Wall Reinforcement Detailing - Poll

[slickdeals]

In your respective firms, is there a standard for detailing reinforcement bars in a concrete shear wall in terms of which bar gets placed closest to the edge of concrete (vertical or horizontal) and why?

CRSI's document on "Designer's responsibility for Rebar Design" seems to recommend vertical bars on the outside layer.
NEHRP's tech document suggests the opposite because the lap splices in vertical bars will perform better being on the inside layer.

 

[jayrod12]

In our office generally we put the verticals on the inside.

This allows for the horizontals to essentially act like stirrups once we add hairpins at the ends of walls.

 

[KootK]

- if it's high seismic, I'll do what NEHRP recommends.

- if it's low seismic, I'll do whatever is best for constructability. Often, if it's pre-assembled cages flown in, it won't matter. If it's bar mats erected against a one sided form, I'll assume that the verticals are place first and then the horizontals are tied to those from the accessible side. Interestingly, this leads to a different bar order on the two sides of the wall.

 

[hokie66]

It depends on the thickness of the wall. With a thin wall, say 200 with two layers of reinforcement, I want the horizontals on the outside to give more room in the centre for concrete placement.

 

[rapt]

I agree with vertical inside for all of the above reasons.

Interestingly, the new Australian code does not specifically say it, but every diagram shows verticals on the inside!

Wherever Boundary elements are required, verticals have to be inside.

 

[cliff234]

We detail the horizontal steel on the outside face because the vertical chord steel at the ends of the wall need ties. The ties wrap around the chord steel and have 1.5” of cover (similar to the cover for ties on concrete columns). The horizontal bars then get placed outside the vertical chord steel (and all other vertical bars) and have the same 1.5” cover. Likewise, the outermost chord bars get wrapped by “U” bars that lap with the horizontal bars.

 

[slickdeals]

Thanks all. Agree with the comments, but it's interesting to see CRSI's document on the subject (though skewed towards high seismic)

http://resources.crsi.org/index.cfm...ne&fileID=2A745B17-AA5A-03FC-9190F6FD419F3868

Refer to pages 6-8.

The ties wrap around the chord steel and have 1.5” of cover

1.5" cover? Interesting. We typically do 3/4" or 1". Other than it's a column like cage at the end, is there any reason why you would use a 1.5" cover?
We typically don't use a 1.5" cover because the link beam flexural steel will directly be in conflict with the shear wall boundary element and creates issues with congestion on heavily loaded links.

Agree with capping U bars. That's my preferred choice as well. Gives the contractor some flexibility with placement.