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RE: Anchorage to concrete

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I recommend the following:

Fuchs, Eligehausen, Breen, Concrete Capacity Design (CCD) Approach for
Fastening to Concrete, ACI Structural Journal V. 92 No. 1, January-February

Eligehausen, Balogh, Behavior of Fasteners Loaded in Tension in Cracked
Reinforced Concrete, ACI Structural Journal V. 92 No. 3, May-June 1995

PCA will be conducting a series of seminars in the application of the CCD
method as it now appears in the IBC 2000.

Regards,  John Silva

> ----------
> From: 	Robert Shaffer[SMTP:rkdn(--nospam--at)]
> Reply To: 	seaint(--nospam--at)
> Sent: 	Wednesday, November 10, 1999 3:34 PM
> To: 	seaint(--nospam--at)
> Subject: 	Re: Anchorage to concrete
> John, 
> Thanks for your responce,  that really helps my understanding that we are
> again trying to insure ductility in the connection and avoid brittle
> failure.  Is there an article on the CCD method you refered to ? 
> Robert Shaffer,  P.E. 
> Santa Cruz, CA 
> "Silva John (sj)" wrote: 
> 	Robert, 
> 	Let me try this one.  The idea of requiring an l/d of 8 was to force
> some 
> 	measure of ductility, rightly or wrongly, into the anchorage.  It
> was 
> 	assumed that for many cases, l/d = 8 would ensure steel rupture, and
> this 
> 	should be encouraged by punishing shallower embedments. 
> 	In many cases, (stem wall anchors, for instance), the concrete
> capacity is 
> 	severely limited by the geometry of the anchorage, and l/d = 8
> cannot ensure 
> 	steel failure at ultimate.  It is important to note, however, that
> if the 
> 	ultimate capacity is limited by the concrete, increasing the bolt
> diameter 
> 	will not increase the anchorage capacity, although it may increase
> the 
> 	initial stiffness. 
> 	e.g., assuming you are not limited by near edges or adjacent
> anchors, and 
> 	looking simply at tension, your 3/4" anchor (let's assume a standard
> hex 
> 	A307 bolt) with 6" of embedment would develop a concrete capacity
> (concrete 
> 	cone failure mode) in nominal 2000 psi concrete of approximately 26
> kips. 
> 	The tensile strength of the bolt at the threads (assuming an
> overstrength 
> 	factor of 1.25) is about 25 kips.  The tensile strength of a 7/8"
> A307 bolt 
> 	is 33 kips.  Increasing the bolt diameter without increasing the
> embedment 
> 	doesn't do much for you in this case. 
> 	With respect to your recommendation for designing embedments in stem
> walls 
> 	or narrow foundations, I would agree that the use of equations based
> on a 
> 	breakout cone failure for this case is inaccurate (this was the
> subject of a 
> 	previous thread, as I recall).  Splitting will be the controlling
> failure 
> 	mode for the concrete in many cases, and the equations for
> development 
> 	length are based (at least in part) on this failure mode. 
> 	(The original post indicated reducing the embedment of the anchor
> bolt to 
> 	2.75" to avoid an edge distance reduction.  I would strongly
> recommend 
> 	against this line of reasoning...) 
> 	Apropos strength design of embedments, I would recommend becoming
> familiar 
> 	with the method adopted for the IBC 2000 (the so-called CCD method).
> It is 
> 	reasonably comprehensive and provides guidance for a wide variety of
> loading 
> 	conditions. 
> 	Regards, 
> 	John Silva