Steel column below slab-on-grade

[priya15]

Are there any concerns with extending structural steel columns (Fy=50ksi) below grade? The footings on one side of the building are 7 feet lower than the rest and so, I am taking my steel columns to the footing while the slab on grade is 7 feet above the top of footing. Is there anything I should worry about? I am specifying hot dip galvanizing for my steel columns. Do I have to provide a concrete enclosure?

 

[jike]

We, typically, would provide a concrete pier to support the column just below the slab-on-grade. I suggest either full concrete encasement or some kind of durable, high quality, corrosion protection on the steelfor the exposed steel section below grade.

 

[StructuralEngGuy]

I agree with Jike. I always provide a concrete pier running from bottom of slab to top of footing.

 

[rowingengineer]

I would suggest painting the column for about 0.3m above and below the SOG surface, with some high level epoxy paint to reduce corrosion at this interface.

When in doubt, just take the next small step.

 

[Ron]

If you are going to encase in concrete, don't galvanize it. Other than that, no structural issue to preclude taking the column to the footing.

 

[demayeng]

Ron, why wouldn't you galvanise it?

I just saw a concrete swimming pool that specified galvanised bars in the splash zone..