Evaluation of Concrete Bridges Based on Decommissioned Bridge Tests = 폐교량 실험에 근거한 콘크리트교의 안전진단 방법 제안

다국어 초록 (Multilingual Abstract)

The performance of the bridge changes over time after its construction. Due to this aging, the serviceability and durability of the bridge would deteriorate, and if the performance degradation is severe, even collapse accidents could occur. Therefore, the current performance of the existing bridges has been evaluated through regular bridge evaluation.
The evaluation of concrete bridges in Korea consists of various methods, such as visual inspection, non-destructive testing, material testing, structural analysis, and loading test. However, since these methods indirectly evaluate the performance of the aged bridges, the actual performance could not be accurately investigated.
This study started to verify how the current bridge evaluation for concrete bridges in Korea could evaluate the actual performance of the existing bridges. To this end, first, the level of the current evaluation guideline was compared with that of foreign countries, and the actual bridge evaluation cases were analyzed to figure out how the evaluation was performed. Then, the actual material strength and member flexural strength were experimentally evaluated by conducting tests the in laboratory on the specimens obtained after the demolition of the concrete bridges after several decades of the service year.
A result of comparing domestic and foreign bridge evaluation guidelines and analyzing the bridge evaluation cases confirmed that although Korea regularly performs various evaluation methods compared to other countries, the current methods are not efficient. After performing material and structural tests, the material strength of the specimens was above the design strength. Moreover, the actual flexural strength of the specimen was higher than the nominal strength calculated by material design strength.
Based on the research results, an efficient bridge evaluation process was proposed. In the essential evaluation regularly, only the condition inspection (visual inspection and rebound test) is performed. Through this inspection, the current condition and changes of the bridge are investigated and tracked. If severe damage or deterioration is investigated in the regular inspection, additional NDT and material tests are performed to determine the extent and cause of the defects. Then, if structural performance degradation is suspected, safety assessment reflecting the bridge’s current condition is performed. As the proportion of old bridges is gradually increasing, the proposed evaluation process could be helpful to conduct an efficient bridge evaluation.

국문 초록 (Abstract)

교량은 준공 이후 시간이 경과함에 그 상태와 성능이 변화하게 된다. 노후화로 인해 교량의 사용성 및 내구성이 저하되며, 성능저하가 심각한 경우에는 붕괴와 같은 끔찍한 사고도 발생할 수 있다. 따라서 정기적인 안전진단을 통해 공용중 교량의 현재 성능을 평가하고 그 결과에 따른 보수·보강 조치로 교량 유지관리를 수행하고 있다.
한국의 콘크리트교량 안전진단은 외관조사, 비파괴시험, 재료시험, 구조해석 및 차량재하시험 등의 다양한 방법으로 공용중 교량의 현재 성능을 평가하고 있다. 하지만 이는 노후 콘크리트교량의 성능을 간접적으로 평가하므로, 실제 성능은 정확히 알 수 없다.
이 연구는 한국의 현행 콘크리트교 안전진단 방법이 노후교량의 실제 성능을 어떻게 평가하고 있는지를 검증하기 위해 시작되었다. 이를 위해 먼저 현행 안전진단 지침을 외국과 비교하여 그 수준을 파악하고, 실교량 안전진단 사례를 분석하여 실제 안전진단이 어떻게 수행되고 있는지를 분석하였다. 그리고 수십년의 공용년수가 지난 콘크리트교량의 철거 이후 확보한 부재를 대상으로 재료시험 및 실내 구조실험을 수행하여 실제 재료 및 부재 강도를 실험적으로 평가하였다.
국내외 안전진단 지침을 비교하고 실교량 안전진단 사례를 분석한 결과, 한국은 외국에 비하여 다양한 안전진단 방법을 정기적으로 수행하고 있지만, 그 효율성은 높지 않은 것으로 확인되었다. 철거교량 부재를 대상으로 수행된 재료시험과 구조실험에서 노후 콘크리트교의 실제 재료 강도와 부재 휨강도 모두 설계 강도 이상을 보이는 것을 알 수 있었다. 실험 대상 부재들은 철거 전 외관조사에서 c등급 이상으로 상태가 양호하였다. 따라서 실험 대상 교량과 같이 공용중 외관 상태가 양호한 경우에는 설계기준 강도로 안전 측의 안전성평가가 가능하였다.
연구 결과에 근거하여 기존 콘크리트교량 안전진단의 실효성을 높이는 개선안을 제시하였다. 정기적으로 수행되는 기본 안전진단에서는 상태평가(외관조사, 반발경도 시험)만을 수행하며, 이를 통해 교량의 현 상태와 변화를 조사하고 추적한다. 정기 안전진단에서 심각한 손상 및 열화가 발견되면 그 정도와 원인을 파악하기 위한 추가 비파괴시험 및 재료시험을 수행하도록 한다. 그리고 구조성능 저하가 의심된다면 교량의 현재 상태를 반영한 안전성평가를 수행하며, 구조계산에 의해서도 안전성이 불충분한 것으로 판단된 경우에는 재하시험을 통해 교량의 실제 응답을 평가하도록 한다. 점차 노후교량의 비율이 증가하는 현 시점에서, 제시된 안전진단 방법은 효율적인 교량 안전진단을 수행하는데 도움이 될 수 있다고 생각한다.

목차 (Table of Contents)

• 1. Introduction 1
• 1.1 Study Background 1
• 1.2 Research Scope and Methods 5
• 2. Evaluation Methods of Concrete Bridges in Korea and Foreign Countries 6
• 2.1 Concrete Bridge Evaluation in Korea 6
• 2.1.1 Current Regulations of Bridge Evaluation 6
• 2.1.2 History of Bridge Evaluation Guidelines in Korea 8
• 2.2 Comparative Analysis of Bridge Evaluation Guidelines for Concrete Bridges in Korea and Abroad 13
• 2.2.1 Condition Inspection 16
• 2.2.2 Safety Assessment 23
• 2.2.2.1 Korea Detailed Guideline (2019) 23
• 2.2.2.2 USA AASHTO MBE (2018) 26
• 2.2.2.3 Canada CSA S6-14 (2014) 32
• 2.2.2.4 UK CS 454 (2020) & CS 455 (2020) 35
• 2.2.3 Loading Tests 39
• 2.2.3.1 Korea Detailed Guidelines (2019) 40
• 2.2.3.2 USA AASHTO MBE (2018) 42
• 2.2.3.3 Canada CSA S6-14 (2014) 44
• 2.2.3.4 UK CS 463 (2019) 44
• 2.2.4 Grade 46
• 2.2.4.1 Korea Detailed Guideline (2019) 46
• 2.2.4.2 USA FHWA (1995) 50
• 2.2.4.3 Canada Alberta Transportation (2020) 51
• 2.2.4.4 Japan MLIT (2014) 52
• 2.3 Analysis of Actual Bridge Evaluation Cases 53
• 2.3.1 Statistics of Problems of Highway Bridges in Korea 57
• 2.3.2 History of NDT and Material Tests in Korea 59
• 2.3.2.1 Rebound Hardness History 60
• 2.3.2.2 Carbonation Depth History 63
• 2.3.3 Comparison of Safety Assessment of Korean and Foreign Guideline 64
• 2.3.4 Finite Element Analysis Modeling Methods of Superstructure of Concrete Bridges 66
• 2.3.5 Current Status of Vehicle Loading Tests in Korea 69
• 2.3.6 Cases of Bridge Evaluation in the Foreign Countries 72
• 3. Experiments with Decommissioned Bridge Members 75
• 3.1 Introduction 75
• 3.1.1 Test Bridges 79
• 3.1.1.1 Seoul Station Overpass (Ramp B) 79
• 3.1.1.2 Mojeon Bridge 81
• 3.1.1.3 Guro Overpass 83
• 3.1.1.4 Gunsunggang Bridge 85
• 3.1.1.5 Sansung-Woochun Bridge 87
• 3.1.2 History of Bridge Evaluation and Initial Status of Specimen 89
• 3.1.2.1 Seoul Station Overpass (Ramp-B) 89
• 3.1.2.2 Mojeon Bridge 90
• 3.1.2.3 Guro Overpass 91
• 3.1.2.4 Gunsunggang Bridge 92
• 3.1.2.5 Sansung-Woochun Bridge 93
• 3.1.3 Concluding Remarks 95
• 3.2 Material Tests 96
• 3.2.1 Concrete Compressive Strength 97
• 3.2.1.1 Core Compressive Strength 100
• 3.2.1.2 Rebound Hardness Test 104
• 3.2.1.3 Ultrasonic Test 106
• 3.2.2 Concrete Modulus of Elasticity 109
• 3.2.3 Reinforcement bars and PS wires 111
• 3.3 Structure Tests in Laboratory 113
• 3.3.1 Structural test specimens 113
• 3.3.2 Experimental Program 117
• 3.3.3 Analysis of Test Results 121
• 3.3.3.1 Strain Compatibility Analysis 121
• 3.3.3.2 Seoul Station Overpass (Ramp-B) 126
• 3.3.3.3 Mojeon Bridge 128
• 3.3.3.4 Guro Overpass 131
• 3.3.3.5 Gunsunggang Bridge 135
• 3.3.3.6 Sansung-Woochun Bridge 139
• 3.3.3.7 Estimation of Effective Prestress Force of Bridges 143
• 3.4 Loading Tests 147
• 3.4.1 Loading Tests Overview 147
• 3.4.2 Analysis of Loading Test Results 154
• 3.4.2.1 Static Loading Tests Deflection Response Ratio 154
• 3.4.2.2 Dynamic Loading Tests 161
• 3.5 Safety Assessment of Existing Concrete Bridges Based on Test Results 163
• 3.5.1 Safety Factor and Rating Factor 163
• 3.5.2 Load Carrying Capacity by Loading Tests 171
• 4. Proposal of Efficient Bridge Evaluation Method for Concrete Bridges 173
• 4.1 Condition Inspection 174
• 4.1.1 Visual Inspection 174
• 4.1.2 Concrete NDT and Material Tests 175
• 4.2 Safety Assessment 178
• 4.2.1 Safety Assessment Regulations 178
• 4.2.2 Evaluation of Flexural Strength 180
• 4.2.3 Loading Tests 181
• 4.3 Proposal of Bridge Evaluation Process of the Existing Concrete Bridges 184
• 5. Conclusions 187
• 5.1 Comparison of Bridge Evaluation Guidelines 187
• 5.2 Actual Cases of Bridge Evaluation 189
• 5.3 Test Results of Decommissioned Bridge Members 191
• 5.4 Proposal of an Efficient Bridge Evaluation and its Necessity 193
• Reference 196
• 국문초록 201

참고문헌 (Reference)

1. 道路橋定期点檢要領, 國土交通省道路局,, , 2019.