Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Is it just me?

[Subject Prev][Subject Next][Thread Prev][Thread Next]
I find it curious that Simpson's technical paper says (basically) "don't 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(--nospam--at)cox.net>
To: <seaint(--nospam--at)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(--nospam--at)sdgseinc.com]=20
Sent: Friday, January 09, 2009 8:40 PM
To: seaint(--nospam--at)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(--nospam--at)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





******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
* Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********