What are tendons in prestressing?
Prestressing tendons (generally of high tensile steel cables or rods) are used to provide a clamping load, which produces a compressive stress to offset the tensile stress that the concrete compression member would otherwise experience due to a bending load.
What are the properties of prestressed concrete?
Properties of various materials used in prestressed concrete must suit the requirements which are connected with the performance of prestressed concrete….The basic requirements of prestressed concrete are:
- High Strength Capacity.
- Low Shrinkage.
- Low Creep.
- High Durability.
What is the tensile strength of prestressing tendon?
Current code provisions are based on years of ex- perimental research and are used with the tradition- al 270 ksi (1860 MPa) prestressing strand. Recent developments have resulted in a higher- strength strand with an ultimate tensile strength of 300 ksi (2070 MPa).
How are prestress losses calculated?
The prestress loss due to elastic shortening in pretensioned members is taken as the concrete stress at the centroid of the prestressing steel at transfer, f cgp, multiplied by the ratio of the modulus of elasticities of the prestressing steel and the concrete at transfer.
Whats is a tendon?
A tendon is a fibrous connective tissue that attaches muscle to bone. Tendons may also attach muscles to structures such as the eyeball. A tendon serves to move the bone or structure.
What is Strand and tendon?
Strand is a flexible structure made of previously cleaned cold drawn wires of the same quality as those now used as prestressing tendons, so that the working stress used for strand is the same proportion of the maximum strength as that now used for small diameter wires.
What is the difference between RCC and prestressed concrete?
Prestressed concrete sections are thinner and lighter than RCC sections, since high strength concrete and steel are used prestressed concrete. In prestressed concrete, whole concrete area is effective in resisting loads, unlike RCC where concrete below the neutral axis is neglected.
What are the types of prestressed concrete?
According to the construction method, there are two kinds of prestressed concrete:
- Pre-tensioned concrete.
- Bonded Post-tensioned concrete.
- Unbonded Post-tensioned concrete.
Which of the following is the type of prestressing tendon used in pre tensioning system?
Explanation: The strand tendons are used in both pre tensioning and post tensioning, they are made by winding seven cold drawn wires together on a stranding machine, the addition of strands in subsequent layers of wire forms strands of 19 or 37 wires, large post tensioning applications can cope with stressing …
What is the diameter of tendon used in prestressed concrete?
Tendons are high strength tensile wires available in various diameter from 1.5mm to 8mm.
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 .
What is prestress loss?
Prestressing is the process of introducing compressive stress to the concrete to counteract the tensile stresses resulting from an applied load. The gradual reduction of this introduced compressive stress in a prestressed member due to various reasons is called losses of prestress.