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Tension anchor in top of CMU stem

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Assume you have a tension anchor bolt in the top of a fully grouted CMU stem wall.  The wall is 8” thick and the anchor is installed at the center.  That would give you 3.8” to each face of the stem wall.  NCMA TEK note 12-3A appears to say that your projected area for pullout (masonry failure) is based on a cone with a radius of 3.8” without regard to the embedment depth.  ACI 530-02 doesn’t seem to make that distinction.  I think that if you have, say 16 “embedment that the pullout area for tension would be approximately 7.63”x32” which would be about 244 sq. inches which seems reasonable to me.  Why would the NCMA be so limiting, or am I way off base?

 

I have a design where the original architectural sections indicated a stem wall depth adequate to install Simpson SSTB anchors as called for their Strong-Wall Shear Walls.  I was told yesterday that the depth will not be as indicated.  If the NCMA TEK notes are correct then I can’t even use a 16” (embedment depth) headed anchor because of the NCMA criteria.  If I am reading the ACI documents correctly then I am OK using the 16” headed anchor.

 

Any help out there?

 

Thanks,

Joe Grill

 

 

Joseph R. Grill, P.E. (Structural)

Shephard - Wesnitzer, Inc.

Civil Engineering and Surveying

P.O. Box 3924

Sedona, AZ  86340

PHONE (928) 282-1061

FAX (928) 282-2058

jgrill(--nospam--at)swiaz.com