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Re: IRC Braced Panels

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Ted,

I'll disagree with you here. From what I have seen the IRC is not fairly restricted but extremely abused. As in my last reply, I have seen way too many homes being allowed to be built by the IRC that shouldn't even be considered by the building officials. There are no guidelines in the code as to when the IRC can be used other than whether the structure is "unusual" or not. There is no definition of what is unusual. Some have said that there are definitions to that regard in the seismic section of the IBC, but that is kind of like a definition twice removed. Building officials won't go to the IBC to the seismic sections to restrict a home that is built in wind areas when the criteria in the IRC doesn't point them there. What they see is a simple sentence giving no guidelines for what is unusual and then make a judgment from there. Building officials in my area simply don't make that judgment they just see that is a residence and say OK it can be built by the IRC. I have had architects, designers, and builders come to me with 5000 sq. ft. plus homes with many offset dimensions in plan, many offsets in roof diaphragm elevations throughout the structure, no load paths to walls, etc, etc. The building official might ask that one or two exterior walls be checked as shear walls, and only then because they may not be the minimum length per IRC. When I have explained this problem to the potential client I have NEVER had one ask for a full lateral analysis. Why spend a couple thousand when a couple hundred will get them their permit?

If the big wind or earthquake does come where then will the liability fall? I can just hear it now "well gee, I had an engineer look at it, and his name is "Brand X" engineering. See here are his calculations." And if we don't do it, we engineers in Smallville don't pay our bills.

J. Grill


----- Original Message ----- From: "Ted Ryan" <coffeemonkey100(--nospam--at)hotmail.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, January 11, 2005 10:07 PM
Subject: Re: IRC Braced Panels


Again, missing the point. Regardless of whether the IRC calc's out or not,
homes built in a manner consistent with the IRC generally perform well in
high seismic or wind events.  The IRC takes into account the redundancies
that we aren't able to in design.  The applicability of the IRC is fairly
restricted so that it isn't used in situations where an engineered design is
warranted.

Ted Ryan


----- Original Message ----- From: "Dennis S. Wish, PE" <dennis.wish(--nospam--at)verizon.net>
To: <seaint(--nospam--at)seaint.org>
Sent: Monday, January 10, 2005 5:51 PM
Subject: Re: IRC Braced Panels


I think most of you know my strong views against the IRC (well the UBC
Section 2320 for Prescriptive light framing) in high risk areas. This
also includes areas open to high winds that might not be at risk from
earthquake and wind.

My first complaint is that the braced panel is not required to resist
overturning by installation of holddowns. I've run an equivalent
analysis on a small 40-foot wide home with a tile roof and with 4'x8'
braced panels at 25-feet on center. The load to the panel was sufficient
to cause an uplift on the wall regardless of the dead load from the clay
tile roof. In most areas, clay tile is not an issue and asphalt shingle
is more likely.

The only reference I recall to resisting uplift is if you use an
alternate braced panel 2'-8" wide up to 10'-0" in height in which case
it is only required to resist a load of around 1800 pounds of uplift (or
maybe it was 1500 pounds). The point is that it won't calc out.

So what purpose does it serve to have an engineered code that
consistently gets more aggressive in designing for better performance by
using more plywood or proprietary shear walls and more hardware? Given
the choice, a developer will go for the least cost and greatest profit.

Here is another thing that drives me nuts. Every year I drive from
California (Palm Springs area) to Chicago. I look at all the new
developments in Arizona, New Mexico, Texas, Oklahoma, Missouri and
finally Illinois. The one state that uses the least materials and is at
the greatest risk is California. The majority of housing tracts that
I've seen in Arizona and New Mexico will actually sheath the entire
home. Yes, I believe they still cut back on some of the hardware that
might help resist uplift, but they are not stingy on sheathing. Yet in
California you will find tract developers cutting the amount of
sheathing on prescriptively built homes (those smaller developers who
are building around ten homes a year) to those large developers catering
to the more affluent who still want to cut back on sheathing in order to
maximize profits. They push their engineers (larger tracts are almost
always engineered) to design with the least materials possible.
In the heat of an argument with the construction manager for Sunrise
Corporation, I was told simply that this is a free enterprise system and
if his engineer can design it with the least materials to pass the
permit stage he is free to maximize his profit margin for the company he
works for.
Yet none of this information is ever disclosed to the home buyer who has
to pay the price of their deductible (if they have sufficient insurance)
to cover their out-of-pocket costs.

Look, we know it is not a life safety issue, but the housing industry
can consider the financial impact poor performance will have on the
homeowner, the insurance industry and the federal government in grants
and low interest loans to help pay for the repair for qualified
homeowners.

Is this really justification for a free enterprise system or for
temporary housing before the cost of real estate rises to house the more
affluent who will pay even a higher premium for a home built
prescriptively to the Residential Codes.

Doesn't make a lot of sense to me.

Dennis S. Wish, PE

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