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

[IceNine]

From the photos, this appears to be something like versa dek long span dovetail composite deck. With negative moment steel, which was visible in the photos, it can span 25’+ (If shored during construction)

 

[StrucDesignPE]

From the photos, this appears to be something like versa dek long span dovetail composite deck. With negative moment steel, which was visible in the photos, it can span 25’+ (If shored during construction)

The permit set only called for 3" 16ga VLI decking with a 5.5" total thickness slab. The versa-dek I believe only comes in 2" or 3.5" depths. Must have revised something.

 

[IceNine]

If you look at Tomfh’s post from 14 oct 19 23:04, you can see the dovetail deck and rebar. Looking at the length of the headed studs, the slab appears thicker than 5.5”
It’s definitely not a VLI composite deck

 

[hpaircraft]

Crane implosion pushed back, maybe mid-day Saturday 19 October:

https://www.wral.com/new-orleans-to-explode-huge-unstable-cranes-ahead-of-storm/18706172/

 

[sandman21]

They may have to wait longer still

New Orleans Law Firms File Motions to Preserve Evidence

 

[hpaircraft]

They may have to wait longer still...

I seriously doubt that motion will affect the crane implosion. It appears to be focused on documentation and evidence. And even if it did cover the wreckage as it stands, authorities have a duty towards public safety that overrides such legalistic concerns.

 

[sandman21]

They already have evacuation zone which would include the crane fall zones. Legal concerns have a way of popping up and delaying things.

 

[Robert Soley]

if someone can get me the plans I'll try and figure out if it should be stable

 

[Robert Soley]

what was the wind like that day? Is it possible the crane sent vibrations in mode?

 

[JAE]

From the photos, this appears to be something like versa dek long span dovetail composite deck. With negative moment steel, which was visible in the photos, it [red]can[/red] span 25’+ (If shored during construction)

Yes but [red]should[/red] you?

With a 5 1/2" total slab thickness, even if it was pure concrete (no deck flutes) and reinforced to the maximum I'm not sure I'd do that.
The long term creep deflections would be significant I think.

ACI, for "recommended" thicknesses of continuous slabs for 25'-9" suggests 11" thick slabs.
Running some quick numbers for a 25'-9" span, I'm getting pretty large D and L deflections...not to mention long term conditions.

 

[NOLAscience]

what was the wind like that day? Is it possible the crane sent vibrations in mode?

I've been pointing towards the wind since Monday, as I was nearby on Saturday morning, and the wind was VERY strong. We had to hold down our tent at the Farmer's Market, even with stakes. One of the umbrellas went airborne and almost hit someone. Wind was the main thing that was different as compared to the days before the collapse. Also, the building below the 15th floor (approx. 150 ft) or so was nearly fully clad. Wind coming down Canal St would roll over the Saenger Theater (about 45 ft tall) and hit the cladding. Then, all of that air would have to go over the highest clad floor to the first open floor or go left or right around the building. I think it would take wind tunnel analysis to figure out the wind speed over that first open floor. The highest sustained wind was 16 mph at the MSY airport. Maybe Lakefront Airport (closer) has some more applicable data for that morning. Also, gust are typically 30% higher than sustained winds.

I think the cranes may have initiated the collapse, regardless of where it appeared to fall. Where is the crane operator? How was he or she able to climb down to the roof and escape the collapse? Maybe he/she felt something or heard something that said, "Get out" a minute before collapse.

Please elaborate on "crane sent vibrations in mode".

 

[Robert Soley]

Vibrations, usually in seismic zones but to a lesser extent impacts and wind to a lesser extent are controlled for. If these were amateur contractors who have never practiced out of state they may never have even heard of vibrations in buildings. Vibrations are like shock waves through the buildings--where if, like a pendulum, the vibration strikes while moving in one direction, it moves further. You can calculate the stress backwards from the deformation. I would guess if they went off of the original plans and instead built slimmer these vibrations would have a greater effect. The vibrations coming from the crane.

 

[hokie66]

Wind,vibrations, cranes...sorry, but these sound like excuses, not reasons for a construction failure like this one. Look elsewhere for your speculations.

 

[3DDave]

Gravity is the typical culprit.

 

[Ingenuity]

Wind,vibrations, cranes...sorry, but these sound like excuses, not reasons for a construction failure like this one. Look elsewhere for your speculations.

I agree with hokie66.

All things considered, like post-shores buckling, large L/D ratio for beams and metal deck slabs, cantilevers with no backspans etc - and the fact that the 2 tower cranes are still standing (just?) - leads to framing issues.

 

[NOLAscience]

Our point is that "Wind,vibrations, cranes", in COMBINATION WITH large L/D ratio of beams and deck span, might be the culprit. Sure, winds have affected cranes since the first one was ever used on a construction site, but the designs of a decade or more ago were more robust to these forces. It seems that every member on this building design had a FS of about 1.00001 for the design loads. Not a good practice, especially with little to no redundancy.

"2 tower cranes standing" -- An element can cause failure without failing itself. I can break a branch with my arms and leg, but neither of those is broken in the process. These cranes are anchored to pile caps and at least wedged into the PT garage decks and framing.

I just don't get the use of "cantilevers with no backspan", but I doubt that the failure started with those, unless we see some other evidence about what happened first in the failure. We'll say the jury is out on that one for now.

 

[3DDave]

It was built as a house of cards and wasn't getting stronger; it seems inevitable that it would collapse and wind, vibration, or a dropped nail could all have been the trigger - but they don't matter if the structure was fundamentally flawed in design or execution. Something would eventually be the triggering event. It's tin-foil conspiracy level logic to care what triggered this.

 

[Robert Soley]

true that it is useless to speculate--if they're taking it down. But I had an idea about a steel cable mesh held by trunnions held in some manner; which could vary; which would dictate the final result of the structure.

 

[NOLAscience]

It's tin-foil conspiracy level logic to care what triggered this.

It is NOT tin-foil conspiracy level logic to care what triggered this. Even if the design was flawed (and we only have access to PERMIT drawings at this point, not the final drawings they were using over the past few months), it is still important to know where and why it started. Something new might be learned. It's not a certainty, but it is worth the effort to try.

And Robert S, where was this: "a steel cable mesh held by trunnions held in some manner".

 

[Robert Soley]

I didn't mean a steel cable mesh held by trunnions was IN the building, but should be the course of action that proceeds