Is it required to hook the ends of the footing rebars?
Is it required to hook the ends of the footing rebars?
(OP)

figure 1

figure 2
I have found some plans that is like figure 1 above that hooks the ends of the footing mat bars.. I was wondering in what section of the ACI(3-18) code that does require to hook the end of the footing mat bars and what is the size of the hooks?
do we really need to provide column ties with-in the footing and does the 2" spacing starts from the hook of the column longitudinal bar or does the 2" spacing start above the footing..?? in what sections of the ACI code proves this?





RE: Is it required to hook the ends of the footing rebars?
I'd say for a normal footing, a hook isn't needed. Plus you might need to thicken the footing just to fit the hook in. #7's need a 14 inch hook. With cover you're up to about a 19 inches thick.
RE: Is it required to hook the ends of the footing rebars?
The column ties are usually required for seismic design. It increases ductility. Check the chapter for seismic requirements.
I am guessing but I believe the 2" is from the construction joint. I am at home and cannot point to a chapter other than we would generally want 2" cover for a column. A tie would be almost useless at the joint. I believe that the bottom tie location should be based on consistent spacing from the top down.
RE: Is it required to hook the ends of the footing rebars?
Other than for seismic reasons, it is relatively common to show two ties within the footing, as it assists in locating the starters and keeping them where you want them during casting of the footing.
Not everything we do in concrete structures can be explained by reference to the ACI code.
RE: Is it required to hook the ends of the footing rebars?
RE: Is it required to hook the ends of the footing rebars?
Cogs = 90º hooks
RE: Is it required to hook the ends of the footing rebars?
RE: Is it required to hook the ends of the footing rebars?
Your inclusion of top steel makes me wonder if this isn't a footing with an overturning moment. If that's the case, I would recommend hooking your bottom bars.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Is it required to hook the ends of the footing rebars?
RE: Is it required to hook the ends of the footing rebars?
Though it was not a requirement unless you needed it for development length as others have stated.
RE: Is it required to hook the ends of the footing rebars?
I can't even imagine not having them, how on earth do you control the placement of the top bars?
RE: Is it required to hook the ends of the footing rebars?
Most footings in my area don't have top bars. And, in most cases were top steel is required, you'll see some standoff ties to create the separation. With larger footings, I imagine this would be required even with the bars hooked.
For bottom steel only footings, this is even easier without the hook, particularly where transport is involved.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Is it required to hook the ends of the footing rebars?
I just want to inquire one last thing . . if the plan states that ties spacing is 1 @ 50 mm,5@ 75 mm , 10 @ 100mm , rest @ 200mm .. where will the 50 mm spacing start? at the hook or above the footing ? if 50 mm starts at the top of the footing ,what will be the tie spacing within the footing.?
sorry if i'm just too slow to learn bros..
RE: Is it required to hook the ends of the footing rebars?
RE: Is it required to hook the ends of the footing rebars?
RE: Is it required to hook the ends of the footing rebars?
Hooks from your piers should be turned the other way.
Dik
RE: Is it required to hook the ends of the footing rebars?
RE: Is it required to hook the ends of the footing rebars?
To kootk, on your reply to me, we end up with top reinforcement almost always due to punching shear and carrying some level of moment at the base of the columns in continuous concrete frames. With single bottom layer of reinforcement punching shear with moment is compromised, due to minimal effective depth on one side. There is always a moment, even if it's conveniently ignored in design/analysis of the superstructure, but you shouldn't ignore it in the detailing! (not round here with earthquakes)
RE: Is it required to hook the ends of the footing rebars?
1) Footings are supporting gravity only framing and;
2) Levels of expected seismic drift are small.
These limitations would be satisfied for most footings installed in North America. The situation is quite analogous to punching shear at roof slab joints where, despite the general demand for moment transfer between columns and slabs, it's rare to see a bottom mat of reinforcing that rivals the top mat in any meaningful way. Another feather in the cap for integrity steel I suppose.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Is it required to hook the ends of the footing rebars?
I am just starting my second 2 story building here. It is 2 story with part 3 story (stairwell to concrete roof). It is 300 sq M (excluding 4 balconies and roof of another 200 sqM)
I always consult with my engineer. Some of the 15no. footings for this project are 2.2M x 2.2M x 0.4M. There is only bottom rebar, typically 16mm matting at 150mm spacing. 17 each way in the case of 2.2m footing. The reason this is 2.2M is mainly due to the 4 cantilever balconies at the sea side, plus the 3 story stairwell (5.4m x 3.2m) and the concrete roof cantilevered 1.2m throughout.
Some of the columns (3) have 16no. x 16mm vertical bars, with stirrups (called rings here) in a 3 set configuration. That means one holding all 16 bars, the second holding 6 bars and the third holding 6 bar. These are sandwiched together as aset. Then we measure 50mm tho the next set. We use 4 sets @50mm. next 6 sets @75mm. next 6 sets @100mm. The remainder are at 150mm. For stirups not requiring sets the same distance above are used. This spacing is also used coming outwards of beams (including bottom tie beam).
The L's (or hooks) at the bottom of the column vertical bars are joined to the matting.
In answer to your last question. We start the stirrups at the L, so it is typically 2/3+ of the way down into the footing concrete.