Hard Rock Hotel under construction in New Orleans collapses... 119

[Retrograde]

That makes some more sense to me then.

It doesn't to me. Boris's original post stated the following:

Post tension constructions in general and Hard Rock hotel in particular have concrete slabs with long spans and thin thicknesses.

But the area of the collapse was not post-tensioned concrete, it was steel framed with composite slabs. Most of Boris's posts sound like he has not bothered to read any of the previous posts in the topic.

 

[dold]

Well now I'm intrigued. Heres a quick SWAG back of the envelope

P < E c x bc x h x H / L

Say (based on memory of pictures and drawings and otherwise dinky design...4" slab on deck spanning 30ft sounds about right)

Ec = 4700rootf'c = 4700*sqrt(28MPa) = 24870MPa (3605ksi for 4000psi mix)

bc = 5ft strip width = 1.52m
h = 4"slab (6" total slab+deck?)= 0.102m
H = 12ft story = 3.66m
L = 30ft slab span = 9.15m

24870MPa * 1.52m * 0.102m * 3.66m / 9.15m =
1542kN

Column load <= 347kip for crummy slab to be a rigid brace

30'x30' bay (generous) x (60psf DL + 100psf LL (generous)) = 144kip per story.


Just for giggles, say bracing force =~ 2% applied axial.

0.02 * 144 =~ 3kip
0.02 * 347kip =~ 7kip

....Not sure where I'm going with this. Lost my train of thought. Thoughts? Not bad for being on a cell phone... Where does this leave us?

 

[JAE]

It leaves us with a lot of conjecture.

 

[MOJOJOHN]

Boris k,

Would you share the reference to the equation you presented?

Regards,

mojojohn

 

[jhardy1]

@dold (and Boris):

24870 MPa * 1.52 m * 0.102 m * 3.66 m / 9.15 m = 1,540,000 kN (not 1,540 kN).

This is simply not credible or meaningful, regardless of whether it represents the critical buckling load of the column, or the stabilising force offered by the floor slab, or whatever. That's why I said in my post of 6 February that:
"it predicts a stability load of a million kilonewtons or more; equivalent to over 100,000 tonnes of applied mass - per column!!!"

Boris needs to cite the reference that he is quoting, and show that he has interpreted it correctly. (For example, if it is some sort of empirical formula, he needs to state what units are supposed to be used.) Until then, Boris' calculation has no meaning or credibility for me.

http://julianh72.blogspot.com

 

[Boris_Kuznetsov]

The formula is based on the following model. Axially loaded column with pins at both ends, top pin connected to a spring representing a floor support. The column has two buckling modes, with and without lateral movement, and two corresponding critical loads. If mode without lateral movement governs, Euler formula is used and support considered as rigid. If mode with lateral movement governs, support considered as elastic.
For existing concrete span to thickness ratios one critical load thousand times exceeds the other. It means that support is very rigid and the formula becomes not needed for practical use.

 

[jayrod12]

Where did you get the formula from is what people are asking.

Because in this case, 3" concrete filled steel deck would not be considered a rigid support by anyone here, which points to flaws in your formula, or interpretation.

If you post the reference you got it from, perhaps the rest of us can more accurately understand or respond.

Currently it feels like you are being intentionally ambiguous. And that is also not allowing anyone to take your comments seriously.

 

[Cool_Controls]

Inspectors falsifying reports

 

[azcats]

Maybe the inspectors were as scared of that building as the workers?

I'm torn on this one. Are these inspectors negligent, criminal, frauds who are ill suited to protect the public? Certainly yes. Do they deserve any significant culpability for the collapse of this particular project? Not likely.

 

[OHIOMatt]

azcats, I am conflicted on this as well. While the design certainly remains at the forefront of my thoughts of the root cause of the collapse, I am getting more uncertain as time goes by. On October 15, 2019, Ingenuity posted a photo showing missing bolts in a connection. There may end up being blame spread around on this one. It will be very interesting to see what the report from OSHA and ASCE says about this.

Either way, this is a bad look. The public puts faith (probably far too much) in plan review and city inspections. This will and should shatter any confidence that was left with this particular building department.

 

[dauwerda]

Are these inspectors negligent, criminal, frauds who are ill suited to protect the public? Certainly yes.

It's hard for me to even go this far unless more evidence is presented to show they weren't inspecting any projects (i.e. residential). Maybe it's because of my background in heavy industrial, so I am not familiar with what happens on large commercial projects, but honestly most local city or county inspectors (that I have come across) have no business on large scale engineered projects (that's not to say they shouldn't be allowed to come inspect them).
My experience has been that local inspectors are well geared to handle residential, wood framed buildings. On large industrial projects I would usually hear things like, "wow, that's a lot of rebar! Does it really need that much?" So after the first foundation inspection they would realize they were way out of their element and pretty much do what it sounds like the inspectors at the Hard Rock Hotel were doing. Maybe in other parts of the county people have other experiences with local inspectors?

In my opinion, local inspectors are their to protect the public in situations where "standard practices" are used and no engineered plans or special inspections are required - i.e. anything covered by the IRC essentially. I don't expect most building departments to have even close to the expertise needed to properly inspect a project such as this one. Whether or not they should have this expertise is perhaps another topic altogether.

 

[waross]

On large industrial projects the inspectors and their supervisors may be more concerned that the value of the project has been properly stated and that the permit fees based on the project value have been properly paid.
Question: When a project runs over budget does the inspection department demand additional permit fees?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[3DDave]

I don't mind fraudulent claims of work resulting in prosecution for fraud, but if an inspector is expected to do more than verify that the work is done according to the submitted and stamped plans I would be surprised. Some engineers are supposed to have spent hundreds to thousands of hours in ensuring the design is suitable and maybe (as in, fat chance) the building department will have someone spot check the work, but there is no way I would expect an inspector to just eyeball things and do a quick stress analysis.

While it may turn out there were signs of excess deflection indicating overloads, those same signs were visible to everyone on the job site passing by that location, and they have access to the engineers to see what was going on.

But, like the FIU bridge, if the engineers won't show up to see for themselves, there just aren't good independent means to force the construction company to do so.

One story that may fit was the Quebec Bridge disaster, where, as the bridge extended further from the anchorage towards the opposite portion, various members were buckling. Workers noted this, the on-site management noticed this, and the blame was set onto the chief engineer who was ill and could not travel to the site. Even though many workers had stopped coming to work, the work continued. The telegram from the chief engineer to stop work immediately was on the desk of the site engineer even as the partial bridge tumbled into the river below.

 

[azcats]

Are these inspectors negligent, criminal, frauds who are ill suited to protect the public? Certainly yes.

It's hard for me to even go this far unless more evidence is presented to show they weren't inspecting any projects (i.e. residential).

My statement was based on the allegation that they were filing reports for a site they hadn't visited. That's pretty damning.

Regarding their qualifications - from the sounds of it the whole building department was unqualified to do the job. Now I'm no fan of big government and question the collective judgement of believing that these people are the gatekeepers of our safety. However, that is how they promote themselves. It's all fine and dandy when the rest (engineers, contractors, fabricators & special inspectors) are competent & not on the take. But...

 

[dauwerda]

My statement was based on the allegation that they were filing reports for a site they hadn't visited. That's pretty damning.

Agreed. My first skim of the article I didn't catch that they were filing inspection reports claiming to have visited the site when they hadn't. I wrongly assumed that they were waiving the inspection and allowing the construction to proceed without an inspection from them and instead relying on third party inspection reports.

 

[Rabbit12]

The IBC requires independent 3rd party inspection reports. My company does EPC work so we are often not allowed to perform inspections. I get the intent of the requirement, but have been noticing that the 3rd party inspections I'm getting are substandard to say the least (at least with concrete and masonry rebar). The inspectors that show up are not qualified and frankly just don't really look at stuff. At least not to a degree where they would capture any mistakes. The reports we get to review are literally check boxes approving the work. No description on what was actually there.

I'm beginning to think we should have the EOR perform inspections (or another licensed engineer). They have skin in the game.

 

[Vance Wiley]

Two deaths in parades so now the city of NO is banning tandem floats.
Seems to me the problem is people wanting to cross between floats and not realizing they are hooked together.
One solution would be flexible "blinds" each side between floats so no one thinks they can go through.
I may be off topic here so please excuse me.
I note the number of deaths is about the same as in the hotel collapse.

 

[bones206]

See related article regarding New Orleans inspection officials under federal corruption investigation that I posted a link to on 14 Oct 19 16:02.

They were accused of not only accepting bribes for permits but bribing their own inspectors to go along with the schemes. This investigation was already underway before the collapse occurred.

 

[ATSE]

City inspectors - who by most accounts get paid better than their private industry counterparts, and usually have a pension at the end of the rainbow - should be expected to be at least as qualified as 3rd party special inspectors (by training and experience).
Neither we as engineers nor the main codes (IBC, ACI 318, AISC 360) expect inspectors to spot check engineering.
But structural inspectors are expected to understand structural drawings, check for the basics, like checking that the contractor is not adding 1000 gallons of water to the ready mix truck, or #4 stirrups in a beam, or flat washers on at least one side of a high strength bolt.

City building departments collect fees for plan check review and inspection. However, with few exceptions, city inspection is a joke. If private industry performed similarly, they can (and should) be held liable for civil fraud and criminal negligence.

 

[phamENG]

Had a city inspector beat me to a job site recently. He passed the foundation excavation and gave the contractor the green light to pour. I failed them because an entire grade beam was missing its reinforcing.