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RE: Thickened footings under interior braced walls (Was: RE Hardy Frames)

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Most of us never put our noses where they don't belong and in my
opinion, engineers don't belong in Conventional Construction because we
can't make the numbers work. Conventional Construction, in its original
intention, was to replace log cabins when the first railroads were
constructed out west and saw mill equipment was shipped from the East to
the West.

To address the issues in your e-mail; 
1. I see one area of argument. Section 2320.11.3 in the last paragraph
states; "....Sills shall be bolted to the foundation OR SLAB in
accordance with Section 1806.6."  I would interpret this (as would the
city inspector who does plan check for conventional construction)
connection to the foundation at the perimeter walls and the slab to be
used for braced wall panels on interior walls (or why even mention slab
unless intended to be used for a braced panel). Our building department
interprets this as differentiating between exterior foundation walls
(slab on grade) and interior slab thickness and is willing to let anchor
bolts extend into dirt. Their rationale is that pinning the sill to a
slab accomplishes the same thing as embedding it into the foundation -
it prevents the wall from sliding.
 
There must be something more definitive on this, but the trouble is
finding it.

(2) Section 2320.11.3 does set a minimum of 48" for wall panels up to
10' which would be a 2.5:1 ratio for shearwalls (or braced wall panels).
Section 2320.11 does not explicitly indicate a wall ratio other than it
does explain alternate braced panels in section 2320.11.4 and sets a
limit on these walls that can not be less than 2'-8" for limits up to
10-feet. For this condition, it sets a resistance to uplift at each end
of 1,800 pounds and then requires a tie-down device be installed for
this capacity. This increases if the alternate panel is on the first
floor of a two story building in which case the uplift is increased to
3,000 pounds.

So here is one question that confuses me: If a project is to be
prescriptively constructed, where is the span charts for beams and
headers over 8'-0" in width? How are the cities allowing more
complicated building designs to be done by conventional framing and not
providing span ratings for headers, beams and girders - who is to design
these? Even something so simple as a garage door header is not clearly
spelled out in the code and I don't find the section that says you must
use the 1-inch per foot rule for wood (16-ft opening therefore a 4x16 or
6x16 beam?

Dennis

-----Original Message-----
From: Thor Matteson, SE [mailto:matteson(--nospam--at)yosemite.net] 
Sent: Friday, October 24, 2003 7:50 PM
To: SEAINT
Subject: Thickened footings under interior braced walls (Was: RE Hardy
Frames)

Dennis,

Our local building inspector called us one day because a contractor's
plans
showed  the sill for an interior braced wall shot down onto a 3-12 inch
slab.  The inspector wanted help finding something in the code that
prohibited this.  Since I like to stay away from the Conventional Light
Frame section, I could not immediately point to something, but he ended
up
finding it himself.

In the very last paragraph of UBC/CBC Section 2320.11.3, it states:
"Sills
shall be bolted to the foundation or slab in accordance with Section
1806.6."    Section 1806.6 calls for anchor bolts "embedded at least 7
inches into the concrete or masonry".   This was enough for our
inspector to
require footings under interior braced walls.  But he was actually
TRYING to
find a way to do that--if you have someone trying to find a way NOT to
require it, they could latch onto the "foundation OR SLAB" phrase;  but
there's still the 7-inch required embedment, and I hope any inspector
knows
the 3-inch clearance requirement from steel to soil for concrete--that
gets
at least a 10-inch "footing".     Which is probably sufficient for those
lame-O braced wall panels anyway.

Main problems I see with Hardy Frames, Strong-walls, Z-Walls, TJ-Shear
Panels,  Shear Max, etc.  are when people try to fit them into
applications
where they need to be put on concrete pedestals, have a cripple wall
built
on top of them, or some other such thing.  My upcoming book <advertising
mode on> (reserve your copy now at www.shearwalls.com) <ad mode off> has
several photos (taken elsewhere) of pre-fab bracing units placed on
severely
spalled concrete curbs, shimmed with square washers, mis-used on second
floors, and "oops--we forgot to attach it to the top-plate" types of
installations.

Artificial shear walls have not infiltrated the construction market in
my
corner of Calif. yet, so can't comment on what contractors prefer.

By the way, you state that  "the braced panels called out in the code
don't require resistance to uplift unless they are less than a 2:1
ratio".
Is this explicitly stated in the code?  My impression is that braced
wall
panels can be used in walls up to 10 feet high (the limit for
"conventional"
framing), which would be 2.5:1.   But like I said, I try not to become
too
familiar with that code section....I don't want to find myself looking
up in
a span table what I could calculate in 1/3 the time!

Thor



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