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Re: out of plane anchorage Question

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Tarek,

I agree that the minimum requirements seem over the top for an 8 foot wall
(420 USD / 300 ASD).  But what is it that is creating the limiting factor of
double trusses every 24"?  A double truss should easily be able to
accommodate higher axial loads.  Is it the anchorage attachment and top
plate bolting that is limiting your anchorage spacing?  If the exterior is
plastered you can use a bent plate seat that captures the top of the wall
with through bolts and steel side plates for the truss and generate a
tremendous amount of anchorage resistance.  Another alternative is a Simpson
GLB style seat for specific trusses with bond beam reinforcement each side
of the seat dowels.


Paul Feather PE, SE
pfeather(--nospam--at)SE-Solutions.net
www.SE-Solutions.net
----- Original Message ----- 
From: "Tarek Mokhtar" <tarooky(--nospam--at)earthlink.net>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, November 12, 2003 8:49 AM
Subject: Re: out of plane anchorage Question


> Paul,
> I did consider doubling up the trusses at some spacing, however
> the min. code requirement of 420 plf would almost dictate a double
> truss @ 24"o.c which is a bit over the top for an 8' tall wall IMHO
>
> Tarek Mokhtar, SE
> Laguna Beach, CA
>
>
>
>
>
>
>
> >Pat,
> >
> >I do not think they intentionally wanted to remove plated truss
construction
> >from masonry or concrete wall structures, and I do not think these
> >provisions prohibit their use, but in essence the provisions have made
this
> >traditional construction approach more difficult.
> >
> >The primary wall anchorage failure experienced was for tilt-up and
masonry
> >warehouse structures with tall walls and large diaphragms.  These are
> >typically panelized systems with parapets utilizing sub-diaphragm design
to
> >develop wall anchorage.  According to the SEAOC blue book, the limitation
on
> >the net thickness of the wood member for bolted connections, where wood
> >member thickness should be a minimum of 4.5 times the bolt diameter for
> >ductile behavior in the connection.  When translated into code language
this
> >became "The wood element shall have a minimum net thickness of 2.5
inches",
> >without differentiation regarding bolted or nailed construction.
> >
> >In my personal opinion, most of the thought at the time was of limited
> >focus, similar to the rho issues with wood construction.  The subject of
> >study was failures of one type and the consideration of the impact on all
> >the other types of construction was not 100% realized until the
applications
> >were applied in practice.  However, with all that being said I personally
> >don't think this is such a bad idea.  It is possible to design
accordingly.
> >The wall anchorage is the weak link in any bearing wall system.
> >
> >I am reasonably confident that a double truss adequately joined to act as
a
> >single element, similar to a girder truss, would comply with the
provisions
> >of the code.  I am also reasonably confident that this could be
adequately
> >explained to most plan checkers.
> >
> >I also think there is definite room for improvement in these
"traditional"
> >systems anyway.  Top bolts set in the grout cells acting perpendicular to
> >the wall perform poorly.  The table values in the UBC do not adequately
> >address this, but if you read the actual equations the calculated
allowable
> >value is pretty limited.  The top plate perpendicular to grain bearing is
> >not the most efficient and reliable way to resolve dynamic out of plane
wall
> >forces.
> >
> >It is not too difficult to detail a more appropriate direct connection
> >system and still use a plated truss system.
> >
> >
> >Paul Feather PE, SE
> >pfeather(--nospam--at)SE-Solutions.net
> >www.SE-Solutions.net
> >----- Original Message -----
> >From: "Pat Clark" <bcinc(--nospam--at)nanosecond.com>
> >To: <seaint(--nospam--at)seaint.org>
> >Sent: Tuesday, November 11, 2003 4:23 PM
> >Subject: RE: out of plane anchorage Question
> >
> >
> >> I thought that the requirement was for the sill plates or ledgers.  Did
> >> they intentionally want to remove all plated truss construction from
> >> masonry and concrete wall structures?
> >>
> >> Patrick Clark, P.E.
> >> Building Concepts, Inc.
> >> 1228 Pep Circle
> >> Gardnerville, NV 89410
> >> (775) 782-8886 x22
> >> (775) 782-8833 fax
> >>
> >>
> >> -----Original Message-----
> >> From: Paul Feather [mailto:pfeather(--nospam--at)SE-Solutions.net]
> >> Sent: Tuesday, November 11, 2003 3:59 PM
> >> To: seaint(--nospam--at)seaint.org
> >> Subject: Re: out of plane anchorage Question
> >>
> >>
> >> Correct, you would have 3x minimum chords for anchorage attachment if
> >> you are using the truss for anchorage.  This makes this "traditional"
> >> construction system a bit harder to implement.
> >>
> >> Paul Feather PE, SE
> >> pfeather(--nospam--at)SE-Solutions.net
> >> www.SE-Solutions.net
> >> ----- Original Message -----
> >> From: "Tarek Mokhtar" <tarooky(--nospam--at)earthlink.net>
> >> To: <seaint(--nospam--at)seaint.org>
> >> Sent: Tuesday, November 11, 2003 3:25 PM
> >> Subject: out of plane anchorage Question
> >>
> >>
> >> >
> >> > consider a 35' x 18' one story masonry building with a wood truss
roof
> >>
> >> > The masonry walls have a 4x nailer on top, where the trusses are
> >> > attached for bearing and out of plane forces.
> >> >
> >> > Section 1633.2.8.1 states that wood elements of the anchorage system
> >> > shall be 2 1/2" minimum, does this mean that the trusses have to be
3x
> >>
> >> > thick?
> >> >
> >> > Tarek Mokhtar, SE
> >> >
> >> > Laguna Beach, CA
> >> >
> >> >
> >> >
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