Column Base Plate Repair/Retrofit?

[jheidt2543]

I have been checking some base plates for some 5" dia. STD pipe columns. The base plates were all fabricated at 3/4" thick, but my calculations show six of them should have been 1" thick. Unfactored loads are P = 1.0 kip, V = 0.85 kip and M = 7.5 ft-kip.

The plates are anchored on a 9" thick post-tensioned slab and very in size to allow the anchor bolts to miss the post-tension cables. The thickness is determined mainly by the moment load and the size of the plates. The columns are not centered on the plate.

Now the question is how to repair/retrofit the six plates. Because of ARCHITECTURAL features applied to the columns cuting the plates off and welding a new base plate on is a LAST resort. I'm considering welding a two piece 1/2" plate over the top of the existing. The welding would be plug welds through the top of the plate onto the base plate and welds around the permiter joint of the two plates.

Comments? Suggestions? Or do I tell them to bite the bullet and cut off the 3/4" plate and weld a 1" thick one on?

Who ever said structural engineering is mundane?

 

[lkjh345]

I take it the pipes must be fairly ecentric from the bolts to force that thick of plate with those small of loads.

Can you weld vertical stiffeners between the pipes and the base plates?

They would decrese the length of the moment arm in the base plate and bring the required thickness down.

 

[jheidt2543]

Vertical stifferns was a thought, but the Architectural column covers seem to be in the way. Yes, the loads are not the high, but the eccentricity of the column on the plate in these cases kicks up the thickness.

 

[kslee1000]

Weld collar plates at the column base, make sure full contact with bearing plate.