Parking Garage Wall Failure 1

[Gumpmaster]

This was a potentially very dangerous incident. Fortunately no one was hurt.

Link

What is the design load for walls like this. Was corrosion was the cause?

 

[CELinOttawa]

There is rusting like more or less all parking structures, but the failure looks like insufficient anchorage of the weld plate embedment.

Hard to tell for sure without a closer look... Am I crazy or does it actually look like the steel plates were spot epoxied on? Weird pretty normal for the decorative panels, but can't be for the concrete panel!

I'd love to see the drawings, and the as builts if anything of the sort exists.

 

[jayrod12]

We've had someone run into cladding panels twice, once just dislodged it, the other popped it right off, basically in the same manner.

Pre-casters provide such narrow panels (4-6") that they can't have much shear resistance (one-way). Nor room for anchor embedment. If the panel holds in one way shear then the anchorage will fail, if it fails in shear then you generally have the wire mesh to keep it from falling down (it acts like a net as well elongating the time to bring the car to a stop lowering the overall force applied).

 

[KootK]

Design load is 10 kip in the IBC. Garage barriers seem to be utterly unfit for purpose whether they are precast or cast in place( Link).

X3 for the insufficient anchorage diagnosis. There appears to be concrete remaining on the interior side of the anchor plates suggesting that they were cast within the spandrel thickness. That would make your breakout frustum even worse than usual.



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[dcarr82775]

At the left side it looks like the H.A.S. on the top and bottom embed plates broke out of the concrete, except you would expect a concrete breakout cone remaining on the H.A.S.. While at the right end it looks like the embeds broke out of the beam/topping.

 

[jayrod12]

I bet the anchors (and embed) on the left broke out first and then the piece rotated causing the embed on the right to twist out of the beam/topping.

 

[TehMightyEngineer]

"Accelerator peddle stuck..."

Sure it did.

Having looked at a number of gross concrete overloads to failure I wonder if some continuous steel reinforcement (likely requiring cast-in-place) would have been better as it could act as a "net" to hold the car and largest pieces from falling even after everything was fractured.

Maine Professional and Structural Engineer.
(Just passed the 16-hour SE exam, woohoo!)

 

[jayrod12]

Although cast in would be nice, I can't see that ever happening. These parkades are dominated by the pre-cast industry and I don't see that likely to change any time soon.

 

[hokie66]

Didn't take much of a hit. The Merc seems to be almost undamaged.

 

[CELinOttawa]

Precast industry or not, there are far better ways of attaching such panels. This includes a product I was involved in developing when I was the lead research engineer for Building Revolutions Limited in New Zealand.

If you can find it (small company, not a lot of marketing dollars) check out the M16SSS (Metric 16mm Seismic Safety Strap). It is small, inexpensive, and would have prevented this from occurring after the initia break.

 

[ajk1]

Shouldn't they have had some comprehensive investigation carried out by independent professionals, of the cause of the failure before stating that they were completely sure that the garage is safe to keep open and that there was no chance that any panel could fall to the sidewalk below? Shouldn't public safety be paramount?

 

[ajk1]

Looking at the enlarged picture of the bracket, it seems to have significant rust on it, although that may or may not have anything to do with the failure. Significant corrosion problems with parking garage structures in areas where de-icing chemicals are used on streets and tracked into the garage, have been known at least since the mid-to-late 1980's. I first became aware of it in 1977. Perhaps 20 years ago this was the way it was still being done, but I would hope that today that critical steel brackets exposed to corrosive chlorides at the slab edge (or connecting adjacent precast tee floor slabs, etc.) would be stainless steel.

 

[JedClampett]

I see these kind of details once in a while. I'm actually surprised it doesn't happen more often. Embedment to weld to angle to weld to embedment. Seems kind of messy. Five items to go wrong in a relatively non redundant connection for a brittle piece of heavy concrete hanging over the street like the Sword of Damocles. And your first sign of a problem is someone yelling, "Watch Out!"
I attended a seminar session by AISC about 35 years ago addressing cladding connections to buildings. In addition to the crappy connections themselves, they're often treated as orphans by the building trades. They're not steel, so steelworkers don't do them. So they're sometimes welded by stonemasons since it's kind of a masonry piece. And they're not the best welders.

 

[KootK]

My local university is populated with 4-20 story buildings from the 80's, most clad with precast. A panel seems to come down every 24 months or so.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Brad805]

CEL, do you have a link to the seismic strap? I cannot seem to find it and I found they have a patent on a plate connector that sounds interesting. I always find the best ideas surfing around on NZ, AU or EU sites for precast ideas. I stumbled onto the Orbiplate just introduced this year. A simple cam to adjust for tolerances. Brilliant, and simple (

http://www.reids.co.nz/panel-connections/orbiplate/).

I do not recall Meadow Burke or Dayton Richmond have anything like that.

Parking garage design makes me cringe. There are so many things that can go wrong, and the industry has some grey areas. Thin skins, brittle connections and little redundancy. Oh, lest not forget the developers fighting to save every penny.

 

[CELinOttawa]

I can try to dig up a link, but last time I looked I couldn't find anything. They sell directly to the contractors and owners, and market through the consulting engineers in NZ. They have no reason to market openly as that simply won't lead to sales... Specification of the product leads to sales, and their strategy is pure direct marketing to engineers. Cheap and effective.

As to the orbiplate, that isn't new at all. I was specifying it in NZ nearly ten years ago... But it is a fantastic product. Just be careful if you ever try to bring some in: The NZ and AUS versions are quite different, with the AUS version cheaper and of some sort of semi-brittle cast material similar to Zamac. Aussie doesn't have the seismic issues of NZ or many areas of North America.

 

[Brad805]

Thanks CEL. I noticed a few NZ consulting firms pop up when I did the search. I wish some of the innovations I see would find there way here. The industry seems to move slower in NA. Importing is not usually practical unless it is something one can import a large quantity, but it gives me ideas that can be the basis for something different that would not infringe upon a patent.

Have you seen any good links for multi-wythe precast composite panels constructed using carbon fiber connectors? Carbon Cast and Aslan has done a lot of research, but I am interested to find more.

 

[rowingengineer]

Are they similar to the fire tie?

http://www.fireties.com/technical-information.php

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[CELinOttawa]

Yup... Something like that, only adapted to take an elephant foot ferrule and have yield zones.

Sadly I can't get anything similar to an elephant foot ferrule in Canada. Pathetic industry in NA for innovation.

 

[3DDave]

I'd say the left (from street) bracket was corroding for a long time. Compare the rust stain on it vs where the right side bracket was. Even with the amount of beam removed, there aren't matching stains on the right.

http://imgick.oregonlive.com/home/o...gonian/photo/2014/12/19/-c857f3af6ca1aec7.JPG

It's interesting that these barriers are rated in resistance to force, not energy absorption, as they are not load bearing, but energy absorbing. If my math is right, this car might have had 2000ft-lbf at impact. If it could take 10,000 lbf, then that's .2 foot (~2.5 inches) of required displacement for fully plastic behavior.