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.


Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

ACI 318 Cracked vs uncracked concrete for anchor analysis

ACI 318 Cracked vs uncracked concrete for anchor analysis

I'm in the process of designing a wedge anchor connection per appendix D of ACI 318-08.  I'm trying to figure out when to assume cracked vs uncracked concrete.

When anchoring to a compression zone, one would assumed uncracked concrete and cracked for tension zone.

What happens when you anchor to a compression zone in a seismic area? Do you assume cracked? or can you still assume uncracked?


RE: ACI 318 Cracked vs uncracked concrete for anchor analysis

I always assume cracked concrete.

RE: ACI 318 Cracked vs uncracked concrete for anchor analysis

You also have to consider that cracking can be caused by shrinkage as well as applied tansion. ACI App D is written so that cracked concrete is the default and a factor is allowed for uncracked concrete. I also would assume cracked concrete unless there were good reasons to use the factor for uncracked concrete.

RE: ACI 318 Cracked vs uncracked concrete for anchor analysis

Another potential for cracking is the high localized stresses as a result of the anchor embedment.  Even if it's a column in compression, the localized stresses surrounding the anchors are not representative of the typical column section.

RE: ACI 318 Cracked vs uncracked concrete for anchor analysis

I agree, assume cracked if you can.  If your design can only work with uncracked, you must consider seismic load reversals, etc. to make sure your uncracked concrete does not become cracked during seismic loading.

I don't have the code with me at the moment so check me on this.  But I don't recall that the localized stresses due to the anchor loadings need to be considered.  I believe that it is the initial condition that is at issue, that is, is the concrete already cracked.  A bending compression zone in a thick beam or a compression only column should be acceptable for this.  I'm going to check this though.

RE: ACI 318 Cracked vs uncracked concrete for anchor analysis

I'll double check in the morning when I can look at ACI 318, but I don't believe that it specifies what types of loads to consider or not consider.  It just says that if analysis shows no cracking at service loads, then you can use the 1.4 factor for uncracked concrete.

I've had to use rebar welded to embed plates on a number of occasions recently to get away from App. D, because I just couldn't get the anchor calcs to work.

RE: ACI 318 Cracked vs uncracked concrete for anchor analysis

I was stopped at a traffic light this morning on my way in to work and I happened to be under and overpass.  There were concrete wall abutments on either side with precast box girders spanning between them.  The overpass was roughly 15' high.  The abutments were doing 15' of retaining, but I'd be willing to bet that analysis would show no service level tension to exist on the exterior face of the walls (yes, this is the tension face for retaining, but I believe the DL of the bridge would more than offset this) let alone service level cracking.  There were, however, significant and numerous cracks (both vertical and horizontal).  

Just something to think about.

RE: ACI 318 Cracked vs uncracked concrete for anchor analysis

I assume always "cracked" concrete in SDC C and higher.
All concrete is cracked, but cracked is wrong definition. It should be replaced by a word tension zone.

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!


White Paper: Agile Product Engineering and Improved Product Outcomes
Today’s product development cycle is fraught with difficulties. Increased demands for complex functionality and reduced product development windows cause engineering teams to borrow practices from the IT industry, swapping outdated serial workflows for a more flexible and collaborative design method known as Agile Product Engineering. 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