Pre Tensioning System

Prestressing systems have developed over the years and various companies have patented their products. Detailed information of the systems is given in the product catalogues and brochures published by companies. There are general guidelines of prestressing in Section 12 of IS:1343 - 1980. The information given in this section is introductory in nature, with emphasis on the basic concepts of the systems.

The prestressing systems and devices are described for the two types of prestressing, pre-tensioning and post-tensioning, separately. This section covers pre-tensioning. Section 1.4, “Post-tensioning Systems and Devices”, covers post-tensioning. In pretensioning, the tension is applied to the tendons before casting of the concrete.

The stages of pre-tensioning are described next.
In pre-tensioning system, the high-strength steel tendons are pulled between two end abutments (also called bulkheads) prior to the casting of concrete. The abutments are fixed at the ends of a prestressing bed. Once the concrete attains the desired strength for prestressing, the tendons are cut loose from the abutments.