Effects of Earthquake Loading Rate and Prestressing on Shear Strength of Cylindrical Squat Walls = 지진하중 변형률 속도 및 프리스트레싱이 원형 저형 벽체 전단 강도에 미치는 영향|RISS 상세보기

다국어 초록 (Multilingual Abstract)

In recent years, Gyeong-ju and Po-hang, two earthquakes were occurred. Because of these two earthquakes, which occurred near the nuclear power plant site, the concern in seismic safety of nuclear power plants was increased. In addition, the importance of identifying the exact seismic performance of nuclear power plants has been emphasized as the number and risk of earthquakes increased. In addition, it was confirmed that the characteristic of Korea earthquake includes high frequency components.
Nuclear power plants are the building that controls radioactive materials and requires high seismic performance to minimize leakage of radioactive materials in the event of an accident. Therefore, the thickness of auxiliary and containment buildings is about 1.2 m. In addition, high reinforcement ratios exceeding the current design criteria are used. In particular, the post-tensioning is applied in containment buildings to withstand internal pressure that may occur in the event of an emergency accident. However, due to the post-tensioning and massive scale of containment buildings, structural experiments have been rarely conducted. In the case of existing experiments, panel experiments with the same details or small-scaled model were conducted. In addition, experiments of cylindrical walls with post-tensioning were rarely conducted.
Unlike planar walls, cylindrical walls do not transfer the shear force directly. The shear force is transmitted along the cross-sectional shape. Because of these characteristics of cylindrical section, confining force is required. However, the confining force of horizontal reinforcing bars cannot be applied, if the proposed expression through existing planar wall experiments is used. Thus, it is necessary to develop a shear strength model for cylindrical walls. In particular, it is necessary to research the characteristics of structure behavior characteristic of the structure against the earthquakes with high-frequency components.
In this dissertation, dynamic loading tests were performed to investigate the effect of high-frequency earthquakes, and shaking table tests were performed for verification. In addition, to investigate the seismic performance of the containment building, a cylindrical wall was prepared and cyclic loading tests were conducted. Based on the experimental results, the failure mode change was not occurred and the seismic performance of reinforced concrete wall was confirmed. In addition, the greater strength of structure was observed under high loading rate.
In the results of the comparison experiment between cylindrical and planar walls, the effect of post-tensioning on maximum shear strength was low in the case of planar wall. However, in the case of cylindrical wall with post-tensioning and crosstie, the maximum strength was increased. On the other hand, in the case of post-tensioned cylindrical walls without cross ties, the delamination cracks were observed. Due to the internal cracks, the maximum shear strengths were decreased. Based on the experimental results, the shear strength equation of the cylindrical wall was proposed.
In the conclusion of this dissertation, based on the test and analysis results, the shear strength equation for cylindrical wall was proposed to predict the seismic capacity of wall. In addition, design recommendations were proposed to prevent premature failure of structure and improve the structural safety of nuclear power plants from seismic loads.

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국문 초록 (Abstract)

최근 몇 년간 경주와 포항에서 두 차례 지진이 발생하였다. 원자력 발전소 부지 인근에서 발생한 지진으로 원전의 내진 안전성에 대한 우려가 증가하였다. 또한 지진 발생 횟수와 위험성이 증가함에 따라 원자력발전소의 정확한 내진성능을 파악하는 것이 중요하다고 강조되어 왔다. 또한, 한국 지진의 특징에는 고주파 성분이 포함되어 있는 것으로 확인되었다.
원전은 방사성 물질을 통제하는 건물로 사고 발생 시 방사성 물질 누출을 최소화하기 위해 높은 내진 성능이 요구된다. 따라서 보조 및 격납건물의 두께는 약 1.2m로 높게 설계된다. 또한 현재 설계 기준을 초과하는 높은 철근비가 사용된다. 특히 격납건물은 비상사고 발생 시 발생할 수 있는 내부 압력을 견디기 위해 포스트 텐션이 적용된다. 그러나, 격납건물의 포스트텐션과 거대한 크기로 인해, 구조 실험은 거의 수행되지 않았다. 기존 실험의 경우 상세가 같은 패널 실험을 위주로 수행되었고, 포스트 텐션을 갖는 원통형 벽의 실험은 거의 수행되지 않았다.
평면 벽과 달리 원통형 벽은 전단력을 직접 전달하지 않는다. 전단력은 단면 형상을 따라 전달되므로, 이러한 원통형 단면의 특성 때문에 추가 구속력이 요구된다. 그러나 기존 평면벽 실험을 통한 제안식을 이용할 경우 수평보강근의 구속력을 적용할 수 없다. 따라서 원통형 벽체의 전단강도 모델 개발이 필요하며, 특히 고주파 성분의 지진에 대한 구조물의 구조 거동 특성에 대한 연구가 필요하다.
본 연구에서는 동적하중시험과 진동대 시험을 통해 고주파 지진의 영향을 확인하였다. 실험결과 고진동수 지진에서 파괴 모드 변화는 발생하지 않았고, 지진하중에서 철근콘크리트 벽체의 내진성능을 확인하였다. 또한, 빠른 가력속도에서 구조물의 강도 증가 현상을 확인하였다. 또한, 격납 건물의 내진성능을 조사하기 위해 원통형 벽체를 작성하고 주기적 하중 시험을 실시하였다.
원통형 벽체와 평면형 벽체의 비교 실험 결과, 포스트텐셔닝이 최대 전단 강도에 미치는 영향은 평면형 벽체의 경우 낮은 것으로 나타났다. 그러나 포스트 텐션과 크로스 타이를 적용한 원통형 벽의 경우 최대 강도가 증가하였다. 반면, 크로스타이가 없는 포스트텐셔닝 원통형 벽의 경우, delamination 균열이 관찰되었다. 내부 균열로 인해 최대 전단 강도가 감소하였고, 실험 결과를 바탕으로 원통형 벽체의 전단강도 방정식을 제안하였다.
본 논문의 결론에서는 시험 및 분석 결과를 바탕으로 원통형 벽체에 대한 전단강도 방정식을 제안하여 벽체의 내진 성능을 예측하였다. 또한 구조물의 조기 파괴를 방지하고 지진 하중에 의한 원자력발전소의 구조안전성을 향상시키기 위한 설계 권고사항이 제시되었다.

번역하기

최근 몇 년간 경주와 포항에서 두 차례 지진이 발생하였다. 원자력 발전소 부지 인근에서 발생한 지진으로 원전의 내진 안전성에 대한 우려가 증가하였다. 또한 지진 발생 횟수와 위험성이 ...

목차 (Table of Contents)

Chapter 1. Introduction 1
1.1 General 1
1.2 Scope and Objectives 7
1.3 Outline of the Ph.D. dissertation 9
Chapter 2. Literature Review 12

Chapter 1. Introduction 1
1.1 General 1
1.2 Scope and Objectives 7
1.3 Outline of the Ph.D. dissertation 9
Chapter 2. Literature Review 12
2.1 Current Design Codes 13
2.1.1 ACI 349 13
2.1.2 ACI 359 (or ASME BPVC.III.2) 14
2.1.3 EPRI 16
2.2 Review of previous research for squat walls 19
2.2.1 Barda et al. (1977) 19
2.2.2 Gulec and Whittaker (2011) 20
2.2.3 Hwang, et al. (2001) 25
2.2.4 Luna and Whittaker (2019) 29
2.3 Review of previous research for cylindrical walls 32
2.3.1 Ogaki, et al. (1981) 32
2.3.2 Cho et al (2007) 35
2.3.3 Völgyi et al (2014) 38
2.3.4 Wu, et al (2017) 40
2.3.5 Previous literatures about delamination failure at containment 42
Chapter 3. Structural Test for Effect of High Frequency Earthquakes 50
3.1 Experiment I: Dynamic loading test 51
3.1.1 General 51
3.1.2 Test Plan 55
3.1.3 Test results 67
3.1.4 Effect of loading rate on reinforced concrete walls 91
3.1.5 Summary of experiment I 93
3.2 Experiment II: Shaking table test 95
3.2.1 General 95
3.2.2 Test Plan 99
3.2.3 Test results 106
3.2.4 Summary of experiment II 115
Chapter 4. Structural Test for Cylindrical Walls 117
4.1 Experiment III: Cylindrical wall 117
4.1.1 General 117
4.1.2 Test plan 121
4.1.3 Test results 130
4.1.4 Summary of experiment III 143
4.2 Experiment IV: Semi-Cylindrical wall 145
4.2.1 General 145
4.2.2 Test plan 148
4.2.3 Test results 159
4.2.4 Summary of experiment IV 181
Chapter 5. Nonlinear Finite Element Analysis 183
5.1 Overview 183
5.2 Modeling information 184
5.3 Comparison with test results 188
5.3.1 Relationship of lateral displacement and force 188
5.3.2 Concrete damage pattern 192
5.4 Finite element analysis for parametric study 197
5.5 Summary 200
Chapter 6. Effects of Design Parameters on Shear Strength of Concrete Wall 201
6.1 Overview 201
6.2 Loading rate effect 202
6.3 Effect of post-tensioning force 208
6.3.1 Vertical post-tensioning 208
6.3.2 Horizontal post-tensioning 210
6.3.3 Delamination on walls and effect of cross-tie 212
6.3.4 Bending moment due to horizontal post-tensioning 215
6.4 Effect of wall shape 221
6.4.1 Cylindrical and planar wall 221
6.4.2 Horizontal strain due to increment of radius 226
6.5 Summary 230
Chapter 7. Shear Strength Model for Cylindrical Walls 232
7.1 Overview 232
7.2 Background 234
7.2.1 Web-crushing and observed failure mode of cylindrical walls 234
7.2.2 Confining force (or deviation force) 237
7.2.3 Elastic analysis of cylindrical squat wall 239
7.3 Shear strength of cylindrical wall 244
7.3.1 Concept of shear strength model 244
7.3.2 Define the forces and prediction of shear strength 250
7.4 Simplified shear strength equation and application 262
7.4.1 Simplified shear strength 262
7.4.2 Application to current code 272
7.5 Verification 275
7.6 Summary 283
Chapter 8. Conclusion 284
8.1 Summary 284
8.2 Recommendations for design and evaluation of NPP wall structures 288
8.2.1 Loading rate effect 288
8.2.2 Delamination due to horizontal post-tensioning 292
8.2.3 Bending moment due to horizontal post-tensioning 293
8.2.4 Effective wall length 294
8.2.5 Finite element analysis modeling 295
References 300
APPENDIX A : Summary of Existing Cylindrical Squat Wall Specimens 310
초 록 314

참고문헌 (Reference)

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2. Shaking table testing of RC walls, Pinho, R., 37(4), 119-142, , 2000

3. Failure modes of low-rise shear walls, Farrar, C. R., Salmon, M. W., Reed, J. W., 119(2), 119-138, , 1993

4. Multiaxial strain softening of concrete, Van Mier, J. G., 19(3), 190-200, , 1986

5. Behavior of concrete under biaxial stresses, Hilsdorf, H. K., Kupfer, H., Rusch, H., Vol. 66, No. 8, pp. 656-666, , 1969

6. Web crushing of reinforced concrete structural walls, Shiu, K. N., Oesterle, R. G., Aristizabal-Ochoa, J. D., Corley, W. G., Vol. 81, No. 3, pp. 231-241, , 1984

7. Response of Reinforced Concrete Beams at High Strain Rates, Shah, S. P., Kulkarni, S. M., V. 95, No. 6, pp. 705-715, , 1998

8. Behavior and analysis of 100 MPa concrete membrane elements, Hsu, T. T., Zhang, L. X. B., 124(1), 24-34, , 1998

9. Analytical model for predicting shear strength of squat walls, Lee, H. J., Fang, W. H., Hwang, S. J., Yu, H. W., 127(1), 43-50, , 2001

10. Triaxial failure criterion for concrete and its generalization, Menetrey, P., Willam, K. J., 92(3), 311-318, , 1995