臺灣博碩士論文加值系統

This research presents the results of an investigation on degradation of ductility under cyclic loading and shear strength evaluation of reinforced concrete (RC) beams. A total of 14 specimen sets (one full-size beam and one the observation specimen in each set) were tested under cyclic loading after being subjected to accelerated corrosion in different corrosion level as well as different three cases for corroded situation as only corrosion for transverse reinforcement (7 specimen sets), only corrosion for longitudinal reinforcement (5 specimen sets), corroded both of transverse and longitudinal reinforcement (2 specimen sets). Each set was subjected to accelerated corrosion using an imposed current for the same time interval.

Following the corrosion, the full-size beam in each set was tested using cyclic loading to examine the seismic performance, whereas the observation specimen was demolished to examine the extent of corrosion. Methods to estimate the actual corrosion weight loss is found by experimental results that use to be modified Faraday’s law. Cyclic loading results indicated that with an increasing corrosion level, the ultimate drift, ductility, plastic rotation capacity, and energy dissipation of the beams initially increased and later decreased. The failure mode switched from flexural failure to flexural‐shear failure. Corrosion increased shear deformation and the spread of plasticity of the plastic hinge region. Estimated corrosion crack method was established based on experimental results and observation. Methods to estimate the residual shear strength and ductility of reinforced concrete beams with corroded hoops are proposed. The relationship between shear strength vs. plastic rotation was investigated.

This research presents the results of an investigation on degradation of ductility under cyclic loading and shear strength evaluation of reinforced concrete (RC) beams. A total of 14 specimen sets (one full-size beam and one the observation specimen in each set) were tested under cyclic loading after being subjected to accelerated corrosion in different corrosion level as well as different three cases for corroded situation as only corrosion for transverse reinforcement (7 specimen sets), only corrosion for longitudinal reinforcement (5 specimen sets), corroded both of transverse and longitudinal reinforcement (2 specimen sets). Each set was subjected to accelerated corrosion using an imposed current for the same time interval.

Following the corrosion, the full-size beam in each set was tested using cyclic loading to examine the seismic performance, whereas the observation specimen was demolished to examine the extent of corrosion. Methods to estimate the actual corrosion weight loss is found by experimental results that use to be modified Faraday’s law. Cyclic loading results indicated that with an increasing corrosion level, the ultimate drift, ductility, plastic rotation capacity, and energy dissipation of the beams initially increased and later decreased. The failure mode switched from flexural failure to flexural‐shear failure. Corrosion increased shear deformation and the spread of plasticity of the plastic hinge region. Estimated corrosion crack method was established based on experimental results and observation. Methods to estimate the residual shear strength and ductility of reinforced concrete beams with corroded hoops are proposed. The relationship between shear strength vs. plastic rotation was investigated.

CHAPTER 1 INTRODUCTION 1
1.1 General of Corrosion 1
1.2 Objective and Scope 3
1.3 Outline of Report 3
CHAPTER 2 LITERATURE REVIEW 5
2.1 Corrosion in Reinforced Concrete 5
2.1.1 Types of Corrosion in Reinforced Concrete 6
2.1.1.1 Uniform Corrosion 6
2.1.1.2 Pitting Corrosion 6
2.1.2 Mechanism of Corrosion in Reinforced Concrete 6
2.1.3 Accelerated Corrosion Technique 10
2.2 Deterioration Process 11
2.3 The Softening Effect of Concrete 12
2.4 Effect of Corrosion on Bond Strength of RC Members 14
2.5 Effect of Corrosion on Flexural Strength of RC Members 14
2.6 Effect of Corrosion on Shear Strength of RC Members 15
CHAPTER 3 EXPERIMENTAL PROGRAM 18
3.1 Specimen Design 19
3.1.1 Limitations on Materials 19
3.1.2 Design of Flexural Beam in a Special Moment-Resisting Frame 20
3.1.2.1 Geometric Limits on Beam Cross Sections 20
3.1.2.2 Longitudinal Reinforcement 21
3.1.2.3 The transverse reinforcement 22
3.1.2.4 Shear Reinforcement 23
3.2 Accelerated Corrosion 28
3.2.1 The full-size beam specimen 28
3.2.2 The Observation Specimen 30
3.3 Material properties 30
3.3.1 Concrete 30
3.3.2 Reinforcing steel 31
3.4 Fabrication of Test Specimens 32
3.5 Cyclic loading setup 33
3.6 Test Procedure 34
3.6.1 Loading History 34
CHAPTER 4 RESULTS AND DISCUSSION 35
4.1 Observations of corrosion rate 35
4.2 Measurement of corrosion 36
4.2.1 Measurement values of the corrosion of reinforcement 36
4.2.1.1 Weight loss calculation 36
4.2.1.2 The average residual of cross-sectional area (Aavg) 37
4.2.1.3 The minimum residual of cross-sectional area 37
4.2.1.4 The maximum pitting depth (pmax) 38
4.2.2 Measurement results 38
4.3 Observation of corrosion crack on concrete surface 39
4.3.1 Corrosion cracks expanded view 39
4.3.2 The total crack width 41
4.4 Determine Corrosion Crack Width from Weight Loss 42
4.4.1 Corrosion crack coefficient 42
4.4.1.1 Corrosion crack due to transverse reinforcements 42
4.4.1.2 Corrosion crack due to longitudinal reinforcements 44
4.4.2 Corrosion crack width 46
4.5 Damage progression 49
4.6 Hysteretic loops behavior and envelope response curve 54
4.7 Test results 58
4.8 Residual Shear Strength 60
4.8.1 The Residual Shear Strength Carried by the Transverse Reinforcements 60
4.8.2 The Residual Shear Strength Carried by the concrete 63
4.8.2.1 Considering concrete softening 64
4.8.2.2 Considering longitudinal reinforcement cross-sectional reduction 65
4.8.2.3 Ductile behavior of concrete strength reduction 66
4.8.3 Residual shear strength analysis 67
4.8.4 Plastic Shear Strength Ratio vs. Plastic Rotation Relationship 69
CHAPTER 5 CONCLUSIONS 72

CHAPTER 1INTRODUCTION1
1.1General of Corrosion1
1.2Objective and Scope3
1.3Outline of Report3
CHAPTER 2LITERATURE REVIEW5
2.1Corrosion in Reinforced Concrete5
2.1.1Types of Corrosion in Reinforced Concrete6
2.1.1.1Uniform Corrosion6
2.1.1.2Pitting Corrosion6
2.1.2Mechanism of Corrosion in Reinforced Concrete6
2.1.3Accelerated Corrosion Technique10
2.2Deterioration Process11
2.3The Softening Effect of Concrete12
2.4Effect of Corrosion on Bond Strength of RC Members14
2.5Effect of Corrosion on Flexural Strength of RC Members14
2.6Effect of Corrosion on Shear Strength of RC Members15
CHAPTER 3EXPERIMENTAL PROGRAM18
3.1Specimen Design19
3.1.1Limitations on Materials19
3.1.2Design of Flexural Beam in a Special Moment-Resisting Frame20
3.1.2.1Geometric Limits on Beam Cross Sections20
3.1.2.2Longitudinal Reinforcement21
3.1.2.3The transverse reinforcement22
3.1.2.4Shear Reinforcement23
3.2Accelerated Corrosion28
3.2.1The full-size beam specimen28
3.2.2The Observation Specimen30
3.3Material properties30
3.3.1Concrete30
3.3.2Reinforcing steel31
3.4Fabrication of Test Specimens32
3.5Cyclic loading setup33
3.6Test Procedure34
3.6.1Loading History34
CHAPTER 4RESULTS AND DISCUSSION35
4.1Observations of corrosion rate35
4.2Measurement of corrosion36
4.2.1Measurement values of the corrosion of reinforcement36
4.2.1.1Weight loss calculation36
4.2.1.2The average residual of cross-sectional area (Aavg)37
4.2.1.3The minimum residual of cross-sectional area37
4.2.1.4The maximum pitting depth (pmax)38
4.2.2Measurement results38
4.3Observation of corrosion crack on concrete surface39
4.3.1Corrosion cracks expanded view39
4.3.2The total crack width41
4.4Determine Corrosion Crack Width from Weight Loss42
4.4.1Corrosion crack coefficient42
4.4.1.1Corrosion crack due to transverse reinforcements42
4.4.1.2Corrosion crack due to longitudinal reinforcements44
4.4.2Corrosion crack width46
4.5Damage progression49
4.6Hysteretic loops behavior and envelope response curve54
4.7Test results58
4.8Residual Shear Strength60
4.8.1The Residual Shear Strength Carried by the Transverse Reinforcements60
4.8.2The Residual Shear Strength Carried by the concrete63
4.8.2.1Considering concrete softening64
4.8.2.2Considering longitudinal reinforcement cross-sectional reduction65
4.8.2.3Ductile behavior of concrete strength reduction66
4.8.3Residual shear strength analysis67
4.8.4Plastic Shear Strength Ratio vs. Plastic Rotation Relationship69
CHAPTER 5CONCLUSIONS72