This section covers the following topics
• Introduction
• Stages of Post-tensioning
• Advantages of Post-tensioning
• Disadvantages of Post-tensioning
• Devices
• Manufacturing of a Post-tensioned Bridge Girder
1.4.1 Introduction
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 post-tensioning.
Section 1.3, “Pre-tensioning Systems and Devices”, covers pre-tensioning. In posttensioning,
the tension is applied to the tendons after hardening of the concrete. The
stages of post-tensioning are described next.
1.4.2 Stages of Post-tensioning
In post-tensioning systems, the ducts for the tendons (or strands) are placed along with
the reinforcement before the casting of concrete. The tendons are placed in the ducts
after the casting of concrete. The duct prevents contact between concrete and the
tendons during the tensioning operation.
Unlike pre-tensioning, the tendons are pulled with the reaction acting against the
hardened concrete.