Reinforcement nearest to the face of members 1

[ramihabchi]

hi,
Is there any reason for why we put horizontal reinforcement in shear walls nearest to the face of the wall and vertical bars from the inside?same for beams why we put shear reinforcement/stirrup from the outside?
Shear works in the two direction so why we put them outside?
In columns for e.g stirups prevent buckling from happening and confine the column to have bigger strength.but in walls and beams what is the reason?

 

[Agent666]

Same reason as you mentioned for columns really. Generally walls have a lower confinement requirement on the general basis of the axial stresses being lower. In my local code, for higher axial loads the confinement of walls is required to follow the rules for columns.

In beams you still need confinement of the core concrete to maintain the concrete shear mechanisms and compressive zone confinement.

 

[hokie66]

In a wall, especially a thin wall, placing the horizontal bars in the outer layer facilitates proper concrete placement. The more room for placement and vibration, the better the consolidation.

 

[MIStructE_IRE]

From a practical perspective, the vertical bars are installed first. Try tying steel by standing the verticals then getting the horizontals inside them.. You’ll have a very disgruntled steel fixer.

From a design perspective, i like the outer lacers as confinement for my vertical compression bars.

 

[ggcdn]

In Canada, it's common practice to put the verts on the outer faces of the wall, and horizontals inside. Rod busters don't really have a problem with it.

The notion that a wall horizontals can act as confinement or even buckling prevention seems pretty dubious to me, especially in a long wall. If you are seriously trying to achieve either of those things, you need cross ties though the thickness of the wall.

 

[IDS]

I won't comment on walls, but for beams the reason for putting the shear reinforcement outside the longitudinal reinforcement is that if you don't, this is what can happen:

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[Agent666]

Never heard of verticals on the outside, but agree with requirements for cross ties for confinement unless at low stresses.

From a durability standpoint I'd rather loose a few horizontal bars first than vertical bars if there was a cover issue.

 

[hokie66]

Each project should be considered on its own. Addressing only walls, there are valid reasons both ways. I tried to make the point above that for relatively thin walls, the horizontal located in the outer layer facilitates placement and compaction of the concrete. But for walls suject to significant bending, I generally want the verticals outermost on the tension side. In the case of cantilevered retaining walls, the outside mat is generally tied first, with the verticals stood first. But then this easier tying procedure is repeated on the inside face, so you get vertical, horizontal, vertical, horizontal.