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CMU's Equivalent Solid Thickness (EST) issue.

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Decartes

Structural
Oct 23, 2001
8
thread507-253979

EST = Equivalent Solid Thickness and is calculated based on the "Absoulte Volume" of the CMU Block divided by the Face Shell Area (usually equal to 7.625"x15.625"/144 = 0.83 ft^3). This "absolute volume" (founded by testing:see includes the ENTIRE horizontal cross-sectional area of the block/wall (which also includes the "toe areas" at the web and face shell intersections). The "An" (Net Area) values from NCMA Tek Notes (TEK 14-1B,2007) is based on the "Mortar Bedding" on the block's horizontal cross-sectional area, i.e. Full or Face Shell(note: face shell thickness may be 1.25" or 1.375" or 2", varies!-Pay attention when using these tables). This "An" is the correct values to use when considering the stress on the "motar bedded area" due to Axial and bending loads, especially for unreinforced CMU. RMEH's 'fa = P/(EST)x(b =12")' is considering "full bedding". Engineer judgement must be used here.
 
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I don't know what question is posed is posed but the reference cited is a local promotional group that relies on more credible sources like the MSJC and NCMA, and the engineers that write or are instrumental in the writing of the ASTM standards and testing practices and the applicable codes.

The NCMA Tek notes (ncma.org) have over 100 TEK notes on various structural and other documents to explain the basics to those not familiar with the technical terms and testing reports. They also are involved on all major building codes and specifications.

The face shell of a unit is determined by ASTM C140 and cannot be assumed to be the values quoted since there is a wide range depending on the units tested or used since often thicker face shell units (up to 2 1/8" thick for UL listed units) are specified for reasons such as fire resistance sound transmission.

The NCMA TEKS explain almost any question and are used by third parties for the creation of promotional literature.

Engineer and international traveler interested in construction techniques, problems and proper design.
 
@concrete masonry:

My post is a response to the thread: thread507-253979: Masonry Wall Net Area vs. Equivalent Thickness

It's not a question, but a reply.
 
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