×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Tension and shear force at top of foundation wall from braced frame

Tension and shear force at top of foundation wall from braced frame

Tension and shear force at top of foundation wall from braced frame

(OP)
Hello,

I'm wondering how people typically deal with large tension and shear values at the top of a foundation wall from a braced frame. It appears that following Annex D Anchorage from CSA A23.3 concrete failure will occur unless I put a pilaster in the wall. I have read the Design of Anchor Reinforcement in Concrete Pedestals LINK and that method seems promising. Does anyone have any comments or typical methods to deal with these forces?



Thanks

RE: Tension and shear force at top of foundation wall from braced frame

That's why we usually put pilasters unless the loads are extremely low.

RE: Tension and shear force at top of foundation wall from braced frame

(OP)
I agree jayrod12, unfortunately this is a residential project with NBCC Part 4 elements so architecturally pilasters may not work.

RE: Tension and shear force at top of foundation wall from braced frame

I've had a few houses that go this route. I've always told them up front, if this is the look you want, it gets designed as a commercial building, including commercial type elements.

I'm assuming the loads are actually significant? What about providing enough reinforcement and detailing accordingly that app D doesn't apply?

RE: Tension and shear force at top of foundation wall from braced frame

(OP)
The loads are significant enough that typical heavy hex anchor bolts without extra wall reinforcing will see failures in the concrete. I like the idea of providing enough reinforcement and detailing to bypass Annex D but I'd be concerned about fitting everything in an 8" wall, therefore I feel that it would require a bump out in wall thickness there to accommodate the steel (which is essentially a pilaster I guess).

I wonder if there isn't some sort of sort of additional framing that could be done to transfer the shear and uplift at the base of the brace into a longer portion of wall or into the floor diaphragm (and subsequently into a longer portion of wall).

RE: Tension and shear force at top of foundation wall from braced frame

Hence my comment about commercial building. 10" wall minimum on these crazy expensive houses. It lets me do what I need in terms of reinforcement. If they can afford 10 bucks a square foot for floor finishes then they can afford the increased wall thickness.

RE: Tension and shear force at top of foundation wall from braced frame

Can you embed the post in the wall and anchor it to foundation wall footing? I've never done it quite like that before, so I'm not quite sure how it will fit up in an 8" wall with horizontal reinforcing on either side.

RE: Tension and shear force at top of foundation wall from braced frame

It's a tough sell to residential contractors but this is the route that I go.

1) Use threaded rebar or deformed bar anchors instead of anchor bolts and position the bars in the center of the wall. This is pretty much the only way that I know of to deal with anchor side face blowout in an 8" wall. This should cover you for tension.

2) If shear capacity becomes and issue. Embed a steel plate with studs in the top of the wall on the brace side of the column and connect your brace gusset plate to that.

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: Tension and shear force at top of foundation wall from braced frame

(OP)
Great comments jayrod12, mike20793, and KootK. Thank you very much for your input! I'll look into these options to determine which is best suited for my situation.

RE: Tension and shear force at top of foundation wall from braced frame

I tend to prefer Koot's method. It seems easiest to construct and easiest to resolve the forces. I'm not sure I'd trust a residential contractor to properly embed a column that's half the wall the depth.

RE: Tension and shear force at top of foundation wall from braced frame

The Achilles heel in my detail tends to be the need for field welding. If you introduce it in a project that would otherwise have no field welding, you'll hear about it.

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: Tension and shear force at top of foundation wall from braced frame

I agree, introducing field welding where there was none before generally doesn't make people happy. You could have drilled and tapped holes in the embedded plate, but then you would need to have a site survey after pouring the slab and prior to fabrication of the brace assembly.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources