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Re: 3/8 inch shear panels

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Points well taken.  A couple of things to keep in mind:
1)  For high shear capacity, why try to accomplish it with the minimum
thickness panel.  Could use 15/32 in. wood structural panel sheathing and
larger nails spaced further apart in many instances.
2)  On details, show sketch of nailing pattern (for example, see nailing
pattern in ICBO ES Report 1952 for high load diaphragms) and have architect or
contractor make it a special condition of construction observation.
3)  If the shear wall has high shear demand, call for special observation of
construction either by engineer of record, or building dept. or contractors
designate.  City of LA has this requirement for shear walls which are highly
loaded.
4) Today we conducted cyclic load tests on shear walls with 15/32 in. sheathing
(OSB) and 10d common nails spaced 2 in./12 in. oc, with edge nailing in two
rows at 4 in. oc in each row.  Load factor was 2.4; more than 50 cycles of
reversed loading above yield limit state, per SEAOSC protocol.  Not bad, I
think.

More info at Wood Solutions Fair, Long Beach 9/30 :).

Bill Cain, S.E. wrote:

> -----Original Message-----
> From:   John Rose [SMTP:jrose36(--nospam--at)earthlink.net]
> Sent:   Thursday, September 03, 1998 20:15 PM
> To:     seaint(--nospam--at)seaint.org
> Subject:        Re: 3/8 inch shear panels
>
> ...The UBC requires that all nailing spaced 2 in. o.c. must be in staggered
> rows; e.g., two rows with nails
> spaced 4 in. o.c. in each row.  Splitting of framing is avoided with this
> pattern....
>
> [Bill Cain]  With all due respect, John, this is good theory. However, in
> practice, the contractors either meet the 2" spacing or stagger so much
> that they don't meet the edge distance requirements.  Either way you will
> often end up with toothpicks!  I can't count the number of times I've had
> to require the framing be replaced because the studs were so badly
> butchered.  Since I've stopped using these tight spacings, I've had few
> problems.
>
> Eph Hirsch's caveats about the hold downs for a heavily loaded panel are
> important.  If you've ever seen Ed Zacher's videos of how plywood pulls
> loose at the corners under cyclic loads (which is also evident in pictures
> I've seen from Northridge), you understand that, although Simpsons's hold
> down tests (done on a steel jig BTW, not a wood post) show a large
> capacity, in reality, the eccentricity of the load for a single hold down
> at a corner and the resulting deformations and bending of the post due to
> the P/A + MC/I (in addition to bolt hole oversizing, crushing of the wood,
> etc.) effect will not give you the performance you are counting on.
>  Simpson makes great products if they are used with a little common sense
> and attention to basic mechanics.  And their catalog warns the designer
> about these effects (although I would prefer to see it a little more
> prominently presented).
>
> Regards,
>
> Bill Cain, SE
> Oakland, CA
>