What is post-tensioning in bridge?
The function of post-tensioning is to place the concrete structure under compression in those regions where load causes tensile stress. Post-tensioning applies a compressive stress on the material, which offsets the tensile stress the concrete might face under loading.
Why is prestressed concrete used in bridges?
A properly engineered prestressed-concrete beam can span longer distances than a reinforced-concrete beam and it is thinner, lighter in weight, and uses less concrete without cracking or breaking.
What is post stress concrete?
Post-tensioned concrete is a type of prestressed concrete where the concrete is strengthened via an arrangement of reinforcement held in tension. Steel cables, called post-tensioning tendons, are placed in plastic sleeves and positioned inside the concrete formwork before the concrete is poured.
How do you prestress concrete?
In pretensioning, the steel is stretched before the concrete is placed. High-strength steel tendons are placed between two abutments and stretched to 70 to 80 percent of their ultimate strength. Concrete is poured into molds around the tendons and allowed to cure.
Is code for post stressing?
3 TERMINOLOGY For the purpose of this standard, the definitions given in IS 4845, IS 6461 (Parts 1 to 12) and the following shall apply. 3.1 Anchorage Device — In post-tensioning, the hardware used for transferring the post-tensioning force from the tendon to the concrete in anchorage zone.
How is concrete post tensioned?
Post tensioning is a technique for reinforcing concrete. Afterwards, once the concrete has gained strength but before the service loads are applied, the cables are pulled tight, or tensioned, and anchored against the outer edges of the concrete. Post-tensioning is a form of prestressing.
Why Post Tensioning is done?
Designers use post-tensioning as a way to reinforce concrete by prestressing it. In prestressed members, compressive stresses are introduced into the concrete to reduce tensile stresses resulting from applied loads including the self weight of the member (dead load).
How does post stressed concrete work?
In prestressed members, compressive stresses are introduced into the concrete to reduce tensile stresses resulting from applied loads including the self weight of the member (dead load). Prestressing steel, such as strands, bars or wires, is used to impart compressive stresses to the concrete.
How will you know if you need to use pre stressed concrete or not?
Generally, prestressed concrete is not necessary for columns and walls, however, it can be used economically for tall columns and high retaining walls with high bending stresses. As a general rule, traditional reinforced concrete is the most economic method for a span of up to 6 m.
What are the ingredients of pre stressed concrete?
Prestressed concrete is a highly versatile construction material as a result of it being an almost ideal combination of its two main constituents: high-strength steel, pre-stretched to allow its full strength to be easily realised; and modern concrete, pre-compressed to minimise cracking under tensile forces.