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Concrete garage deck collapses

Concrete garage deck collapses

Concrete garage deck collapses

(OP)
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

RE: Concrete garage deck collapses

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.

RE: Concrete garage deck collapses

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.

RE: Concrete garage deck collapses

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.

RE: Concrete garage deck collapses

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

RE: Concrete garage deck collapses

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.

RE: Concrete garage deck collapses

(OP)
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,

RE: Concrete garage deck collapses

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?

RE: Concrete garage deck collapses

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?

RE: Concrete garage deck collapses

(OP)
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?

RE: Concrete garage deck collapses

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.

RE: Concrete garage deck collapses

I think the first order of buisness here would be some core samples of the deck.

This will give you an idea of the concrete psi and a look at the rebar.take them from uneffected,and effected areas.

once you have this data in hand you will be able to see if the    deck can hold the loads on it.

as far as a repair,is the deck a slid unit type construction or mono poured?

RE: Concrete garage deck collapses

oh, one more thing,
if water has penetrated the deck and lays in "pockets" or void,once frozen it will cause as used above"pop-outs".
 the same as a bridge,cold air is coming from all direction and water in the deck will freeze fast.
you have seen the signs"bridge may freeze before road"
you get the point.

also you said that the hole is adout 2in deep,but how big is it in area?

RE: Concrete garage deck collapses

(OP)
Thanks 37Ed.. The floor is a mono-pour and the section where the concrete has dropped out is about 8ft. x 10ft. x 2" deep. It looks like the rebar has rusted so badly that it expanded and fractured the concrete.

I would bet that there are other areas in this garage that mey be afflicted with this problem, as it's a valet parking building I can only see a small portion of the garage.  

The garage is heated so no problem with freezing.  


RE: Concrete garage deck collapses

HEATED!
NOW YOU REALLY HAVE A PROBLEM!
IS THE CLIMATE CONTROLLED TO 15 DERGREES CONSTANT,IF NOT YOU WILL GET ALL HELL OF STUFF GOING ON.
ANY WAY THIS IS A PROBLEM WE CAN GUESS ABOUT FOR LONG TIME TO COME,BUT YOU DID THE RIGHT THING,REPORT,AND ASK POINTED QUESTIONS.
BROVO

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