max. spacing between stirrup links in the beams
max. spacing between stirrup links in the beams
(OP)
Dear experts
is there any item in ACI-code mentioned the maximum spacing between the stirrup links in concrete beams, for example if i have beam with width 600mm i can put only two links or i have to decrease the spacing between the links by add more links.
is there any item in ACI-code mentioned the maximum spacing between the stirrup links in concrete beams, for example if i have beam with width 600mm i can put only two links or i have to decrease the spacing between the links by add more links.
Thank you





RE: max. spacing between stirrup links in the beams
11.4.6 provides for minimum amounts of shear reinforcement which sometimes controls and limits your spacing.
11.5 includes torsion design and further has limits similar to above (see 11.5.5 and 11.5.6)
The above is for 318-11 and older. 318-14 is reconfigured so you'd have different section numbers.
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RE: max. spacing between stirrup links in the beams
Most codes around the world seem to limit it to between 300 and 600mm and some relationship to Depth or Effective Depth of member (varies between codes). The depth relationship is sometimes related to the level of shear stress eg Canadian code.
RE: max. spacing between stirrup links in the beams
Thank you
RE: max. spacing between stirrup links in the beams
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: max. spacing between stirrup links in the beams
Now adding to this discussion, how does one curtail this shear reinforcement down towards midspan?
When you go back to min. shear reo, does one still need to uphold this min. transverse spacing rule?
RE: max. spacing between stirrup links in the beams
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: max. spacing between stirrup links in the beams
No, I think Trenno is on the same page, i.e. transverse leg spacing. I suspect he is thinking about wide flat beams which we often call band beams. A common approach is to call these one way slabs, and you often don't need shear reinforcement using the slab provisions. But I could be wrong...eh, Trenno?
RE: max. spacing between stirrup links in the beams
The AUS code isn't too clear on when you can curtail this down.
For example, a 2400w x 500d beam will require 6 legs (3 loops... I hate single leg stirrups) crossing the beam's width. Having 6 legs continue, @ say max long. spacing, for the whole beam span seems overkill.
Obviously one still needs to think about constructibility issues here, beam cages etc etc...
RE: max. spacing between stirrup links in the beams
As I understand it, if you need the shear reinforcement (minimum still means you need it), then the spacing limit applies. If you do not need it for shear rules but are supplying it further towards mid span than is required by the minimum shear rules, it is up to you. It then gets down to the spacing you need to support the top reinforcement mat and tendons if there. With over-weight concretors jumping up and down on it, I still like 600 - 800 maximum, so 2 ties (3 spaces) across a 2400 wide band beam.
RE: max. spacing between stirrup links in the beams
If one were willing to look past the letter of the code and constructability issues, I could see an argument for ditching the interior legs. If you could hypothetically narrow the beam such that spacing rules were satisfied and Vc + Vs still worked based on that hypothetical section, I'd be okay with it.
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: max. spacing between stirrup links in the beams
RE: max. spacing between stirrup links in the beams
RE: max. spacing between stirrup links in the beams
One work around would be maintain one full loop (full width) at say a larger spacing for midspan areas, therefore the top bars will be nicely secured and you're not being heavy with your ligs.
RE: max. spacing between stirrup links in the beams
We have a similar clause in New Zealand concrete code as mentioned, but the spacing across the section for each leg need not be less than 250mm between vertical legs, unless the 0.33 x sqrt(f'c)b_w x d limit applies, then the lower limit is reduced to 200mm. In NZS3101 its really clear in that there are separate clauses for the spacing of stirrups along the axis of the beam and the spacing of individual legs perpendicular to the member axis. Our code is pretty much based on ACI 318 with some more stringent requirements due to the seismic side of things, so I'm surprised ACI doesn't cover it.
The reasoning for having relatively evenly spaced legs is so it prevents tension across the bottom of the section due to the strut angle for shear forces getting to the stirrups being too shallow. If you imagine a wide shallow beam with a single perimeter stirrup, there is a tension across the bottom of the section due to the shear having to strut at a shallow angle to the stirrup/corner bar.
See attached clause from NZS3101.
RE: max. spacing between stirrup links in the beams
In midspan areas where it is only being provided for top reinforcement support, the logical maximum spacing is the maximum spacing for rebar chairs. The is no code shear reinforcement requirement there so shear spacing requirements do not apply.
If you do as you suggest for a 2400 wide band beam then the legs would be at about 2300 transverse and whatever spacing you select along the beam. 2300 is far too much. If there are PT tendons being supported, I would be looking at an absolute maximum of 1000 spacing, which is why I suggested 2 ties = 4 legs. For reinforcing only, with the supported reinforcement height being 350-400mm, I would think 1000 centres is still the maximum as things get pretty unstable with heavy worker loads on them.
RE: max. spacing between stirrup links in the beams
Here's the ACI clause for reference. It's taken to refer to longitudinal spacing but I can see how the wording leaves room for improvement.
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.