What Reinforcements are used in the Process of Prestressing?
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Following are the three major types of reinforcement used for prestressing work:
The reinforcement used in process of prestressing are as follows :-
(i) Spalling reinforcement :-
Spalling stresses are established behind the loaded area of anchor blocks and this causes breaking away of surface concrete. These stresses are induced by strain incompatibility with Poisson’s effects or by the shape of stress trajectories.
(ii) Equilibrium reinforcement :-
Equilibrium reinforcement is required where there are several anchorages in which prestressing loads are applied sequentially.
(iii) Bursting Reinforcement :-
Tensile stresses are induced during prestressing operation and the maximum bursting stress occurs where the stress trajectories are concave towards the line of action of the load. Reinforcement is needed to resist these lateral tensile forces.
Reinforcements used in the process of prestressing:
Especially in case of prestressing, we are using strands of Steel and it’s called tendons.
Tendons are made of high strength Steel.
Three major types of reinforcements which are used in Prestressing:
Combination of reducing the structural thickness reduced conventional reinforcements quantities and fast construction often results in un prestressed structure.
The type of steel used in prestressing may be:
The following properties of the steel are appreciated:
Note that the permissible stress in prestressing steel is not more than 80% of yeild strength.
Permissible stress = 0.8fy
This fy is found just like any HYSD bar by considering the 0.2% proof stress.
In prestressing, we use strands of steel usually called as tendons. They are made of high strength steel. However, there are other terms in pre stressing based on the size of the tendon. The following are the terms in an increasing order of size.
There are three different types of reinforcement are used in prestressing are:
1. Equilibrium reinforcement – when the prestressing load is applying on some Anchorage, then that type reinforcement are used.
2. Spalling reinforcement – when the spalling stress is induced behind the loaded area of anchorage block, then we can use spalling reinforcement.
3. Bursting reinforcement – maximum bursting stress is induced when tensile stress is developing during prestressing then the bursting reinforcement is used.
High tensile steel is used for prestressed concrete.
According to strength, can be classified as 1470MPa, 1570MPa, 1670MPa, 1770MPa and 1860MPa.
According to diameters
4mm, 4.8mm, 5.0mm, 5.1mm, 6.0mm, 6.35mm, 7.0mm, 7.8mm. etc
Basically that wire called tendon