The slab-on-grade is post-tensioned. It will be poured together with the column spread footing. Architect preferred the steel column has a regular block-out so the base plates, grout, and anchor bolts can be hided. But to do that, the tendon of the slab will need to cut/stop at the block-out area. That means the slab at column strips is not post-tensioned. Is it OK? Thanks a lot for your help.
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Steel column block-out at post-tension slab-on-grade 2
- Thread starter aquacata
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- #2
rowingengineer
Structural
How big is your block out, can't you just move the tendon around your block out?
why are you pouring the footing and slab together?
How could you do anything so vicious? It was easy my dear, don't forget I spent two years as a building contractor. - Priscilla Presley & Ricardo Montalban
why are you pouring the footing and slab together?
How could you do anything so vicious? It was easy my dear, don't forget I spent two years as a building contractor. - Priscilla Presley & Ricardo Montalban
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- #3
The largest block out is 30" by 30" (30" is the diagonal side, along column grid, it is 42" each way.). It is a good idea to layout the tendon around the block-out even though I don't know the tendon spacing yet. Thanks!
The post-tensioned slab engineer wanted to pour the interior footing and slab together maybe because it is convenient and faster to construct. Do you see a problem with this? My only concern is, will the post-tensioned tendons in slab cause a uplift force on my footing?
My other concern is, I want to use the slab/soil friction to take my large base shear at the column. If I have a 8" deep cloumn block out, the top of the 5" thick slab is 8" higher than the interface of the anchor bolt to the footing (which is the top of the footing). Can I add L shape dowels from the footing to the slab turn-down around the block-out and say the base shear is transfered to the slab?
The post-tensioned slab engineer wanted to pour the interior footing and slab together maybe because it is convenient and faster to construct. Do you see a problem with this? My only concern is, will the post-tensioned tendons in slab cause a uplift force on my footing?
My other concern is, I want to use the slab/soil friction to take my large base shear at the column. If I have a 8" deep cloumn block out, the top of the 5" thick slab is 8" higher than the interface of the anchor bolt to the footing (which is the top of the footing). Can I add L shape dowels from the footing to the slab turn-down around the block-out and say the base shear is transfered to the slab?
rowingengineer
Structural
I normally wouldn't join the footings to the slab, causes shrinkage restraint.
How could you do anything so vicious? It was easy my dear, don't forget I spent two years as a building contractor. - Priscilla Presley & Ricardo Montalban
How could you do anything so vicious? It was easy my dear, don't forget I spent two years as a building contractor. - Priscilla Presley & Ricardo Montalban
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- #5
Then you pour the footing first, leaving dowels from the footing to the slab, then pour the slab?
Or you don't use the slab to take the base shear? So you have a column block-out with expansion joint around. The slab just has turn-downs sitting on the footing?
Or you don't use the slab to take the base shear? So you have a column block-out with expansion joint around. The slab just has turn-downs sitting on the footing?
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- #6
Then you pour the footing first, leaving dowels from the footing to the slab, then pour the slab?
Or you don't use the slab to take the base shear? So you have a column block-out with expansion joint around. The slab just has turn-downs sitting on the footing and there are no dowels from the footing to the slab?
Or you don't use the slab to take the base shear? So you have a column block-out with expansion joint around. The slab just has turn-downs sitting on the footing and there are no dowels from the footing to the slab?
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- #7
rowingengineer
Structural
I use blockouts around the column and don't provide a reinforced connection from the column to slab. Is the base shear that high?
How could you do anything so vicious? It was easy my dear, don't forget I spent two years as a building contractor. - Priscilla Presley & Ricardo Montalban
How could you do anything so vicious? It was easy my dear, don't forget I spent two years as a building contractor. - Priscilla Presley & Ricardo Montalban
- Thread starter
- #8
The base shear is high. 70 kips at one column. I am using the L dowel from the footing to the slab, instead of the hairpin from the blockout to the slab. I like the hairpin better cause it transfers shear directly. But since the slab will be poured first, it looks to me that to have hairpin in the blockout will interfere with the column erection. L-dowel may not be that direct and effective, but it should still work. How do you think about the whole thing?
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