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Re: out of plane anchorage Question

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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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