Out of Plumb Steel Column

[jim57]

Asked to look at a 4" square column in a single story store. Column supports a header is about 12' tall and out of plumb about3/4". This does not meet the l/500 criteria. Are there any other codes or analysis to determine if this is a concern. I'd like to try and leave it as is ,but need to prove it is ok with calcs

 

[BAretired]

If the column load is P, then the lateral force applied to the roof is 0.75P/12 = 0.0625P assuming pin ends on the column. If the roof can sustain that lateral force without excessive deflection, it should be okay.

Edit: This is not quite right. The lateral force should be (0.75/12)P/12 = 0.0052P. The first 12 is to change 3/4" to feet. The second 12 is the height of column.

BA

 

[jim57]

Not certain how the load is applied to the roof for deflection. The column is supporting a lvl that supports the roof. Also is the .75 the deflection and the 12 for 12' ? Should we convert the units? Thanks for the quick response. Still not certain how to present his to the building dept. Thanks

 

[MotorCity]

Other than aesthetics, does the out of plumb present a problem or serviceability issue? If not, I would consider leaving it. To prove it is ok with calcs, you need to determine the end fixity. If you assume pinned ends and the column is inclined, it will act like a diagonal strut similar to a web member in a truss. If you decide it has a fixed base, you will have a p-delta effect to consider.

 

[jayrod12]

The 0.75 in BAs calculation is the 3/4" out of plumb you described. Perhaps if you sketch what the connection is like at the top of the column including connection details from the beam to the supported roof members we can comment further.

 

[JAE]

...and clarify if the out-of-plumb direction is parallel to or perpendicular to the LVL beam it supports.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[XR250]

If the bottom of the LVL is not braced laterally and the slant is perp. to the LVL, then it will want to twist it unless you put a huge saddle on top and then the moment ends up in the column.
Kinda of what BA stated.

 

[BAretired]

My earlier post was incorrect. See edit.

BA