforced concrete structure optimization
homogenization of the FRS
use of standard equipments already qualified for other projects under lower seismic level

5. Outline 01 Introduction 02 SI Design of CAP1400 03 Shaking Table Test
2018/11/19
Outline 01
Introduction 02
SI Design of CAP1400 03
Shaking Table Test 04
Conclusions

6. Goal of Base-isolated CAP1400
2. SI Design of CAP1400
Goal of Base-isolated CAP1400
Making the seismic design benchmark of safe shut earthquake (SSE) to 0.6g in horizontal direction instead of the original 0.3g
Floor response spectra with seismic isolation should be less than CAP1400 NI design floor response spectra, in order to reduce drawings modification in CAP1400 NI original design
Control displacement between structures and adjust them to a suitable scope

7. The type of the isolated bearing is lead rubber bearing(LRB)
2. SI Design of CAP1400
The isolated bearings are laid under the basemat, and the spacing is 3m~4m.
The type of the isolated bearing is lead rubber bearing(LRB)
The LRB is made of a low damping rubber bearing with lead plugs insertions. The lead core is considered as a perfectly plastic material.
it has a high horizontal stiffness before yielding. After yielding, the horizontal stiffness is mainly provided by the elastomer

8. 2. SI Design of CAP1400
The analysis model of the nuclear island stick model is composed of auxiliary and shield building, containment internal structure, steel containment vessel and reactor coolant loop.
This isolation bearing is usually modeled with three uncoupled linear springs.
The LRB is made of a low damping rubber bearing with lead plugs insertions. The
experimental response of the LRB bearing is depicted in the Figure below. The
lead core is considered as a perfectly plastic material: it has a high horizontal
stiffness before yielding. After yielding, the horizontal stiffness is mainly provided by
the elastomer.
simplified model for FRS calculation

9. Seismic isolation for CAP1400 Nuclear Island
2. SI Design of CAP1400
Seismic isolation for CAP1400 Nuclear Island
From the comparison results above, the floor response spectra in horizontal direction reduce significantly in the frequency range that larger than 1Hz, but amplify in the frequency range that less than 1Hz.
Although modern isolation systems substantially decouple the superstructure from horizontal ground shaking, none mitigates response to vertical ground motion.
The amplification of the response spectra in the low frequency range of horizontal direction and in the vertical direction has been evaluated. They have little contribution to the response of the components and systems contained in the superstructure.
Horizontal FRS with and without SI
Vertical FRS with and without SI

10. Outline 01 Introduction 02 SI Design of CAP1400 03 Shaking Table Test
2018/11/19
Outline 01
Introduction 02
SI Design of CAP1400 03
Shaking Table Test 04
Conclusions

11. To provide realistic data to validate the numerical method
2018/11/19
3. Shaking Table Test
（1）Goal of the test
The test results were compared with three-dimensional finite element simulation results.
To provide realistic data to validate the numerical method
Focused on the response of superstructure and the isolation unit.
The geometric similarity coefficient for reduced-scale model is designated as 1/16, which is full in consideration of capability of shaking table, structural size parameters and dynamic characteristics

12. 2018/11/19
3. Shaking Table Test
（2）Design of Model
The geometric similarity coefficient for reduced-scale model is designated as 1/16.
Four reduced-scale isolated bearings (LRB400) are used in the reduced-scale model.
The geometric similarity coefficient for reduced-scale model is designated as 1/16, which is full in consideration of capability of shaking table, structural size parameters and dynamic characteristics

13. 3. Shaking Table Test （3）Arrangement of measuring points
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3. Shaking Table Test
（3）Arrangement of measuring points
Displacement sensors
Acceleration sensors
Force sensors

14. 2018/11/19
3. Shaking Table Test
（4）Dynamic characteristics of prototype structure
Base-isolated Model
Non Base-isolated Model
The frequencies of the first two modes of the base-isolated model are slightly decreased.
The non-isolated model has a great change in the structural characteristics after the earthquake.
From the table above, we can see that, after the 0.6g earthquake was inputted, the frequencies of the first two modes of the base-isolated model are slightly decreased. Overall, its dynamic characteristics remain unchanged, which demonstrates that the base-isolated model can keep elastic state.
However, the model of the non-isolated structure has a great change in the structural characteristics after the earthquake, and the damage degree of the non-isolated structure is more serious than that of the isolated structure.

15. 3. Shaking Table Test （5）Acceleration response
2018/11/19
3. Shaking Table Test
（5）Acceleration response
Fig.4 illustrates the benefits of seismic isolation using an acceleration distribution plot in isolation layer and superstructure, in which node 1 represents lower raft, and nodes 2~5 represent superstructure of different elevations. From the plot, we find the acceleration of superstructure in horizontal direction reduce significantly.
The acceleration time histories of analysis and test results are compared in Fig.5. According to the comparison of acceleration results under different load conditions, the test results match the analysis results very well, especially under the unidirectional loading condition.
Acceleration time histories of
analysis and test results
Acceleration distribution plot in model

16. 3. Shaking Table Test （5）Acceleration response Hysteretic curve under
2018/11/19
3. Shaking Table Test
（5）Acceleration response
From the results, it can be seen that the shape of the hysteresis curve is more stable, and closer to the numerical simulation results under unidirectional loading condition. And under the multi direction loading, the measured hysteresis curves show a more complex shape, but the overall trend is consistent with the numerical simulation results.
Hysteretic curve under
biaxial loading condition
Hysteretic curve under
unidirectional loading condition

17. Outline 01 Introduction 02 SI Design of CAP1400 03 Shaking Table Test
2018/11/19
Outline 01
Introduction 02
SI Design of CAP1400 03
Shaking Table Test 04
Conclusions

18. 4. Conclutions
Base isolation technology extends the natural period of the structure, and increases the damping to reduce the input of earthquake of the superstructure.
The peak acceleration response of the isolation layer is much smaller than the acceleration of the non-isolated structure.
The hysteretic curve is full, which shows that it has good energy dissipation capacity.
The calculation and analysis of the isolated structure are in good agreement with the experimental results.
Finite element analysis and shaking table tests were performed for the isolation and non-isolation models of CAP1400 nuclear island structure. By the comparison with the test and analysis results, the following conclusions are obtained

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