NYC Parking Garage Collapse 14

[phamENG]

I wonder where they came up with the 120 psf design load?

Hmm...what if it wasn't designed for a 120psf uniform distributed load? After all, that's a COO, not an engineer's calcs. That number could get lost in translation similar to the question of how many men vs how many women are listed.

Current practice is to take point loads as spread over 2.5ft square unless there's a compelling reason to do otherwise. Let's assume they did the same (not sure how long that practice has been around). 2.5ftx2.5ft=6.25sf. 120psf*6.25sf=750lbs. 750lbs x 4 wheels = 3000lbs. My own quick googling found the 1926 Essex Super 6 Sedan, weighing in at 2,540lbs. So a 3,000lbs design weight per vehicle may have been reasonable.

Fun speculation. Sadly I doubt that the original calculations for that building are still around, so we'll likely never know.

 

[phamENG]

There's a thread over on the climate change board about EVs in parking decks.

Thanks, but apart from this one (occasionally) and the business/ethics board, I avoid all the non-technical stuff on here. The best part of not being around people much is that I don't have to listen to them shout past each other with no intention of listening. No need to expose myself to it here.

 

[Alistair_Heaton]

Maybe they need to go over to the aviation PCN system.

 

[hokie66]

Cars don't have to take off and land, Alistair. At least, not intentionally so. The PCN system is for pavement strength, and the landing areas are the control.

 

[bumbler]

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

If we're going to be looking at Hummers, we should use a gas-powered hummer as a point of reference.

H2 Hummer = 6614lb/(190"*81"/144) = 61.9 psf
GMC Hummer EV = 9063lb/(217"*87"/144) = 69.1 psf
69.1/61.9 * 100% = 11.7% increase

I'd be interested in seeing a breakdown of EVs vs. their gas equivalents. For a normal open-to-the-public parking garage, a 12% increase in the basic live load doesn't really worry me as far as life safety goes. We already design for 1.6*40psf = 64psf, and most cars don't weigh as much as Hummers. A Honda Civic weighs as much a Hummer EV battery.

 

[JLNJ]

Google Earth of the ATL rental car parking garage. I presume they took this into account during the design phase...

 

[CWB1]

I didn't see parking like that until I visited NYC...codes don't really cover them - they'd be subject to unique loading criteria decided by the building official and SEOR.

Working in the auto industry has sent me to garages like that in quite a few cities. Our internal garages often have sections solid with rows of forgotten development/executive/museum/other vehicles, crashed/certification/other vehicles that cant move for legal purposes, and production holding lot (shipping) overflow. There's also a surprising number of external fleets like rental companies and some cabbies where drivers simply need a type of vehicle, not a specific vehicle so most can be blocked in. A bad but likely true joke is that horns werent connected to key fobs for the public's benefit, its often the only method in a sea of the same make, model, & color on our lots.

I'd have assumed that all garages were designed for solid occupancy to simplify regulating their use if nothing else. I've seen plenty of "max occupancy" signs for warm bodies but dont recall ever seeing one for cars. I've also supplied static tire/skid/other pressure loads so vehicles and equipment could be placed for trade shows and marketing photo-ops and normally hear concern about damaging floor/roof coverings, not collapsing the structure itself. OTOH, smarter folks probably make a habit of running that math before calling me.

 

[SWComposites]

Designing for solid occupancy may not have been the intent in the 1920’s.
Plus this thing probably had deterioration.

 

[Alistair_Heaton]

PCN is used in apron and parking areas as well. Its not just runways.

And different areas of the airport are different strengths. And you do get situations where a 747 can park up and nothing happens but someone thinks hey a 747 parks there normally I can stick a little biz jet over there easy and it punctures and sinks.

 

[hokie66]

I agree with all that. Aprons and taxiways are like the ends of the runways. The least critical area is the centre of the runway.

 

[Alistair_Heaton]

It gets way more technical than that with runways. That are even bits which are design to sink the aircraft but support a fire engine.

We don't as stick monkeys get taught much about it. You pick some stuff up looking down holes taxing by when they are fixing it.

 

[la belle vie]

I wonder if the building was originally designed as a garage that was expected to have every floor loaded to the max. Did they use live load reduction factors back in the 1920s?

 

[MJCronin]

FOX NEWS Awakens .... Electric vehicles may be too heavy for old parking garages: report
EVs weigh more than similarly-sized internal combustion engine vehicles !!!!

OMG !!!! .... Who coulda seen this comin' ???

https://www.foxnews.com/auto/electric-vehicles-heavy-parking-garages-report

MJCronin
Sr. Process Engineer

 

[Sym P. le]

And the good news, we will now be able to get in/out of our vehicles again when they makes stalls larger to accommodate denser fuel efficient vehicles.

 

[bones206]

Some of the violations related to the structure:

https://a810-bisweb.nyc.gov/bisweb/ECBQueryByNumberServlet?requestid=2&ecbin=34810259P

https://a810-bisweb.nyc.gov/bisweb/ECBQueryByNumberServlet?requestid=2&ecbin=34810258N

https://a810-bisweb.nyc.gov/bisweb/ECBQueryByNumberServlet?requestid=2&ecbin=34810260M

https://a810-bisweb.nyc.gov/bisweb/ECBQueryByNumberServlet?requestid=2&ecbin=34408003X

https://a810-bisweb.nyc.gov/bisweb/ECBQueryByNumberServlet?requestid=2&ecbin=34408002Y

 

[Sym P. le]

access denied

 

[bumbler]

Did they use live load reduction factors back in the 1920s?

I'm also really curious about this and I found a nice article from SK Ghosh that goes back to the 1997 SBC, but haven't looked beyond that. I knew parking garage live load just changed from 50psf to 40psf from previous editions to ASCE 7-16 but hadn't realized how much it has fluctuated over the years.

Link

Also, per the ASCE 7-16 C4.7.4 the code writers are already rounding up from a conservative estimate 34.8psf to 40psf to account for possible heavy use of SUVs. I wonder if we'll see a similar increase to 45psf or back to 50psf with the rise of EVs.

 

[oldrunner]

Per page 19 of the New York City 1922 and 1929 building codes: Floor Loads: "120 psf for any other purpose...." Roof loads are 40 psf. Could not find a reference to combined roof load (which can be snow and ice) and the 120 psf floor load.

 

[oldrunner]

In addition: 2022 NYC building code: Basic garage load is 40 psf with a concentrated load of 3000 lbs on a 4.5 x 4.5 inch square area. Ground snow load is 25 psf and the ice load references ASCE 7. Many of the NY codes are web accessible.

 

[dold]

Some of the violations related to the structure:

For those who can't access:

Also, there don't seem to be any permits for any work that would have been required to remedy these issues.

I think we can all agree that everything is pointing towards lack of maintenance. Was it overloaded compared to the original design loads? Probably not. Current codes? Also probably not. Was it overloaded for the actual condition of the structure? Maybe.

Things like this (collapses) also happen due to incidental failures, like an attachment of a wall to a floor simply failing due to corrosion or fatigue, which leads to instability, for example. This could happen if the garage was completely empty and a random vibration finally snapped a rusty piece of rebar. Or a freeze-thaw cycle finally knocks one last brick loose and a beam slides off it's bearing, etc.