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Re: Allowable Compressive stress-ACI 530

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David Williams wrote:

> I'm designing a 12'-6" tall reinforced CMU wall using 12" block (actually
> the wall is taller than that, but it'll have a lateral support @ 12.5').  I
> have to use allowable stress design  (local building code requirement).
> Equation 2-17 in subsection is used to calculate allowable
> compressive stress in the masonry due to axial loading.  The equation uses a
> ratio of h/r which is the ratio of the effective height of the wall to the
> "radius of gyration" of the member.
> My question is: How is the radius of gyration to be calculated?  Is it the
> height of the wall divided by the square root of 3?
> David L. Williams, P.E.
> Snyder Engineering, Inc.
> Columbia, MO  65202

>From the Masonry Designers' Guide for 12" CMU

Face shell mortar bedding r=5.08 in.
Full mortar bedding r=4.29 in.

Davis G. Parsons II, PE RA AEI
a practical structural engineer
in Fort Worth, Texas

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