What is an unbonded tendon?
Unbonded tendons comprise individual strands coated in an anti-corrosion grease or wax, and fitted with a durable plastic-based full-length sleeve or sheath. The sleeving is required to be undamaged over the tendon length, and it must extend fully into the anchorage fittings at each end of the tendon.
What is the difference between bonded and unbonded tendon?
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].
What is unbonded post tensioning?
It is achieved by casting concrete into pre-assembled forms in combination with rebar and steel cable (strand) reinforcement. These cables are tensioned (stretched) to approximately three-quarters of their ultimate strength. Once the concrete cures to its required strength, the tensioning is released.
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.
Are unbonded tendons used for rehabilitation?
Although the use of unbonded tendons as the major prestressing technique in design and rehabilitation has been favored for reasons of ease of construction, cost-effectiveness, and maintenance, the overall structural behavior of prestressed with externally unbonded tendon under flexural loading is yet to be well …
What are bonded and unbonded prestressed concrete member?
Bonded post tension : if concreting is done over the tendons directly, then a bond forms between concrete and tendons. Unbounded post tension: when concreting is done using ducts for the tendons, then tendons doesn’t comes in contact with concrete, and hence no bonds formed.
Why is unbonded tendon coated with grease?
The grease allows the strand to move inside the plastic sheath, provides corrosion protection to the strand and reduces the amount of friction between the strand and the plastic sheath during post-tensioning.
What is Strand and tendon?
Strandnoun. Each of the strings which, twisted together, make up a yarn, rope or cord. Tendonnoun. (anatomy) A tough band of inelastic fibrous tissue that connects a muscle with its bony attachment.
What is difference between tendon and strand?
is that tendon is (anatomy) a tough band of inelastic fibrous tissue that connects a muscle with its bony attachment while strand is the shore or beach of the sea or ocean; shore; beach or strand can be each of the strings which, twisted together, make up a yarn, rope or cord.
What are the three major types of reinforcement used in prestressing?
Three major types of reinforcement used in prestressing
- (i) Spalling reinforcement. Spalling stresses are established behind the loaded area of anchor blocks and this causes breaking away of surface concrete.
- (ii) Equilibrium reinforcement.
- (iii) Bursting Reinforcement.