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

RE: seismology committee

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Dennis,

I won't step into the debate of the use of the term "bashing", but I will
reinforce Martin's point about extend of the "power" of SEAOC's Seismology
committee.   I think that it is unfair to lump all the critizism of the
seismic code at SEAOC's Seismology committee.  From what I understand,
with the advent of the NEHRP provisions and the adoption of those
provisions into the model codes, the SEAOC Seismology has lost much of it
past power.

Keep in mind that in the past the UBC seismic portions WAS the SEAOC Blue
Book.  This is no longer the case with the IBC and was never the case with
the BOCA and SBBC codes.  From my understanding, the seismic code of today
and the future is a product of NEHRP which is a product of the BSSC
committees.  I am sure that at least some of the SEAOC Seismology
committee members are also participants in the BSSC process, especially
since California IS still one of, if not the most, earthquake aware states
in the country.

Scott

On Wed, 7 Feb 2001, Structuralist wrote:

> Martin,
> Why is it when criticism is levied, it suddenly becomes bashing? My comments
> were not to bash any group but to criticize that Seismology has chosen to
> address these issues internally and continues to isolate the members of the
> professional community who would like to participate. From your comments it
> seems that if a rational exists for Rho, it will be accepted as a buffer
> when the rational is simply impractical.
> You are correct, an envelop solution misses the big picture and penalizes
> not only the structural elements but the clients budget.
> While probability statistics are useful when helping to make a decision, the
> NAHB-RC has produced sufficient probability studies that may or may not be
> skewed to their particular bias for Conventional Construction. Who can argue
> with Statistics - is Hamburger correct or is Jay Crandell correct (or their
> respective groups who have produced valid statistical studies).
> "Where are the Bodies?" Frank Lew's famous words that will forever haunt us.
> 
> The first step is to stop accusing professional practitioners of bashing the
> seismology committee and start realizing that what these qualified
> practitioners (verses theorist of statistical studies) must contend with is
> the business of structural engineering and the increasingly strong pull from
> the other direction (Conventional Construction) that is slowing making well
> engineered residences only affordable by the wealthy.
> 
> Enough of us are seeing these changes in the industry and it's time to put
> it all into proper perspective.
> 
> The failing of the Seismology Committee is that they wish to remain isolated
> from those who are not physically able to participate and therefore, simply
> ignore the concerns of those outside. While each of those studies are
> underway that you mentioned, you might consider that the time to discuss
> this with the practitioners is before you have committed to code.
> 
> Geez, it frustrates me when it becomes so easy to accuse others of bashing
> when in reality the ones who are getting bashed are the practitioners who
> are lost in the use and interpretation of the code. But then again, this is
> the reason SEAOC does not need me as a member - I have nothing to offer.
> 
> Respectfully,
> Dennis S. Wish, PE
> -----Original Message-----
> From: Martin W. Johnson [mailto:MWJ(--nospam--at)eqe.com]
> Sent: Wednesday, February 07, 2001 10:41 AM
> To: seaint(--nospam--at)seaint.org
> Subject: seismology committee
> 
> 
> 
> 
> Since we seem to have started another round of seismology bashing, I thought
> I'd
> mention a few things that the committee has been doing;
> 
> We have had discussions about the rho factor.  Clearly it is arcane and not
> easily justifiable.  It has curious step functions which cause wide
> variations
> to occur with minor structure changes.  Gary Searer's letter used these step
> fuctions to argue his point by showing these exaggerations.  Currently a
> group
> within SEAONC is meeting and having discussions about a possible revamp.  As
> a
> part of this, Ron Hamburger wrote an interesting paper in which he used
> probabilistic design methods to show that the concept of redundancy has
> validity
> in improving the margin against collapse - in other words, that we should
> not
> necessarily throw the entire concept of redundancy out. It is probably going
> to
> take several months for this committee to work something out.
> 
> I have personally pushed for a  code change proposal for the IBC 2002
> supplement
> (and also in ASCE-7, which will be the basis for the NFPA code) to allow
> more
> free use of flexible diaphragm assumptions in light-frame construction
> (i.e.,
> without having to perform an analysis to justify the analysis methodology
> used).
> The down side is that it is going to be within the "simplified method" which
> has
> a 25 percent penalty in lateral force.  Personally, I do not like the
> "envelope"
> method of analysis.  In it's pursuit of defining what the maximum force in
> any
> one element might be, it overlooks the big picture, in that the next
> summation
> of base shear is significantly increased relative to what has historically
> seemed to be adequate.  The only justification for the approach is that it
> is a
> way to satisfy a reviewer without more elaborate analysis.  Putting up with
> a 25
> percent penalty may actually result in lower base shears than using an
> envelope
> procedure, with significantly less work.
> 
> I have for a year been pushing for the committee to take a fresh look at the
> irregularity tables, which also contain curious step functions.  (why is it
> that
> special design rules for an in-plane offset of a plywood shear wall suddenly
> kick in when the length of offset is equal to the length of wall?  Does a
> foot
> or two really make that much difference?  Certainly the wall holdown doesn't
> notice the difference.) Finally that work is getting started.
> 
> We are looking hard at the FEMA 350 documents and developing recommendations
> to
> help engineers to interpret their use.  Basically, we are putting the
> engineers
> who developed the SEAOSC document that has been published on their web site,
> and
> which some engineers have argued as being too conservative, into a room with
> some SEAONC engineers, and letting them slug it out.  They are actually
> coming
> to an agreement, thanks to the hard work of Bob Lyons.
> 
> We have held discussions about the possibility of developing some sort of
> small-building design document, that would strip out a lot of the clutter
> that
> is focussed on large or unusual buildings (what I called a "Blue Book
> Lite").
> Probably something will be done about this in the next few years, although I
> can't at this time see what can be done about the complexity of the
> materials
> design sections that have been developed and put into the code by AISC,
> AF&PA,
> ACI. etc.  The SEAOC eventual product  probably cannot be presented in the
> form
> of an "alternative code," since building officials only want to adopt and
> enforce a single code, but rather as a subset document that would just
> extract
> out the contents of the current code.  Another model is the old "Simplified
> Design" document that was published by PCA a number of years ago, which
> presented simple rules-of-thumb equations that could be used to generate
> designs
> that were "about right."
> 
> We have also been doing some more esoteric work such as working with AISC do
> develop guidelines for designing BRBF systems, reviewing the findings of the
> PRESS test program, and working to develop more rational methods for
> foundation
> seismic design (which is progressing very slowly).
> 
> While there is no end of things to do, there are definite limits on the time
> and
> energy of the engineers to pursue them.  Nothing gets done quickly, it takes
> months to review things and develop a consensus.
> 
> What we have NOT been doing is being a hidden behind-the-scenes dictator of
> building codes.  Actually, the seismology committee does not have all that
> much
> power in defining building codes.  The BSSC committees that develop the
> NEHRP
> provisions probably have the most influence in that regard, and those
> committees
> are deliberatly balanced between practicing engineers, academicians,
> producers
> and building officials (so much for the "practicing engineers only"
> arguement).
> WIthin SEAOC there has been a movement to move the seismology committee away
> from direct code development towards basic science and to find ways to work
> more
> closely with national organizations such as BSSC and NCSEA.  Within the
> seismology committee, our code change proposals for the IBC supplement had
> to be
> argued to the NCSEA to gain their support for submittal to the IBC.  So
> there
> was an entire layer of review between us and the code process.  That aside,
> we
> still do a very thorough review and take positions on of code change
> proposals
> developed by other parties as well as the NEHRP draft documents.
> 
> regards,
> Martin
> 
> 
> 
> 
> 
>