The message you may be looking for is from Ron Hamburger. It gives
background on the development of the factor.
Bill Cain, S.E.
Here it is:
On Fri., July 30, 1999 wrote:
"From: "Ron O. Hamburger" <ROH(--nospam--at)eqe.com>
Date: Fri, 30 Jul 1999 14:45:57 -0700
Subject: Redundancy Factor
A recent thread of discussion on the list server has called my attention to
what I believe is an uintentional and also unfortunate problem with this
factor in the 97 UBC.
When the committee first developed this factor, the intent was that the
rmax represent the % of the story shear carried by the most heavily loaded
element. We then proceeded to define what an "element" is. For example,
each brace is an element, etc. When we got to shear wall structures, the
intent was that each individual wall pier across a horizontal plane cut
through the building would be an "element". Then, someone on the committee
noted that if you had a 100' x 100' tltup type structure, with a number
of20' wide panels, this would be considered to have high redudance (because
each 20' panel would be an element) however, if you had the same structure
with cast-in-place walls, then it would be non-redundant, as the whole side
of the strucure would be only one element. In order to solve this problem,
for shear walls, we introduced the rule that when a shear wall exceeded
10'in length, each 10; segement (or part thereof) could be considered an
element. The intent was as follows - If you have a wall line with 10 -
4'piers between windows, each pier would be an element. If you had a wall
line with a 40' wall, you would have 4 elements. Somehow, in the word
smithing that went into the actual code language, this logic got badly
messed up. Now each wall segement is multiplied by 10/lw.This has the
desired effect for long walls, but has a penalty effect for short wall
segments. This was, in my opinion, never intended. This has some serious
negative impacts on wood frame construction.
Please consider this matter, at your next Seismology Committee meeting."
From: rlewis(--nospam--at)techteam.org [SMTP:rlewis(--nospam--at)techteam.org]
Sent: Thursday, January 13, 2000 2:47 PM
Subject: Need old RHO messages
I would appreciate anyone who can doing me a favor. I have been
trying to dig
through the SEAInt archives for over an hour and can't find the
remember reading last fall. Back then I was casually reading all
messages on 10/Lw term in the RHO calculation for UBC Eq. 30-1