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Bonded VS. Unbonded Post Tensioned Systems

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Bonded VS. Unbonded Post Tensioned Systems

Bonded VS. Unbonded Post Tensioned Systems

Yousef ZAA

(Structural)

(OP)

3 Dec 18 14:08

I know there is no direct answer for this question but from your experience which is better Unbonded or Bonded post tensioned systems
I'm a little bit biased for unbonded because of its post flexural capacity that makes the system endure 2 or 3 times factored load before failure, but i was told that bonded is better for serviceability and crack control. I need some opinions and again i know there is no direct answer!

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RE: Bonded VS. Unbonded Post Tensioned Systems

rapt

(Structural)

3 Dec 18 22:10

Yousef AA

There is also the possibility that the unbonded tendons endure 0 times factored load before failure if the strands slip in the anchorages which rely on a friction grip on the strand.

RE: Bonded VS. Unbonded Post Tensioned Systems

Yousef ZAA

(Structural)

(OP)

4 Dec 18 07:30

Rapt, thank you. Are saying that bonded systems have a better strand's friction grip?

RE: Bonded VS. Unbonded Post Tensioned Systems

rapt

(Structural)

4 Dec 18 21:29

No,
I am saying that bonded tendons do not rely on the friction grip long term after the grout has reached strength. You could cut the anchorages off and would only lose some development in the next 1-2m of the tendon. If you do it with an unbonded tendon, you have no tendon.

RE: Bonded VS. Unbonded Post Tensioned Systems

KootK

(Structural)

16 Dec 18 23:00

Quote (OP)

I know there is no direct answer for this question but from your experience which is better Unbonded or Bonded post tensioned systems

1) Bonded systems are better with respect to all performance metrics in my opinion, including crack control. The only advantage of un-bonded PT that I can think of is that it's considered to be more economical on some markets.

Quote (OP)

I'm a little bit biased for unbonded because of its post flexural capacity that makes the system endure 2 or 3 times factored load before failure

2) Bonded systems are actually better in this respect as well, in part for the reason that rapt mentioned. Even in markets where unbonded PT floors are used, it's quite common for engineers to use bonded systems for transfer girders etc in order to improve the reliability of such critical members.

1) Bonded systems are better with respect to all performance metrics in my opinion, including crack control. The only advantage of un-bonded PT that I can think of is that it's considered to be more economical on some markets.2) Bonded systems are actually better in this respect as well, in part for the reason that rapt mentioned. Even in markets where unbonded PT floors are used, it's quite common for engineers to use bonded systems for transfer girders etc in order to improve the reliability of such critical members.

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News

The unbonded steel strand is coated with a layer of grease and a plastic sheath on the steel strand (which can be called bare wire). In engineering construction, because of the grease and sheath on the surface of the unbonded steel strands in the concrete, the steel strands are isolated from the concrete, can be loosened freely, and remain unbonded with the concrete, so it is called unbonded steel. stranded wire.

There are also galvanized unbonded steel strands used for reinforcement projects, that is, galvanized steel strands are coated with grease and plastic sheaths to double guarantee the anti-corrosion effect.

Bonded steel strands do not have this layer of protection.

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