What are the systems of prestressing?
There are two main systems of pre-stressing : the pre-tensioning system in which the wire, bar or cable is tensioned before the concrete is cast, and the post-tensioning system in which the tensioning is carried out after the concrete has attained considerable strength.
What is prestressing and how it works?
Prestressing is the introduction of a compressive force to the concrete to counteract the stresses that will result from an applied load. There are two methods of introducing prestressing to a concrete, namely pre tensioning and post tensioning. Pre tensioning happens before the casting of the concrete.
What are the two methods used for prestressing?
Internal prestressing can be done by two methods: Pre-tensioning. Post-tensioning.
Which is one of the system used for prestressing?
3. Which is one of the systems used for pretensioning? Explanation: Hoyer’s long line method is the system used in pretensioning and the other systems like Freyssinet, Gifford-Udall, and Magnel-Balton are post tensioning systems and large numbers of beams are produced in an individual alignment.
What is Lee McCall system?
Lee-McCall system: This method is used to prestress steel bars. The diameter of the bar is between 12 and 28 mm. Bars provided with threads at the ends are inserted in the performed ducts.
What is end anchorage of prestressing system?
Dead end anchorages are used at non stressing end of a tendon. They are used where the end of a prestressing cable is buried in concrete or is inaccessible during the stressing operation of the tendon.
What is bonded and unbonded tendons?
Bonded tendons (Figure 1) are seven-wires strands inserted inside a plastic or steel duct, and after stressing the strands, grout is injected to fill the duct. Unbonded tendons (Figure 1) are made up of greased seven-wires strands covered with plastic sheathing [2].
Why do we do prestressing?
Prestressing can reduce the volume of concrete required in construction, lowering the use and transportation of materials, as well as boosting durability and service life. Concrete is intrinsically resistant to compressive stresses, but its resistance to tension is much lower.
Which of the following are the systems of post-tensioning?
Explanation: The Freyssinet anchorage system is widely used in Europe and India consists of a cylinder with a conical interior through which the high tensile wires pass and against the walls of which the wires are wedged by a conical plug lined longitudinally with grooves to house the wires.
What is anchorage system?
Anchorage as the name signifies is a component of post tensioning system which is used to anchor the tendons into the concrete while terminating or joining two tendons. Main function of anchorage is to transfer the stressing force to the concrete once the stressing process is completed.
What is Gifford Udall system?
Gifford Udall System This system originated in Great Britain, is widely used in India. This is a single wire system. Each wire is stressed independently using a double acting jack. Any number of wires can be grouped together to form a cable in this system. There are two types of anchorage device in this system.
What is a prestressing system?
Therefore, the prestressing systems should comprise essentially a method of stretching the steel and a method of anchoring it to the concrete. Different systems are adopted for pre-tensioning and post tensioning.
What is prestressing method of reinforcement?
Other Methods of Prestressing in this method, reinforcing bars is coated with thermoplastic material such as sulphur or low melting alloy and buried in the concrete. After the concrete is set, electric current of low voltage but high amperage is passed through the bar.
What is the purpose of prestressed concrete?
Prestressing is therefore a technique which consists in inducing favorable internal forces. These are designed to reduce the weakness of concrete in tension. The design of reinforced concrete prestressed elements often includes the use of passive steel bars in parallel to the prestressed steel.
What are the different types of prestressing systems and anchorages?
Types of Prestressing Systems and Anchorages in Prestressed Concrete. 1 1. Freyssinet System. Freyssinet system was introduced by the French Engineer Freyssinet and it was the first method to be introduced. High strength 2 2. Magnel Blaton system. 3 3. Gifford Udall System. 4 4. Lee McCall System. 5 5. Other Methods of Prestressing.