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

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Stan,
This is not the case in the Coachella Valley (Palm Springs, Cathedral
City, Rancho Mirage, Palm Desert, Indian Wells, La Quinta, Indio,
Thermal, Desert Center, 1000 Palms and the high desert). Each one of
these cities require Holddowns on prescriptive construction only on
"Alternate Braced Wall Panels" that is a maximum of 2'-8" for walls
plates up to 10'-0". In fact until the 97 UBC Section 2320, I do know of
job instances where interior braced walls were anchored to the slab with
no foundation. I have not checked since the codification of the 97 UBC
but I do remember that the question came up at the start or before and
the head of the La Quinta plan check for conventional construction.
I did not catch the wording of the code that Thor enlightened me about
(foundations below sill plates) and have not brought this to the city's
attention if it in fact needs their attention.

Shearwall design is only required by engineered projects. This is what
differentiates Braced panels from Shearwalls - the former has no
analysis performed and rocking must be assumed as it is not required to
resist uplift and also as Thor pointed out, the H/b ratio increases to
2.5 for 48" walls that are 10'-0" plate to plate.

Dennis

-----Original Message-----
From: Stanley E Scholl [mailto:sscholl2(--nospam--at)juno.com] 
Sent: Saturday, October 25, 2003 10:45 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Thickened footings under interior braced walls (Was: RE
Hardy Frames)

I believe that most cities in CA have adopted modifications to the Code
and won't allow any kind of shear wall or frame without a footing to
support it and to hold it down from uplift, and they require calcs. to
prove that the hold down is adequate (grade beam calcs.). 
For interior shear walls the footing and slab can be monolithic with
reinf. top and bottom and will usually work. Thus a thickened slab with
a
12" x 12" section under the wall will work for light loads. If you call
it a "grade beam", 3000 psi concrete and deputy inspection is required. 
No agency that I know of would allow any kind of a shear wall on a 4"
inch slab only.

Stan Scholl, P.E.
Laguna Beach, CA


On Sat, 25 Oct 2003 13:10:42 -0700 "Dennis Wish"
<dennis.wish(--nospam--at)verizon.net> writes:
> 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
> is 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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