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

[IceNine]

GPR tech,
In looking at the photos, it appears they switched to moment frames at the cores.

 

[MOJOJOHN]

First, I would like to thank all the people who are contributing to this
Forum. Your observations are valuable to all of us who are trying to
understand this failure.

In reply to Ideem, I agree. The problem is clearly more than a bad cantilever
detail. The steel frame would should have absorbed a couple of cantilevers collapsing
without the building coming down like it did.

As to some reasons why, all of which have been quoted by others previously:

1. Bolts were shown missing in one post.
2. A weakness was identified where hardly any steel beams cross the building
longitudinally just below line 10.
3. The failure photo below show a large section of the building falling virtually intact.
4. Steel was seen in previous post not crossing steel beams at the studs, but stopping at them.

Were many bolts missing in addition to the clear design errors on the permit plans? The practice is
normally to place a couple of bolts in the beam as it is set, and before the floors are added, to place the rest.

Though the failure may or may not be related to the cantilevers, it is clear that many much more serious problems
existed at lower levels as illustrated by the photo below.

By the way, these beams are not composite steel beams. I checked a few and found that the studs were not
sufficient for composite action. They merely attach the slabs through the deck to the beams.

Regards,

Sorry. I do not know how to upload my image. Look at the failure video for part of the building falling virtually undamaged.

 

[MOJOJOHN]

The building failed longitudinally along line 11 next to the elevator and stair towers. There are hardly any steel beams crossing the line from line 10 to line 11 as noted above.

The failure at line 11 separated the building into two parts, that which stood up and that which failed. This mass of falling concrete would be more than enough to cause the failure of the steel structure below considering the weakness of the lightly connected sections of building.

Note that the portion that fell was no longer connected to the cores for lateral stability. Connections of the beams to columns were likely shear only with little moment resistance. Nothing was holding it back but metal deck and steel reinforcing. Once it started to lean, failure was assured.

Failure below is still a possibility but a frame by frame look at the failure video leads me to suspect it occurred from the area of the top down.

 

[MOJOJOHN]

One last comment before bed:

A post by Tomfh on 14Oct19 at 23:04 clearly shows that there is no top reinforcing bars crossing line 11 beam which is seen in front of the workman by himself in the green shirt. You can see the line of Nelson studs on top of the beam where the reinforcing steel stops.

The reinforcing steel should have extended over the beam on both sides for negative moment and may have helped stop the progressive collapse but for some reason it was misplaced.

"Plagiarism is stealing from one, research is stealing from many."

Regards,

 

[IceNine]

MOJOJOHN,
Take a closer look, it appears the bars do extend beyond line 11.

 

[dold]

I understand the intent of this thread is to discuss and dissect the true, physical nature of the collapse. But I hope we can all agree that there was no single deficiency that this collapse can be attributed to: not the missing bolts, not the lack of beams crossing the corridor, not the cantilevers, etc.

This was entirely preventable. This particular collapse is absolutely due to a failure in the HUMAN element of our system of design and construction. Collapse was inevitable. If it wasn't going to be the cantilevers, it was going to be the deck. If it wasn't the deck, it was going to be the load path. On and on... We can all sit around and agree that there were countless design flaws in this structure, at least based on what we have seen so far.

In my opinion this collapse is unprecedented in terms of the human/ethical factor of engineering. Look at the Hyatt bridge collapse. We know what caused that: the failure of a single component due to a (hastily) approved substitution that did not recieve proper attention. Not due to extreme incompetence. FIU bridge: due to (perhaps) a true misunderstanding of the nature of materials and forces and their interactions, and a lack of what amounts to backbone on the part of review, and almost certainly a degree of pride in most parties. The Hard Rock collapse seems to be the result of true, unfettered incompetence. There are so many checks along the pipeline that could have prevented this, starting at the EOR, and ending at the AHJ. I can't go beyond that and fault the GC or subcontractors for refusing to build an obviously deficient structure, as that is decidedly not their job (or is it?). The real question here is where that breakdown occurred, and why.

This has seriously dismayed some of the professionals in my office. Truly shocking how something like this could happen. I'm curious to hear what some of the other - professional - reactions to this have been? Thoughts?

 

[MOJOJOHN]

IceNine,

Thank you.

Please show me where the steel going between 10 and 11 is. I have looked at the plans, a good mark up in green forum member and photos and cant seem to find it.

I am getting older, maybe I need stronger glasses!

Regards,

 

[BadgerPE]

I assume this is the post you are looking for? It is from JAE on 10/15/19 @ 17:06 (not sure if this time is location specific in the world or if it is GMT).

 

[OHIOMatt]

dold, you asked for reactions.

Regardless of what is determined to be the ultimate cause of the collapse, this tragedy was completely avoidable. The video of thee buckled shore posts taken on Thursday before the Saturday collapse should have been enough evidence to evacuate the building and determine what is going on.

This thing passed through numerous hands before it got to the erection phase. I believe that design changes occurred after the permit set was issued, but the following groups had access to the design drawings. The design still has some very questionable issues based upon photos of the actual construction.

1. The EOR and team should have internal checks and back checks associated with the design process.
2. The architect should have been able to look at the permit drawings and question them. Looking at member sizes and spacings and comparing it to other projects, should have at least aroused suspicion of a problem.
3. The building department. While they are not structural engineers, they should have enough knowledge to see obvious design deficiencies, at least to the point of asking questions, requesting calculations for validation, ect.
4. The Structural Steel Fabricator should have recognized that sizes and total tonnage of steel did not correlate to a building of this size.
5. The structural Steel Detailer should have flagged some of the obvious issues in the permit drawings.
6. I assume that this project used delegated design for connections, the engineer designing connections should have recognized some of the obvious design issues.
7. The deck supplier should have noticed the span issues with the deck specified.
8. The shoring designer could have questioned noticed some of the design issues.
9. The EOR should have seen the fabrication drawings and noticed problems before this went to the shop.

Once we get to the erection phase
10. The erector should have questioned the design (seems like this did happen to some extent)
11. The shoring contractor (this did happen as noted in the video by the guy removing the shoring posts)

Maybe, red flags were raised throughout the process and the public has not been made aware them. My point is, that so many people saw the design and could have flagged it. I have to believe (maybe I just really want to believe) that questions were asked along the way. I think that the telling part of this story will be in the communications related to the project. I would expect there to be an extensive RFI log and e-mail chain on this project. Hopefully this will provide some insight on how this could have gotten to this point.

I have read the report for the FIU bridge collapse. I believe that the final report will raise similar issues in regards to who can shut work down and evacuate strutcures.

 

[NOLAscience]

I'd love to know more about the interaction(s) between the EOR and the architect, Harry Baker Smith. The architect has a professional responsibility to propose a design that can be supported by the structural engineer (and provide for other services, such as electrical, mechanical, HVAC, etc.) without the need for 'skyhooks'. When the column layout from the architect is not aligned from floor-to-floor, the design becomes needlessly complicated and expensive. I know it's up to the structural to do whatever the architect calls for as far as column placement and beam spans, etc., but the architect's proposal has to be reasonable, too.

If you look at the plans for the upper floors, there are a ridiculous number of column lines.

 

[thebard3]

3. The building department. While they are not structural engineers, they should have enough knowledge to see obvious design deficiencies, at least to the point of asking questions, requesting calculations for validation, ect.

Isn't that why they issue (or deny) building permits in the first place?

Brad Waybright

It's all okay as long as it's okay.

 

[OHIOMatt]

thebard3

One would think so, but in my experience, it is extremely uncommon for the building department to make any substantive comments on a buildings structural design. The one exception to this is the west coast, they either have reviewers that are well versed in building structures or they outsource the structural review.

In my home jurisdiction, they add a stamp to the plan set that reads something like "The design of the building structure has not been reviewed, it is up to the professional of record to ensure the safety and stability of the structure".

Most of the time, when I do get comments, they are of little to no value. Things like "Provide H-clips at roof sheathing boundaries".

I have seen obvious errors overlooked more times than I can count. There is a misconception in the public that by the building department issuing a permit, that the building meets the requirements of the code. It all comes down to the engineer of record. I guess that is why, in our state, that building officials are immune from civil liability.

 

[Rabbit12]

OHIOMatt, your experience is similar to mine. Really the only comments I get from a building official are almost always specific to code language. There is no code language against bad details or long deck spans.

 

[3DDave]

Yup. Unless there is some factor the building permit people know about in particular (residential fence height; set back limits), I would not expect any deeper review than checking the plans are stamped by a current licensed engineer. If that were not the case, then there would be no point to having licensing in the first place.

 

[IRstuff]

The converse of that is that if the jurisdiction's reviewing could make substantive changes to the design, then they would be liable, and having deeper pockets than the engineer, they would never entertain taking on that kind of risk.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[EZBuilding]

Permit comments pertaining to Structural engineering appear to vary depending upon municipality. Building Department's regularly make comments regarding to Zoning, health safety and architectural elements - among many others. A review by the building department on the Structural framing elements should be considered to be as important as the review of these other elements. There is not enough incentive, however, as it compares to the money in zoning issues, the fire departments involvement in health safety and the public's perception of architectural elements. Structural engineering is sadly viewed as a "check-box" to many players in the construction/development industry. In combination with shrinking fees, increased complexity in project delivery and increased expectations from owners this has structural engineering squeezed from all sides. This is not to preclude the responsibility of the engineer of record, or any other party, on this topic. Once the dust settles and if the collapse can be attributed to some of the design faults described on this thread I hope that one of lessons learned is that building departments should provide a service to the public beyond just a rubber stamp when it comes to a review of the Structural Engineering a building.

 

[MOJOJOHN]

BadgerPE,

Thank you, that was the post I was looking at.

IceNine, I see no reinforcing steel across the 10 line down to the 11 line in the above repost by BadgerPE. Am I missing something?

Also I was discussing this area with a very large building contractor today and it was his feeling that
the crane attachments would likely damage the otherwise un-reinforced strip as the crane moved under load, possibly breaking spot welds.

Regards,

 

[hpl575]

Looking at link of video, thanks JohnRBaker and dold, at start of thread

https://www.youtube.com/watch?v=D_LxF8IjH3s

Unfortunately the video starts a little late to capture start of collapse, rewind and pause at 0 seconds. If video was shot from North, take a look at the North Elevation, there appears to be a sliding cantilever deck usually used during construction (not permanent structure) , yellow in color, that was originally supported by the third level from the top that has already displaced to nearly the level below, less than a second into the video the deck has already reached the level below. The sliding deck appears to be supported on the edge by a thin cantilever concrete metal deck slab. There does not appear to be any reshores below the sliding deck at the concrete slab edge.

Photo posted by GPR Tech on 24 Oct. 2019 shows similar deck, does not appear to be reshores under this one either.

No reshores under a thin cantilever deck seems highly unusual to me, and I have designed supports for several of these types of decks.

Can't tell from the video if collapse is just now reaching the cantilever deck or the cloud of dust beyond is just now reaching from the collapse of the deck.

 

[IceNine]

MOJOJOHN,
If you look at the second photo in Tomfh's post, 14 Oct 19 23:04, you can see rebar crossing the 10 and 11 lines.
It is hard to see because the rebar is parallel to the deck flutes, but if you look closely, it's there. There are two rows of bolsters on the deck and you can see the rebar extend past the beam with headed studs closest to the man in the green shirt.
None of this rebar is shown in the permit drawings.

 

[NOLAscience]

Also I was discussing this area with a very large building contractor today and it was his feeling that the crane attachments would likely damage the otherwise un-reinforced strip as the crane moved under load, possibly breaking spot welds.

Ah, so we are back to the thing that was different about the morning of October 12th as compared to previous days: WIND pushing on the cranes.

New information has come out today. One of the bodies was recovered and identified by the man's widow at the Orleans Parish Coroner's Office. She reported that he was a plasterer and she was told that his body was found on the 7th floor. The 7th floor is part of the parking garage structure, right below the 8th floor transfer slab (podium slab). Just food for thought.