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RE: RE: Question for East Coast Engineers

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Everyone knows (or thinks they know) where I stand on Conventional Framing
issues. To put it simply - I'm not against the idea, I'm against releasing a
prescriptive method to any owner or builder that is incomplete. This section
of the code lacks a great deal of information that may become simply
assumption or "rule-of-thumb" field decisions. Obvious example - header
sizes.
My second issue is one of disclosure - the largest proponents of
Conventional Framing is the developer or builder who profits the greatest
from it's use. The home-buyer is unaware of the level of performance which
their home was design against. This disclosure would allow a home owner more
choice as to the extent and type of insurance coverage they might need, or
allow them to calculate the effect of exceeding their deductible against
their earning to debt ratio.
This section of the code allows builder to disregard the mitigation of
damage built into other sections of the code and to advertise a quality
structure comparable to an engineered home. This is, in my opinion, false
advertising.
Case in point. Homes in our area rarely exceed typical floor plans for a 50
x 100 lot. Based upon set-back requirements homes rarely exceed 60' deep (to
front of garage) and 40' wide (including a 5' setback on each side). Roof
trusses span the 40' and are generally mission tiled. The builder installs
4x8 shear panels on the load bearing side - spaced at 25' maximum per code.
Interior braced panels are gypsum sheathed wall (not extended to the roof
since ICBO never issued a revision to this mistakenly omitted section).
In the direction parallel to these walls, seismic will generally govern. Rw
is 6 since gypsum used inside. This means that there is an uplift on the
panels. However, the code only requires holddowns under the provisions of
alternate braced walls for a 2'-8" x 10 high panel typically at the front of
a garage. Therefore the uplift (over 1,500 lbs.) is neglected under the
provisions of the code.
Was this the intention of the code? Is it advisable to allow gypsum to be
used as a shear resisting element in seismic zone 4 after what we found from
Northridge? Should it be allowed full value (150 plf, 300 plf both sides).
Next, the rear wall of the garage is typically the interior braced panel
since it occurs at a foundation (roof trusses will change at this location
to allow for the ridge to move on the garage). Therefore it is easier to
install a drag truss above this common wall or panel it all the way to the
roof.
I have calculated many of these (probably around 100 in the last five
years). The drag truss at the back of the garage (50% of the tributary
shear) generally requires a capacity of around 5,500 lbs. based upon wind
load governing in the transverse direction. In less my math is wrong - if I
consider 300 plf for gypsum both sides, you need 18 linear feet of wall -
something not readily available in a 20' wide garage with a door entering
the house, cutouts for plumbing and venting and protrusions for vents and
hot water heater.
Simply put, there is no way that this is even adequate outside of
restriction areas such as Los Angeles that have reduced the value for
gypsum.

The engineering community and the insurance lobbyist need to help create
legislation in Seismic Zones 3 and 4 which make it mandatory to disclose to
potential buyers that the structure was designed and constructed at the
minimum allowable standards allowed by code. The provisions can rate the
performance standard based upon submittals or issuance's of permits where
the building official can place a rating - non-engineered, engineered,
custom (no I would not say over-engineered:>))

If this were done, we would not have an argument about conventional framing
as far as I was concerned. This would also allow engineers to advertise
"safer buildings through Structural Engineering". The developer / Builder
then has to consider the owner of their product before he considers how to
spend his profits.

Dennis Wish PE



-----Original Message-----
From: Rhkratzse [mailto:Rhkratzse(--nospam--at)aol.com]
Sent: Thursday, May 14, 1998 5:42 AM
To: seaoc(--nospam--at)seaoc.org
Subject: Re: RE: Question for East Coast Engineers



In a message dated 5/7/98 3:27:19 PM, RR wrote:

<<Building Officials have a
problem with any group who propose code provisions which are intended to
force the public into hiring the proponent in order to comply with the code
provision.
>>
Yup, and if BOs ran medicine brain surgery wouldn't be restricted to brain
surgeons, would it?  Shouldn't we (they) be looking at the value of the
provision rather than--or at least in addition to--the potential benefit to
the proponent?  I mean, we're not used-car salespeople, are we?  (Are we?)

Ralph Hueston Kratz, S.E.
Richmond CA