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Re: Required wall attachment to a flexible diaphragm.

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Are you suggesting that you apply the 1.4 factor and compare this force to
the ultimate value which Simpson (but not Zone 4) publishs and not to the
allowable value?  You then can apply the 0.85 factor to the force and
compare this to the allowable value which would address the bolts in wood

Mike O'Brien, P.E.

-----Original Message-----
From: Gerard Madden <GerardM(--nospam--at)>
To: 'seaint(--nospam--at)' <seaint(--nospam--at)>
Date: Thursday, August 26, 1999 4:16 PM
Subject: RE: Required wall attachment to a flexible diaphragm.

>Agreed. the bolts in single shear from these HD's & CT'soften govern.
>But not always-(double shear in thick lumber). The 1.4 factor always
>applies. It may not govern but it applies. I would show it on a
>calculation sheet regardless, proving it works, even if I suspect it is
>not the controlling factor. The actual strength of the steel body for a
>simpson HD is listed in the table is is at least 20kips. But the
>footnotes also state that it is inappropriate to use this value in
>Gerard Madden, P.E.
>Civil Engineer, Associate
>CRJ Associates, Inc.
>email: gerardm(--nospam--at)
>tel: 650.324.0691
>fax: 650.324.0927
>> -----Original Message-----
>> From: Mike O'Brien [SMTP:mikeo(--nospam--at)]
>> Sent: Thursday, August 26, 1999 4:05 PM
>> To: seaint(--nospam--at)
>> Subject: RE: Required wall attachment to a flexible diaphragm.
>> The way I see it is since deflection criteria typically governs in
>> determining the published values of stout premanufactured hardware,
>> like
>> Zone4 CTs or Simpson, and most of the deflection derives from the
>> bolts in
>> the wood, the 1.4 factor for steel elements is not necessary, but
>> rather the
>> 0.85 factor for wood elements (bolts in wood) would actually be the
>> more
>> correct factor.  As further evidence of this, look in the Simpson
>> catalog
>> and compare the HD6A, HD8A and HD10A.  They all have the same body and
>> base
>> material, all have the same anchor bolts and all have the same stud
>> bolts.
>> The only thing that varies is the number of stud bolts.  Intuitively,
>> this
>> shows that the bolts in wood govern, and therefore, the 0.85 factor
>> could be
>> used.
>> The other option is to remain a little on the conservative side and
>> not
>> apply the 0.85 factor, but rather use 1.0 when selecting this
>> hardware.
>> Mike O'Brien, PE
>> >
>> > The force (Fp) applies to Anchor bolts, prefabricated HD's &
>> > CT's etc..,
>> > and all elements of the wall anchorage system (Struts, cross-ties,
>> > chords, and subdiaphragms.) Note that Steel elements must be
>> > designed to
>> > resist 1.4 times the force generated by the Fp equation (In ASD &
>> > steel design). That means anchor bolts, metal straps (steel only,
>> not
>> > nails in wood- [that's the way I read it]), and simpson/kc
>> > metals/zone 4
>> > hardware must be selected to meet this increased force. But the wood
>> > elements, i.e. struts, bolted and nailed connections, and
>> > subdiaphragms
>> > need only be designed to resist 0.85Fp.
>> >
>> > Gerard Madden, P.E.
>> > Civil Engineer, Associate
>> > CRJ Associates, Inc.
>> > email: gerardm(--nospam--at)
>> > tel: 650.324.0691
>> > fax: 650.324.0927
>> > web: