huangyhg

out of plumb column
a 3-story steel framed building that i designed is currently in construction. lateral resistance for the structure are braced frames.
we were called out to the site because at one location, a column is out-of-plumb 3" within the first story. the column does not appear deflected over this length, just leaning to one side. the building is already framed and floor slabs are in place. the movement was noticed when a stud wall was being framed in front of the column. architectural pilasters have been built around the columns on the second and third floors, so i can't tell if the column is deflected or out of plumb over those lengths. since the pilasters were built, i'm assuming that the column is reasonably (within aisc tolerances) plumb on the upper stories. i've requested the steel survey to see if this is the case. we have the foundation survey, and the footing is in the correct location.
i've analyzed the column for the p-delta effect caused by the movement, and it still works. i just have additional lateral forces i need to transmit into the rest of the structure. however, i believe i need to determine possible residual stresses in the column caused by bending. my assumption is that the movement occurred during erection and before the floor deck/slabs were in place. i'm hoping that the survey will confirm that. what is the best way to determine these stresses? i've modeled the column with imposed deflections - is this an acceptable approach? or should i specify some form of testing? just wondering what the typical approach is to this problem (if there is one).
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you need to wait for the survey. actually it is not too difficult to diy to get a first hand feeling. just use the plumb bulb, or laser leveling device, both can get from local hardware stores.
i probably wouldn't leave a 3" displacement stays in place, unless you can tell the owner that it isn't a defect, and it might eventually comes vertical again, once the building frame moves in another direction.
i wouldn't be surprised if there was one beam fabricated too long and one too short. i had a similar problem on an 11 story hotel.
as long as you can assure yourself that stresses are within allowables, it should be ok. i know of no testing that can be done.
once the concrete is poured, it is unlikely that the column will ever be moved.

is it possible to reinforce the column in a way which would remove or reduce the eccentricity? if so, that is worth considering.
ba
is this column stops below the beam, or it goes to the second floor? for the latter case with the column "leaning", how could the second floor not affected? and how the column splice could be made without some fitting took place, if it had occurred at time of construction?
are the columns one piece or is there a field splice? there is generally some play in the splices and this is how an erector can pull the columns back into plumb.
make sure the erector shims the column splices per aisc fabrication, erection and quality control, section m4, "fit of column compression joints".
thanks for the replies, it's very helpful.
the column is a single piece. as far as how the upper columns might not be affected - it could be that they are slightly out of plumb (relative to 3" that is); however they are covered by a masonry pilaster, so determining how much the are out of plumb seems difficult - without removing the masonry obviously. with the floor slab already placed, removing the column is not an option. my thought is to reinforce the existing column if it is overstressed, as baretired suggested.
my assumption is that the second floor beams tying into the column were fabricated incorrectly and that the column was pulled/pushed (with guys cables perhaps?) to connect the beams. so the column may just continue up reasonably straight (offset 3" from the proper location) on the upper floors. or perhaps the column was "pulled" back slightly on these floors and is just not enough difference for the mason building the pilasters to notice. just guessing since i wasn't out there when this piece was erected.
again, i'm hoping that the steel survey will shed some light on the subject. my main concern is that if the column was adjusted during erection, there are inherent bending stresses remaining in the section that i need to add to my p-delta and axial loads. at this point, i'm thinking that enforced displacements are the best way to model it and come up with the bending stresses.
to all - below is an answer that i received from aisc on this topic. wasn't sure if anyone had an opinion on this. my question is first, followed by the response...
i understand that as part of the direct analysis method, notional loads may be applied to a structural model to account for out-of-plumbness effects. however, how can one account for the stresses in the column due to out-of-plumbness? for instance, if a column is out of plumb for a single story, but is drawn plumb on higher stories during steel erection? it seems that there would be bending stresses present in the column; is there a point where these loads are negligible?
i think you've made an excellent observation. to my knowledge, the dam does not explicitly account for residual stresses due to pulling the frame into a plumb position. i have not seen this mentioned in any of the papers on the dam. however, consider that ei and ea are both reduced with a pretty substantial (and quite rounded-off!) 0.8 reduction factor that would seem to be enough to capture this effect.

brad davis, ph.d., s.e.
consultant
american institute of steel construction
866.ask.aisc

3" out of plumb?? wow!! hard to believe this was not noticed by the steel erector during erection. it would be hard not to to notice!!
what is the floor-to-floor height at this level?
i think your idea of using a forced displacement analysis is correct. my guess is the force required to displace a column 3" (assuming a 'norma' floor-to-floor height of something around 15 feet) is pretty substaintial, and will induce a considerable moment in you column
lkjh345 - floor to floor height is 14-feet. it is somewhat remarkable that the contractor did not notice it until the stud wall and pilasters were being built.
i'm thinking that you are correct in that aisc's answer assumed 'normal' tolerances. 3" in a 14 foot height is definately not normal.
is it possible that the steel is fabricated correctly, and the anchor bolts were set 3" over from their proper location? just a thought.
i think i would have a tough time living with leaving a column 3" out of plumb.
is it possible to shore up the floors and roof adjacent the column, cut the base plate free of the anchor bolts, and the pull base plate over till the bottom of the column is aligned with the upper parts of the column? thus removing the induced moment. just another thought.

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