Out of plumb column

[drewtheengineer]

A steel column was installed out of plumb (1-1/2" in 8'-6&quot. I know this is out of the L/500 allowable. Does anyone see a problem with analyzing the column as is (in other words checking the increased load due to the angle, shear through the connections at the top and bottom of the column and additional load through floor diaghram above). Is there any code or standard shooting this method down?

Thanks,
Drew

 

[austim]

I would encourage you to just go ahead and reanalyze the column as it has been built. If you want to be slightly conservative, add the 1/500 tolerance to the measured inclination in your design model.

Surely there can be no regulation that prohibits non-vertical members? eg, you can find fancy architected bridges with inclined piers in many locations.

I would take the tolerance on verticality to apply only to members that have been assumed to be truly vertical for the purpose of analysis and design.

 

[jheidt2543]

I agree with Austim's response, but I am curious - why not straighten the column? Shore the beam on both sides, cut the connection, straighten the column to vertical and reconnect it. Problem solved! I shouldn't take but have a day.

 

[drewtheengineer]

Thanks guys.

Jheidt2543, that's what I would do, however, the steel column is actually a fix to an existing concrete column that was originally installed out of plumb. The steel wraps around the concrete. The owner does not want to shell out that kind of money.

Thanks again for the help.

Drew

 

[BPike]

Don't forget to account for the horizontal loads that are generated by the column being out of plumb - these may be significant.

 

[drewtheengineer]

BPike,
Yeah, the axial load was insignificant. The horizontal load was my concern but did not amount to very much after all. Thanks.

 

[FinnB]

The way I would look at an out of plumb column is as a truly vertical column with the axial load applied at an eccentricity equal to the distance the column is out of plumb.This gives an axial load and an applied moment due to eccentricity. Design for axial and moment and you are OK. The connection between the concrete and steel coumn also has to be designed to take account of moment.

 

[BantrelStructural]

It would actually depend on whether the lateral load restraint system was a moment frame, (particularly if this column was a participating element), or some other system like shear walls or bracing. If for example the column was part of a line of columns that were braced, and ignoring beam connection eccentricity, then this column would be acting simply as a compression strut, and any lateral forces generated as a result of the incline would be handled by the bracing. On the other hand if this column were part of a moment frame bent, then the out-of-plumb could cause P-delta affects on the column, possibly increasing moments (it could also reduce them depending on which direction the principle sidesway moments are occuring on the column).