What are the types of devices used for post tensioning?
The essential devices in any Post-tensioning systems are normally as follows:
- Casting bed.
- Anchoring devices.
- Couplers (optional)
- Grouting equipment (optional)
What happens when you hit a post tension cable?
Hazards of Post-Tensioned Slabs: Once the concrete is poured and sets, the cables are tensioned. Once tensioned, the cables cannot be de-tensioned. The hazard exists when workers cut into the slab and rupture the tensioned cable. People have been dismembered and killed when cables are cut and burst out of the concrete.
What kind of steel are post tension cables made of?
PC Strand is a 7-wire cable made from high carbon steel. It is used in both pre-stressed and post-tensioned concrete construction applications. PC strand is often used in stadium construction.
Which is better post tension or rebar?
Post-tensioning, which is a form of prestressing, has several advantages over standard reinforcing steel (rebars): It reduces or eliminates shrinkage cracking-therefore no joints, or fewer joints, are needed. Cracks that do form are held tightly together. It allows slabs and other structural members to be thinner.
How deep are post tension cables?
Post-Tensioning Construction Basics For residential construction, tendons at 48 inches on center are common. Commercial foundations will have much more steel. Tendons can be easily routed around obstructions. A residential post-tensioned concrete slab will typically be 8 inches thick and use 3000 psi concrete.
What is Lee-McCall system?
Lee-Mccall system This is a system in which high tensile alloy steel bars are used as the prestressing tendons. These bars are provided in 22 mm, 25 mm, 28 mm and 30 mm diameter and in lengths up to 20 meters. The anchoring of the bars is done by screwing special threaded nuts.
What is meant by end Anchorage?
A mechanical device used to transmit prestressing force to the reinforced concrete in a posttensioned member.
How far apart are post tension cables?
Post Tension Cables & Rebar The cables (steel bands wrapped together) are set up within the concrete in a grid pattern (usually about 48 inches apart) and are called tendons when they are covered by a plastic outer shell and held by an anchorage.