Extending Existing Column B.F.F.

[waytsh]

I would like to bounce this off you guys. I need to lengthen an existing column and preliminarily I am thinking of using the attached detail. Is there a better way to do this? If I do go this route I am not sure how to check the stresses in the base plate and the new splice plate when they are welded together in this manner. Thoughts?

Thanks in advance.

 

[KootK]

Just axial load? If so, I think that your detail's a good as any. And I'm not sure that there would be meaningful stresses on the cap plate and welds. That said, I'd be inclined to make the cap plate of a similar thickness to the flange thickness of the columns and then add welds that seem reasonable given those thicknesses.

 

[waytsh]

KootK,

Thanks for the quick response. The base of the column is pinned and the top fixed so there is some minor moment and shear demand at the splice location but it will be primarily axial. I agree with your assessment regarding the stresses in the splice plates. It doesn't seem like it should be a problem if the extensions are minimal and the plates adequately thick. I would still be curious if someone knows how these are analyzed for my own curiosity.

Thanks again

 

[KootK]

1) If it's not possible to have the joint finished to bear, the welds might need to transfer the axial loads coming through on their own.

2) For plate thickness, perhaps one assumes a misalignment that would have the flanges not overlap and design the plate to be able to at least handle that shear demand.

 

[wannabeSE]

Don’t forget to think about the order of construction. It might be impossible to construct with cast in place anchors if the new pier is placed first and a shop welded extension is used. Do you plan on having the bottom base plate field welded to the stub column.