radius of gyration - square concrete column double tee wal

huangyhg

radius of gyration - square concrete column & double tee wal
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,   
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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).
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?

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.
i found the .3.  i'll try the i & a calculation.
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.