Hollow Core Plank Details
Hollow Core Plank Details
(OP)
We've occasionally used prestressed precast concrete hollow core planks on projects and have always struggled to develop adequate details for the connections between the planks and supporting walls.
The biggest difficulty comes with using the planks as roof elements with no topping. Other than embedding steel plates in the planks and bolting clip angles to the walls, we haven't found any details that correctly use reinforcing bars, developed properly, that work.
Are there any resources, websites, etc. that provide details for this? PCA and PCI don't seem to show a lot of concepts.
I'm developing a large sense of animosity towards planks these days! Don't care for the product due to the above.
The biggest difficulty comes with using the planks as roof elements with no topping. Other than embedding steel plates in the planks and bolting clip angles to the walls, we haven't found any details that correctly use reinforcing bars, developed properly, that work.
Are there any resources, websites, etc. that provide details for this? PCA and PCI don't seem to show a lot of concepts.
I'm developing a large sense of animosity towards planks these days! Don't care for the product due to the above.






RE: Hollow Core Plank Details
RE: Hollow Core Plank Details
The other thing that is often done is that the concrete above some of the hollows in the planks gets broken out near the end of the panel so you get a channel to put reinforcement and concrete in. We do this quite often where two planks are meeting end to end and bearing on one wall to tie the two planks together over the wall.
Carl Bauer
www.bauerconsultbotswana.com
RE: Hollow Core Plank Details
dikcoates@alpha.to
RE: Hollow Core Plank Details
RE: Hollow Core Plank Details
I've seen similar details to what pylko and carlbauer described. Maybe I'm being too particular, but to be honest, none of them, in my humble opinion, satisfy code provisions of ACI.
For example, a hollow core supported by a concrete masonry wall. The hollow core usually sits about 4 or 5 inches on the 8 in. wall and a vertical bar extends out of the wall, and is bent 90 degrees into the HC. The bar either aligns with the "rebate" or keyway between the individual planks, or the top part of the plank is chipped away to allow the bar into the core which is fully grouted.
The problem I have with this detail, is that the bar is never developed properly per ACI chapter 12. If the wall were to be pulled outward, say by lateral wind suction, there is nothing that directly resists this force. The bar can't do it because it is simply extending vertically out of the top of the wall and doesn't turn into the plank until about 4 to 6 inches above the wall. This results in a 4 to 6 inch rebar cantilever that really can't resist anything. The plank friction on the top of the wall can't be included either.
Even with a topping slab, where the bar is turned into concrete above the HC plank, there isn't a direct load path.
The only thing we've come up with is requiring embedded plates to the underside of the plank directly adjacent to the wall. We then add an angle that is welded to the plate and bolted to the wall, just below the plank. However, every contractor/owner we've tried this on has complained.
RE: Hollow Core Plank Details
That probably does not cover your concerns at a roof level, though.
RE: Hollow Core Plank Details
Carl Bauer
www.bauerconsultbotswana.com
RE: Hollow Core Plank Details
I was engaged by the National Precast Concrete Association of Australia to develop a computer program for precast (pretensioned) prestressed hollow core planks. The whole membership of the Association was available for consultation. Its input was "empirical", i.e. "we have done it like that for years". A perch of 30 mm on an unreinforced ledge of a precast beam was considered adequate for a plank spanning 9 m.
Fortunately, there was one guy who shared my thoughts after I showed him research going back to 1930, and we ended up with a product (called PCP4.EXE) that does away with a lot of the nonsense that has grown "empirically".
Regards to all, Helmut
http://www.engs-comp.com/