Anchor Bolt Tension in BP subject to Moment 1

[RRBegin]

Can someone point me to a sample calc for determining the tension force in an anchor bolt for a base plate subject to overturning forces? I need to determine if an as-built arrangement of four 1/2" diameter anchor bolts is adequate. I already did a quick check using a simple couple to determine the tesion in the bolts and they appear inadequate; I would like to do a more rigorous analysis (moving neutral axis) but don't have any reference material in my current office. I seem to remember my old Gaylord and Gaylord Steel Design text having a simplified method.

Anyone...anyone...Bueller...?

Thanks
Ron

 

[civilperson]

Using only the bolts is conservative, one side in tension and the other in compression. Divide the moment by the bolt spacing to find the tension and combine with any shear for analysis.

 

[Lion06]

civilperson-
I believe that is what he already did with his "simple couple" analysis.

RRBegin-
I would refer to you AISC Design Guide # 1. A new version just came out, but even if you have the older version it should give you what you are looking for. The main difference between the new and old one is that the new looks at rectangular compression block rather than the more traditional triangular compressive stress diagram. The new one is also more suited to LRFD.

 

[RRBegin]

Thanks, folks. As I noted, I do not have any reference material in my office and was hoping to look at these today. I was hoping someone had posted a pdf or could point to a sample on line that I could follow.

I will dig through my reference material in my attic when I return home and pull out some of my old stuff.

 

[civilperson]

Alternately, on the compression side, use the allowable concrete bearing stress as a rectangular block to find the centroid of the compression. The distance from the centroid to the tension bolt is the distance for your bolt couple, (this is a iterative proceedure requiring Tension equals Compression).

 

[COEngineeer]

i think simpson has a program already that covers appendix b.

http://www.simpsonanchors.com.

There are a lot of different failure scenarios that is a pain to do it all by hand.

 

[PackerFan]

Here is a sample calc based on a 2500 lbs tension load and a 9000 lbs-in moment using a 3/8" diameter anchor. This calculation assumes that the base plate will be in compression due to the moment. These equations are just developed using free body diagrams. This will give you the distribution on the anchors and the resulting compression on the concrete. This was sent as proof to Hilti's calculation method used in PROFIS.

http://www.mytempdir.com/1280576

 

[PackerFan]

Here was the output in question if you are interested.

http://www.mytempdir.com/1280584

 

[RRBegin]

Thank you, everyone.

PackerFan-can you send me your post directly? I work for a federal agency and they have blocked the url where your sample is posted.

The address is RONunderscoreBEGINatFWSdotGOV

 

[Lion06]

Since COEngineer mentioned PROFIS from Hilti, I have to ask the question. Why would they do that?
My ACI 318-05 clearly states in D.2.2 on page 381 - "....Specialty inserts, through bolts, multiple anchors connected to a single steel plate at teh embedded end of the anchors, ADHESIVE OR GROUTED ANCHORS, and direct anchors such as powder or pneumatic actuated nails or bolts, are not included......"
Does anyone see this including Hilti or Powers adhesive anchors in appendix D?

 

[desertfox]

Hi RRBegin

Have a look at this site for your bolted connection problem
with a moment applied.
I cannot open your calcs so I can't comment on those.

http://www.roymech.co.uk/Useful_Tables/Screws/Bolted_Joint.html

regards

Desertfox

 

[WillisV]

StructuralEIT - because mechanical expansion anchors ARE included in Appendix D. Simpson also has an Appendix D calculator. Very few post-installed mechanical anchors currently meet Appendix D specs - two of those that do are Hilti HSL-3 Heavy Duty and Simpson Strong Bolts. For adhesive anchors you are correct its still back to the manufacturer's catalog.

 

[PackerFan]

Currently the only products that can be used with cracked concrete and App. D are Hilti (Kwik Bolt TZ, HSL-3, HDA) and Simpson (Stong-Bolt, however, no ICC report yet). You should see the first adhesive anchors approved for App. D within the next couple of months. You will need to go to

http://www.icc-es.org

to get the ICC report, that document will have the design information to use App D.

 

[RRBegin]

Thanks, again. PackerFan has provided a sample.

Ron