Column Reinforcing

[ToadJones]

I know this has been a dead horse topic here.....

I am reinforcing a column (beam Column) with flange coverplates.
The column needs more flexural capacity.

I'd like to avoid using continuous welds.

The moment is concentrated at the top....imagine a pin-pin column with a concentrated moment at the top.

I'd like to hear others approach for engaging the coverplate and how far to continuously weld the coverplate at the top before I go to an intermittent weld.

I am inclined to design the end continuous weld for MQ/I with "M" being the full allowable moment capacity of the section.

 

[JLNJ]

Are you driving the load directly into the cover plates or does the load need to get from the column into the plates?

 

[ToadJones]

needs to get into the plates

 

[BAretired]

Provide enough weld at the top to fully develop the plate, then go to intermittent welding.

BA

 

[SAIL3]

Seems like there is still some life left in it...
Assume that conc mom at top is the only loading present.
I believe the formula for the total force in the weld is VQ/I.
In this case V is constant for the full length of col....now what??
There are two design inputs:
1/ What length of col requres this reinf....then add to this a
development length(aka BA's suggestion).....this is similar to
splicing a beam, but only looking at 1/2 of the splice.
2/ As BA suggested use cont weld to fully develop the cover pl and
then go to itermittent weld ...the size and spacing as per code
to ensure stability of pl., etc.

 

[slickdeals]

It should be 12MQ/I. See WillisV's response in thread507-160349

 

[ToadJones]

slick-
I think the "12" there is a built in unit conversion, so it is the same as my MQ/I, no?

 

[Lion06]

I always come back to just provide enough weld at the ends to fully develop the plate in tension (agree 100% with BA). It usually just isn't that much weld. I guess it can be conservative in some cases, but it also provides future flexibility to use to full capacity of the section and are not trying to calculate a load that is limited by the welds of a reinforcing plate to the WF.

 

[ToadJones]

Yea, the plates are 1/2" x 5" on both flanges.
Full yield would be 0.5" x 5" x 36 ksi = 90 kips per plate.

With a 1/4" weld, I'd only need 90kip/ (0.928 kips/in * 4) = 24"
Divided by 2 for fillets both sides and I'm looking at 12" of weld.

Agreed?

 

[Lion06]

Yes, agreed. Just as an aside, I typically wouldn't go less than 12" anyway. Just kind of a feel-good number for me (even if the numbers work to be smaller).

 

[Lion06]

You could probably use 1.392 instead of 0.928.

 

[BAretired]

How is the end moment applied to the builtup section?

BA

 

[ToadJones]

as an eccentric load on the column....