Boundary Steel In Shear Walls
Boundary Steel In Shear Walls
(OP)
We have a concrete shear wall with vertical concentrated steel at the ends (something like boundary elements). My question is related to the spacing requirements for ties in these elements.
I was told that ties for these elements would only be required if:
1) The reinforcement is required for compression
- or -
2) The reinforcement ratio is greater than 1%.
(per ACI Chapter 14)
I was also told that if the ties are required by either of the above provisions, there is no code-prescribed spacing limitation (IE you wouldn't need to meet the detailing requirements of ACI 318-08 7.10.5) . So in this example, even if we have a 10" wide wall the ties could be spaced 12" OC.
I'm not sure I buy this however. Section 10.10.3.6 implies that if you include your compression steel in a wall, even if it is less than 1%, you need to provide code-minimum ties.
To simplify my questions:
If I have a compression member integral with a wall with greater than 1% steel, do my ties have to meet 7.10.5?
If my steel is only required for tension, but is greater than 1%, do I need to provide ties and do the spacing limitations of 7.10.5 apply?
Ultimately, I'd like to match my tie spacing to my horizontal wall spacing. I have horizontals at 12" OC, but in a 10" wall if I have to meet 7.10.5 for my boundary ties those would need to be at 10".
This is in Seismic category B.
I was told that ties for these elements would only be required if:
1) The reinforcement is required for compression
- or -
2) The reinforcement ratio is greater than 1%.
(per ACI Chapter 14)
I was also told that if the ties are required by either of the above provisions, there is no code-prescribed spacing limitation (IE you wouldn't need to meet the detailing requirements of ACI 318-08 7.10.5) . So in this example, even if we have a 10" wide wall the ties could be spaced 12" OC.
I'm not sure I buy this however. Section 10.10.3.6 implies that if you include your compression steel in a wall, even if it is less than 1%, you need to provide code-minimum ties.
To simplify my questions:
If I have a compression member integral with a wall with greater than 1% steel, do my ties have to meet 7.10.5?
If my steel is only required for tension, but is greater than 1%, do I need to provide ties and do the spacing limitations of 7.10.5 apply?
Ultimately, I'd like to match my tie spacing to my horizontal wall spacing. I have horizontals at 12" OC, but in a 10" wall if I have to meet 7.10.5 for my boundary ties those would need to be at 10".
This is in Seismic category B.






RE: Boundary Steel In Shear Walls
RE: Boundary Steel In Shear Walls
If a compression load creates a demand for reinforcing in excess of 1%, you need ties meeting the column provisions. Otherwise, you don't need the ties.
I'll do a little more fact checking when I'm back at the office and have ACI handy.
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: Boundary Steel In Shear Walls
Are you sure about this section reference? My 318-08 doesn't have this clause.
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: Boundary Steel In Shear Walls
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Boundary Steel In Shear Walls
RE: Boundary Steel In Shear Walls
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: Boundary Steel In Shear Walls