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Tension equations for anchors in CMU

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A couple of days of slack time have prompted a flurry of posts to the list by yours truly.  Today, I’m trying to put together a small spread sheet for allowable tension for an anchor in the top of a CMU wall.  Not a big deal for hand calcs, and I’ve done this a number of times, but I’m trying to minimize embedment requirements for holdown anchors possible being a little more “custom” from job to job as embedment depths I’ve called out before tended to be pretty conservative for more lightly loaded holdowns.  Most stem wall construction around here is CMU.


I hadn’t noticed this before, but equation 2-4 in ACI 530/02 uses l sub be for one determination of A sub p.  The definition for l sub be seems incorrect for the tension application and should be used for shear applications toward a free edge.  The strength design section uses l sub b for calculating A sub pt.  The definition for A sub pt and the explanation for overlapping cones and deduction of areas of A sub pt which fall outside the masonry surface, seems to make more sense, and I think should be used in the service load equations also.  Is there a typo error?  Has there been any errata’s?  The way equation 2-4 is written seems extremely conservative to me.


So, wazup?







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

Shephard - Wesnitzer, Inc.

Civil Engineering and Surveying

1146 W. Hwy 89A Suite B

Sedona, AZ  86340

PHONE (928) 282-1061

FAX (928) 282-2058