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Prescriptively Attach Metal Ceiling Framing to a Concrete Slab

jar546

jar546

CBO
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How do you prescriptively attach metal ceiling framing or even false soffit to a concrete slab, whether post-tension or not? Is there a way to approve the addition of metal ceiling framing to a concrete slab in a high-rise building?
 
Not that I am aware of. Is there a way to do it without an engineer, maybe.

Depending on your state's licensing laws, an architect may be able to spec out the framing and specify a listed anchor for the attachment. Not prescriptive, but not fully engineered either.
 
jar546 said:
How do you prescriptively attach metal ceiling framing or even false soffit to a concrete slab, whether post-tension or not? Is there a way to approve the addition of metal ceiling framing to a concrete slab in a high-rise building?
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"Prescriptively" means using information that's printed ("prescribed") in the building code. I am not aware of anything in the IBC, the IEBC, or the IRC that prescribes how to attach steel furring to a concrete slab.
 
How is the location of the tendons identified in a ceiling? I'll probably never need to know but I would really like to know.

Here is an example of when they didn't know there was a post-tensioned slab. It was an expensive mistake. There was more than what is shown.

46847161995_8e81eeaff6_b.jpg

47711105382_e3935c1998_b.jpg
 
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jar546 said:
Yep, we had two tendons snapped last year due to contractors not following the renovation plans.
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That's terrifying.

I'm an architect as well as a BO. When I was in architecture school, we went to a building overlooking the construction of a new parking garage so we could watch the post-tensioning procedure. While we were watching, one of the clamps failed and the tendon (which was at just about full tension) released catastrophically. It launched a huge chunk of concrete across the width of the entire garage, where the chunk landed on the car of a salesman who was just leaving the site. He was killed instantly.

You just DON'T take chances with post-tensioned structures.
 
Yankee Chronicler said:
That's terrifying.

I'm an architect as well as a BO. When I was in architecture school, we went to a building overlooking the construction of a new parking garage so we could watch the post-tensioning procedure. While we were watching, one of the clamps failed and the tendon (which was at just about full tension) released catastrophically. It launched a huge chunk of concrete across the width of the entire garage, where the chunk landed on the car of a salesman who was just leaving the site. He was killed instantly.

You just DON'T take chances with post-tensioned structures.
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One of the contractors that was in the office today just told me about a high-rise building he was working in, another contractor hit one of the worst possible tendons and the damage was just over $3M because it involved several floors.
 
Has there been research as to how long the cables retain tension?


jar546 said:
it involved several floors.
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I'm curious about how a tendon could affect several floors. Did it happen repeatedly? $3M could be an exaggeration... I mean think about it ...$3M
 
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ICE said:
Has there been research as to how long the cables retain tension?



I'm curious about how a tendon could affect several floors. Did it happen repeatedly? $3M could be an exaggeration... I mean think about it ...$3M
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We see restoration projects on post-tension buildings every 10-20 years and during that time they are checked & retightened.
 
jar546 said:
We see restoration projects on post-tension buildings every 10-20 years and during that time they are checked & retightened.
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How is the tension checked and to what value? “Retightened” indicates a loss in tension. What level of loss? Are there symptoms such as sagging floors, doors acting weird, etc.?
 
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ICE said:
How is the location of the tendons identified in a ceiling? I'll probably never need to know but I would really like to know.

Here is an example of when they didn't know there was a post-tensioned slab. It was an expensive mistake. There was more than what is shown.

View attachment 11756

View attachment 11757
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That doesn't look like post-tensioned concrete. That looks like pre-stressed concrete. In post-tensioned work, the tendons are in sleeves that are embedded in the slab (or beam). Once the concrete has fully cured, but before the shoring is removed, they attach a monster hydraulic jack to the end of the tendon and pull it tight to just short of the elastic limit, then they put a wedge-shaped plug around the end of the tendon and release the tendon, jamming the wedge into a socket. In post-tensioned work, I've never heard of one in which the tendons run in two directions.
 
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