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RE: Design of Top Plates

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You are ignoring the rim joist at every level that will redistribute the load from above. So, what you really need to consider is the load from one level only and check your double plate for that load.

Oshin Tosounian, S.E.
Los Angeles, CA

------Original Message------
From: "Speck, Todd M" <tmspeck(--nospam--at)pbsj.com>
To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
Sent: December 28, 2000 5:33:07 PM GMT
Subject: Design of Top Plates


John Riley's ledger question brings up a question I've had for some time
that no one I've queried has been able to answer.

His "Studs are 2x6, D.Fir-Larch(N), @ 16".  Load from each floor is about
1100
plf."

Assuming the floor trusses are spaced at 24" o.c.

My question is this: How does one justify the strength of the top plates?

For quick calculations,  assuming the roof load is 550 plf you need to
transfer 3850 plf (550 plf roof + 1100 4th + 1100 3rd + 1100 2nd) from the
second floor trusses to the top plates directly beneath the 2nd floor
trusses.  with trusses spaced at 24" o.c. that's a 7700 lb point load to the
dbl top plate.  The studs are spaced at 16" o.c. so there will be a location
where the truss bears at midspan of the dbl top plate.

I've never had anyone be able to account for the shear and flexure stresses
that the dbl top plates are loaded with.   Is there something I'm just not
seeing or do engineers somehow ignore this??

All help would be much appreciated on this matter,  since I've never had
anyone give me a decent solution to this.



-----Original Message-----
From: John Riley [mailto:jpriley485(--nospam--at)peoplepc.com]
Sent: Wednesday, December 27, 2000 9:20 PM
To: seaint(--nospam--at)seaint.org
Subject: Ledger


For a 4-story, wood-framed, senior housing facility, the building official
requires that the stairways be sheathed with gypboard on the outside, one
layer of 5/8", and the gypboard cannot be interrupted by ledgers.  Neither
will he allow the floor joists to bear on the stairway walls.

Studs are 2x6, D.Fir-Larch(N), @ 16".  Load from each floor is about 1100
plf.

Can a ledger be lag-screwed or thru-bolted through the gypboard?  What I
have in mind is a single 2x12, D.Fir-Larch(N) with the floor joists attached
with Simpson hangers.

Are the values in UBC Table 23-III-B-1 applicable?  Modifiable?

Is there a better way to approach the problem?

__________________
John P. Riley, PE, SE
Riley Engineering
20 Oakwood Drive, Blue Grass, Iowa 52726
Tel & Fax:  319-381-3949
jpriley485(--nospam--at)peoplepc.com