Pre-tensioning and Post-tensioning both methods are used under the pre-stressing process which has few edges over the orthodox non-stressed structures like greater span to depth ratio, higher moment, and shear capacity. These methods are generally adopted in the making of PSC girders, sleepers, etc.
pre-tensioning
1- In this method, the concrete is prestressed with tendons before it is placed in position.
2- This method is developed due to bonding between the concrete and steel tendons.
3- Pre tensioning is preferred when the structural element is small and easy to transport.
4- In this method, similar prestressed members are prepared.
5- Pre-tensioning members are produced in mold.
post-tensioning
1- In this method prestressing is done after the concrete attains its strength
2- This method is developed due to bearing
3- Post-tensioning is preferred when the structural element is heavy
4- In this method products are changed according to the structure.
5- Cables are used in place of wires and jacks are used for stretching.
For more information watch this video
