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# RE: Story Drift: 1994 UBC vs. 1997 UBC

• To: <seaint(--nospam--at)seaint.org>
• Subject: RE: Story Drift: 1994 UBC vs. 1997 UBC
• From: "Bill Allen" <Bill(--nospam--at)AllenDesigns.com>
• Date: Thu, 12 Aug 1999 17:51:28 -0700

```O.K., I think I have almost totally lost faith in the 1997 UBC.

I have moved beyond cantilevered columns and have stopped trying to see if
they would work in a "real world" building based on 1630.9.

Now, I started looking at plywood shear walls.

I have done some calculations based on the following:

Length of shear wall (b)=4 ft.
Height of shear wall (h)=8 ft.
3/8" CDX plywood w/8d @ 3"-3"-12"

Fv=490 PLF.

Using the shear load and neglecting any gravity loads, I used a hold down
force of h * Fv = 3920 lbs.

Based on this I selected a HD5A with a 4x4 post.

Nothing unusual so far, right?

Well, based on my calculations, the Dm is (sit down please) 8.6 inches which
is 0.09 * h (nowhere CLOSE to 0.025 * h).

You can review, throw darts, tear apart and further discuss these
calculations. They are at:

http://www.AllenDesigns.com/SW/ShearWallDeflections.htm

Yes, every engineer will have a slight editorial about a detail assumption
(I could have used Struct. I and a PHD instead of a HD) but please look at
the "Big Picture" and comment.

I feel like I'm doing calculations in metric all of a sudden.

Regards,

Bill Allen, S.E.
ALLEN DESIGNS
Laguna Niguel, CA

```