RE: Definition of A sub B in Rho evaluation

• To: <seaint(--nospam--at)seaint.org>
• Subject: RE: Definition of A sub B in Rho evaluation
• From: "Bill Allen" <Bill(--nospam--at)AllenDesigns.com>
• Date: Fri, 21 Jul 2000 12:47:43 -0700
```Ahah!

You left out the 10/Lw modification in the 100x100 building =8O

Seriously, while you have several variables to deal with I think the
original point is that, if you have two buildings with identical lengths of
shear wall and idential seismic mass (remember, although I know that's
difficult, that the original issue was whether the overhang eaves were to be
considered when calculating Ab), since Ab is in the denominator, I agree
that a larger Ab is conservative.

Recall the original problem with Ab=1600 SF or Ab=1936 SF. If r-sub-max=0.5,
then

for Ab=1600 SF, rho=1.00.

for Ab=1936 SF, rho=1.09.

Regards,

Bill Allen, S.E. (CA #2607)
ALLEN DESIGNS
Laguna Niguel, CA
http://www.AllenDesigns.com

||-----Original Message-----
||From: Paul Feather [mailto:pfeather(--nospam--at)san.rr.com]
||Sent: Friday, July 21, 2000 11:31 AM
||To: seaint(--nospam--at)seaint.org
||Subject: Re: Definition of A sub B in Rho evaluation

<snip>

||Since rho is calculated as 2 - 20/r*sqrt(Ab),  as Ab
||increases rho will
||increase getting closer to 2.  This in turn will increase the
||base shear V
||and the element shear vi.
||
||I do not see how a larger Ab is unconservative.
||
||For example I like to look at a box with walls on four sides.
|| If the box is
||10 x 10, Ab is small and the box is fairly redundant.  If the
||box is 100 x
||100, Ab is larger and the box is considered less redundant.
||This makes
||sense to me if you think in terms of demand on single
||elements (diaphragm,
||chords, drags, etc.)
||
||Anyway, my two cents worth,
||
||Paul Feather
||
||
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