Shear-Sliding Capacity of Reinforced Concrete Shear Walls Subjected to Cyclic Lateral Loading = 반복 횡하중을 받는 철근콘크리트 구조벽의 미끄러짐 전단 성능

다국어 초록 (Multilingual Abstract)

Reinforced concrete walls in nuclear power plant (NPP) buildings consist of web walls and orthogonal cross walls arranged in a grid configuration. In addition, due to the presence of openings for equipment and facilities, the walls are subdivided into multiple wall piers. This structural layout results in complex load-transfer mechanisms. Moreover, due to the low aspect ratio and the large volume of walls that require construction joints, the seismic response is governed by shear and shear–sliding behavior. Therefore, for both the economical seismic design and accurate seismic performance evaluation of NPP buildings, these characteristics must be properly considered.
In the dissertation, the shear–sliding behavior of squat reinforced concrete walls was investigated through cyclic lateral loading tests. In addition to the newly conducted tests, a comprehensive shear–sliding wall database was established by incorporating existing experimental results. Based on this database, the influence of key design parameters—such as flange geometry, wall thickness, reinforcement ratio, bar diameter, aspect ratio, surface roughening method, and loading direction—on shear–sliding behavior was examined. As a result, it was found that, in addition to the effects of previously reported parameters, the shear-sliding strength of walls with flanges was higher than that of walls without flanges, and the shear-sliding strength increased as the aspect ratio decreased.
In addition, to investigate the seismic behavior of nuclear power plant walls with multiple openings and wall piers, and to verify the strength evaluation method proposed by EPRI (2018), cyclic loading tests were conducted on reinforced concrete walls with multiple openings. The results showed that the EPRI evaluation method, which estimates the total story strength as the sum of the strengths of individual wall piers, is appropriate because shear and shear–friction failures provide sufficient deformation capacity for load redistribution. However, the method did not accurately predict the failure mode of each pier, primarily due to the simplified consideration of compressive and tensile forces in the strength equations.
Based on the investigation of the shear–sliding wall database, a shear–sliding strength model was developed. In the proposed model, the shear–sliding strength of walls was determined by the combined contribution of shear-friction in the compression zone and dowel action in the tension zone. Considering the flexural stress distribution, the governing failure mode and the wall strength was determined by comparing the shear–sliding strength with the corresponding flexural capacity. Compared with existing strength equations, the proposed model showed improved accuracy in predicting both the failure mode and overall strength, capturing the strength trends associated with key design parameters.
Additionally, a nonlinear shear–sliding backbone model was developed to capture the strength degradation of squat walls. The deformation capacity was defined by the fracture of tension reinforcement engaged in catenary action, which was modeled using the curvature profile of concrete-embedded bent rebar. In conjunction with the proposed strength model, the degraded strength under large sliding displacements was represented as the combined resistance of reduced shear-friction in the compression zone and the transition from dowel to catenary action in the tension zone. Proposed model captured the strength degradation behavior of existing shear-sliding test results and provides a theoretical basis for performance based seismic design of reinforced concrete squat walls.

국문 초록 (Abstract)

원자력 발전소(NPP) 건물의 철근콘크리트 벽체는 웨브 벽체와 직교 벽체로 구성된 격자형 배치를 가지며, 기기 및 설비를 위한 개구부로 인해 다수의 벽체 세그먼트로 구성되어 있다. 이러한 벽체의 구조적 특징으로 인해 복잡한 하중 전달 경로가 형성된다. 또한, 많은 벽체 물량으로 인한 시공이음부와 낮은 형상비로 인해, 벽체의 내진 거동은 전단 및 전단미끄러짐 거동이 지배적이다. 따라서, 원자력 발전소 건물의 경제적 내진 설계와 정밀한 내진 성능 평가를 위해서는 이러한 특성이 적절히 고려되어야 한다.
본 논문에서는 철근콘크리트 저형 벽체의 전단미끄러짐 거동을 규명하기 위해 반복 횡하중 실험을 수행하였다. 추가로 기존의 실험 결과를 포함한 전단미끄러짐 벽체 데이터베이스를 구축하고, 플랜지 형상, 벽체 두께, 철근비, 철근 직경, 형상비, 면 거칠기, 가력 방향 등 주요 설계 변수의 영향을 분석하였다. 그 결과, 플랜지를 갖는 벽체의 전단미끄러짐 강도는 플랜지가 없는 벽체보다 큰 강도를 보였으며, 형상비가 작을수록 강도가 증가하는 경향을 보였다.
또한, 다중 개구부와 벽체 세그먼트를 갖는 NPP 벽체의 내진 거동을 실험적으로 규명하고, EPRI(2018)에서 제안한 강도 평가 방법의 타당성을 검증하기 위해 반복횡하중 실험을 수행하였다. 그 결과, 서로 다른 파괴 모드를 갖는 개별 세그먼트의 강도를 합산하여 층 강도를 평가하는 EPRI의 방법은 적절한 것으로 나타났으며, 이는 전단 및 전단마찰 파괴가 하중 재분배가 가능할 만큼 충분한 변형 능력을 지님을 의미한다. 그러나 각 세그먼트의 파괴 모드 예측은 압축력과 인장력에 대한 단순한 고려로 인해 정확하지 않았다.
전단미끄러짐 벽체 데이터베이스 분석을 바탕으로, 플랜지, 형상비, 고강도 철근의 영향을 적절히 반영한 전단미끄러짐 강도 모델을 제안하였다. 제안된 모델은 휨 응력 분포를 고려한 압축대의 전단마찰 거동과 인장대의 장부 작용을 합산하여 벽체의 전단미끄러짐 강도를 평가하며, 휨 강도와의 비교를 통해 지배 파괴모드를 결정한다. 기존 식들과 비교할 때, 제안 모델은 강도 예측 정확도가 향상되었으며, 주요 설계 변수에 따른 강도 변화를 잘 예측하였다.
아울러, 전단미끄러짐 거동의 강도 열화 예측을 위해 비선형 전단미끄러짐 포락 곡선 모델을 개발하였다. 벽체의 변형 능력은 인장 철근의 현수 작용 시의 철근 파단에 의해 정의되었으며, 콘크리트에 매입된 철근의 곡률 분포를 이용해 모델링하였다. 제안된 강도 모델과 연계하여, 큰 미끄러짐 변형 하에서 압축대의 전단마찰 저하와 인장대의 현수 작용을 고려하였다. 제안된 모델은 기존 전단미끄러짐 실험 결과를 합리적으로 예측하였으며, 철근콘크리트 저형 벽체의 성능 기반 내진 설계를 위한 이론적 근거를 제공한다.

목차 (Table of Contents)

• Abstract i
• Contents iv
• List of Tables x
• List of Figures xi
• List of Symbols xvi
• Chapter 1. Introduction 1
• 1.1 Industrial Background 1
• 1.2 Characteristics of Shear Wall in NPP Auxiliary Building 3
• 1.3 Research Motivation and Problem Definition 5
• 1.4 Scope and Objective 8
• 1.5 Outline of Dissertation 11
• Chapter 2. Literature Review 13
• 2.1 Previous Researches on Shear-Friction 13
• 2.1.1 Birkeland and Birkeland (1966) 13
• 2.1.2 Mattock and Hawkins (1972) 15
• 2.1.3 Loov (1978) 15
• 2.1.4 Randl (1997) 16
• 2.1.5 Harries et al. (2012) (SI Units) 17
• 2.1.6 Calvi et al. (2022) 18
• 2.2 Previous Researches on Dowel Action 19
• 2.2.1 Hetényi (Beam on Elastic Foundation) (1946) 19
• 2.2.2 Rasmussen (1962) 24
• 2.2.3 Soroushian et al. (1986) 25
• 2.2.4 Vintzileou and Tassios (1987) 25
• 2.2.5 Maekawa et al. (1996) 26
• 2.2.6 Randl. (2007) 28
• 2.2.7 Sørensen et al. (2017) 29
• 2.2.8 Preti et al. (2023) 30
• 2.2.9 Pejatović et al. (2024) 31
• 2.3 Current Design & Evaluation Codes 34
• 2.3.1 ACI 318-19 (ACI Committee 318, 2019) or ACI 349-13 (ACI Committee 349, 2013) (SI Unit) 34
• 2.3.2 Eurocode2 (British Standards Institution, 2004) (SI Unit) 36
• 2.3.3 Eurocode8 (British Standards Institution, 2004) (SI Unit) 38
• 2.3.4 fib model code (International Federation for Structural Concrete, 2010) (SI Unit) 40
• 2.3.5 AASHTO-LRFD (American Association of State Highway and Transportation Officials, 2020) (Imperial Unit) 41
• 2.3.6 ASCE/SEI 41-23 (American Society of Civil Engineers, 2023) 43
• 2.4 Previous Researches on Shear-Sliding of Shear Wall 47
• 2.4.1 Paulay et al. (1982) 47
• 2.4.2 Schuler et al. (2016) 48
• 2.4.3 Baek (2017) 51
• 2.5 Strength equations for seismic evaluation of NPPs: EPRI (2018) 53
• 2.5.1 General process of SOV 53
• 2.5.2 Barda et al. (1976) (Imperial Unit) 56
• 2.5.3 Gulec and Whittaker. (2011) (Imperial Unit) 57
• 2.5.4 ACI 318-19: Shear strength (SI Unit) 58
• 2.5.5 MCEER 09-0010 (Imperial Unit) 59
• 2.5.6 Benjamin and Reed (1983) (Imperial Unit) 60
• 2.5.7 ACI 318-19: Shear-friction strength 60
• Chapter 3. Experimental Studies on Shear-Sliding of RC Walls with Construction Joints 61
• 3.1 Cyclic Loading Test of RC Walls with Flanges 61
• 3.1.1 Flange Wall of NPP 61
• 3.1.2 Test Plan 65
• 3.1.3 Test Results 73
• 3.1.4 Effect of Design Parameters 96
• 3.1.5 Evaluation of Shear-Friction Strength 101
• 3.2 Cyclic Loading Test of Squat RC Walls 105
• 3.2.1 Uninvestigated Parameters 105
• 3.2.2 Test Plan 109
• 3.2.3 Test Results 120
• 3.2.4 Effect of Design Parameters on Peak strength and Crack Width 137
• 3.2.5 Evaluation of Test Results 145
• 3.3 Summary 150
• Chapter 4. Evaluation of Shear-Sliding Wall Database 153
• 4.1 Wall Database 153
• 4.2 Effect of Design Parameters 155
• 4.2.1 Strength 155
• 4.2.2 Deformation Capacity and Stiffness 159
• 4.3 Comparision with Existing Studies 161
• 4.3.1 Contribution of Strength Components 161
• 4.3.2 Strength Evaluation and Strength Limit 166
• 4.4 Summary 169
• Chapter 5. Experimental Studies on Shear Wall with Multiple Openings 170
• 5.1 Cyclic Loading Test of Squat Walls with Multiple Openings 170
• 5.1.1 SOV Method for SPRA 170
• 5.1.2 Test Plan 174
• 5.1.3 Elastic Finite Element Analysis 178
• 5.1.4 Test Results 185
• 5.2 Summary 205
• Chapter 6. Shear-Sliding Strength Model for RC Wall 207
• 6.1 Outline of the Proposed Strength Model 207
• 6.2 Shear-Sliding Contribution to Overall Displacement 213
• 6.2.1 Displacement Characteristics of Shear-Sliding Failure 213
• 6.2.2 Contributions of Displacement Components 216
• 6.2.3 Proposed Backone Curve 217
• 6.3 Shear-Sliding Strength 220
• 6.3.1 Strain and Stress Distributions 220
• 6.3.2 Axial Force Equilibrium 224
• 6.3.3 Flexural Capacity Before Peak Strength 225
• 6.3.4 Shear-Sliding Capacity Before Peak Strength 226
• 6.4 Calculation of Peak Point 229
• 6.4.1 Stress Distribution at Peak Point 230
• 6.4.2 Contribution of Strength Components 232
• 6.5 Validation of Proposed Strength Model 233
• 6.5.1 Comparison with Existing Test Results 233
• 6.5.2 Trends of Shear-Sliding Strength According to Design Parameters 236
• 6.5.3 Parametric Study of the Proposed Model 241
• 6.6 Summary 249
• Chapter 7. Shear-Sliding Strength Degradation Model for RC Wall 250
• 7.1 Outline of the Proposed Strength Degradtion Model 250
• 7.2 Deformation Profile of Reinforcement under Catenary Action 252
• 7.3 Maximum Curvature of Reinforcement 256
• 7.3.1 Sectional Analysis: Dataset Generation 258
• 7.3.2 Symbolic Regression Using PySR 260
• 7.4 Calculation of Fracture Point 262
• 7.4.1 Sliding Displacement 262
• 7.4.2 Sliding capacity at Fracture Point 263
• 7.5 Calculation of Ultimate Point 265
• 7.6 Validation of Proposed Strength Degradation Model 266
• 7.6.1 Comparision with Existing Test Results 266
• 7.6.2 Parametric Study on Curvature Influence Length 271
• 7.7 Limitation and Future Research 272
• 7.8 Summary 273
• Chapter 8. Summary and Conclusions 274
• References 276
• Appendix A. Wall Database 284
• A.1 Test Strength and Wall Geometry 284
• A.2 Reinforcing Bar Detail 287
• A.3 Hysteresis curve and Code Evaluation 295
• Appendix B. Details on Determination of Peak Point 301
• B.1 Stress Distribution at Peak Point 301
• B.2 Contribution of Strength Components 303
• Appendix C. MATLAB Code 306
• C.1 Main Program 307
• C.2 Generation of Flexural and Sliding Capacity Curve 309
• C.3 Calculation of Peak Point 312
• C.4 Calculation of Fracture Point 314
• 초 록 316