Explain freyssinet system of prestressing with respect to process and application with sketches.

Explain freyssinet system of prestressing with respect to process and application with sketches.
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1 Answer

Answer :

Process: -

1. The freyssinet system was the first to be introduced among the post – tensioned system high tensile steel wires 5mm to 8mm diameter about 12 in number are arranged to form a group into a cable with spiral spring inside.

2. The spiral spring provides the means for a proper clearance between the wires and thus provides a channel which can be cement grouted.

3. It further assists to transfer the reaction to concrete. The whole thing is enclosed in a thin metal steel.

4. The anchorage consisst of a cylinder of ordinary good quality concrete and is provided with corrugation on the outside.

5. It has a center conical hole and is provided with heavy hoop reinforcement.

6. These cylinders are kept in the proper position and the central conical plugs are pushed into the conical holes after cable are tightened.

7. The central hole passing axially through the plug permits cement grout to be injected through it.

8. In this way the space between the wires will be filled with the grout.

This provides additional restraint against the slipping of the tendons.

Application

1. Bridge decks and piers

2. Nuclear containment vessels

3. Liquefied natural gas (LNG) storage tank

4. Off share platforms.

5. Wind turbine towers etc.

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