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[SEAOC] UBC 94 Concrete Shear Wall Design

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From: 	INTERNET:TAS052262(--nospam--at)aol.com
Sent: 	Sunday, August 25, 1996 5:51 PM
To: 	INTERNET:SEAOC(--nospam--at)SEAOC.ORG
Subject: 	[SEAOC] UBC 94 Concrete Shear Wall Design


>I've a few questions on UBC sec. 1921.6.5, Design of shear walls for flexural
>and axial loads:
>
>1. In sec. 1921.6.5.3, is Pu the axial load for the entire wall, or is it the
>boundary element axial load? Is Po the axial load capacity for the entire
>wall, or is it just for the boundary element. It seems to me that Pu & Po all
>should be considered as boundary element forces, but Code is not clear on
>that.
>
>2. In sec. 1921.6.5.4, is Ag the gross section area for the entire wall, or
>is it just for the boundary element which sometimes is portion of the wall,
>and sometimes is not even part of the wall.

The axial load and the moment on the shear wall is to act on the entire wall.
You should be designing the whole wall for combined axial and bending with the
appropriate load factors.  The detailing requirements for boundary elements
should be handled after checking the wall for the combined loading.

We have been using PCA column for our design program.  With the irregular column
add on package, you can design columns (walls) of any shape and steel layout.

The old 0.2*f'c requirements were very approximate and sometimes required such
large boundary reinforcing that the wall's bending capacity caused the shear
demand exceeded the  shear capacity resulting in a wall which was not ductile.
The point of the new requirements is to require the special detailing where the
strain exceeds 0.003.

I use a Mathcad worksheet for the calculations but use the PCA program for any
irregular shapes.

Eric Brown, SE

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