shear reinforcment in concrete beams
shear reinforcment in concrete beams
(OP)
Attached a cross section of 5' wide beam. My analysis indicates 2 legs of a stirrup are required for shear reinforcement.
My question: is there a problem with putting the reinforcement at one side of the beam as shown?
My question: is there a problem with putting the reinforcement at one side of the beam as shown?






RE: shear reinforcment in concrete beams
DaveAtkins
RE: shear reinforcment in concrete beams
RE: shear reinforcment in concrete beams
The Aust. code AS3600 limits the transverse shear leg spacing to the lesser of 600mm and beam depth.
RE: shear reinforcment in concrete beams
The only problem I see with it, is that it throws your stiffness all off and can induce a torsion
Does anyone agree with that?
RE: shear reinforcment in concrete beams
RE: shear reinforcment in concrete beams
RE: shear reinforcment in concrete beams
RE: shear reinforcment in concrete beams
Most beams with small depths, probably you'll have doubly reinforced beams in which you need reinforcements to resist compression, every corner bar and each alternate bar in the outer layer of the beam, should be supported by a link. That's the BS 8110 code requirement for containment.
Clefcon
RE: shear reinforcment in concrete beams
RE: shear reinforcment in concrete beams
Section 11.5.4 provides spacing limits for shear reinforcing. Note that it does not define direction for that spaceing in section 11.5.4.1; only states a maximum of d/2 for non-prestressed members. One might argue that it applies in both directions from the axis of the reinforcing.
Of course the question I ask is; Why do your reinfocing that way?
RE: shear reinforcment in concrete beams
It just doesn't appear to engage the entire section. If you only were to count on the portion of the beam enclose in the stirrups for your φVc then you'd be OK perhaps for strength but the non-stirrup area would sort of "hang" off the side of the beam and be susceptible to cracking and even maybe separation from the main beam.
RE: shear reinforcment in concrete beams
They must at least line up with the columns. JAE's suggestion to use a reduced width to calculate capacity used to be allowed by the Australian code as long as that width was used for all design calculations.
Think about how a concrete beam works in flexure and shear and how loads are being transferred (truss analogy etc) along the member and to the supports. This will tell you where you need the reinforcement and ties.
RE: shear reinforcment in concrete beams
rday- your comment about top steel being in compression and needing enclosure. Can you elaborate? if this is just simple beam behavior, the top bars are of course in compression, but they are not relied on for calculating strength
RE: shear reinforcment in concrete beams
RE: shear reinforcment in concrete beams
RE: shear reinforcment in concrete beams
RE: shear reinforcment in concrete beams
I think you would need fabricated closed stirrups for torsion.
EIT
ACI 7.11.1 reads "Such ties or stirrups shall be provided throughout the distance where compression reinforcement is [italic]required[/italic]." I don't think bars in the compression zone require stirrups, just because they are there.
RE: shear reinforcment in concrete beams
As stated by StructuralEIT compression steel in a beam requires ties as a column.
In the US the applicable code would be ACI318. Review chapter 7.
RE: shear reinforcment in concrete beams
For the early question: It looks like the beam requires minimum shear reinf. under the "Normal Beam (deepth larger than width)" theory, however, actually you have a "Wide Beam" which behaves quite differently. Check into requirement for the later category, if shear reinforcement is still required, I would provide more than one stirrups just to ensure there is no weakness at any location on the beam section. I would not off-set the shear reinforcement, because it creates zones with different rigidities (stirrups combined with the longitudinal bars and the concrete is essentially a composite truss, as opposed to regions without stirrops).
RE: shear reinforcment in concrete beams
RE: shear reinforcment in concrete beams