Stiffening a Tube Column

[NewbieStruct]

How would you stiffen an existing tube column? I am designing an addition to existing building. An existing column is failing with the new loads. Is there a way you can stiffen an existing column? The owner does not want to incur shoring costs etc.

 

[rb1957]

can you improve the end fixity ?

can you strap on a two-piece jacket around the outside ?

round column ? can you add a square column to the outside ?
sqaure column ? can you add a round/octagonal/hexagonal column to the outside ??

 

[NewbieStruct]

It is a tube steel column (3x3 square)

 

[MiketheEngineer]

Weld some angle iron around the corners?? Weld stiffening "fins"

How much room do you have??

 

[dhengr]

NewbieStruct:

You don’t bother to say how it’s loaded, how it’s failing, it’s thickness, or what the cap pl. and base pl. look like and how they are attached; all important in addressing your problem. You might add 2.5" x .375" bar stock, or some such, to each face with stitch welding at the edges of the new pls. They must also be attached properly to the cap and base pls. You may still have to do some shoring at this stage to unload the existing column, straighten it, and attach the reinf’g. bars. Then, at this point, it might be just as easy to put in a new column.

 

[msquared48]

Depending on your connections top and bottom, I would consider adding another HSS3X3 to one side and stitch welding them together.

I would deload the existing column with shoring before adding the new member.

You could also drill two 1/2" holes at the top of the column and add non-shrink grout in the center of the tube too to stabalize the sides from local buckling. Overall buckling could still be a problem though.

Mike McCann
MMC Engineering

 

[rb1957]

if you support on the side, don't you still have the same column allowable ? (you've reinforced only one buckling axis)
but you have 1/2d the stress (by doubling the area).

adding plates to each side of the tube would help both ... reducing the stress and increasing the allowable.

 

[JAE]

I would look at welding on channels on two sides.

If your existing column is failing prior to yielding, then you can add the channels to increase stiffness and thus increase the maximum load up to yield (vs. buckling). In that case you wouldn't need to attach the channels to the base or cap plates at all as long as the 3x3 tube itself has greater capacity than the load based on yielding.

 

[ooox]

Can you reduce the effective length by adding a restraint mid span/ mid length?