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RE: nds dowel bearing strength

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Dave,

One thing to keep in mind if you are doing any seismic and are in UBC
country is the shallow anchor provisions. Even though it is in the parts
and portions section of the code and not really applicable for a wood
sill to a foundation, or a ledger to a cmu or concrete wall, the
embedment to diameter ratio (E=>8D)should be followed whenever possible
as good practice. Also, remember that the NDS is not calculating the
anchor capacity in concrete, it's calculating the allowable capacity of
the wood assembly.

Trying to save 2" of bolt length doesn't seem worth it unless you are
talking 1000's of anchors on a single job. If you are going into
existing concrete or CMU, you need to check the ICBO rated capacity of
the anchor in the material and check that with your NDS value for the
wood.

The math in the nds might be giving you those values, but if you really
want to verify the minimum embedments, check the required embedments
from the new PCA publication for anchorages in concrete.

HTH,
-gerard
Santa Clara, CA

-----Original Message-----
From: da [mailto:dadie(--nospam--at)sbcglobal.net] 
Sent: Saturday, September 28, 2002 4:46 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: nds dowel bearing strength

> Is the concrete strength that relevent?  Shouldn't the wood strength
nearly
> always control?
>
> Pat Clark, P.E.

basically my question arose because i was developing a spreadsheet for
non
typical applications.  what i found was pretty interesting.  the 6.0 in
min
concrete embedment is conservative to very conservative for table 8.2E.
the
table below shows what i came up with for the REAL min embedments in f'c
=
2000 psi concrete & douglas fir (G=0.50) - (to obtain the exact same
table
values).  yes i know that these numbers are too small for normal design
use.

side member thk / bolt dia / real min embedment

1.5 / 0.5 / 2.25
1.5 / 0.625 / 2.5
1.5 / 0.75 / 3
1.5 / 0.875 / 3.5
1.5 / 1 / 4

2.5 / 0.5 / 2.25
2.5 / 0.625 / 3
2.5 / 0.75 / 3.25
2.5 / 0.875 / 3.75
2.5 / 1 / 4.25

3.5 / 0.5 / 2
3.5 / 0.625 / 2.75
3.5 / 0.75 / 3.25
3.5 / 0.875 / 4.25
3.5 / 1 / 4.5

i call this table "8.2E2 - bolt design values (Z) for single shear (two
member connections)
for sawn lumber to masonry" - f'm = 1500 psi, FEM = 3 * f'm = 4500 psi,
douglas fir (G=0.50)
the Z parallel values are about 93% of the concrete values in the table
and
the Z perp. values are very close to equal to the concrete values.

side member thk / bolt dia / real min embedment / Z parallel / Z
perpendicular

1.5 / 0.5 / 2.5 / 580 / 350
1.5 / 0.625 / 3 / 830 / 500
1.5 / 0.75 / 3.5 / 1140 / 580
1.5 / 0.875 / 4 / 1510 / 620
1.5 / 1 / 4.5 / 1940 / 670

2.5 / 0.5 / 2.25 / 670 / 440
2.5 / 0.625 / 3.5 / 1050 / 570
2.5 / 0.75 / 4 / 1390 / 740
2.5 / 0.875 / 4.5 / 1760 / 950
2.5 / 1 / 5 / 2170 / 1110

3.5 / 0.5 / 2.25 / 670 / 460
3.5 / 0.625 / 3.25 / 1050 / 690
3.5 / 0.75 / 3.5 / 1520 / 840
3.5 / 0.875 / 4.75 / 2070 / 1030
3.5 / 1 / 6 / 2550 / 1250

hago
da



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