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# Redundancy Factor

• To: "Ron O. Hamburger" <ROH(--nospam--at)eqe.com>
• Subject: Redundancy Factor
• Date: Fri, 30 Jul 1999 17:50:17 -0700
• Cc: seismo-all(--nospam--at)seaint.org, seaint(--nospam--at)seaint.org

```[part two of copied message to Dennis Wish: rho factor findings conclusion,
and recommendations for change.]

In another exercise, I added in numerical values. On my 30ft square floor
plan I used a 34 ft sq roof weighing 15 psf, but weightless walls, and
two-3ft long shear panels each ext wall (at only 202 lbs/ft, where V=0.14W
net in ASD.) Rho came out less than one by a little bit at 0.93. Then I
expanded the floor plan and roof plan to 41.64 ft square, (no eave this
time)at a lighter 10 psf roof wt, and weightless walls. This change gives
the same seismic W and uses the same shear wall schedule as before, but
bigger floor area A sub B. Now rho is 1.23, a substantial increase over 0.93
for the same bldg wt W, and the same shear walls as before. What's
"rational" in that?

The same upward jump in rho would occur in two identical houses, except that
the second is in zone 3 instead of 4, and each wall's shear panels are
reduced to about 3/4 as long in the second house, in proportion to the
reduced base shear. Shortening these panels however raises the rho factor,
when the basic lbs/ft shear stress and layout hadn't changed at all. What's
rational in that?

I conclude the rho factor in its shear wall form is not ready for prime
time, let alone continuation in the 2000IBC that's essentially finalized.

I strongly suspect from carefully reading that 1996 Blue Book Appx C
Commentary on rho, which reads erratically like its author didn't
understand, and from the results I found in running examples, that
Seismology never gave any due attention to how their obviously moment-frame
and braced-frame oriented rho factor would work out for wood shear walls in
houses and the like. They have been posturing as knowing what they were
doing, when they surely didn't know.

Further I would say that the Committee, in extending its work to apply to
shear wall houses, is INCOMPETENT to do so (lack of familiarity and the
education that comes from being involved), is NEGLIGENT for putting out a
code in finished form on its own without overcoming its lack of competency,
and has committed MISREPRESENTATION and DECEIT by dishonestly asserting in
its commentary various untrue claims as to the result being collective,
expert, well-considered judgment, and asserting that the rho factor cures
redundancy problems in ALL the given forms of lateral systems. These are all
professional practice offenses the PE Board disciplines for, and on flimsier
interpretations than I have just made.

I'd posted some days ago that I'd talked with Norm Scheel, a residential
design engineer and immediate past SEAOC Code Comm Chair, about
residential's hassles. He too is disgusted. We discussed the desirability of
an in-between code for woodframe residential that we would use when
conventional isn't allowed or isn't wise, but when the rigorous, full-house
seismic code from Seismology Committee (the only alternative now to
conventional) is poorly applicable or wrong, or unjustifiably complex and
exacting, or otherwise inefficient and unnecessary for obtaining decent
performance in the type of structures that houses are, or dangerous to the
engineer using it, like due to ambiguity.

As you noted the Seismology Committee has been strikingly silent on
answering the questions many of us have posed on residential- oriented
applications. It seems the committee doesn't know, and blames the messengers
who discovered they don't. Further, the decades-old sole purpose of the
Committee having autonomy from the SEAOC Board is so it can answer questions
promptly and evolve its position without waiting for SEAOC Board approval
each time the need arises. Your outrage at the Ron Gallagher interview
comment to Goldstein in "Plan Review" was entirely correct in that you
protested a lengthy and glaring abuse of privilege by the Committee.

One thing I cannot avoid concluding: Seismology Committee as we know it is
NOT, by temperament, interest, or intimacy with the applicatation, capable
of solving the present problems about seismic for woodframe residences.
Seismology Committee should admit this, should formally resign from
residential woodframe and declare that it cannot and will not assert itself
as a code authority in that area, and should then give the problem of
finding an organizational remedy back to the SEAOC Board of Directors it is
properly accountable to. Nothing less will do. No chance of getting a
simple, efficient, safe-for-engineers residential seismic code exists as
long as Seismology thinks it owns the show.

Hope this is responsive on some of it. More to follow in a couple of days.

Chuck

[end of copied in message; end of part two of two of main message. -C.G.]

```