Baseplates for round 1.5m diameter column

[GalileoG]

Hi all,

I am curious as to how one would go about designing a baseplate for a very large round HSS column with a diameter of 1.5m (that's about... 60")

Should I use one large square baseplate or a circular baseplate that's hollow at the center?

If option 2, how different can the design be? Can I still use the equations provided by the AISC guide if I were to go for option 2? If not, would FEA be the only alternative? I would like to do it manually though. Would Roark have a solution for this? <shrug>

All help is appreciated.

Thanks

 

[prsconsultant]

I have seen details similar to your condition for Stacks. Usually a single circular plate is used. Making it hollow would cost much more labor than savings in material cost.

 

[hokie66]

I would use the one big plate, but design it as a circular ring. The internal part will not do a lot, but not worth cutting it out.

 

[GalileoG]

Thanks for the responses.

The equations on the AISC design guide for baseplates will not apply, correct? Or can they if I make the right assumptions?

 

[SteveGregory]

I don't know what your reactions might be. Could you have an angle rolled to the outside radius of the HSS much like the flange for a circular duct or pipe? Then the vertical leg would be welded to the HSS and the outstanding leg would provide a bearing surface and anchorage point.

 

[csd72]

We do this type of connection all the time.

1. of you use a ring of bolts and model it as a solid circle then you will be able to derive the following formula for bolts tension:
Pbolt = 4M/ND where M=column moment, N=number of bolts, D=diameter of circle through center of bolts.

2. if you use a ring plate thats hollow in the center then all the bending in that base plate will become bending in the wall of the column. I doubt it would work.

3. We tend to use triangular gussets, twice as high as they are wide, to tansfer the load higher into the wall of the tube. We use one gusset per bolt for high moments or one per 2 bolts for lower moment applications.

4. The gussets induce a ring load in the tube near their top which needs to be checked. If this doesnt work then you may need a second ring plate at the top of the gussets to take the horizontal reactions. Formulas for these types of situations can be found in blodgetts 'design of welded structures'.