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Re: Is it a shearwall or not??? Need some help

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One can assume anything.

The EQ meanwhile will determine the path of least resistance whatever the
"assumption".

It will decide what was and what wasn't a "shear wall".

Caveat...Caveat...

jim
----- Original Message -----
From: "Dennis Wish" <dennis.wish(--nospam--at)gte.net>
To: <aec-residential(--nospam--at)polhemus.cc>
Cc: "SEAINT Listservice" <seaint(--nospam--at)seaint.org>
Sent: Thursday, November 02, 2000 9:15 AM
Subject: Is it a shearwall or not??? Need some help


> I have a small project which I need some advice. Because I am on the
SEAINT
> list in digest format, I would appreciate it if anyone who responds can
send
> it to me directly at admin(--nospam--at)structuralist.net. Here is the problem:
>
> The building is a concrete commercial building about 50 years old, two
> stories - 45-feet deep by 38-feet wide. The roof and floors are framed
from
> a center wall parallel to the 38-foot width. This means that the floor
> framing does not exceed 19-feet on either side of the interior bearing
wall.
>
> At the second floor, this partition is the full depth of the diaphragm -
> roughly 45-feet and is sheathed in gypsum board on both sides. On the
first
> floor, this interior bearing wall is less than 35 feet long with various
> openings. It is sheathed with gypsum on one side and paneling on the
other.
>
> The client wants to place a 27-foot opening in the second floor wall to
join
> the two office spaces.
>
> Problem:
> Inasmuch as there are no existing drawings or analysis, I am afraid that
if
> the wall were designed for shear (150 plf times two sides or 300 plf) I
> would be redirecting the shear into the exterior concrete wall sections.
The
> problem is that the second floor exterior walls are sufficient for shear,
> but the first floor is glass storefront with minimal shear resistance in
the
> form of a cantilevered panel that sits back 8-feet from the glass front.
>
> Assumption.
> I need to know if the conclusion I wish to draw is a valid assumption:
>
> The first floor bearing wall (interior) is significantly weaker than the
> second floor wall if shear is considered - about 1/4 of the second floor
> wall capacity. I would assume that the wall, although bearing, is not
> designed to transfer shear from the roof to the foundation since the first
> floor wall would never be able to meet the demand.
>
> It is possible that the building had been remodeled numerous times and
shear
> removed with each attempt, however, I don't believe I need to go further
> than to assume the building to be laterally stable at the time I started
> work on it. Therefore, I would treat this second floor wall as only a
> bearing partition and make the opening.
>
> The problem of trying to recreate the shear at the second floor is more
> difficult as the opening at the second floor occurs above the solid
portion
> of wall below - leaving me a difficult time trying to beef up the second
> floor panels and tying them down (uplift and compression).
>
> The size and ratio of the building plan is such that an interior shearwall
> at the second floor would not be necessary. It is also unusual for a
> building this size to use an interior shear wall when the owners of
> commercial structures like to leave room for the potential of removing or
> opening up the space at each level.
>
> Question:
> Does my assumption seem to be valid - that is, assume the wall is not a
> shearwall and simply provide the header and post connections to transfer
> down to the first floor foundation.
>
>
> Regards,
> Dennis S. Wish, PE
> Structural Engineering Consultant
> structures(--nospam--at)engineer.com <mailto:structures(--nospam--at)engineer.com>
> (208) 361-5447 E-Fax
> ICQ #95561393
>
>
>