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Re: out of plane anchorage Question

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Paul,

Thank you for your helpful replies, what I had in mind was an A35
clip for the transfer between the truss and the nailer which under
the current code would not work

Tarek Mokhtar, SE
Laguna Beach, CA



>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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