The radius of gyration is the square root of (moment of inertia divided by
area). Remember to use only the face shells in computing "I" and "A" if
only the face shells are bedded.
Roger C. Davis
SDS Architects, Inc.
From: David Williams [mailto:dwilliams(--nospam--at)snydereng.com]
Sent: Friday, June 22, 2001 2:50 PM
Subject: Allowable Compressive stress-ACI 530
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 188.8.131.52 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
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