From many years people has been using ordinary reinforced concrete for various works . So far this reinforced concrete is serving us well. As you may already know that reinforced concrete(RCC) is made of concrete and reinforcing steel. The concrete is very good in compression like Hulk but when tension comes it becomes feeble like Bruce Banner. So we are providing reinforcing steel in concrete. These reinforcement helps to take tensile stresses which develop in the concrete same way as Black Widow helps Bruce. But there is a little catch. This reinforced concrete has its own limitations. These addition of reinforcement wont help much when span or size of the member increases up to such level that it would become uneconomical.
So around 140 years ago P. H. Jackson of San Francisco applied patent in which prestress was introduced by tensioning the reinforcing rods in pavement construction and idea of Prestressed concrete took its first breath.
Pre-stressing is basically a process in which initial internal stresses are introduced in member by means of external loads. This internal stresses are compressive in nature which would help the member to resist flexure tensile stress such that there is no tensile stress in member or its values remain within required tensile stress limits. These internal stresses are applied in such a manner that stress resulting from superimposed load is counterbalanced to desire level. Now as we can adjust tensile stress in member, size of the member required would be less which would leads to economy.
