Free-standing reinforced Beam-Column

[Robvh1984]

I am designing a free-standing beam-column that is supporting a piece of the world trade center for a memorial. It is 8" thick roughly 14.5' high. Klu/r is roughly 150. (fixed base & r=.3h) How would I go about designing this member? Should I consider it for sidesway? All beam column examples I see only have the moments applied at the tops and bottoms of the columns. My moments (lateral wind and eccentricity from the piece of steel) are not exactly at the top. Attached is a pdf of memorial.

-Robert Miller, E.I.T.
KPA Structural Engineers

 

[ishvaaag]

You can proceed along the AISC guidelines for design in AISC 360-10 Chapter C, mainly section C2.

Essentially you need to consider initial imperfections, both in-member P-delta and structural P-Delta, better subdivide your column in segments for a more ensured consideration of P-delta effects, use a reduced stiffness, and use beam column checks from the code.

 

[JAE]

Is this a pair of concrete walls that are supporting the piece of steel?

It looks like perhaps one of the walls actually supports the steel and could be designed as a concrete beam/column. Simply apply your loads and check the Pu and Mu combinations of values at various heights for a rectangular column.

 

[ishvaaag]

That is, JAE, ewinforced! I found strange not finding the (steel) beam-colum in th sketch. By the sketch it looks as stiff as to safely proceed as you indicate.

 

[Robvh1984]

The beam-column is the pair of concrete masses. My main concern is the P-delta effect and how to assume bracing or limit deflection to make P-delta negligible.

-Robert Miller, E.I.T.
KPA Structural Engineers

 

[ishvaaag]

If so massive P-Delta must be small. But you can always subdivide the column in segments of reduced flexural stiffness, particularly if the solicitations are to such level that such reduction of stiffness is to be present, this way you will be capturing most of the effects of the structural and in-member P-Delta with one P-Delta able program, or you might work iteratively with one that is not. Start from some bad geometrical imperfections and then you can check the segments after the stable equilibrium with the ordinary equations. Respect the stiffness ACI 318 used to have statements on how to proceed depending upon the hypothesis being considered (I don't practice by it, in Spain).

 

[csd72]

Are these precast panels? If so then someone will need to check them for lifting stresses and anchorage loads.

Due to their thinness I would treat them as walls and see how that works.

For this level of load I would normally ignore the axial load and check for bending only. Pdelta effects require a significant P, which you do not seem to have.

Also ensure that you have allowed for people hanging off this thing in your calculations - it will happen.