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Re: Twisted column

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Hi Drew,

Have you considered to make the column composite? Either encases, which might be a bit more costly by having rebars, ties outside the steel column encasing it or by making it to be inside a CFT (concrete filled tube). You can cut the pipe in half, if needed put some shear studs in it where the pipe faces the web and put the two halfs outside your damaged column and fill it with concrete from the bottom. The composite solution will be good for the future also since the composite CTT with the old column at its core, can take future hits and not get too much damage. The concrete inside will prevent local buckling of old column as well and will be able to transfer the load of the column even with the current damaged condition to the CFT column. As you have mentioned, the twisting of the existing column is also of concern which can make the flexural torsional buckling a possibility for this open shape with relatively thin elements. The problem I see with replacement is that first of all you need to support the load during the removal and replacement process and that can be quite costly and time consuming , but, more importantly you need to redo the connections, including the top and base connection and the one in the middle, that also can be quite costly in time, design work and money.

Best .

 On 5/15/2013 10:56 PM, h.d.richardson(--nospam--at) wrote:

As I see it there are at least two alternatives.

Plan A:
Either load test the column or find some fancy computerized (finite element, maybe?) to assess the adequacy. Either may be expensive and you may still have to carry out a repair.

Plan B:
Do a simple hand analysis to assess how much "safety margin" there is; and, if you are not satisfied with the results do a repair using the money you saved by not following Plan A. You said it was a pre- manufactured building, therefore, it probably has very little "safety margin". If so a repair may well be required.

My suggested repair would be to box it in using 1/4" or 3/8" plate (stitch welding should be OK but that's up to you) and fill it with concrete. The resulting column should be many times stronger and more torsionally rigid and be much more resistant to "dents and dings"

Truncated 1572 characters in the previous message to save energy.

Abolhassan Astaneh, Ph.D., P.E., Professor
Department of Civil and Env. Engineering
781 Davis Hall, MC 1710
University of California,
Berkeley, CA  94720-1710,  USA

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