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RE: deck collapse

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I appreciate Roger's comments. We live in an era where information comes
immediately and not incompletely. We jump the gun too often and have not
learned to collect information, disregard speculation and stop thinking
that there is a conspiracy under every stone. 
How often do we find solutions to problems come from walking away and
getting our mind off the facts for a while. It cleans out the garbage
and the cobwebs and allows us to approach a problem from a new
perspective.
I've often solved problems while guitar playing, or sitting in a bathtub
or driving in a car. To sit and stare at the pictures does not resolve
an issue, but understand why the materials behaved the way they did
prior to the collapse is most important. It was reported that the
balcony swayed before collapsing and this might be important if the
movement was in time to music the students were listening to and their
movement was contributing to the lateral movement of the non-laterally
support columns at the outside face of the balcony. Remember where this
occurred - in a Zero Zone for seismic activity on an open structure
generally unaffected by wind loads (except for uplift) with columns that
might be allowed to sway and the only lateral restraint contributing to
the balcony being the stair stringer connected (or not) at the concrete
level.

With all of this said, we don't even know yet whether the stairs were
permitted or not OR if the stairs might have been included in the
overall remodel permit.

I think that it was a tragic accident that can be avoided or reduced (I
can't remember the last time this happened in Chicago) by posting the
limit of the number of people that can safely use the balcony at one
time. Load Limits mean nothing to the public but posting a limit by the
number of people on the balcony may be more effective.

Dennis Wish PE


-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com] 
Sent: Wednesday, July 02, 2003 3:01 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: deck collapse


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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