Subject: Charles Greenlaw Response to "Unblocked Plywood Diapghragm Deflection Calc."
Date: Sat, 22 May 1999 04:36:07 EDT
You have done it again. You hit the ball out of the stadium for a "homerun."
In your May 21, 1999, 12:58:42 am, Pacific Daylight Time, SEAOSC List Server
posting you stated:
[C.G] "I can't relate this to FEMA 273 which I don't have and am not
interest in yet, in observance of the Satchel Paige principle."
[F.M] As I recall Satchel Paige is quoted as saying: "Do not look back they
might be gaining on you." Is this the correct quote or did you have another
quote in mind?
Please do not apologize that you do not have a copy of FEMA 273. Keep your
innocence (virginity) and "just say No."
If you like the 1997 UBC, you will love FEMA 273/274 and 310, a
"Prestandard." What is a " Prestandard?" It sound like a "Prestandard" is
like a drug that is available to the public that has not been completely
tested for approval by the Food and Drug Administration.
Seriously, As I understand it, the University of California Systemwide has
designated FEMA 310 as the "de facto" standard for the evaluation of
University of California buildings. FEMA 310 is the "Reader's Digest"
version of FEMA 273. Refer to Lynn Howard's SEAOSC List Server postings on
[C.G.] "These look like rank guesses, not like authoritative results of
research. I hope they are not supposed to be used for other than very rough
[F.M.] FEMA 273, Chapter 8 has many numerical values that look like "rank
guesses." In FEMA 273, Chapter 8, Table 8-1, Numerical Acceptance Factors
for Linear Procedures - Wood Components. Why are the "m" values for Gypsum
Plaster on Wood Lath, Gypsum Plaster on Metal Lath, Gypsum Sheathing and
Gypsum Wallboard greater than the "m" values for Structural Panel or Plywood
Panel Sheathing or Siding? The authors of FEMA 273 have told me that these
"m" values are based on research, but they have not referenced the relevant
research so one can make one's own evaluation.
[C.G] "Where's FEMA in this? Church, state or is it all the same?
[F.M.] With all due respect, FEMA 273/274 and 310 are sent from Washington,
D. C. to help us. A takeoff on "I am from the Federal Government and I am
here to help you." Call FEMA Publication 1-800-480-2520 for a copy of
FEMA273/274, but not FEMA 310, which is being handled by ASCE.
I am glad I am not young any more and will have to apply these FEMA
Guidelines on "real buildings." George Greenlaw, there is a whole new
"cottage industry" developing out there. Establish a "900" number (not an
"800 number) and provide a peer review or "fee for service" to interpret and
answer questions concerning FEMA 273/274 and 310. You will make a million
One of my pet peeves is how the issue of "Linear Treatment of Overturning"
is treated in FEMA 273. A Draft March 30, 1999, BSSC Case Studies Project
Report (Final Copy will be available in September 1999) based on the
application of FEMA 273 to "real" buildings states: "The provisions for
determining overturning effect using the Linear Procedures in FEMA 273 are
not adequate. Without the use of the sidebar on page 2-38, FEMA 273
calculated overturning effects produce deficiencies inconsistent with
observations of past building performance. With the use of the sidebar, an
odd inconsistency may result in which the superstructure is not in
equilibrium with the reduced foundation forces."
I can hardly wait for the comments from the authors of FEMA 273/274 and 310
who will say I have "stepped over the line" again by raising questions
concerning FEMA 273/274 and 310. I have tried to work within the FEMA
Committee System, that developed these FEMA Guidelines, to attempt to resolve
many of the important questions and issues, but with little success, so I
feel I have a professional obligation to bring these matters to the general
structural engineering profession for its consideration.
Stay well! Keep your SEAOSC List Server postings coming. It is later than
Frank E. McClure FEMCCLURE(--nospam--at)aol.com May 22, 1999