Non-Load Bearing Concrete Column Reinforcement

[Bestdarnengineer]

I'd like to get someone else's opinion on this topic. I'm currently looking at detailing a concrete column encasing a steel column supporting roof load. The wrap is about 3'-8" square only extending above the curtain wall so it terminates below the roof elevation. I can design it per ACI 318 and reduce the steel to 0.5%, but I'm trying to prevent the questions bound to arise with that much rebar and ties in a "oramental" feature.

Has anyone come across this sitution that could provide insight? I'm primarily concerned with crack control and would prefer not to kill a fly with a cannon.

 

[hokie66]

If the steel column is supporting the roof and the concrete is not load bearing, it sounds to me like it is a beam, not a column. In that case, your main loads on the cantilevered concrete beam may be due to thermal movement in the roof structure. Without a better idea of your situation, that's the best I can do.

 

[azcats]

I'll preface this by stating that I haven't done much with concrete in years.

I would agree that the concrete is more flexural in nature. 318-05 had a section stating that the minimum reinforcing for flexural members could be ignored if you provide an area of steel 1/3 greater than required by analysis.

It might even be a good idea to isolate it from the column via foam, an inside permanent form or sonotube. You could reduce your area and also not have to worry about interaction with the column.

 

[Bestdarnengineer]

hokie66 and azcats - Thanks for your replies. Designing as a beam and providing a bond breaker between the concrete and steel is a very logical approach. Since these concrete elements will be highly visible, I'm thinking I'll design it as a beam with skin reinforcement and include closed stirrups as a precaution. I was mainly trying to get away from using 22 #6 bars in something that wasn't supporting any load.

 

[kieran1]

I’m not familiar with the ACI code but surely if the concrete is non load bearing and only encasing the structural steel column then small gauge wrapping mesh would suffice??

Kieran

 

[csd72]

agree with kieran,

structural codes apply to structural members only.

a few bars through holes in the web to stop it sliding down and then a small gauge mesh to minimise face cracking and to hold it together

 

[ILstructural]

At the recommendation of a local batch plant, we've been specifying self-consolidating concrete for architecturally exposed columns.