Return to index: [Subject] [Thread] [Date] [Author]

Re: High-load plywood shear walls

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Theoretically it is possible under UBC provisions to design for 2x870 = 1740
plf, based on 15/32" APA Structural I Rated Sheathing 32/16 (or 19/32" APA Rated
Sheathing 40/20) both sides of wall and nailed with 10d com nails spaced 2" oc
(e.g., 4" oc staggered in two rows) at panel perimeter and 12" oc at
intermediate studs. This would require min. 3x framing or preferably larger at
locations where panel edges butt, and of course for bottom plate (shear greater
than 350 plf). Design must be checked for hold-down capacity which is
theoretically 35x1740 = 60,900 lbs and probably limits design; ult. capacity
should be at least 180,000 lbs, is this practical?  Also need to check bearing
of end posts on studs (suggest using reduced bearing capacity of 385 psi for
Douglas fir framing), and deflection. Panel edges on opposite sides of wall
should be offset so they don't occur on same studs. APA Help Desk
(help(--nospam--at)apawood.org) has details of how to offset nails in bottom plate so they
don't occur at same elevation.  Since wall is tall, there will be horizontal
blocking which should be 3x or larger also at top/bottom edges of panels. Lots
of things to look out for, and need complete detailing on construction drawings.
Maybe special inspection? You're certainly pushing the envelope.
John Rose/APA

Charles Greenlaw wrote:

> APA has published design info for plywood shear walls using wide-faced
> framing and multiple lines of nails each edge. In this way it is possible to
> mobilize much more of a plywood sheet's strength than with only one line of
> edge fasteners. Allowables in excess of 1000 plf per face are available.
> Plywood thickness likely is not what controls, rather the fasteners and what
> they fasten into. Split-resistant backing at horiz interior edges would also
> be nice.
>
> Inquire of APA for particulars. Maybe John Rose will reply on the list.
> Maybe the proponents of concentric hold-downs will have some tips too.
>
> Do take good care of the external connections, bearings, anchorages, and
> foundation stability concerns that are part of the system. Overturning
> effects will be in big numbers. Possibly several anchored vertical "edge"
> members at each edge, that are good columns for the height, will be needed.
> I don't see how steel helps for boundary members, since it is hard to fasten
> to with nails, and bolts in shear slip in their bolt holes and make the
> rigidity go away. Those parts that lack good ductile overstrength or cause
> rocking deflection should have some concession to the Omega factor included
> in their design basis, so they can't give up or go wimpy before the shear
> sheathing does.
>
> Charles O. Greenlaw SE   Sacramento CA
>
> At 06:03 PM 04/19/2000 -0700, you wrote:
> >     What is the most anyone has ever calced for a plywood shearwall? Can I
> use 3/4" plywood both sides and use values above the tables in the UBC?
> Will I need 4x panel edge members?
> >
> >     I have a 35'+ high wall and need to keep it as thin as possible.  Non
> load bearing, interior shear wall.  I already plan on using LVL studs and
> steel boundary members.  Don't want to use masonry.  Need to push the
> limits, and suggestions?
> >Jake Watson, E.I.T.
> >
> >Salt Lake City, UT
>