×
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

Bending in anchor rods.
2

Bending in anchor rods.

Bending in anchor rods.

(OP)
I have a situation where I have a column base that (among other loads) has a tension and shear case. To transfer the shear to the top of my pedestal I was using bending in the anchor bolts (i.e. assuming the grout has cracked and no friction [due to tension]). The thing about it is: my anchor bolt has a larger diameter than the grout thickness, so I'm wondering if this may be overkill. (But it's what I have always done.) [After I figure the bending, I check the combined tension and bending in the bolts (together with the shear).]

I found an older thread on this but that was with the base plates sitting on leveling nuts.

http://www.eng-tips.com/viewthread.cfm?qid=192488&page=312

The link [in that thread] to an AISC discussion on this subject doesn't work.

Thoughts?
 

RE: Bending in anchor rods.

(OP)
Thanks JAE.

RE: Bending in anchor rods.

I haven't had a chance to check out those links, but App. D is pretty clear that if you have a grout bed that you take a 0.8 hit on the steel capacity.  That's all I've ever done.

RE: Bending in anchor rods.

JAE's references seem to be saying you should not take shear on anchor rods.  That seems to be contrary to standard practice.

BA

RE: Bending in anchor rods.

Look in AISC Design Guide 1.  2 Methods for low to moderate shear loads recommended: if you do not mind some slipping of the baseplate to engage the rods then you can take all of the shear in just 2 of the anchor rods with the 0.8 factor Lion06 mentions applied to the steel, if you want to engage all 4 rods (assuming a 4 corner rod pattern) you need to use welded plate washers and then check the rods in combined bending/shear/tension as you have been doing. No 0.8 necessary when doing this.  


For higher shears there are several alternate methods including lugs (which I do not like for constructability issues), embedding the column base, or using angles welded to the side of the baseplate and post-install anchored to the concrete to take the shear.  

RE: Bending in anchor rods.

I'd say 75% of all the large industrial projects I have worked on had shear lugs in one form or another. Most firms I have worked with seem to set a nominal shear load that they will go without lugs on; say 5 or 10 kips.
I have had some problems in the past with "cross" or "T" shaped lugs....forming the grout pocket isn't fun and is screwed up half the time.
I have seen and used some details with a piece of HSS welded to the bottom of the baseplate. The block-out in the form work is easier to make and with a properly placed grout hole in the baseplate they usually go pretty well.  

RE: Bending in anchor rods.

Does this 0.8 factor apply to only the anchor rods or does it apply in a shear lug design also?
Been a while since I had to design a lug.  

RE: Bending in anchor rods.

Agree with Toad and Willis.

If column base has more than 5-10 kips, a shear lug is specified (typical for braced frames).  

Contractors may complain that it is 'hard' to do, or they don't know how to do it, but it is done everyday (more common in some regions than others).  They can either hang forms or cast in some foam block that can be chipped out later.  

Download AISC Design Guide 1 from AISC website which has step-by-step calc instructions and guidelines.

RE: Bending in anchor rods.

We have a different detail for braced frames to take out the shear.  I've never used a shear lug.  We provide embed plates with rebar designed for shear friction for the gusset to be welded to.

RE: Bending in anchor rods.

this might sound harsh, but if you have a contractor that can't form for a lug, you shouldn't have him on the team.  

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