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

[DCEngr1]

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,

 

[Lion06]

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).

 

[DCEngr1]

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?

 

[Lion06]

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.

 

[DCEngr1]

I found the .3. I'll try the I & A calculation.

 

[DCEngr1]

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.