Why are post tension tendons draped?
One interesting difference is that the tendons will often be “draped” so that they are low at the midpoint of a beam and high at the supports—this places the steel at the point of highest tension where it can keep the concrete held together tightly.
What is bonded and unbonded tendons?
Light and flexible, unbonded monostrand can be easily and rapidly installed – providing an economical solution. Bonded post-tensioning systems are com- prised of tendons from one to multiple strands (multi- strand) or bars. For bonded systems, the prestressing steel is encased in a corru- gated metal or plastic duct.
What is bonded post-tensioning?
Bonded post-tensioned concrete is the descriptive term for a method of applying compression after pouring concrete and during the curing process (in situ). The concrete is cast around a plastic, steel or aluminium curved duct, to follow the area where otherwise tension would occur in the concrete element.
What is grouting in post-tensioning system?
The grouting of the ducts surrounding post-tensioning tendons provides the necessary mechanical connection to transfer the stresses between the tendons and the concrete and also protects the tendons from corrosion.
How far apart are post tension cables?
about 2 to 4 feet
These circles are usually about 2 to 4 feet apart. They indicate the end of the post tension cables. Sometimes these circles are not visible because of landscaping or because the patching of the cone-shaped voids blends in.
What is the difference between bonded and unbonded post tensioning system?
Unbonded Post-Tensioning typically consists of single (mono) strands or threaded bars that remain unbonded to the surrounding concrete giving them the freedom to move locally relative to the structural member. Bonded Post-Tensioning comprises tendons from one to multiple strands (multistrand) or bars.
Why Post Tensioning is done?
Designers use post-tensioning as a way to reinforce concrete by prestressing it. In prestressed members, compressive stresses are introduced into the concrete to reduce tensile stresses resulting from applied loads including the self weight of the member (dead load).
What are the methods of post tensioning?
Some of the popular methods of post-tensioning in prestressed concrete are:
- Freyssinet system.
- Magnel system.
- Leonhardt system.
- Lee-McCall system.
- Gifford-Udall system.
