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

RE: storage racks with partially restrained moment connections - wind frame analysis in high seismic zones

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Peter,

There have been a lot of changes in the code that do not reflect the
"current" practice.  If there were no changes to current practice, we would
still be building tons of URM buildings, and pulling bodies out of
buildings.

The days of SEAOC developing the Blue Book and that becoming the seismic
section of the building code are simply over.  The various SEAOC's have a
voice in the process, but the NEHRP development process is now a lot more
open especially geographically.

My committee has received criticism for being way to liberal with steel
storage racks, and now the perception is that we are being too draconian.
TS13 is a group of engineers dedicated enough to volunteer their time just
to make the code a better guide for the practicing engineering community.
They obviously aren't doing it for the accolaids.  There are few accolaids
for the work of those volunteers presented on this list.

I have solicited several times on this list to engineers interested in
nonbuilding structures to join the process.  I have received few responses.
The NEHRP is not a true consensus process.  The members of Technical
Subcommittee 13 were few in number, but are by no means closed.  When
someone came to TS13 with an interest and a willingness to help, we made it
happen.

The code proposals are developed in the NEHRP then the Provisions go to ASCE
7 or IBC for development as a true ANSI consensus.  But at that point it is
difficult to present any significantly new proposals.  Proposals acceptable
in NEHRP may not be acceptable in the ASCE 7, and they are voted on in
committees like the Seismic Task Committee prior to forwarding to the full
ASCE 7 task committee.  ASCE 7 and IBC are subject to public hearings,
voting, and comment.

The person crafting the proposals for steel storage racks for the NEHRP is
Victor Azzi who represents and has his expenses paid for by the RMI.  Victor
has been part of the NEHRP process for about 10 years.  If you contacted me,
the RMI or Victor with any interest in code development; I am sure your
comments and help would have been welcomed.  We have recieved no offers of
help on steel storage racks other than Victor.  And I think that he has done
an outstanding job.

Prediciting lateral drift and providing adequate space to prevent pounding
has been a concern for a long time.  When designing a building you must
provide an amplified lateral drift due to the possibility of inelastic
response.  That is the function of the omega sub zero.  You always have that
option, but most engineers don't want to go through all that trouble.

Send your proposal for opening up that "smoke filled" room to the BSSC,
request membership to TS 13,  and join the process.

Regards,
Harold O. Sprague


> -----Original Message-----
> From:	Peter Higgins [SMTP:76573.2107(--nospam--at)compuserve.com]
> Sent:	Thursday, March 22, 2001 11:08 AM
> To:	INTERNET:seaint(--nospam--at)seaint.org
> Subject:	RE: storage racks with partially restrained moment
> connections - wind frame analysis in high seismic zones
> 
> Harold,
> 
> I must be getting senile if I can't express that I realize that it's not a
> drift limit. It's something far worse.
> 
> It's a requirement that the installation satisfy this separation (H/20 is
> what you gave me). That means a rack must be placed more than 5% of its
> height from a structure to ensure separation. In a typical 20" tall rack,
> this is 12" from any other structure or element. In a 40' rack (not at all
> untypical) this is 24". Racks do not move this much in an earthquake, and
> therefore the separation is excessive. Indeed, the spectral displacement
> of
> the earth for the UBC earthquake on aluvium is only around 6". 12" is
> probably overkill. 24" is ridiculous. It also fails to recognize the
> common
> fact that most racks have different drifts in their principal directions.
> 
> The problem is that I don't know of a single rack installation among the
> thousands in my experience which would satisfy the requirement, including
> my own where I have often been criticized for "wasting valuable space".
> Further, I know of no other colleague insisting upon this extreme
> separation.
> 
> Conclusion: This regulation neither reflects theoretical reality, nor
> actual practice.
> 
> However, I find out (in a list server of all places) that it is formal
> NEHERP regulation. I have no idea how this came to be. Never got a formal
> notice of code change, public announcement, etc. It certainly neither
> reflects what's out there, nor what the earthquake will do. Then I'm told
> that it comes from a single person associated with the RMI?  It's a
> classic
> case of code being promulgated without any public comment, and exactly
> what
> some other threads have been about.
> 
> Boy, talk about the old smoke filled rooms. They had nothing on our modern
> smoke free conference tables. I have a high regard for NEHERP and the
> persons involved, but I never knew NEHERP was this easy to manipulate.
> 
> Regards,
> 
> Peter Higgins
> 
> Message text written by INTERNET:seaint(--nospam--at)seaint.org
> 
> Regards,
> 
> Peter Higgins
> > 
> 
> Peter,
> 
> I have repeated it several times,  THIS IS NOT A DRIFT LIMIT!!!
> 
> Please read the NEHRP and the RMI.
> It is what the movement the installation is to accommodate.
> 
> Regards,
> Harold O. Sprague<
>