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RE: IBC and Rho factor

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A point of clarification here. The limitation of Rho to 1.0 for light frame
shear walls was actually approved to the be incorporated to the 2003 IBC in
April of 2000. Long before ASCE 7 incorporated it per your email. The
proposal was submitted by the SEAOC Seismology. It intended to include the
concrete and masonry shear walls also. However, Dr. Ghosh, rightfully in my
opinion, spoke against extending it to those types of walls. (what good is a
4 ft concrete shear wall anyway?!)

On a side note:

The change has also been approved by the LA Basin Regional code Group and
will be adopted by ordinance throughout southern California jurisdictions.
We took up the same issue in our Tri-chapter (Bay area) code committee. Most
didn't think this is a real issue in residential (or light frame)
construction anyway, since you normally have many shear walls and most are
lightly loaded. We even asked our Plan check staff to see if this is a major
point of contention with designers, and all indications were that it is not.
And, some of the committee members were of opinion that it is not such as
bad idea to penalize short walls even in light frame constrion.

Ben Yousefi, SE
San Jose, CA

-----Original Message-----
From: Allen Adams [mailto:aadams(--nospam--at)]
Sent: Tuesday, October 01, 2002 11:38 AM
To: seaint(--nospam--at)
Subject: Re: IBC "Oops" (Was Residential Design Discussion)

One of Dennis Wish's core complaints in regard to this issue is the penalty
that the rho factor inflicts on short walls. This problem HAS been
addressed and is in the process of resolution. The Draft copy of ASCE 7-02
defines rho for walls essentially the same as in UBC 97, but then adds:
"... where the ratio 10/lw need not be taken greater than 1.0 for buildings
of light frame construction." Once ASCE 7-02 is formally approved, it will
be incorporated into the IBC.

If California would adopt the IBC, the problem that Dennis has addressed
would soon go away. But it is now a political matter, not a technical
matter: rather than directing your ire at volunteers who work on the
committees, contact your California State Assemblyman and State Senator.
They are the only ones now who can solve the problem (by getting the State
to adopt the IBC). There is not a mechanism in place to make changes to the
UBC (ICBO will soon be absorbed into the ICC), and I doubt the State has
the will to finance a replacement (it seems that the State was getting a
free ride on Code development). We can yell 'til we are blue in the face,
but it seems obvious to me that the UBC isn't ever going to be changed
again, no matter how outrageous it might be. As long as California chooses
to stay with the UBC, SEAOC is powerless - like eveyone else - to correct
the problems. So direct you energy to your Assemblyman and State Senator -
tell them to support adoption of the IBC (you are wasting your time telling
them to support changes to the UBC - it isn't going to happen). The UBC is
a dead horse. I'm not saying anything about how I thing things SHOULD be, I
am only telling it like I see it.

But somebody did address the issue of the rho factor, and they did push it
hard enough to get it approved in ASCE 7. Somebody worked within the system
to correct a problem. I don't know who on the ASCE committee was behind the
change; maybe it was even SEAOC members (my guess is that SEAOC had a hand
in it). Whoever it was, they should be thanked with as much energy as was
expended previously criticizing them.

Allen Adams, S.E.
RAM International

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