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RE: Hyatt Regency

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Harold,

Do you know if a comprehensive, accurate report is available on the
Internet (not "Barney Fife's Armchair Engineering Review") based on all
of the testing and evidence of the case?

Dave K. Adams, S.E.
Lane Engineers, Inc.
Tulare, CA
E-mail:  davea(--nospam--at)laneengineers.com




-----Original Message-----
From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com] 
Sent: Monday, April 10, 2006 9:30 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Hyatt Regency


Of the specimens we tested, failure occurred with a load of 20.5 kips on
the 
rod.  (The NBS estimated the failure load to be 20.2 kips.)  Plastic 
deformations were observed in our specimens at 13.5 kips.  By
comparison, 
the factored ultimate load should have been about 64 kips for the as
built 2 
rod configuration.

There was a noticeable buckle in the web when the rods were just snug
tight 
(no measurable load) .

Our estimates of dead load were 8.768 kips for each of the 2 walkways 
(slightly higher than the NBS study).  Assuming  the rupture load at
20.5 
kips, DL of 2 x 8.768 kips, and 2 walkways of 120 sf trib area each
results 
in a failure live load of about 12.4 psf on each walkway.  That is about
19 
people averaging 160 pounds occupying 240 square feet.

When weighing various proposed strengthening scenarios Dr. George Hauck 
observed in his 1983 ASCE paper.   "... It is ironic, and indeed 
frightening, to conjecture what the possible result of such
modifications  
might have been: The walkways could have collapsed under a much greater
but 
still reasonably probable live load, with a yet more devastating
effect."

Regards,
Harold Sprague





>From: "Robert Kazanjy" <rkazanjy(--nospam--at)gmail.com>
>Reply-To: <seaint(--nospam--at)seaint.org>
>To: seaint(--nospam--at)seaint.org
>Subject: Re: Hyatt Regency
>Date: Sun, 9 Apr 2006 18:41:09 -0700
>
>Harold-
>
>Thanks (as usual)  :)
>
>for the expanded insight.
>
>Do you have any idea of the actual live load on the structure?
>
>cheers
>Bob
>
>On 4/9/06, Harold Sprague <spraguehope(--nospam--at)hotmail.com> wrote:
> >
> > I participated in one of the many studies following the collapse.  
> > It is true that the capacity of the connection was cut in half by 
> > the change
>of
> > the original one rod vs. the 2 rod configuration.  But the 
> > connection
>was
> > grosely inadequate for even the original single rod connection.  I 
> > would have to dig out my research, but the FAILURE load was 
> > somewhere about a
>30
> > psf load for the design as originally configured.  Note that is the 
> > FAILURE load not a service load.  The FAILURE live load on the 
> > configuration
>that
> > was constructed was about 12 psf.  The design service live load was 
> > supposed to be 100 psf.  As you can tell even the original 
> > configuration was well in
> > excess of normal margins.
> >
> > The constructability change was noted on the shop drawings and 
> > approved
>by
> > the structural engineer.
> >
> > The weld failure due to combined bending and tension was the 
> > initiation
>of
> > the collapse but the connection was doomed for a lot of reasons.
> >
> > Regards,
> > Harold Sprague
> >
> >
> >
> >
> >
> > >From: "Robert Kazanjy" <rkazanjy(--nospam--at)gmail.com>
> > >Reply-To: <seaint(--nospam--at)seaint.org>
> > >To: seaint(--nospam--at)seaint.org
> > >Subject: Re: Hyatt Regency
> > >Date: Sun, 9 Apr 2006 11:02:56 -0700
> > >
> > >Adrew-
> > >
> > >My understanding of the KC failure is the same; in the original 
> > >design
> > the
> > >hanger rods were supposed to take the entire load with each floor 
> > >level system only taking that floor level load.
> > >
> > >For constructablility, separate hanger rod sections were 
> > >substituted
>such
> > >that the top floor level system took it's own load AND the load 
> > >from
> > below.
> > >
> > >The welded channel sections that made up the floor level details 
> > >were
>not
> > >originally meant to be part of the series load path.
> > >
> > >When the overall design concept change was made,  the channel 
> > >detail
>was
> > >not
> > >a strengthened to take increased localized load.
> > >
> > >A detail that was adequate for it's own load failed under the 
> > >increased series load
> > >
> > >at least that's what I recall of the info I've read about the 
> > >failure.
> > >
> > >cheers
> > >Bob
> > >
> > >
> > >
> > >On 4/9/06, Andrew Kester, PE <akester(--nospam--at)cfl.rr.com> wrote:
> > > >
> > > > Harold,
> > > >
> > > > I have never heard of that explanation as a contribution to the
> > failure
> > >of
> > > > that walkway... Is that something recent that has come out? It 
> > > > made
>me
> > > > curious, because until 9-11 it was considered the most deadly
> > structural
> > > > disaster in US, and probably still is in the category "due to
>engineer
> > > > error". So I pulled out Salvadori's book "Why Buildings Fall 
> > > > Down"
> > (yes,
> > >it
> > > > is written for the layperson but still a good historical ref), 
> > > > and
>the
> > > > diagram showing the failure does show the hanger rod nut pulling
> > through
> > >the
> > > > joint where the two channels were welded together.
> > > >
> > > > But Salvadori explains the main reason for failure was the 
> > > > original
> > >design
> > > > called for a single long rod to support two walkways, which was 
> > > > more difficult to construct then if you use two shorter rods. 
> > > > The shop
>dwgs
> > > > showed two rods connecting to the 4th floor box beam instead of 
> > > > one,
> > >which
> > > > the engineers mistakingly approved (or in my shop dwg stamp,
> > "REVIEWED"
> > >and
> > > > took no acceptions....) The result was the fourth floor walkway 
> > > > box
> > beam
> > >now
> > > > supported the second-floor walkway hanger rather then the load 
> > > > going directly into the hanger rod. Now it was supporting its 
> > > > own walkway
> > >weight
> > > > and live load, so the load could have been 2x the design load in
> > theory,
> > > > causing the fourth floor box beam to fail by allowing the nut to
>pull
> > > > through the joint between the channels.
> > > >
> > > >  Hard to explain without a dwg, but imagine a two story bldg 
> > > > where
>you
> > > > take a second story column, instead of being continuous to the 
> > > > first
> > >story
> > > > column, you move it 2 feet over onto a beam. Now that column 
> > > > load is
> > >going
> > > > into the beam and the connection between the beam and column, 
> > > > and
>the
> > > > connection was not designed for that, so it fails. (Not 
> > > > explaining
>for
> > >you
> > > > Harold, for someone not familiar with the incident.)
> > > >
> > > > I can certainly see how a poor or incorrect weld in this 
> > > > instance
> > would
> > >be
> > > > a huge contributing factor to the failure.
> > > >
> > > > Sounds like Salvadori may have glazed over the weld issue for 
> > > > simplification purposes. Either way there were shop dwg 
> > > > coodination mistakes. I also wonder why they did not just use a 
> > > > HSS section
>rather
> > >then
> > > > build their own? Were HSS just not that popular in the late 70s?

> > > > Or
> > >throw a
> > > > PL 1/4 on the bottom of the channels to reinforce that area...
> > > >
> > > >
> > > > Andrew Kester, PE
> > > > Structural Engineering Consultant
> > > > Lake Mary, FL
> > > >
> >
> > _________________________________________________________________
> > On the road to retirement? Check out MSN Life Events for advice on 
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>to
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> >
> >
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