Contact US

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!

*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

Post Installed Anchorage Lap/Fix

Post Installed Anchorage Lap/Fix

Post Installed Anchorage Lap/Fix

We've got a CMU core that is being used as a major lateral element on our project. Our detail shows a lapped dowel between the CMU wall and a concrete stemwall below. Unfortunately the contractor missed this detail and are looking for a post-installed fix.

Being that the wall reinf is working hard in the CMU walls above, we were working with some heavy (#7) vertical reinf. We'll obviously have a hard time fully developing the strength of the wall vertical reinforcing with an drill/epoxy installation in the top of a 10" concrete wall.

Thinking our solution could potentially lie in one of the following?

  • Unsure if we have the ability to drill/epoxy a "lap" to the vertical reinforcing in the wall below?
  • Unsure if we have the ability to core/grout a "lap" to the vertical reinforcing in the wall below?
  • Design the drilled/epoxy anchors for the actual design load of the wall reinf above. Ensure concrete wall reinforcing below is sufficient enough to transfer load out of that epoxy failure cone and into the reinforcing?
  • Design the epoxy anchors to transfer shear load, install some sort of exterior strap/plate to transfer the tension load (via shear)?

Any and all thoughts/input would be appreciated!

RE: Post Installed Anchorage Lap/Fix

Hilti has some info on post-installed development and splice lengths in their technical guide.

I think you can create a "lap" with the bars in the wall below, but be prepared to drill pretty darn deep and wrestle with the "we've never had to do it that way" criticism.

RE: Post Installed Anchorage Lap/Fix

Are we talking about #7 bars as localized zones in the corners? Or #7 @ 16" all of the way around? If it's just zones, I'd consider chipping away enough of the stem walls to get mechanical couplers on the bars in there. If a "stem wall" is like a 4' tall thing and it's #7 all of the way around, then I'd be inclined to just demolish the stem walls and rebuild them. Yeah, the lapping stuff can sometimes be made to calc out. If you're doing it all round the stem wall perimeter, however, there just isn't going to be anything left of that stem wall worth having.

RE: Post Installed Anchorage Lap/Fix

I'm not overly concerned about the contractor squawking if we make them drill deep. Unfortunately we're looking at #7 @ 16" all the way around for these guys which make it a little worse. We're at the bottom floor of an elevator core so we're looking at a 5'-6" concrete wall (10" thick) that forms up the elevator pit that we're sitting on top of.

RE: Post Installed Anchorage Lap/Fix

Well, at least it's not 8' OC. As JNLJ mentioned, Hilti's got some decent info in their design guide on post installed rebar: Link. You're effectively doing a lap splice and an offset lap splice at that. So it's going to be those kinds of depths.

In addition to that option, I'd propose hydro demolishing the tops of the stem walls down 8", so that you can get mechanical couplers on the bars, and the building the walls back up with repair material. I feel that this might be economically competitive with the drill & adhesive solution. More importantly, to me, is that I feel as though so much drilling, so deep, is going to beat the heck out of your wall. If you're working the core this hard in flexural tension, then you're working your zones similarly hard in flexural compression. I worry that your wall will wind up splitting apart like barrel staves when that happens as a result of internal cracking developing from all of the closely spaced drilling. I don't know how realistic such a failure really is but it's the picture that pops into my head. It's not as though this is something that Hilti will be considering.

RE: Post Installed Anchorage Lap/Fix

Sure enough, the Hilti guide has a pretty great graphic of the situation.

RE: Post Installed Anchorage Lap/Fix

Thanks, Koot, much appreciated. I had been looking at the Hilti post-installed rebar guide and it seems at least plausible. Would definitely be a pain for them to drill and epoxy every 16" with a 30"+ embed depth. That said, I do see your concern about potentially weakening the concrete there. I'm a little confused on the graphic they're showing - do you get the idea that they assume the presence of horizontal reinforcing (of which we have due to typical horiz bar) will act to limit that splitting mechanism? Seems like something that is hard to real numbers to, but I agree that it potentially just doesn't feel great.

RE: Post Installed Anchorage Lap/Fix

You're most welcome Nulukkizdin.

Quote (Nulukkizdin)

I'm a little confused on the graphic they're showing - do you get the idea that they assume the presence of horizontal reinforcing (of which we have due to typical horiz bar) will act to limit that splitting mechanism?

No, I believe that they are showing the horizontal bars simply because they complete the strut and tie model implied by the offset lap splice condition. Such bars would surely help with vertical cracks oriented perpendicular to the wall but they wouldn't do anything for the the through thickness cracking that moderately concerns me. Maybe you just agree to have some dowels installed and pull tested over 4' length of wall to see how it goes before you commit to the whole thing.

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! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close