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Anchor Bolt Embedment

Anchor Bolt Embedment

Anchor Bolt Embedment

I am trying to find the calculation to figure out the minimum embedment needed.  A project of ours has had the foundations poured and the GC noticed that all the Anchorbolts are extending anywhere from 5-1/2" to 8-1/2" above finished grade when only 3" was specified.  All Bolts were suppose to be 1'10" embedment and know they are not.  How do I go about figureing out if the 1'10" was the minimum depth needed.  I normally dont deal with the anchor bolts but the guy that does is on vacation.

If you have any information I would appreciate it.  


RE: Anchor Bolt Embedment

You can start by looking at the area of a 45 degree shear cone from the base of the anchor bolt, multiplied by the square root of the f'c of your concrete mix (and your proper load factor), or what the mix has presently cured to.  If that force is greater than your factored or unfactored pullout force, then you're ok.  If not, consider adding afterset bolts or epoxy anchors.

Another thought, with the bolts that high, how will you tighten the bolts to the steel or wood plate?  Usually anchor bolts are not threaded the full lentgth unless they are threaded rod.

Mike McCann
MMC Engineering

RE: Anchor Bolt Embedment

You'd really need to go back to the design calculations and see what was figured.  You can go to ACI-318 App. D, but even there, it would help to have the original calcs to work off from.

RE: Anchor Bolt Embedment

We did not do the original calcs for the embedment and the company who did is no longer in business.  The clients do not have a copy of the calcs either.  I wish they did.   

RE: Anchor Bolt Embedment

What kind of a building is this?  Steel Mainframe?

Mike McCann
MMC Engineering

RE: Anchor Bolt Embedment

Sounds like a pre-engineered building. Thread problems aside, 16+ inches of embedment remaining sounds like a lot. Once you have a look at the loads and the bolt stresses I bet you will come out OK (unless it didn't work in the first place!).

RE: Anchor Bolt Embedment

Depends on the loading and the type of anchor bolt/rod.  If they are tensioned and are 'J' type bolts, you may have a problem.  If they are for nominal loading, you likely don't.  'J' bolts don't have as much capacity as headed bolts.  If headed bolts, then depending on the diameter and proximity to eachother, it should be easy to calculate.


RE: Anchor Bolt Embedment

Call the contractor and find out the length of the anchors ordered.  Then subtract the projection from this over all length to get the embed length. Follow appx-D of ACI-318 to calculate the actual anchor capacity.  

RE: Anchor Bolt Embedment

It is a Pre Engineerd butilding.

They are J bolts and in some areas have uplifts of of 35 kips.  The main area I am concerned with has a 30 ton crane as well as a 15 ton crane next to it.  In these areas the base plate distance from center to center is only 18".  There is also anywhere from 1/2" to 1" bolts throughout the building.

Does anyone have a "easy button" just lying around.

RE: Anchor Bolt Embedment

Like the good advise given before; you'll have to check with the contractor on the overall lengths of the bolts ordered and calc you embedment strength based on ACI 318-Appx D.  Also you may want to verify the grade of anchor bolt used and check it against your up lift requirements. The contractor should be able to tell you what grade of anchor bolt was installed.   

I lent out my "easy button" and it wasn't returned.  

RE: Anchor Bolt Embedment

Thanks for all the information.  I got it figured out.  I think

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