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(Mike) RE: Wall anchorage at flexible diaphragms

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Mike,

Yes, thank you for your response. For the sake of simplicity of the example
I used, I didn't include the 3x info and assumed using the appropriate
section for load combinations. Certainly important things to account for and
consider, as you said.

Thanks again,
Dave




-----Original Message-----
From: Mike Valley [mailto:mtv(--nospam--at)skilling.com]
Sent: Thursday, August 03, 2000 12:58 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Wall anchorage at flexible diaphragms


Dave:

Your summary is generally consistent with my reading.  However, there
are two additional points to consider.

1) If you are using the Allowable Stress Design load combinations
specified in Sec. 1612.3.1, you may NOT use the 1/3 stress increase.
If you are using the load combinations in Sec. 1612.3.2 you MAY use
the 1/3 stress increase.  The Blue Book did not make this distinction.

2) I believe that item 5 of Sec. 1633.2.8.1 is poorly written, as
shown by your example.  You have correctly interpreted the forces to
be used in design, and I believe that your interpretation is
consistent with the intent and the letter of the code.  However, you
(and the Blue Book writers) failed to mention the second half of item
5.  This second item requires that the "wood elements...have a minimum
actual net thickness of 2.5 inches."  I believe that the intent is to
force the use of 3x ledger or sill plates.  However, the letter of the
code would also apply to your joists!  I believe that this result is
unintended.

-Mike

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Michael Valley, P.E., S.E.                   E-mail: mtv(--nospam--at)skilling.com
Skilling Ward Magnusson Barkshire Inc.              Tel:(206)292-1200
1301 Fifth Ave, #3200,  Seattle  WA 98101-2699      Fax:        -1201

-----Original Message-----
From: Dave Adams [mailto:davea(--nospam--at)laneengineers.com]
Sent: Thursday, August 03, 2000 11:10 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: Wall anchorage at flexible diaphragms


Hello all,

I'd like to run my understanding of UBC Section 1633.2.8.1 and 1999
SEAOC
"Blue Book" Section C108.2.8.1 & commentary by you all and see if I'm
off
base or missing something regarding the component forces to use for
"working
stress" levels. Say I have a masonry wall with a wood plate on top
that is
fastened to the wall with anchor bolts, roof joists landing on top
that are
fastened to the wood plate with Simpson framing anchors, and a plywood
diaphragm nailed to the roof joists.

For working stress design, the following material multipliers are to
be used
with the forces derived per Section 1632 for the design of the
anchorage
elements:

Masonry (anchor bolt failure mode):  1/1.4 with a 1/3 increase
Anchor bolts themselves:  1.4 times 1/1.4 with a 1/3 increase
Wood plate (anchor bolt failure mode):  0.85 times 1/1.4 with a 1/3
increase
Fastening of framing anchors to wood plate & to roof joists:  0.85
times
1/1.4 with a 1/3 increase
Framing anchors themselves:  1.4 times 1/1.4 with a 1/3 increase
Roof joists & fastening of diaphragm to joists:   0.85 times 1/1.4
with a
1/3 increase

Is this correct?

Regards,
Dave K. Adams, P.E.
Lane Engineers, Inc.
PH: (559) 688-5263
E-mail: davea(--nospam--at)laneengineers.com


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