steel baseplate design 1

[MiguelD]

I AM TRYING TO DESIGN A STEEL BASE PLATE FOR A COLUMN CONNECTION BUT I AM HAVING TROUBLE FINDING A DESIGN GUIDE. CAN ANYONE GIVE ME THE TYPES OF THINGS TO CHECK FOR AND FAILURE MECHANISM AND A POSSIBLY A DESIGN GUIDE TO FOLLOW.

PU= 10 KIPS
VU= 4.5 KIPS
MU= 53 KIP-FT
4 ANCHOR BOLTS
4000 PSI CONCRETE
PROPOSED 16X16 BASEPLATE 1/2" THICK
POSSIBLY AN HSS 10"X10"X3/8"

ALL HELP IS APPRECIATED I AM A RECENT GRADUATE AND NORMALLY I WOULD ASK MY LEAD ENGINEER BUT HE IS ON VACATION AND THE OTHER LEAD ENGINEER IS NOT THE TYPE ONE ASKS QUESTIONS TO.

~md

 

[Lion06]

AISC's Design Guide number 1 is for Baseplate Design.
It has several useful examples.
If you or someone in your office is a member of AISC, you can download it for free from

http://www.AISC.org

 

[COEngineeer]

Go to the index of your steel manual and find "Column base plates". It should have an example too. Dont forget to do appendix D (aci318) for the anchor bolts calculation. Good luck! It is not easy to swallow in one day.

Never, but never question engineer's judgement

 

[Lion06]

You have a very small axial load and a large moment. I am showing you need a 1.25" thick baseplate and likely some large anchor bolts (I am coming up with something on the order of almost 22Kips of tension in each of 2 anchor bolts).

 

[MiguelD]

THANKS FOR THE SUGGESTIONS I CHECKED THE NEWEST STEEL MANUAL I COULD NOT FIND AN EXAMPLE I WILL KEEP LOOKING THOUGH. I ALSO CHECKED THE AISC WEBSITE FOR THE DESIGN MANUAL BUT AISC IS CURRENTLY REVISING THIS MANUAL AND I COULD NOT GET IT. I AM NOW LOOKING TO USE A TRANSFORMED AREA METHOD AND TREATING THE BASEPLATE AS CONCRETE BEAM WITH THE ANCHOR BOLTS AS THE STEEL.

 

[Lion06]

I don't beleive AISC is redoing that DG. The second edition of it just came out a couple years ago.

 

[rulljs]

AISC is in the process of writing a rev. 3, I called and spoke with them about it a few weeks ago and it didn't sound like it would be available until next year sometime. (maybe not until September if I recall correctly)

Also, I was not able to get a copy of rev. two and was told it was not available on the site anymore due to some errors in the publication.

The person I spoke with was very knowledgable on the subject and not only provided me with the above information but was also able to answer the question I was planning on using the guide for.

 

[MiguelD]

IT APPEARS THAT THERE WERE SOME PROBLEMS WITH THE SECOND EDITION AND THEY HAD TO PULL IT OFF THE WEBSITE. THEY ARE ONLY REDOING DG1. AT LEAST THATS THE INFO I GOT WHEN I TRIED TO DOWNLOAD IT.

DOES ANYONE HAVE ANY EXAMPLES I CAN FOLLOW WITHOUT INFRINGING ON COPYRIGHTS?

 

[COEngineeer]

page 14-17 on 3rd edition has examples. Not sure why you cant find examples.

Never, but never question engineer's judgement

 

[MiguelD]

I AM USING THE 13TH EDITION BUT I FOUND IT ON THE 3RD EDITION ON THE PAGES YOU HAVE SPECIFIED THANKS! HOWEVER THESE ARE FOR AXIAL COMPRESSION AND DO NOT TAKE INTO ACCOUNT FLEXURE.

 

[msquared48]

MiguelD:

Better go by the design example when youfind it as there is a prying action that is incorporated into those equations that are not included in the transformed area/concrete beam method you speak of. BE CAREFUL HERE!!!

Mike McCann
MMC Engineering

 

[asixth]

I'll assume the base plate doesn't provide and rotational fixity, so I would check bolt shear for any horizontal thrusts that result... tearout as per ACI318 Appendix D for uplift forces... and punching shear if your base plate is located on a suspended slab or similar.

As for the lead engineer that doesn't want to mentor graduates, I think they should have a good hard look at themselves and ask themselves why they are a "structural engineer" for, there are no "i's" in "team". I found myself in the same postion when I first graduated and it was incredibly frustrating, almost to the point where I thought I was absolutely wasting my time and felt my development lagged a bit because of it.

 

[MiguelD]

asixth i wholeheartedly agree with you sometimes i do feel like you just described. Thankfully there are other engineers here on the forum that can help and also i am thankful we have a really good new structural department head at my company the only bad part is he is usually busy and i don't like bothering him to often. As a young engineer though I would like to urge senior engineers to take time to mentor the new generation because if they dont we are going to have a new generation of engineers who can use software but have no actual knowledge of the workings of that software and frankly that thought scares me.

 

[edwin17th17]

guys what do you think about the argument that only 2 bolts should be considered for shear since base plate has oversized holes..

 

[COEngineeer]

If your base plate is for taking a lot of shear, then you probably want to weld the washer to the base plate.

Never, but never question engineer's judgement

 

[Lion06]

I agree with COEngineer. If you need the anchor bolts for shear, then weld plate washers with standard holes to the baseplate after the column is erected.
Be sure to check the anchor bolts (including the concrete failure modes) for combined tension and shear if you do that.

 

[edwin17th17]

you did not get my questiion...

what im saying it is standard practice in my company to check the actual shear against 2 bolts only not 4.. this is due to oversized holes.. baseplate are always oversized for erection purposes..

we dont weld washers we use shear lug if shear is too big..

 

[nutte]

Edwin, without welding washers to the base plate, and with the super-oversized holes used, you should count Zero bolts for shear, not 2.

 

[KCRatnayake]

For the calculation of anchor bolt group shear capacity, ETAG Annex C suggests that only row of bolts that closes to the edge of concrete element will take the full shear load. Not to mention that the applied shear load direction plays a vital role in calculating the concrete shear capacity in bolt groups.

By welding washers to the baseplate, we can enhance the concrete shear capacity which may be critical. Also, it enhances the bolt group shear capacity with regard to the steel failure.

 

[LobstaEata]

A good friend of the engineering community (Alex Tomonovich) has been kind enough to share many of the spreadsheets he has developed over the years. Attached is one of his spreadsheets for steel baseplate analysis based on the ACI 318-99 code. It's a little dated, but still should be adequate for a preliminary design. It should also provide you with a good "go-by" for learning and may be used as a basis when you compare against the latest code provisions. Hope this helps.