Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Posting of Gary Searer SE Pre-meeting Proposal for changes to Rho

[Subject Prev][Subject Next][Thread Prev][Thread Next]
This message is too long to be posted to this list.

I am pleased to have posted the original 8/15/2000 submittal "Evaluation of
the Reliability/Redundancy Factor - Rho" by Gary Searer, SE of Wiss, Janney
& Elstner Assoc. Inc. on the Structuralist.Net Discussion forum. The papers
are posted on the discussion forum which is accessible from the
Structuralist.Net Professional Website at The paper was submitted to
the SEAOC Seismology Committee's August meeting and briefly reviewed by the
committee. I urge each of you who are affected by unreasonably high
calculations for Rho on building which contain reasonable redundant systems
to review the document and submit comments to the Seismology Committee.

In addition, Gary has submitted three additional publications related to the
first document;

1. Gary has submitted a suggested proposal for revision to the code for the
calculations of Rho. A brief discussion of the document and a copy of it in
PDF format is accessible from this same forum.

2. Based on the compromises made to the proposed new code, Gary has included
a summary of the revised corrected solutions to his many examples published
in the 8/15/2000 document (also on this forum).

3. Finally, Gary has posted a summary of the changes and his conclusions as
to what benefit if any can be gained by his revisions.

Each document has been listed as a separate forum topic to allow your
comments and opinions. At the end of each forum message is a link to the
SEAOC main office e-mail (The e-mail links to all committees are no longer
accessible on the SEAINT and SEAOC websites and is not listed in the new
2000-2001 Roster. I would conclude that they no longer want to hear from
members other than through their office management.

Please review the documents and send your comments and opinion on to the
Seismology Committee by clicking on the link. It is not necessary for you to
be a member of SEAOC as the provisions are published in the same code that
we all use or will use if and when the IBC is adopted.

Personal Opinion

FWIW, I admire the effort and work that Gary has put in on these documents.
Still, I feel it is a Band-aid approach for a factor that has value in some
buildings but not all. Furthermore, as Gary has proven, the calculations for
Rho will penalize a building with obvious redundancies. An evaluation that
incorrectly penalizes a structure with known redundancies is, in my opinion,
inappropriate for publication. A Band-aid is only temporary until other
flaws are discovered.
There have been many examples of small wood framed structures (under 8,000
square feet) with many interior partitions as well as exterior shear
elements that we know to be redundant and which, calculate with penalties.
This is frustration and costly to the owner - an expense that the Seismology
committee ignores.
The SEAINT website has a paragraph defines structural engineering as:
"..the science and art of designing and making, with
economy and elegance, buildings, bridges, frameworks and other similar
structures so that they can safely resist the forces to which they may be
subjected." It's about time to strike the "economy" from the credo.

The Seismology Committee has forgotten that there are two sections
of the codes, Prescriptive Conventional Construction provisions vehemently
supported by the NAHB and full-compliance stubbornly protected by the SEAOC
Seismology Committee.
As neither side intends to compromise (Jay Crandell,PE of NAHB has made this
clear to me and members of Seismology have responded in kind to Gary Searer)
the worlds longest bridge will be necessary to bride the differences in

In this war, the homeowner comes out the loser, that is unless they have the
financial resources or understanding of the construction differences to
cover the cost of expected performance improvements. The Seismology
Committee does not realize that rather than improve the quality of homes,
the segregate the lower and middle income homes constructed by independent
developers who know how to maximize their profits. While we skidded on ice
over the years and still were able to convince builders that the additional
hardware matters, the voice of the NAHB is not only coming through strong,
but taking away any thought of responsibility to the homeowner that we have
fought to protect. Instead, the difference in cost has created an incentive
for builders to use prescriptive methods and it's allowance within the code
clears the conscience of any builder against the cost of repair that may
break an owner.

My point is that middle income homes are now being designed and constructed
to lesser standards that they were just a year or so ago when the
differences between methodologies were not nearly so far apart. Buffin Homes
is one of ten or more developer / real estate companies in my area who sold
a prescriptly designed home last year for $80K. The same home built to the
same prescriptive method sells today for $160K and the builder pockets the
additional profit. New builders are removing the irregularity and
simplifying their design to provide middle income homes constructed to
acceptable prescriptive methods. Life-safety is enough, home owners need to
be responsible and realistic about the quality of performance - as the NAHB
would have us believe.

There must be a balance between responsible engineering and quality of
construction. In my opinion, the Rho factor has no place in residential
design. The Seismology Committee has not intention to relent on this issue
as principle and theory is more important than protecting people through
mitigation without being overly conservative. We have gone from designing
economically to not caring about cost.

So much for my five dollars worth of inflation!

Dennis S. Wish, PE
The Structuralist Administrator for:
AEC-Residential Listservice
(208) 361-5447 E-Fax
ICQ # 95561393