Prestressed Concrete
The prestressed concrete short name is a PSC. In the case of ordinary reinforcement concrete which consists of concrete and mild steel, compressive stresses are borne by concrete while tensile stresses are borne by steel. The concrete surrounding steel reinforcement does not take tension as concrete is weak in tension. Thus only that portion of concrete, which lies above the neutral axis is considered to be useful in resisting compressive stress. This results in heavy section.Pre Stressed concrete is basically cocnrete in which internal stresses or a suitable magnitude and distribution are introduced so that the pre-compressive stress in concrete will balance the tensile stress produced in concrete due to external loads. Due to this, the whole of the concrete can participate in resisting the external forces. In reinforced cocnrete members, the prestress is commonly introduced by tensioning the steel reinforcement.
Table of contents
- what is prestressed concrete
- Prestressed material
- Uses Of Prestressed Concrete
- Properties Of prestressed concrete
- Advantages of Prestressed concrete
Pre Stressed Material
- High tensile steel
- High strength cocnrete
Concrete used in PSC of good quality and of high strength. A well compacted dense concrete has a less elastic strain and has less shrinkage plastic flow thus reducing the loss of prestressing considerably. Prestressed concrete may be classified into a number of ways, depending upon the method of applying prestressing and purpose of Structure.
- External or internal prestressing system
- Linear or Circular prestressing
- Pre Tensioning and Post Tensioning system
- Full prestressing and partial prest
External or internal prestressing System
External Prestressing is achieved by external reactions introduced through different support conditions.Linear or Circular Prestressing
Linear prestressing is applied in straight members such as beams, slabs, piles etc. Circular prestressing is applied to a circular structure such as tanks, pipes, silos etc. Where prestressing tensions are wound around the circumference.Pre tensioning and Post Tensioning System
In the pretensioning system, the tensions are pre-stressed before the concrete is placed. In post-tensioning system, the member is concreted and a duct is formed in member either with a tube or with a metal sheet. When the concrete is sufficiently hard, the tendons are tensioned and anchored at the concrete member of its ends.
Full Prestressing or Partial prestressing
IF there are no tensile stresses in concrete under working load, concrete is said to be prestressed. If some tensile stresses are produced in cocnrete under working load conditions. it is said to be partially prestressed.Uses Of Prestressed Concrete
- Long span bridges
- High buildings
- Hollow slabs
- simple span box girders
- cable bridges
- Flat slab floor
Properties Of prestressed concrete
- It has lighter members who give saving in the materials.
- These members are economical than R.C.C. Members.
- It possesses improved resistance to shearing forces.
- The Prestressed Cocnrete members are stiffer than R.C.C. members.
Advantages of Prestressed concrete
- Precast prestressed concrete is used in the construction of dynamically loaded structures such as railway bridges and machine foundation and in the construction of long span floors and roofs.
- Prestressed concrete members have more resistance to shear forces.
- Prestressed cocnrete offer great technical advantages in comparison with other forms of construction. Fully pre-stressed members which are free from tensile stresses under working loads are having more efficiency when compared with RCC and other composite materials.