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Uplift on Base Plate

Uplift on Base Plate

Uplift on Base Plate

(OP)
I can find a lot of references on designing base plates for compression and/or for bending, but not anything for uplift case only. Or any reference for plate bending with point loads(bolts) placed at different locations on a plate with one fixed edge? I have to check some already installed plates

RE: Uplift on Base Plate

Some of the checks you are seeking are under the prying aspect on hangers, equal till the root... a inverted hanger is your case. So whenever the bolts and plate thickness are safe in the hanger setup it will be for your plate, but of course you will need to check the fixity one way or another. Welds you can dimension for the particular weld arrangement by Pilkey or other reliable source to size the welds. Then the other more important check is plate capacity for the -if necessary- prying enhanced forces at the bolt points.

How to treat the prying action you can see in the AISC Manual but for not too thick plates some use 125% of the standing tension.

Also, sometimes is more logical to transfer the tension in shear than in bending action. To such purpose you fillet weld fins to the column and bolt down between the fins against the foundation.

In all your design problem also happens for the tensile side of weakly loaded columns where flexion predominates.

RE: Uplift on Base Plate

Check out the following reference for anchor bolts and uplift.

AISC Steel Design Guide Series - Column Base Plates by J. T. DeWolf and D. T. Ricker.

Analysis and Design of Structural Connection by L.H. Martin

RE: Uplift on Base Plate

I have found the CONDOR Technical Report TR 34/80 "Yield Line Analysis" helpful for the checking of base plates under bolt loads.  This report develops the maximum bolt forces for particular bolt patterns, plate thickness and edge fixities based on work by Burridge and others.  

It is also useful for beam splice joints.  Appendix M of the New Zealand steel code NZS 3404 Part 1 has also some guidelines.

If you need something in a hurry, I could fax a copy of the CONDOR stuff to you.  So you would have to provide a number etc.


RE: Uplift on Base Plate

If you really want to go into details analysie the baseplate with a finite element program.

A plate with connected with the representative of the column etc. It is quite simple and if you have done it once you could alter the file for the future.

I know that there is a FEA based baseplate design program available. Look for it if you need a more frequent detailed analysis.

Cheers,

Kocos

RE: Uplift on Base Plate

(OP)
I checked the book by Dewolf, and the uplift case only doesn't fit for my situation (4 bolts outside column flanges instead of 2 inside) maybe I have an older version?Is Condor T/R a New Zealand publication?

Anyway, I am going to try the hanger approach, I originally considered it but didn't know if it was accurate for such thick plates (>1").

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