worry about eccentricity," but they still have a footnote in their catalog
that says the specifier is responsible for post design.
You would be standing front and center if a shear wall end-post you designed
failed because of eccentric loading.
Thor Matteson, SE
www.shearwalls.com
> From: "Bill Allen" <t.w.allen@cox.net>
> To: <seaint@seaint.org>
> Subject: RE: Is it just me?
>
> This is a multi-part message in MIME format.
>
> ------=_NextPart_000_0000_01C972EF.A1B58D70
> Content-Type: text/plain;
> charset="us-ascii"
> Content-Transfer-Encoding: quoted-printable
>
> Thanks, Oshin.
>
> =20
>
> =20
>
> T. William (Bill) Allen, S.E.
>
> ALLEN DESIGNS <http://www.AllenDesigns.com>=20
>
> Consulting Structural Engineers
> V (949) 248-8588 . F(949) 209-2509
>
> -----Original Message-----
> From: Oshin Tosounian [mailto:oshin@sdgseinc.com]=20
> Sent: Friday, January 09, 2009 8:40 PM
> To: seaint@seaint.org
> Subject: RE: Is it just me?
>
> =20
>
> Bill,
>
> =20
>
> Don't bother. Check this first:
>
> =20
>
> http://www.strongtie.com/literature/TechTopics/eccentric_holdowns.htm
>
> =20
>
> Oshin Tosounian, S.E.
>
> _____ =20
>
> From: Bill Allen [mailto:t.w.allen@cox.net]=20
> Sent: Friday, January 09, 2009 4:02 PM
> To: Seaint
> Subject: Is it just me?
>
> =20
>
> When specifying a Simpson PHD hold down, one of the footnotes reads =
> "Post
> design by Specifier." In looking at the HDQ8 in 2-2x4s, the capacity is
> listed as 5,715 lbs. Based on an eccentricity of 3"(CL=3D1.5" + 1.5" for =
> one
> 2x), the weak axis bending moment due to the eccentricity is 1,428 =
> ft.-lbs.
> Assuming the 2-2Xs are face nailed adequately to transfer VQ/I stresses,
> this moment results in a bending stress of 3,266 psi on the gross =
> section.
> The allowable stress on a 2x4 DF-L section is of course quite a bit =
> lower
> than this, not even considering combined stresses.
>
> =20
>
> Have I forgotten how to properly draw a free body diagram or is there
> something else going on here?
>
> =20
>
> Otherwise, is it misleading to list 2-2Xs with a hold down of this =
> capacity?
>
> =20
>
> Regarding the VQ/I stresses, if the height of the studs are 8 feet, then =
> the
> shear on the post is Pe/h =3D (1428)/(8)=3D 179 lbs. Then VQ/I =3D
> (179)((3.938)/(7.875)=3D90 lbs/in. Using 10d FN (capacity =3D 115 x 1.60 =
> =3D 184
> lbs each), the spacing would be 184/90 =3D 2" o.c.
>
> =20
>
> This doesn't seem right to me.
>
> =20
>
> If the two studs aren't nailed adequately to transfer VQ/I stresses, =
> then
> the bending stress due to the eccentricity is even higher (6,528 psi) =
> since
> S reduces to 2x1.313=3D 2.625 in3 from 5.25 in3.
>
> =20
>
> Maybe I should put away the calculator on Friday afternoons.
>
> =20
>
> If anyone would care to shed some light on the calculations, I would be =
> most
> appreciative.
>
> =20
>
> Thanks,
>
> =20
>
> T. William (Bill) Allen, S.E.
>
> ALLEN DESIGNS <http://www.AllenDesigns.com>=20
>
> Consulting Structural Engineers
> V (949) 248-8588 . F(949) 209-2509
>
> =20
>
>
>
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