STEEL SLOPPED COLUMN 1

[mlevario99]

I have a project under construction where we have some slopped columns. They support a cantilever beam condition. The angle of the column is 75 degrees with the horizontal. The grid of the columns is in a radius. The height of the column, from the finish floor to the top of column is 23'-1" is a steel pipe HSS 8.625X0.322. It was noticed the columns is bowing, about 1.5", they use a string to measure. The top of the column has a cap plate with holes so it can be bolted to the beam instead of welded. To me, it seems like during erection the column was forced a little so the holes could fit. I am suggesting to shore the beam, remove the bolts and allow the column to move so it can be straight, then weld the cap plate to the beam flange.

Any opinions on why the column bowed?

I am including some pictures of one column.

thanks

 

[SWComposites]

Has column buckling been checked? For both construction loading and design loading? What is the buckling margin? It looks quite slender.

 

[mlevario99]

They did run a string and is a bow, not a kink.

The other end of the beam is a shear connection.

Kootk sketch makes sense, if the cap plate of the column was not horizontal when they installed the beam on top of the column, and they installed the bolts this will make the column bow the way is bowing.

thanks for all the comments.

 

[Eng16080]

The bean in the picture is a W24x55, with a 17'-6" back span and a 6'-0" cantilever, the column is a HSS 8.625 x 0.322. So, no, the beam is not undersize nor the column.

Presumably you actually checked that the beam and column are not undersized. I wouldn't just assume they're adequate (which is how your comment reads to me).

Not sure if it's related to the issue, but that's a very slender beam section. I wasn't aware they made 24" deep beams that light. Just had to look it up.

 

[cliff234]

Quote (XR250)
If this was load induced curvature, presumably this would an issue whether the column was straight or slanted. If so, why don't we see this more often?

I suspect that it is easier to accurately make square cuts in members versus skewed cuts. I've seen a few pretty interesting kinks in diagonal braces over the years due to the detailed connection angle being slightly off from the actual angle of the brace. That's why we don't see this problem with square connections.

 

[human909]

I think almost everyone above has pretty much nailed this one. Fixity and/or curvature induced due to installation tolerances.

If this was load induced curvature, presumably this would an issue whether the column was straight or slanted. If so, why don't we see this more often?

I have seen this before and it was much more severe than this. It was cause by unintended fixity. (Again, a slender hollow section connected to a continuous beam.)

At a hunch, I'd expect that there is plenty of reserve strength still here due to the fixity and it isn't a strength concern. The bowing doesn't look great but it is likely structurally sound.

Still a fix might be necessary for cosmetic reasons. I'd look at releasing fixity AND/OR providing a stiffer column. The latter may be not an option as it seems to be embedded in concrete. So release the fixity and possible move the point of support by a 10mm or so.

 

[SWComposites]

Well I would make darn sure there isn't a buckling (beam-column instability) issue with the column in its bowed condition.