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RE: Shear Transfer from roof diaphragms....

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Dan, you can have continuous blocking and still meet the ventilation
requirements by providing holes within 1" of the underside of the roof
sheathing.  The area of the hole must meet the requirement of 1/150 of
the net free ventilating area.  We do this all the time.  The 1" is the
minimum required air space between the insulation and the roof sheathing
as found in the 2000 IBC 1202.2.  Note that in the IBC the wording is
more specific than in the UBC for example to provide 50% of the
ventilation in the upper portion of the space to be ventilated, and at
least 3' above the eave blocking.  If you calculate it out you may only
need alternate full height blocking anyways so ventilating the area is
not a problem. 




From: Dan Boltz [mailto:dboltz(--nospam--at)mckinleyassoc.com] 
Sent: Thursday, November 13, 2003 6:08 AM
To: SEAINT
Subject: Shear Transfer from roof diaphragms....

.....a little follow up from yesterdays email.  I stamp everything I
design
and no senior engineer is present in this office to review my designs.
This
is the hand I'm currently dealt and know that I need a second set of
eyes
reviewing everything that is structurally related.  The design code is
IBC
2000 and the roof pitch is 5:12.  The man who stated that I didn't need
to
look at shearwalls was unfortunately my boss who is a PE but not a
practicing engineer who is familiar with lateral design.

The Simpson A35 and LTP4 connectors look good if end blocking is
present,
but I don't believe that continuous end blocking will work due to attic
ventilation requirements.  If the distance above the top plate is 18"
and
the eave height is 11", what Simpson connector is available to transfer
loads out of the roof diaphragm perpendicular to the roof truss?

Where is the IBC 2000 specific about minimum requirements for lateral
support?

Also, is it common to have roof trusses at 24" o.c. and wall studs at
16"
o.c.?  How is the double top plate analyzed for this situation?

Thanks.


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