Fluted steel column capacity

[gcs3pe]

The 8'6" steel fluted column in these pictures is in service in the top floor of an old factory (1900+/-) building that was converted into condominiums in the early 1990s. It supports the roof structure of the building, but a client is hoping it's got the capacity to support one corner of a new roof deck.

Anyone got an idea where I might find the structural properties of such an item? (crickets chirping) And if not, anyone want to tell me how they'd approach calculating its capacity?

There are no markings on the column other than the fluting and the decorative top to tell me what kind of steel it may be. It could be wrought iron for all I know, but shows no grain or texture.

 

[gcs3pe]

second pic

 

[gcs3pe]

third pic

Thanks!

 

[Teguci]

Install shores around the column but leave a small gap between the shores and structure.

Load up the structure to simulate live load and safety factor.

Measure the deflection difference and verify that there is still a gap (column is still taking all of the load).

 

[JStephen]

I was reading a brochure on the architectural history in Waxahachie, and it mentioned one of the buildings having cast-iron columns. Is that a possibility for this piece? (Not that it helps much to know that!)

 

[ishvaaag]

Really it has all the looks of cast iron. There are some old books of the era that give values, will try to find some pdf that I may have.

 

[ishvaaag]

Whilst looking for such pdf, not as old but from a Construction Materials book from the seventies',

Cast Iron

Modulus of Elasticity at 75% of limit load, (must be tangent modulus) between 700000 and 1300000 kgf/cm^2

Breaking (limit) stress 150 kgf/cm^2 tensile action
Breaking (limit) stress 600 kgf/cm^2 compresive action

Working stress factor, as recommended by no less than PONCELET and Morin, 1/5 to 1/4 of the limit breaking stress, so

Allowable stress (tensile) 30 to 37.5 kgf/cm^2
Allowable stress (compression) 120 to 150 kgf/cm^2

What above as per
Materiales de Construcción
Antonio Camuñas, Guadiana de Publicaciones 1970

Quite likely the above values of the safety factors had some consideration, yet, not knowing, better not count on it, or start from breaking stresses and adjudicate your own safety factors anew and some statement of buckling effects.

 

[ishvaaag]

... some consideration of buckling, I was trying to write.

 

[ishvaaag]

for 2.7 m tall doubly pinned
(both laterally X and Y in plan restrained hinges)
7.5 to 7 cm diameter cast iron column

L/1000 initial imperfection, Pn=13.58 tonne
L/500 initial imperfection, Pn=6.96 tonne
L/200 initial imperfection, Pn=2.82 tonne

limit axial loads as per some updated check more or less to modern codes ...

column strength reduction factor to be multiplied and be checked against factored loads ... not a good prospect.

 

[hokie66]

Looks like some of the cast iron columns I have seen. The third photo seems to show that the column has already been extended in the residential conversion. I would be concerned with instability at that point.

 

[ishvaaag]

A downloadable great book on the matter

http://gallica.bnf.fr/ark:/12148/bpt6k91011q.r=Résal.langES

 

[csd72]

Definately either wrought or cast iron. Steel doesnt work very well cast into those types of shapes.

 

[JStephen]

See the attached scan, from Eshbach's Handbook of Engineering Fundamentals, 2nd Edition, from 1952.