Discuss about the post-tensioning systems

In most of post-tensioning systems, when the cable is tensioned and the jack is released to transfer prestress to concrete, the friction wedges, employed to grip the wires, slip a small distance before the wires can be firmly held between the wedges. The magnitude of slip depends upon the type of wedge and the stress in the wires. This loss of prestress occurs only in post-tensioned members as no anchorages are used in pre-tensioned members.