Transverse Tension in Bars
Transverse Tension in Bars
(OP)
I am being told by another fellow engineer that one can count on a transverse continuous horizontal bar that a hooked bar goes over will carry tensile load hence the development length of the hook does not have to develop! I never heard of such a thing before.
Does anyone know if ACI has any provisions allowing continuous transverse bars to carry load in tension transversely?
I searched ACI 318 and did not find any.
Does anyone know if ACI has any provisions allowing continuous transverse bars to carry load in tension transversely?
I searched ACI 318 and did not find any.
Regards,
Lutfi






RE: Transverse Tension in Bars
I've seen this detailed only as an aid to ease of construction, but never as something to count on to develop.
RE: Transverse Tension in Bars
Regards,
Lutfi
RE: Transverse Tension in Bars
There is nothing in Chapter 12 of 318 that indicates a transverse bar helps reduce or eliminate the need for ldh.
A question could be sent to ACI via their website to see what they say.
RE: Transverse Tension in Bars
Regards,
Lutfi
RE: Transverse Tension in Bars
In theory, I believe the other engineer is correct; however, it is not necessarily recognized as a code provision (the perpendicular rebar interrupts the "splitting tensile" stress distribution caused by compression of the concrete from the hook).
RE: Transverse Tension in Bars
I agree with the modification factors.
Interesting point that you bring up about the horizontal bar theory; but as you said, it is not a code recognized provision.
I should be on the beach enjoying the wonderful Florida weather today!
Regards,
Lutfi
RE: Transverse Tension in Bars
There are other requirements for larger stirrups, and these provisions apply specifically to stirrups per ACI 318, but my best guess is that he's referencing that type of behavior. I hope he's not really suggesting that the transverse bar somehow carries tension transverse to the longitudinal axis of the bar.
RE: Transverse Tension in Bars
RE: Transverse Tension in Bars
RE: Transverse Tension in Bars
RE: Transverse Tension in Bars
Regarding Lion06's analogy to stirrups--I've never heard that the hook of a stirrup is considered to develop the stirrup at, say, the start of the radius of the hook. Stirrup anchorage details are prescriptive, not predicated on developing the bar from some critical section--that would be at the location of the shear crack, which is of course random, as is stirrup placement, to a degree. I think it's more a concern of having stirrups spaced closely enough that developing yield isn't necessarily critical for any individual stirrup.
RE: Transverse Tension in Bars
The initial stress distribution is that the hook puts the concrete above the hook in compression. That holds as long as the paste-to-bar bond holds or the concrete breaks in splitting tension from the compression concentration along the line of the hook. If you reinforce the area of concrete perpendicular to the expected tension crack, you will then throw the stress distribution back to a bond failure. Studies have shown that with higher strength concrete, the hooked bars can actually straighten and pull out without failing the concrete (except locally at the bond interface).
RE: Transverse Tension in Bars
I respectfully disagree. Because an inclined shear crack can develop anywhere and it is assumed that any stirrup crossing the plane is effective it has to be assumed that any stirrup crossing the plane is fully anchored on both sides of the crack, otherwise it wouldn't be effective. Additionally, ACI 318 11.5.4 says that both ends of the shear reinforcing shall be developed according to 12.13. 12.13.2.1 says that for #5 bars and smaller, a standard hook around a longitudinal bar shall be provided. For #6 bars and larger an additional development length is provided. The point I was trying to make is that for typical stirrup sizes, they are considered completely anchored (100% developed) just by virtue of the standard hook around the longitudinal bar regardless of where the crack occurs.
RE: Transverse Tension in Bars
As for the tension steel, I use the detail all the time to theoretically increase the size of any pullout cone - as shear reinforcing per se. If the embediment is too short, I put a plate on the end and run a couple of transverse bars over it. Never had a problem with it.
But, perhaps this is not the concern here...
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com