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Radius of Gyration - Square Concrete Column & Double Tee Wall Panel

Radius of Gyration - Square Concrete Column & Double Tee Wall Panel

Radius of Gyration - Square Concrete Column & Double Tee Wall Panel

(OP)
I need some formulas for figuring radius' of gyration for a square precast concrete column & a double-tee wall panel.  I have an example problem in a book that indicates r=7.2" for a 24" square column????  It also shows that r=7.23" for a prestressed 8'x24" deep double-tee wall panel.  

Thanks,    

RE: Radius of Gyration - Square Concrete Column & Double Tee Wall Panel

Well, the ACTUAL r for that 24" square column is 6.93".  ACI allows you to use 0.3*the least dimension.  
The radius of gyration is very simply the square root of (I/A).

RE: Radius of Gyration - Square Concrete Column & Double Tee Wall Panel

(OP)
I know the general formula, and that is what I figured.  But, the example shows 7.2".  How about the 7.23" for the double-tee wall panel?

 

RE: Radius of Gyration - Square Concrete Column & Double Tee Wall Panel

Yes, 7.2" is the 0.3 clause of ACI.  0.3*24" = 7.2"
Also, calc it out for the TT.  I've never heard of a TT wall panel, but just look at the I for the axis under consideration, then calc it out and see what you get.  That doesn't seem unreasonable to me.

RE: Radius of Gyration - Square Concrete Column & Double Tee Wall Panel

(OP)
I found the .3.  I'll try the I & A calculation.

RE: Radius of Gyration - Square Concrete Column & Double Tee Wall Panel

(OP)
I calculated r using the standard formula ~ 7.61".  Some times, sections are reduced to effective sections.  Apparently, that is not the case here.  Thanks for your suggestions.

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