Due to the inherent characteristics of the production process and materials used in prestressed concrete, the stress in the prestressing tendons continuously reduces throughout the entire process—from tensioning and anchoring to the installation and service of the member. This reduction in stress value is referred to as the prestress loss.

Causes of Loss

The primary causes include:

1. Prestress loss due to deformation of the anchorage and retraction of the tendon.
2. Prestress loss due to friction between the prestressing tendon and the wall of the duct.
3. Prestress loss due to the temperature difference between the prestressing tendon and the stressing equipment during the heat curing of concrete.
4. Prestress loss due to relaxation of the tendon.
5. Prestress loss due to shrinkage and creep of the concrete.
6. Prestress loss in circular members (e.g., tanks, ducts) reinforced with spiral prestressing tendons, caused by the local compression of the concrete.