Reinforced concrete is one of the most widely used composite materials in civil engineering. A composite material is defined as a solid material that results when two or more different materials are combined to form a new material with properties superior to those of the individual components. Component materials are chosen so that the strengths of each are enhanced and the weaknesses of each are avoided. Reinforced concrete is composed of a concrete matrix surrounding strategically placed steel bars. Plain concrete is very strong in compression but weak and brittle in tension, whereas steel is very strong and ductile under tensile loads. In reinforced concrete members, concrete forms the body of the member and provides stiffness and resistance to compression loads. The steel reinforcing bars (rebar) are placed where tensile loads are expected, so that once the concrete cracks, the steel is present to resist the tension.
In most composite members, including reinforced concrete, composite action requires that loads be transferred from one material to another through bond. This interface where bond occurs has the potential to be the weakest part of the member. In uncracked reinforced concrete, the shear forces that are transferred across this interface between the steel and the concrete can be seen as orthogonal compression and tension fields, where the compression fields begin in a band around the lugs and expand outward at approximately 45š angles to form cones of compression, as shown in Figure 1.1. This type of stress field tends to cause three possible types of damage: conical pull-out cracks, radial splitting and crushing around the lugs on the rebar. Each of these types of damage can lead to bond failure and, consequently, failure of the member.
CONTENTS
List of Figures
List of Tables
List of Variables
Chapter 1 - Introduction
1.1 Background
1.2 X-Ray Tomography
1.3 Objectives and Scope of Research
1.4 Overview of Report
Chapter 2 - Previous Work
2.1 Introduction
- 2.1.1 Tepfers
2.1.2 Eligehausen, et. al.
2.1.3 Malvar
2.1.4 Previous Works Conclusions
Chapter 3 - Test Matrix
3.1 Specimens
- 3.1.1 Pull-Out Specimens
3.1.2 Uniform Tension Specimens
3.1.3 Parameters That Determine Bond Specimen Response
3.1.4 Test Matrix
Chapter 4 - Material Test Results
4.1 Introduction
4.2 Compressive Strength
4.3 Tensile Strength
- 4.3.1 Split-Cylinder Tension Test
4.3.2 Modulus of Rupture Test
4.4 Elastic Modulus
4.5 Tape Strength
4.6 Wire Strength
4.7 Fracture Energy
- 4.7.1 Introduction
4.7.2 Specimens
4.7.3 Counter-Weight System
4.7.4 Construction
4.7.5 Test Set-Up
4.7.6 Instrumentation
4.7.7 Test Procedure
4.7.8 Results
4.7.9 Analysis and Discussion of Results
4.7.10 Evaluation of Test Procedures
Chapter 5 - Tests on Embedded Bars
5.1 Test Set-Up
- 5.1.1 Pull-Out Test Set-Up
5.1.2 Uniform Tension Test Set-Up
5.2 Test Procedure
5.2.1 Pull-Out Test Procedure
5.2.2 Uniform Tension
5.3 Bond Test Results
- 5.3.1 Measured Data
5.3.2 Observations
5.3.3 Errors and Complications
Chapter 6 - Analysis of Embedded Bar Test Results
6.1 Correction of Measured Data
6.2 Comparison with Eligehausen’s Analytical Bond Model
6.3 Comparison with ACI models
6.4 Thick Walled Cylinder Model
- 6.4.1 Pre-Cracking Stress State.
6.4.2 Effective Lug Angle at Peak Load
Chapter 7 - Conclusion
7.1 Summary
7.2 Conclusions
7.3 Recommendations
- 7.3.1 Impact on Current Practice
7.3.2 Further Research
Bibliography
Appendix A - Load-Displacement Curves
Appendix B – Uniform Tension Specimen Photographs
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An Experimental Investigation of Bond in Reinforced Concrete
