Bonded VS. Unbonded Post Tensioned Systems

[Yousef ZAA]

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!

 

[rapt]

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.

 

[Yousef ZAA]

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

 

[rapt]

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.

 

[KootK]

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.

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.