×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

ACI Chapter 17 - Composite Flexural Members - Spread Footing

ACI Chapter 17 - Composite Flexural Members - Spread Footing

ACI Chapter 17 - Composite Flexural Members - Spread Footing

(OP)
I have a situation where the concrete contractor placed footing too thin. Instead of the specified 13'x8'x1'-6", it is 13'x8'x1'-0".

Punching shear, one-shear and flexure in both directions do not check.

I'm thinking of doing a grid of #3 U-Stirrups (or U-dowels / hairpins) to transfer horizontal shear between placements at the horizontal cold joint.

A couple of issues I have:
- Simpson and Hilti adhesives require 12" embedment for full development. Is there a way I can provide a percent of this embedment, by increasing my provided steel? I can base the percentage on Appendix D numbers relative to ultimate steel strength in tension. Make the U-strippups spaced far enough apart to not overlap breakout cones. Then increase my joint steel, which would decrease sustained tension in each dowel.

- In relation to the adhesive above, I suppose the adhesive is in sustained loading, since its an isolated footing with gravity loads - correct? Is this a good idea - adhesive under sustained load?

- In regards to horizontal shear, my Vuh at the joint (which is use in ACI 17.5.3) is actually the sum of components of shear flow (at that distance away from the column) due to bending in two directions since they are acting concurrently? - correct?

- Lastly, what is the minimum development for the hoop portion of the dowel? I'm looking at PCA Notes 318-11, sheet 12-12, and see no requirement.

RE: ACI Chapter 17 - Composite Flexural Members - Spread Footing

- ACI requires full development of the dowels either side of the joint with no allowance for prorating.

- They have some alternate methods for this kind of thing in other parts of the world. Call you local Hilti rep, tell him or her what you're up to, and I'm sure they'll point you in the right direction.

- Agree with adhesive under sustained loads but, if you're using the Euro methods, I think it's more of a true shear dowel thing than shear friction so probably a pass there.

- Agree with bidirectional additive.

- I'm not sure that the hoops actually get you anything that standard 90 don't provide from a code standpoint. As such, I probably wouldn't do hoops.



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: ACI Chapter 17 - Composite Flexural Members - Spread Footing

Quote (GerryBertier)

I'm thinking of doing a grid of #3 U-Stirrups (or U-dowels / hairpins)

Keep in mind, from a practical installation standpoint, U-stirrups are a bit of a pain to install. First, the drill hole pairs have to be in close tolerance (spacing and vertical), and second, adhesive anchored anchors/rebars require a 'twisting/rotation action' of the installed anchor/rebar after the hole is partially filled with resin: U-bars make such a installation impossible. Go with hairpins.

RE: ACI Chapter 17 - Composite Flexural Members - Spread Footing

(OP)
I've decided to recommend just removing the footing and replacing it with the correct thickness.

Even if Hilti can provide me development in less than 9", and I use the ACI 12.13.2.1 by providing a longitudinal bar through every hook (I only have 6" overlay which doesn't meet 6" min hook dev), I'm calculating #3 at a 5" OC grid, which is just unreasonable.

My column load is a little less than 300 kips, so its nothing to mess around with.

RE: ACI Chapter 17 - Composite Flexural Members - Spread Footing

The right choice. The only other solution I would have entertained would be to cast your 18" footing on top of the deficient one...if you had enough depth to the finished surface.

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


Resources

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