concrete garage deck collapses

huangyhg

concrete garage deck collapses
i heard a news report today that a parking garage collapsed in the chicago area. the report alarmed me.
a friend recently bought a condo in a building 30 floors high.  when i drove into the valet parking garage of the building, i noticed that the concrete parking deck above where i was standing had a 8' x 10' section where the concrete had dropped out exposing very rusted rebar. it looks like this condition has been developing for a very long time.  the building is about 35 to 40 years old. i told my friend to report it to the building manager, before she does should she be concerned and why?   
would appreciate your comments, thanks
find a job or post a job opening
at the very least the building manager needs to be made aware of the potential for harm to person or property.  thus reporting it makes sense from that viewpoint.
should your friend be concerned?  yes, the location you mentioned could be a local, isolated incident or it could be representative of the general disrepair of the garage.  if it is representative of the latter then the potential for major structural failure is higher, i.e. the garage collapse you first mentioned.
going back to my first paragraph, the building manager has a duty to maintain the building such that no harm befalls anyone or anything.  as it usually is, it appears that this manager is waiting until the very last minute possible to open the checkbook and make the necessary repairs.   
regards,
qshake
eng-tips forums:real solutions for real problems really quick.
here's the chicago tribune article.  it appears that it may have been a garage under construction,
evanston construction site accident kills man, hurts 2nd
published september 17, 2005
a man was killed and a co-worker injured friday in a construction accident at a downtown evanston parking garage.
firefighters were called about 2:30 p.m to the sherman plaza garage, under construction near davis street and benson avenue. the workers were trapped under scaffolding that collapsed near a stairwell on the sixth floor, fire officials said.
"we were three blocks away doing training and were there within two minutes of the dispatch," said fire chief alan berkowsky.
when firefighters arrived, a construction crane operator who was not part of the garage-building crew was helping lift debris off the men, berkowsky said. the two men were lowered to the ground in a basket attached to the crane, he said.
the workers were taken to st. francis hospital in evanston, where one man was pronounced dead around 4:15 p.m. and the other was in good condition, officials said.
fire officials declined to give the victims' names.
the city-owned garage is part of a condominium-retail development.
this same thing happened at a mall parking lot 2 story garrage here in the tulsa area a couple of years ago.  i think the only damage was to an rv parked in the lower level.  they got engineering and construction teams in immideately to correct and improve the aging garrage.  the soils in this area make it really challenging for the foundation design of any structures.
so, did a parking garage collapse, or was it scaffolding only, and was it an existing garage, or new construction.  i am thoroughly confused by the posts in this thread.
rmw
i've been told and have used this rule alot,when somthing looks wrong,most of the time it is!!!
if your friend saw the deck,if you saw the deck,and it brought you concern for saftey than not only dose the building manager have a duty, but now you do too!
you really need to let the building manager know what you have seen.further you need to contact your local building inspecter  just in case the manager or owner drops the ball.
better safe than sorry.
thank you all for your comments. the problem was reported and i understand that the building is aware of it.
i would be interested in knowing more about the technical and structural aspects of such a condition and what could happen if not repaired correctly.
when looking up at the underside of the deck, about 2" in depth of the concrete in the area mentioned is missing exposing the rebar which is very rusted. i would think that rusted rebar would also be an indication that something is terribly wrong.  being in chicago, i suppose that road salt from the vehicles parked above could contribute to such a condition.  if salt is a contributing factor, i would expect that this condition may be throught the structure, but that's just a wild guess.  something else i learned that you concrete experts may want to know, is that the building was constructed with something called "light weight concrete"  
my lay-man understanding of concrete is not sufficient to create an alarm and stir the pot so i appreciate the opinions of all you experts.
thanks,
your rusting rebar is easy to explain.rebar is very porous steel.
when hit by humid air it will rust over night.any water will cause this stuff to surface rust fast.
during the concrete pour of the deck it is bombarded with wet,water,concrete.
this in itself will cause contact rust,it will be there for ever,and ever.
the concrete after cure will stop the rusting process.the alkline in the concrete stops the rust process.
salt is not ,is not a factor in rusting rebar.and i am ready to argue the point!
next you need more detail on "light weight concrete".are we talking  gypcrete" or what?
just another comment.  37ed is right, rebar is very porous.  when rebar gets wet, it rusts, and when it rusts, it expands.  what forms are holes called 'pop-outs' where the concrete has given way to the pressure of the expanding rusty steel.  what this means for your garage is that there must be water intrusion somehow through the slab.  what probably happened was that there was a crack formed from settling of the structure, and it happened to show itself in the spot where you were looking.  
is this area ever exposed to rain?
here are answers to two posted questions.  i was told by my friend that this building was one of the first to be built with 'light weight concrete' other than that i do not have any other information. maybe the sales person who sold her the unit told her that, i will see if i can find out any more, if i do, i'll post it.
the garage is an indoor parking garage and is not exposed to any rain. the only moisture that the garage would be subjected to would be melting snow, ice and salt slush that gets attached to cars during our chicago winter.
i suppose the garage is also hosed down with water for regular cleaning.
also, is it possible to repair concrete and make it structally sound when half the thickness of the slab (bottom half) has fallen out?  would this be done with gunite?
in britain, lightweight concrete is commonly used to fill bridge service bays and suchlike.
<thread highjack> i am investigating a bridge using lightweight concrete structurally and there appear to be significantly greater deterioration problems than with adjacent similar bridges using normal concrete.