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RE: Min. Steel in Concrete Column

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I've used sand fill between parallel walls, where thickness needs to be over
5-feet for other than structural reasons. But on a 4-ft square column, the
formwork costs are likely to exceed any savings in concrete. 

> -----Original Message-----
> From: Lutz, James [mailto:JLUTZ(--nospam--at)]
> Sent: Tuesday, February 06, 2001 9:33 AM
> To: seaint(--nospam--at)
> Subject: RE: Min. Steel in Concrete Column
> Have you considered making the section hollow to reduce the 
> gross concrete
> area, and hence the steel? This is sometimes done on large 
> bridge piers. The
> concrete and steel saved might not be worth the additional 
> form cost, and
> you would need an extra cage, but if you have oversized this 
> column just to
> create a footprint for equipment support, it's an option 
> which will greatly
> reduce the column weight and might save you a little foundation cost. 
> -----Original Message-----
> From: Lao, Larry [mailto:LaoL(--nospam--at)]
> Sent: Monday, February 05, 2001 2:59 PM
> To: 'seaint(--nospam--at)'
> Cc: Kuhn, Bob; Wiegert, Tom; Lao, Larry
> Subject: Min. Steel in Concrete Column
> 	We have a 4'x4' concrete column under 110 k axial load 
> (D+L) and 60
> k-ft bending, both are at the bottom of the column, the 
> column height is
> 18', about 4k of shear on top of the column. The 4'x4' was picked for
> supporting upper mechanical device.
> 	Obviously, the min. steel requirement in UBC will put about
> 0.01*48*48=23 in^2 vertical bars into the column, which will 
> provide about
> 2200k-f bending capacity or 4,000 kips of compression 
> capacity. I remember
> have seen some requirement in the code, saying that if a 
> design can provide
> 100% capacity over the demand, the 1% steel requirement can 
> be ignored,.
> Basically, this is to prevent excessive rebars in a 
> non-structural-sized
> column. Can anybody back me up on this?
> 	Thanks