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Re: Design of Anchorage to Concrete

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This is an excellent question.  There are many instances where anchor bolts are found within 4Db of the edge of a concrete wall or curb.  Most all proprietary prefabricated shear panels have large hold-down anchors (also hold-downs and shear bolts for site built shear walls) which technically violate the UBC provisions.

While I, admittedly, have been unable to find the origin of this prescriptive requirement, I believe that it comes from tension or shear breakout cone "geometry" intersecting the edge of the wall higher up, thus reducing allowable tension or shear.  Apparently UBC has set a minimal level for a "standard" application.

We've found ACI-318-99  App D to be of tremendous assistance in calculating the effects of edge distance.  Through a rigorous analysis of actual forces and distances we have been able to show that reduced edge distances do work for the allowable loads in the TJ Shear Panel.  If you would like a copy of these calculations, don't hesitate contacting a Trus Joist Representative.  We appreciate the interest.

Scott Soule, S.E.


>>> VerneK(--nospam--at)aol.com 10/25/02 10:56AM >>>
I have been asked to design some bolts for pullout and shear using section 
1923 of the UBC. Specifically, it is for the  "TJ shear panels" which are 
commonly used at the front panels of 
garages where there are very little room and the wall bear over a 6" to 8" 
garage curb. Since the face of wall is always at one edge of the curb,  the 
edge distance to the bolt is always 1.75" to 2".

In section 1923.3 (design of shear), it states that the edge distance shall 
in no case be less than 4 diameters. In my case, I am using 7/8" diameter 
bolts which amounts to an edge distance of 3.5".
Why is it so critical to have such a large edge distance, especially for an 
unloaded edge?

regard,
Verne 

    

    




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