Determination of Pull Out Capacity of Steel Bar in Concrete
CHAPTER 1
INTRODUCTION
1.1 Introduction of Research
Steel-reinforced concrete is a widely used structural material. The effectiveness of the steel reinforcement depends on the bond between the steel reinforcing bar and the concrete. Reinforced concrete is a composite material in which concrete 's relatively low tensile strength and ductility are counteracted by the inclusion of reinforcement having higher tensile strength and ductility. The reinforcement is usually, though not necessarily, steel reinforcing bars and is usually embedded passively in the concrete before it sets. Reinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and structural failure.
For concrete is a mixture of coarse (stone or brick chips) and fine (generally sand or crushed stone) aggregates with a binder material like usually Portland cement. When mixed with a small amount of water, the cement hydrates to form microscopic opaque crystal lattices encapsulating and locking the aggregate into a rigid structure. Typical concrete mixes have high resistance to compressive stresses about 28 MPa. However, any appreciable tension (due to bending) will break the microscopic rigid lattice, resulting in cracking and separation of the concrete. For this reason, typical non-reinforced concrete must be well supported to prevent the development of tension.
The utility of reinforced concrete as a structural material is derived from the combination of concrete that is strong and relatively durable in compression with reinforcing steel that is strong and ductile in tension. Maintaining composite action requires transfer of load between the concrete and steel.
This load transfer is referred to as bond and is idealized as a continuous stress field that develops in the vicinity of the steel-concrete interface. For reinforced concrete structures subjected to moderate loading, the bond stress capacity of
INTRODUCTION
1.1 Introduction of Research
Steel-reinforced concrete is a widely used structural material. The effectiveness of the steel reinforcement depends on the bond between the steel reinforcing bar and the concrete. Reinforced concrete is a composite material in which concrete 's relatively low tensile strength and ductility are counteracted by the inclusion of reinforcement having higher tensile strength and ductility. The reinforcement is usually, though not necessarily, steel reinforcing bars and is usually embedded passively in the concrete before it sets. Reinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and structural failure.
For concrete is a mixture of coarse (stone or brick chips) and fine (generally sand or crushed stone) aggregates with a binder material like usually Portland cement. When mixed with a small amount of water, the cement hydrates to form microscopic opaque crystal lattices encapsulating and locking the aggregate into a rigid structure. Typical concrete mixes have high resistance to compressive stresses about 28 MPa. However, any appreciable tension (due to bending) will break the microscopic rigid lattice, resulting in cracking and separation of the concrete. For this reason, typical non-reinforced concrete must be well supported to prevent the development of tension.
The utility of reinforced concrete as a structural material is derived from the combination of concrete that is strong and relatively durable in compression with reinforcing steel that is strong and ductile in tension. Maintaining composite action requires transfer of load between the concrete and steel.
This load transfer is referred to as bond and is idealized as a continuous stress field that develops in the vicinity of the steel-concrete interface. For reinforced concrete structures subjected to moderate loading, the bond stress capacity of