The present work aims at finding suitable mineral-bonded strengthening layers to protect steel-reinforced concrete (RC) structures from impact events. The strengthening layers are applied to the impact-facing side and absorb large parts of the impact energy. In this way, they protect the RC structures from the impact events. The multilayered strengthening layers consist of a cover layer and a damping layer. The cover layers possess a high strength and a high modulus of elasticity. The impactor directly hits the cover layer, which spreads the impact force to larger areas of the damping layer below. The strengths and moduli of elasticity of the damping layers are minor, and they absorb impact energy, converting it into friction, heat, or potential energy.
Several materials have been tested as damping layers, including a concrete mixed with waste tire rubber aggregates, two types of lightweight concrete, and two types of infra-lightweight concrete. The cover layers tested include carbon-fiber-reinforced concrete and various short-fiber-reinforced concretes, some of which are reinforced with 3D hybrid pyramidal truss reinforcing structures.
At first, the dynamic material properties were determined with the help of a tensile and a compressive split Hopkinson bar. The small-scale experiments serve to investigate the dynamic material behavior. At the same time, they are the basis for an eventual later numerical analysis of the strengthening layers. A numerical analysis enables the variation of the material parameters.
Lastly, large-scale tests with RC cuboids that were fully supported were performed. A choice of cover and damping layer materials was compared to unstrengthened RC cuboids. The first set of experiments strived to vary the damping layer to find the most suitable one that absorbs the highest amount of incident energy, thus minimizing the damage to the RC cuboid. Afterward, the best damping layer material was combined with different cover layers to figure out the best cover layer option.:Abstract i
Kurzfassung iii
List of Symbols xv
List of Abbreviations xix
1 Objectives, Working Program, and Structure 1
1.1 Motivation 1
1.2 Overall Objectives 1
1.3 Working Program 1
2 State of the Art and Theoretical Background 3
2.1 Impact on Structural Elements 3
2.1.1 Soft and Hard Impact 3
2.1.2 Failure Modes Under Hard Impact Conditions 3
2.1.3 Large-Scale Impact Experiments 4
2.1.4 Impact Protection Layers 4
2.2 Introduction of Impact Protection Principles 4
2.2.1 Impact Protection in Nature 4
2.2.2 Technical Impact Protection Examples 9
2.2.3 Summary of Impact Protection Principles and Usable Materials 14
2.3 Mineral-Bonded Damping Layer Materials 15
2.3.1 Waste Tire Rubber Concrete 15
2.3.2 All-Lightweight Aggregate Concrete 16
2.3.3 Infra-Lightweight Concrete 17
2.4 Mineral-Bonded Cover Layer Materials 18
2.4.1 Strain-Hardening Cementitous Composites 18
2.4.2 Textile Reinforced Concrete 19
2.4.3 Hybrid-Fiber Reinforced Concrete 19
2.5 Bond Between Different Strengthening Layers 20
3 Materials under Investigation 21
3.1 Specimen Preparation 21
3.2 Damping Layer Materials 22
3.2.1 Waste Tire Rubber Concrete (WTRC) 22
3.2.2 All-Lightweight Aggregate Concrete With Liapor Aggregates (ALWAC-L) 23
3.2.3 All-Lightweight Aggregate Concrete With Ulopor Aggregates (ALWAC-U) 23
3.2.4 Porous Lightweight Concrete (PLC) 23
3.2.5 Infra-Lightweight Concrete (ILC) 23
3.2.6 Comparison of the Damping Layer Materials 24
3.3 Cover Layer Materials 27
3.3.1 Pagel TF10 CARBOrefit With Carbon Textile Reinforcement (P-C) 27
3.3.2 Strain-Hardening Limestone Calcined Clay Cement (SHLC3) 27
3.3.3 Comparison of the Cover Layer Materials 28
3.4 Partially Loaded Areas 30
4 Methodology of Split Hopkinson Bar Experiments 35
4.1 Experimental Setup and Methodology 35
4.1.1 Compressive Split Hopkinson Bar 35
4.1.2 Tensile Split Hopkinson Bar 36
4.1.3 Instrumentation 39
4.2 Evaluation Process 39
4.2.1 Impedance 40
4.2.2 Raw Data Analysis, Filtering, and Time-Shifting of Pulses 41
4.2.3 Stresses and Strains 42
4.2.4 Deformations 50
4.2.5 Forces and Impulses 51
4.2.6 Energy Absorption 52
4.2.7 Fracture Energy 53
4.2.8 Averaging of the Results 54
5 Compressive Split Hopkinson Bar Experiments 57
5.1 Failure Modes 57
5.2 Stresses and Strains 58
5.2.1 Dynamic Compressive Strength 58
5.2.2 DIF 59
5.3 Deformations 60
5.4 Forces and Impulses 61
5.4.1 Relative Transmitted Force 61
5.4.2 Impulse Transmission 63
5.4.3 Reduction of the Pulse Inclination 64
5.5 Energy Absorption 64
5.6 Conclusions 66
6 Tensile Split Hopkinson Bar Experiments 69
6.1 Failure Modes 69
6.2 Stresses and Strains 70
6.2.1 Dynamic Tensile Strength 70
6.2.2 DIF 71
6.3 Deformations 72
6.4 Forces and Impulses 73
6.4.1 Relative Transmitted Force 73
6.4.2 Impulse Transmission 74
6.4.3 Reduction of the Pulse Inclination 75
6.5 Energy Absorption 75
6.6 Fracture Energy 77
6.7 Conclusions 78
7 Methodology of Cuboid Experiments 79
7.1 Experimental Program 79
7.1.1 Specimen Dimensions and Experimental Setup 79
7.1.2 Experimental Scheme 81
7.2 Measurements Taken During the Experiments 83
7.2.1 Light Barriers 84
7.2.2 Resistor 84
7.2.3 Strain Gauges 84
7.2.4 Laser Doppler Vibrometer 85
7.2.5 Accelerometers 85
7.2.6 Load Cells 85
7.2.7 High-Speed Cameras and DIC 85
7.3 Measurements Taken Before and After the Experiments 86
7.3.1 Impactor Indentation 86
7.3.2 Burst Mass 86
7.3.3 Ultrasonic Pulse Velocity Measurements 86
7.3.4 Stimulation 87
7.4 Evaluation Process 88
7.4.1 Fracture and Damage Process 88
7.4.2 Impactor Velocity, Deceleration, Force, Stress, and Stress Rate 88
7.4.3 Impactor Indentation, Strain, and Strain Rate 90
7.4.4 Vertical Cuboid Deformation, Velocity, and Acceleration 92
7.4.5 Lateral Cuboid Deformation, Velocity, and Acceleration 93
7.4.6 Relative Cuboid Elongation in X- and Y-Direction 93
7.4.7 Strain Measurements on the Reinforcement Bars 94
7.4.8 Path and Derivative of the Support Forces 95
7.4.9 Burst Mass 96
7.4.10 Ultrasonic Pulse Velocity Measurements 96
7.4.11 Stimulation 97
7.4.12 Impulse and Momentum Conservation 99
7.4.13 Energy Conservation 100
7.4.14 Estimation of the Eigenfrequency of the Cuboids 101
8 Damping Layer Variation in Cuboid Experiments 103
8.1 Fracture and Damage Process 103
8.2 Impactor Velocity, Deceleration, and Force 105
8.3 Impactor Indentation 108
8.4 Vertical Cuboid Deformation, Velocity, and Acceleration 110
8.5 Lateral Cuboid Deformation, Velocity, and Acceleration 113
8.6 Relative Cuboid Elongation in X- and Y-Direction 115
8.7 Path and Derivative of the Support Forces 118
8.8 Ultrasonic Pulse Velocity Measurements 120
8.9 Stimulation With the Impulse Hammer 121
8.10 Stimulation With the Steel Impactor 124
8.11 Overview Over Forces, Stresses, Strains, and Their Rates 128
8.12 Impulse and Momentum Conservation 133
8.13 Energy Conservation 135
8.14 Dimensioning of the Required Damping Layer Thickness Depending on the Loading Velocity 136
8.15 Conclusions 137
9 Cover Layer Variation in Cuboid Experiments 139
9.1 Fracture and Damage Process 139
9.2 Impactor Velocity, Deceleration, and Force 141
9.3 Impactor Indentation 144
9.4 Vertical Cuboid Deformation, Velocity, and Acceleration 145
9.5 Lateral Cuboid Deformation, Velocity, and Acceleration 147
9.6 Relative Cuboid Elongation in X- and Y-Direction 149
9.7 Path and Derivative of the Support Forces 150
9.8 Ultrasonic Pulse Velocity Measurements 152
9.9 Stimulation With the Impulse Hammer 153
9.10 Stimulation With the Steel Impactor 155
9.11 Overview Over Forces, Stresses, Strains, and Their Rates 157
9.12 Impulse and Momentum Conservation 162
9.13 Energy Conservation 163
9.14 Conclusions 164
10 Conclusions of the Cuboid Experiments 167
10.1 Main Findings 167
10.2 Most Relevant Sensor Positions and Measurements 167
10.2.1 Digital Image Correlation (DIC) of the Impactor 167
10.2.2 Lateral Acceleration 167
10.2.3 Digital Image Correlation (DIC) of the RC Cuboid 168
10.2.4 Ultrasonic Pulse Velocity (UPV) Measurements 168
10.2.5 Stimulation With the Impulse Hammer and the Steel Impactor 168
10.3 Suggested Improvements to the Setup 168
10.3.1 High-Speed Cameras (HSC) 168
10.3.2 Acceleration Sensors 169
10.3.3 Support Forces 169
10.3.4 Strain Gauges 169
10.3.5 Temperature Sensors 169
10.4 Comparison of the Material Behavior in Compressive SHB and Cuboid Experiments 169
10.4.1 Scattering of Measured Values 169
10.4.2 Failure Modes 170
10.4.3 Loading and Strain Rates 170
10.4.4 Influences of Inertia 170
10.4.5 Forces and Stresses 171
10.4.6 Energy Absorption 171
11 Summary and Conclusions 173
11.1 Compressive SHB Experiments 173
11.2 Tensile SHB Experiments 173
11.3 Damping Layer Variation in Cuboid Experiments 174
11.4 Cover Layer Variation in Cuboid Experiments 174
11.5 Conclusions 175
12 Outlook 177
12.1 Split Hopkinson Bar Testing 177
12.2 Strengthening Procedure 177
12.3 Large-Scale Impact Testing 177
12.4 Design 178
Bibliography 179
List of Figures 193
List of Tables 199 / Die vorliegende Arbeit beschäftigt sich mit der Verstärkung von Stahlbetonbauteilen gegen Impaktbeanspruchungen. Es wurden mineralisch gebundene Verstärkungsschichten entwickelt, die auf der impaktzugewandten Seite aufgebracht wurden und große Teile der Impaktenergie umwandelten, um somit die darunterliegenden Bauteile zu schützen. Die Verstärkungsschichten sind mehrlagig aufgebaut und die Materialien werden in Deck- und Dämpfungsschichten unterschieden. Dabei sind die Deckschichtmaterialien solche, die eine große Festigkeit und Steifigkeit besitzen. Sie werden direkt durch den Impaktor getroffen und sollen die Impaktlast auf einen größeren Bereich der darunterliegenden Dämpfungsschichten verteilen. Die Dämpfungsschichten sind weniger fest und steif und sollen die Impaktenergie in Reibungs-, Wärme- und innere Energie umwandeln.
Als Dämpfungsschichtmaterialien wurden ein Beton mit Altgummizuschlägen, zwei unterschiedliche Leichtbetone und zwei Infraleichtbetone geprüft. Unter den geprüften Deckschichtmaterialien befanden sich ein Carbonbeton und unterschiedliche Mischungen mit Kurzfaserbetonen, die teilweise auch mit hybriden 3D Bewehrungsstrukturen bewehrt wurden.
Zunächst wurden die Materialen unter dynamischer Druck- und Zugbelastung im Split-Hopkinson-Bar geprüft. Diese kleinteiligen Versuche sollen dem Verständnis des dynamischen Materialverhaltens dienen und bilden gleichzeitig die Grundlage für eine mögliche spätere numerische Analyse der Verstärkungsschichtmaterialien, die gleichzeitig die Variation der Materialeigenschaften von Verstärkungsschichten erlaubt.
Anschließend wurden die unterschiedlichen Dämpfungs- und Deckschichtmaterialien in einem größeren Probenmaßstab untersucht. Die Probekörper, die unverstärkt sowie unterschiedlich verstärkt untersucht wurden, waren vollflächig gelagerte Stahlbetonquader. Zunächst wurde das Dämpfungsschichtmaterial variiert, um die Dämpfungsschicht zu finden, die am meisten Energie umwandeln und somit die Schädigung der Stahlbetonquader am effizientesten reduzieren kann. Diese wurde danach unter unterschiedlichen Deckschichten kombiniert, um das geeignetste Deckschichtmaterial zu ermitteln.:Abstract i
Kurzfassung iii
List of Symbols xv
List of Abbreviations xix
1 Objectives, Working Program, and Structure 1
1.1 Motivation 1
1.2 Overall Objectives 1
1.3 Working Program 1
2 State of the Art and Theoretical Background 3
2.1 Impact on Structural Elements 3
2.1.1 Soft and Hard Impact 3
2.1.2 Failure Modes Under Hard Impact Conditions 3
2.1.3 Large-Scale Impact Experiments 4
2.1.4 Impact Protection Layers 4
2.2 Introduction of Impact Protection Principles 4
2.2.1 Impact Protection in Nature 4
2.2.2 Technical Impact Protection Examples 9
2.2.3 Summary of Impact Protection Principles and Usable Materials 14
2.3 Mineral-Bonded Damping Layer Materials 15
2.3.1 Waste Tire Rubber Concrete 15
2.3.2 All-Lightweight Aggregate Concrete 16
2.3.3 Infra-Lightweight Concrete 17
2.4 Mineral-Bonded Cover Layer Materials 18
2.4.1 Strain-Hardening Cementitous Composites 18
2.4.2 Textile Reinforced Concrete 19
2.4.3 Hybrid-Fiber Reinforced Concrete 19
2.5 Bond Between Different Strengthening Layers 20
3 Materials under Investigation 21
3.1 Specimen Preparation 21
3.2 Damping Layer Materials 22
3.2.1 Waste Tire Rubber Concrete (WTRC) 22
3.2.2 All-Lightweight Aggregate Concrete With Liapor Aggregates (ALWAC-L) 23
3.2.3 All-Lightweight Aggregate Concrete With Ulopor Aggregates (ALWAC-U) 23
3.2.4 Porous Lightweight Concrete (PLC) 23
3.2.5 Infra-Lightweight Concrete (ILC) 23
3.2.6 Comparison of the Damping Layer Materials 24
3.3 Cover Layer Materials 27
3.3.1 Pagel TF10 CARBOrefit With Carbon Textile Reinforcement (P-C) 27
3.3.2 Strain-Hardening Limestone Calcined Clay Cement (SHLC3) 27
3.3.3 Comparison of the Cover Layer Materials 28
3.4 Partially Loaded Areas 30
4 Methodology of Split Hopkinson Bar Experiments 35
4.1 Experimental Setup and Methodology 35
4.1.1 Compressive Split Hopkinson Bar 35
4.1.2 Tensile Split Hopkinson Bar 36
4.1.3 Instrumentation 39
4.2 Evaluation Process 39
4.2.1 Impedance 40
4.2.2 Raw Data Analysis, Filtering, and Time-Shifting of Pulses 41
4.2.3 Stresses and Strains 42
4.2.4 Deformations 50
4.2.5 Forces and Impulses 51
4.2.6 Energy Absorption 52
4.2.7 Fracture Energy 53
4.2.8 Averaging of the Results 54
5 Compressive Split Hopkinson Bar Experiments 57
5.1 Failure Modes 57
5.2 Stresses and Strains 58
5.2.1 Dynamic Compressive Strength 58
5.2.2 DIF 59
5.3 Deformations 60
5.4 Forces and Impulses 61
5.4.1 Relative Transmitted Force 61
5.4.2 Impulse Transmission 63
5.4.3 Reduction of the Pulse Inclination 64
5.5 Energy Absorption 64
5.6 Conclusions 66
6 Tensile Split Hopkinson Bar Experiments 69
6.1 Failure Modes 69
6.2 Stresses and Strains 70
6.2.1 Dynamic Tensile Strength 70
6.2.2 DIF 71
6.3 Deformations 72
6.4 Forces and Impulses 73
6.4.1 Relative Transmitted Force 73
6.4.2 Impulse Transmission 74
6.4.3 Reduction of the Pulse Inclination 75
6.5 Energy Absorption 75
6.6 Fracture Energy 77
6.7 Conclusions 78
7 Methodology of Cuboid Experiments 79
7.1 Experimental Program 79
7.1.1 Specimen Dimensions and Experimental Setup 79
7.1.2 Experimental Scheme 81
7.2 Measurements Taken During the Experiments 83
7.2.1 Light Barriers 84
7.2.2 Resistor 84
7.2.3 Strain Gauges 84
7.2.4 Laser Doppler Vibrometer 85
7.2.5 Accelerometers 85
7.2.6 Load Cells 85
7.2.7 High-Speed Cameras and DIC 85
7.3 Measurements Taken Before and After the Experiments 86
7.3.1 Impactor Indentation 86
7.3.2 Burst Mass 86
7.3.3 Ultrasonic Pulse Velocity Measurements 86
7.3.4 Stimulation 87
7.4 Evaluation Process 88
7.4.1 Fracture and Damage Process 88
7.4.2 Impactor Velocity, Deceleration, Force, Stress, and Stress Rate 88
7.4.3 Impactor Indentation, Strain, and Strain Rate 90
7.4.4 Vertical Cuboid Deformation, Velocity, and Acceleration 92
7.4.5 Lateral Cuboid Deformation, Velocity, and Acceleration 93
7.4.6 Relative Cuboid Elongation in X- and Y-Direction 93
7.4.7 Strain Measurements on the Reinforcement Bars 94
7.4.8 Path and Derivative of the Support Forces 95
7.4.9 Burst Mass 96
7.4.10 Ultrasonic Pulse Velocity Measurements 96
7.4.11 Stimulation 97
7.4.12 Impulse and Momentum Conservation 99
7.4.13 Energy Conservation 100
7.4.14 Estimation of the Eigenfrequency of the Cuboids 101
8 Damping Layer Variation in Cuboid Experiments 103
8.1 Fracture and Damage Process 103
8.2 Impactor Velocity, Deceleration, and Force 105
8.3 Impactor Indentation 108
8.4 Vertical Cuboid Deformation, Velocity, and Acceleration 110
8.5 Lateral Cuboid Deformation, Velocity, and Acceleration 113
8.6 Relative Cuboid Elongation in X- and Y-Direction 115
8.7 Path and Derivative of the Support Forces 118
8.8 Ultrasonic Pulse Velocity Measurements 120
8.9 Stimulation With the Impulse Hammer 121
8.10 Stimulation With the Steel Impactor 124
8.11 Overview Over Forces, Stresses, Strains, and Their Rates 128
8.12 Impulse and Momentum Conservation 133
8.13 Energy Conservation 135
8.14 Dimensioning of the Required Damping Layer Thickness Depending on the Loading Velocity 136
8.15 Conclusions 137
9 Cover Layer Variation in Cuboid Experiments 139
9.1 Fracture and Damage Process 139
9.2 Impactor Velocity, Deceleration, and Force 141
9.3 Impactor Indentation 144
9.4 Vertical Cuboid Deformation, Velocity, and Acceleration 145
9.5 Lateral Cuboid Deformation, Velocity, and Acceleration 147
9.6 Relative Cuboid Elongation in X- and Y-Direction 149
9.7 Path and Derivative of the Support Forces 150
9.8 Ultrasonic Pulse Velocity Measurements 152
9.9 Stimulation With the Impulse Hammer 153
9.10 Stimulation With the Steel Impactor 155
9.11 Overview Over Forces, Stresses, Strains, and Their Rates 157
9.12 Impulse and Momentum Conservation 162
9.13 Energy Conservation 163
9.14 Conclusions 164
10 Conclusions of the Cuboid Experiments 167
10.1 Main Findings 167
10.2 Most Relevant Sensor Positions and Measurements 167
10.2.1 Digital Image Correlation (DIC) of the Impactor 167
10.2.2 Lateral Acceleration 167
10.2.3 Digital Image Correlation (DIC) of the RC Cuboid 168
10.2.4 Ultrasonic Pulse Velocity (UPV) Measurements 168
10.2.5 Stimulation With the Impulse Hammer and the Steel Impactor 168
10.3 Suggested Improvements to the Setup 168
10.3.1 High-Speed Cameras (HSC) 168
10.3.2 Acceleration Sensors 169
10.3.3 Support Forces 169
10.3.4 Strain Gauges 169
10.3.5 Temperature Sensors 169
10.4 Comparison of the Material Behavior in Compressive SHB and Cuboid Experiments 169
10.4.1 Scattering of Measured Values 169
10.4.2 Failure Modes 170
10.4.3 Loading and Strain Rates 170
10.4.4 Influences of Inertia 170
10.4.5 Forces and Stresses 171
10.4.6 Energy Absorption 171
11 Summary and Conclusions 173
11.1 Compressive SHB Experiments 173
11.2 Tensile SHB Experiments 173
11.3 Damping Layer Variation in Cuboid Experiments 174
11.4 Cover Layer Variation in Cuboid Experiments 174
11.5 Conclusions 175
12 Outlook 177
12.1 Split Hopkinson Bar Testing 177
12.2 Strengthening Procedure 177
12.3 Large-Scale Impact Testing 177
12.4 Design 178
Bibliography 179
List of Figures 193
List of Tables 199
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:90362 |
| Date | 13 March 2024 |
| Creators | Leicht, Lena |
| Contributors | Curbach, Manfred, Braml, Thomas, Sovják, Radoslav, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | info:eu-repo/grantAgreement/Deutsche Forschungsgemeinschaft/GRK 2250 - Mineral-bonded composites for enhanced structural impact safety/287321140//A6/II Damping layers as impact strengthening |
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