NYC Parking Garage Collapse 14

[gte447f]

I'm surprised to see structural folks on this board commenting about probable overloading and 40psf live loads being insufficient. I find that scenario to be pretty unlikely. It is much more likely to be a matter of deferred maintenance and deterioration of materials.

 

[phamENG]

I agree gte447f - "average" car weight is just under 50psf. In a normal garage with aisles, etc., an evenly spread 40psf covers that and then some. In this case, it might be a bit light, but I'd expect the factor of safety to be sufficient to prevent collapse (1.6*L=64psf) unless there was a serious flaw. But apparently, it was designed for 3x that anyway.

Given the age, deferred and/or ignored maintenance is more likely.

Was it overloaded? Technically, yes, but also no. Loaded less than the design load, but more than the structure could withstand in its current degraded state.

 

[Alistair_Heaton]

Gte i am pretty certain they are by modern codes. Quite what the building loads it was design for if any is any ones guess. The fact it has survived them.....

But you are correct the primary cause is more than likely as you say.

 

[JedClampett]

Will I receive a refund on my $85.00 daily parking fee if I return my ticket ???

You'll have to pay until your car is removed.

 

[hokie66]

Maybe these were those ultra heavy battery powered cars.

 

[dik]

The live loads stipulated are far greater than you would experience in a parkade, even with cars parked side by side and the isles filled... likely about 30 psf LL for that condition. The number of men and women is to determine the number of washroom units required, likely.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[CWB1]

I'm surprised to see structural folks on this board commenting about probable overloading and 40psf live loads being insufficient

I'm rather surprised (terrified TBH) by the comments about the dense parking bc its not uncommon.in long-term or fleet storage garages.

 

[Sym P. le]

... to determine the number of washroom units required, ...

Then I guess that's why they don't stipulate occupancy for dogs in a parkade. The opportunity for relief rises quickly with the number of parked vehicles.

 

[dik]

I don't know what the current weights of EVs are... but, I'd be surprised they would be more than an equivalent 40 psf (about the lightest parking garage design live load I'm aware of).

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

[quote="average" car weight is just under 50psf.][/quote]

Missed that... the average car weight with vehicles parked side to side and end to end would likely be about 20 or 25 psf max. I'm in error... the heaviest SUV is the Lexus LX570 at 6000 lbs which is about 6000/18/8 = 42 psf for an 8x18 parking spot. The average vehicle is a lot less than that...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[phamENG]

dik- is not about the typical parking spot. It's about the footprint of the vehicle. They didn't park those vehicles in standard spots. They crammed them together.

My SUV (newer Traverse, so big but not quite "full sized") has curb weight/footprint of about 43psf. Add in the junk that we carry around all the time, and it's over pushing 45psf pretty easily. My little commuter sedan is a little lower, but not by much.

I'm rather surprised (terrified TBH) by the comments about the dense parking bc its not uncommon.in long-term or fleet storage garages.

If you're in an area that has those, sure. I live in a pretty good sized metro area... call it 3rd tier... and grew up in a larger one in Florida and I didn't see parking like that until I visited NYC.

And while they may not be uncommon, they make up a pretty small percentage of parking garages generally. So codes don't really cover them - they'd be subject to unique loading criteria decided by the building official and SEOR.

 

[oldrunner]

I don't understand how the last few responses have missed the previous graphic that showed a 120 psf live load. To me, a 40 psf load is typically for a residence. Also there is a factor of safety built into the design analysis - even in 1927 or 28 - but I'll have to check my dad's old codes for that. My first concrete design course was in 1953 in allowable stress and then had to re-learn later in the mid 60's and then played around with factors of safety when looking at a distressed project. To start some sort of analysis, if would be helpful to know what the concrete strength is. The bar might be around 30ksi yield. But New York winters can be pretty rough and I would question water leakage turning to ice and cracking the brick or concrete over about hundred years. Seen this in old 100 year old bridges. Have fun somebody.

 

[dik]

I noticed that... but parking the heavy SUV taking up 8'x18' each space, and you will not get much closer is 42psf... the vehicle is 17'x6'ish... and you need room to get in and out. A really good parking garage is about 300 sq.ft. per vehicle and if you consider isles, that's 200 sq.ft. per vehicle... that leads to 6000lbs / 200 sq.ft = 30 psf as a realistic maximum load. That's in line with the 40 psf min. design loading for parkades that I've come across. I'm pretty sure my numbers are pretty much on the mark.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[TugboatEng]

The SUV's we see are on the still mostly uncollapsed portion of the floor. We can't see what vehicles were in the area that broke through and possibly initiated the collapse.

 

[phamENG]

Oldrunner- didn't mention it in the last few because I mentioned it in my first one. The last few are more about what a 'realistic' loading would have been and not the design load.

dik - look at the first picture in the OP. A typical garage, yes, you get plenty of room to maneuver. This one? No. You get about 80sf per car. They are parked by attendants, not the vehicle owners. They squeeze them tighter than sardines.

 

[Cool_Controls]

As a point of reference a GMC Hummer EV pickup has a width of 86 inches and a total length of 216.8 inches and weights 9,063lbs. So does that mean it represents a load of approx 71psf (assuming no other space allowances)?

9063/(213x86/144)=71.2

 

[BrianPetersen]

You need the width in that formula, not the wheelbase.

 

[Cool_Controls]

I just realized my mistake thanks. Fixed it

 

[phamENG]

As a point of reference a GMC Hummer EV pickup

That's an interesting look at an unintended consequence. For a typical garage, it's not much of an issue. Over a typical parking spot, that electric hummer will still be less than the ultimate design load of a new garage...but that means it also eats up almost the entire safety factor. And that's not good.

EV's still have a small market share, but it's growing. How quickly and how far it will go remains to be seen. But hopefully somebody's thinking about our parking garages, because a sudden increase in weight of most vehicles by 60% will be a big problem for existing dense and multi-level parking solutions.

(For the record: I'm not anti-EV. I like them. I'd like to get one. I also live in a place where EV + solar panel array = logical investment from a fuel cost perspective, which is not the case in a lot of places. I'd also like to see the industry clean up the resource sourcing and improve battery technology a bit more before I make the leap. Even then, I'd probably go plug-in hybrid.)

 

[dold]

There's a thread over on the climate change board about EVs in parking decks. *Trigger warning* [URL unfurl="true"]https://www.eng-tips.com/viewthread.cfm?qid=505043[/url]

FYI: A 1924 Model T was roughly 128" long x 56" wide, and weighed between 1200-1900 lbs depending on the exact model. (according to 3 minutes of googling). So, ~25-38 psf. I wonder where they came up with the 120 psf design load?

Also note, the roof level design load was 75 psf.