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Re: deck collapse

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Scott,

Throughout your post, you refer to, "they."  I don't know who "they" are.

The deck collapsed just after midnight on Sunday morning and was demolished 
by 6:00 p.m. Sunday afternoon.  There are not very many structural engineers 
that are available around the clock to be called out on a moment's notice.

I am assuming that W-J-E was on contract with the City of Chicago to 
investigate situations like this, and W-J-E is a highly respected and 
reputable firm whom I expect will do an exemplary job.  However, 2 pairs of 
eyes are better than one pair, and 4 pairs are better than 2 pair.  Was it 
not a solitary California Structural Engineer (James F? whose name eludes me 
right now) that pointed out that A490 bolts were misused in the Kansas City 
arena roof collapse?

I can walk around sites for hours, asking why, why, why?  I can take roll 
after roll of pictures, but if I don't take a picture of the right thing, all 
those photos are meaningless.  For a single motor vehicle fatality, police 
will shut down the road for hours until their investigators (plural) map, 
measure and photograph the scene.  And after that the vehicles involved are 
taken to an impound lot as evidence and for further investigation.

I have come to the conclusion that short of being grossly underdesigned, 
everything that fails in the same manner is sympathetic failure; the one 
element that fails in a completely different manner is probably the element 
that failed first and caused the resultant collapse.  If one looks at the 
elements that all failed in the same manner, it is easy to come to the 
conclusion that the structure was overloaded, as overload is what causes 
sympathetic failures.  But coming to that conclusion can cause one to 
overlook what initiated the failure.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Scott Maxwell wrote:

. > Andrew,

. > I have heard on at least one news report the same thing that Chris
. > said...they were unsure if a permit had been issued for the deck.
. > According to the report that I saw, the building had been renovated in the
. > recent past to convert it from 6 appartments to 3 (as Chris mentioned).
. > There apparently was a permit for that work, but no one knew for sure
. > whether or not that permit also covered the deck or if there was a
. > seperate permit issued.

. > As to the issue of clearing away the rubble from the site...have you
. > considered that make they were able to determine the cause of the collapse
. > in that amount of time?  After all, you have made the determination that
. > it cannot possibly be due to accidental circumstances (at least in your
. > mind) but rather due to negligence by someone (the engineer, contractor,
. > owner, etc) and you have been on the site for exactly ZERO seconds looking
. > at the rubble.  My point (without the sarcasim now) is that it is entirely
. > possible that they may have already gotten all the information that they
. > needed to determine the cause of the collapse, thus it was perfectly OK to
. > remove the debris so that people would not be inconvienved in getting in
. > and out of their homes.  In otherwords, it is entirely possible that they
. > had gotten all the information that they needed (i.e. photographs, etc)
. > for their investigation.  After all, this was a rather small wood deck
. > with no things like exterior cladding.  Think of it in proportional
. > sense...it took less that a year to clear away the debris from the WTC
. > collapse and it was TWO 100+ story buildings (with floor plans of
. > several hundred feet by several hundred feet) with added debris from
. > furnature, interior partitions, and exterior walls compared to the time
. > for clearing away the debris for this collapse that was only a 20
. > something by 20 something foot deck (at least from what others have said).
. > Thus, if you look at it from a proportional sense, then someone could make
. > the arguement that if you consider the amount of time clearing away the
. > debris at this incident then the time for the WTC was totally
. > insufficient, yet I doubt that there is too many people that feel the
. > debris at the WTC was cleared away too quickly.

. > This leads me to my suggestion...maybe we should try avoiding to
. > conclusions without all the information in hand, eh?  After all, while I
. > do believe that the lack of WMDs discovered in Iraq TO DATE raise some
. > questions about the primary rationale that was advertised for the need for
. > war, I also believe that anyone who wants to claim that Bush lied or
. > twisted information is just an idiot who is jumping to conclusions.  The
. > point is that we don't have enough information to make a make a conclusion
. > on either the Iraq issue nor the cause of the collapse.  So, I would
. > suggest a little patience before you get too hot under the collar about
. > anything and get all the INFORMATION.

. > As to the structural issues at hand...you have focused on pure gravity
. > live load issues.  Have you considered that the collapse may have occurred
. > due to insufficient lateral resistance?  And I am not necessarily tallking
. > about something sufficient enough to reist a significant earthquake.  At
. > least one person on the list has mentioned eyewitness reports that stated
. > that the deck was "swaying".  Thus, it is possible that the deck just
. > swayed too much creating a significant P-delta "extra" load that then
. > caused the live load to be "exceeded" even though there may not have been
. > enough people present to exceed 60 psf.  Admittedly, such a possibility
. > would still lead to a claim that the engineer (if there was one) should
. > have accounted for this.  My point is that you seem to be "target locked"
. > on how you believe that the engineer may have goofed which means that you
. > could be potentially be doing the same thing that you seem to be accusing
. > the person who designed the deck of doing...not looking at all the
. > possibilities (although I could be wrong...you could have thought of such
. > things yourself already).  Thus, again, maybe we should wait a little be
. > longer before we jump to conclusions.

. > HTH,

. > Scott
. > Ypsilanti, MI

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