Miami Beach, Champlain Towers South apartment building collapse, Part 14 41

[SFCharlie]

A continuation of our discussion of this failure. Best to read the other threads first to avoid rehashing things already discussed.
Miami Beach, Champlain Towers South apartment building collapse
Miami Beach, Champlain Towers South apartment building collapse, Part 02
Miami Beach, Champlain Towers South apartment building collapse, Part 03
Miami Beach, Champlain Towers South apartment building collapse, Part 04
Miami Beach, Champlain Towers South apartment building collapse, Part 05
Miami Beach, Champlain Towers South apartment building collapse, Part 06
Miami Beach, Champlain Towers South apartment building collapse, Part 07
Miami Beach, Champlain Towers South apartment building collapse, Part 08
Miami Beach, Champlain Towers South apartment building collapse, Part 09
Miami Beach, Champlain Towers South apartment building collapse, Part 10
Miami Beach, Champlain Towers South apartment building collapse, Part 11
Miami Beach, Champlain Towers South apartment building collapse, Part 12
Miami Beach, Champlain Towers South apartment building collapse, Part 13

SF Charlie
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[Spartan5]

Interview with professor of structural engineering: Sounds of a catastrophic collapse

https://www.youtube.com/watch?v=HyRdXg8Dve0

I wish they'd given more examples, but what this does tell us is that the engineers absolutely do take the sounds heard seriously.

Indeed the sounds are important and should be take seriously. Open to plenty of interpretation though absent correlation with concurrent visible events.

From Part 6 (4-1/2 months ago):

The pool slab probably didn’t collapse in unison all at once. It was likely a slow progressive failure too.

Say the slab just gave up, maybe along the construction joint. It may have started with one piece of corroded rebar that gave; pop. Then another with more load now; POP. Then another with even more load; BANG. Then the slab starts to fall; BOOM. First onto cars maybe. Then areas where no one is parked (even “louder” and more pronounced of a crash).

All of this “noise” would have been transmitted through the structural members of the the building. The floor being covered with insulating flooring materials (possibly/probably) vs the ceiling and walls which are exposed.

Regarding “established timeline,” there isn’t much of one. Short of the final collapse, there are only a few discrete points where you can say that something happened before a particular time. But other than that…

 

[Optical98]

What equipment was in the maint or mechanical room in the garage beside the elevator shaft? The fire pump?

 

[SwinnyGG]

Interview with professor of structural engineering: Sounds of a catastrophic collapse

https://www.youtube.com/watch?v=HyRdXg8Dve0

I wish they'd given more examples, but what this does tell us is that the engineers absolutely do take the sounds heard seriously.

Of course they do.

Note that they interviewed an engineer, not an inexperience random person off of the street who has no experience.

If that professor had been in the building during the collapse made it out, her experience would probably have provided a wealth of information to the teams that came after to analyze what happened. Unfortunately, the people who were actually there were laymen.

 

[Keith_1]

What is the point of discussing the roof, it is a concrete deck with a built-up hot mop. The worst case for replacing a stand would be cutting the membrane installing a new anchor bolt, flash it with lead and bitumen; fill the void and patch the felt.

These are regular residential condenser units, and it is absolutely insane to use a crane to fly up a few units on roof that has stair access. The unit size is around 1,400 feet so you're looking at a 2-ton unit which only weighs around 150 lbs. The air handler is a lot harder to install.

 

[Nukeman948]

The special circumstances mentioned by the PE who did the electrical and fire system evaluation for the deck requiring lights and fire alarm devices was that it was a path of egress.

Sorry, I have no information on dates or permits for the fire alarm.

If he wants to call that a path of egress that's fine. The AHJ always has the final word on that. But fire alarms and exit signs are intended to evacuate people to a safe location. I see that two exit signs were to be added at the gates for the pool deck but one of them would lead people to the valet parking area under the building with no other exit sign to lead them to a safer location. If he doesn't consider the pool deck to be a safe location, then why would it be safe under part of the building?

Another issue is from my interpretation of the fire codes: a pull station is required at the exit point of every floor and at the final exit point from the building as marked by exit signs. So would that mean at the pool deck gates? Do they even make weatherproof pull stations that are also seagull rated?

Devices were in the stairwell, but not in the enclosed deck per the inspection.

The enclosed parking level should be covered by NFPA 88A and I haven't used that standard or kept up on changes over the years but I do remember that having an automatic sprinkler system and exhaust fans reduces or eliminates the need for some of the fire protection devices. I believe the stair towers are considered part of the building and not part of the garage, with pull stations as you exit the stairs and go into the garage, almost like the garage is considered outside of the building.

 

[Keith_1]

I have never heard a building fail, but the remaining bars those beams were carrying alot of tension. I imagine that a reinforcing bar stretched to failure would sound like a gunshot going off.

 

[Jeff Ostroff]

Just in case anybody was wondering when the phone call was made from the alarm company to the Miami Dade police and what was said, I have included here below that transcript from my video that I did on the 911 calls back in July. Just shows the exact timestamp as well as exactly what was said between both the alarm company and the 911 operator.

Call came in to 911 1:16:39 AM

- [Computer Voice] Thursday. June 24th, 2021 zero-one-16 and 39 seconds.

- [Operator] Miami-Dade Police.

- [Man] Hello, this is Central Alarm Control. We're calling it the fire alarm for a business.

- [Operator] Okay, one second.

- [Man] Mhmm.

- [Jeff] Now here, the 911 operator is going to leave this guy on hold for quite a few seconds here before coming back. I don't know what they were doing.

- [Operator] What's the address?

- [Man] The address is 8777 Collins Avenue.

- [Operator] 8777 Collins avenue?

- [Man] Yes.

- [Operator] What kind of alarm did you say?

- [Man] A fire alarm.

- [Operator] What's the name of the account?

- [Man] It is Champlain Towers South.

- [Operator] Your company?

- [Man] I am with Central Alarm Control.

- [Operator] Operator?

- [Man] My name is Silvio.

- [ Operator] Call back number?

- [Man] Mine is 3-0-5 2-3-8 0-8-0-0.

- [Operator] And a premise number?

- [Man] The premise number would be, give me one moment, 3-0-5 8-6-5 4-7-4-0.

- [Operator] I'm number 1-2-6.

- [Man] 1-2-6? Okay, thank you very much.

- [ Operator] You're welcome.

 

[Keith_1]

NFPA for Type II construction requires pull stations within 34 inches of a means of egress, I have never heard of placing one within a stairwell.

In Type II construction you do not need to have enclosed parking structure alarmed.

The only thing that I can think of in terms of additional exterior "emergency lighting" is that there is a conflict between the NFPA and the "Sea Turtle" light code, exterior lights in buildings that can be seen from the ocean are highly restricted too the point that there is basically no useful illumination provided. This would have to be triggered by the fire alarm, simply to protect the turtles.

 

[Nukeman948]

NFPA for Type II construction requires pull stations within 34 inches of a means of egress, I have never heard of placing one within a stairwell.

Well, I said "with pull stations as you exit the stairs". Referring to the original drawings it is shown just on the outside of the stairwell, just as you exit the stairs.

And now that you bring it up, a quick Google search shows:
NFPA 72 requires a pull station within 60 inches of every individual exit, and for groups of doors that are more than 40 feet wide away from each other, there must be a pull station on both sides of the grouping. The placement of fire alarm pull stations is critical to ensuring they provide the protection intended.

Could you please post a link to this 34" standard? I can't seem to find it.

 

[Demented]

So would that mean at the pool deck gates? Do they even make weatherproof pull stations that are also seagull rated?

They do. I don't think the wording of seagull rated is in it, but they do make weatherproof ones with clear plastic flip-up covers that are rated for use on oceanside. My unit is located away from the water so I only have a weatherproof one located outside my front door, but the units closer to the water have the plastic cover. Also, I have seen these located at pool gate entrances on ocean front properties, along side child-proof privacy swing doors with spring actuated self closing hinges. I haven't a clue as to the legality of that, but in the lower 3 counties here, this is a common thing. Turtle safe amber alert strobes are also available on the market. The local fire marshal has the authority to mandate and approve different colors that are not NFPA approved clear.

In case anyone's missed it, I've attached a PDF of the mechanical and electrical system evaluation that references fire alarm devices needing to be installed on the deck level and garage parking.


Precision guess work based on information provided by those of questionable knowledge

 

[Nukeman948]

I don't think the wording of seagull rated is in it,

Thanks for the info, the ocean is several hundred miles from me so I never had to consider such things. The seagull thing was a poor attempt at humor.

The PDF is nice but it doesn't tell me what kind of devices were to be added or where they would be located. Doesn't really matter now that the building is gone.

 

[Demented]

Thanks for the info, the ocean is several hundred miles from me so I never had to consider such things. The seagull thing was a poor attempt at humor.

The PDF is nice but it doesn't tell me what kind of devices were to be added or where they would be located. Doesn't really matter now that the building is gone.

The humor attempt was by no means poor, and I promise you is a concern here. Though our seagulls spend their time away from the shore at the soon to be golf courses we call Florida mountains (landfills).

Strobes/siren alarms are my assumption as to what would be installed there. The lack of indication of what and where, even by Morabito is somewhat frustrating, but it's at least somewhat of an indication of no fire alert systems being in those general areas, thus likely why other alarms were not triggered until it was too late as there likely were no alarm wires to be severed and cause an alert be it at the control panel or front desk.


Precision guess work based on information provided by those of questionable knowledge

 

[Nukeman948]

Strobes/siren alarms are my assumption as to what would be installed there.

And at least two pull stations.

We have those winged rats here too but you guys don't seen to have as much snow to shovel.

Another thing to keep in mind is that the NFPA, NEC and all of the other building codes and standards that we work to are minimum requirements and we can always add more protection and better building practices as long as you can convince the customer it is worth paying for. Sometimes the "Authority Having Jurisdiction" can be our friend by giving us more work and a better world.

 

[MaudSTL]

[23 Nov 21 05:14]

In the interest of accuracy:

1. If you read G19 in the Detailed Data tab of the Timeline spreadsheet, you will understand the references to 1st Collapse, etc. Links provided in Rows 8-16.

2. You mischaracterize Sarah Nir’s reaction to the 1:10 collapse. Refer to the links in Rows 8-16 of the Detailed Data tab for contemporaneous statements. Sarah was not casual…she was furious and wanted Shamoka to call the police to get them to stop what she thought was illegal night time construction. In the recent Herald story she affirms that she was “really mad.”

 

[Keith_1]

This conversation is just off the rails, to the point of absurdity. Getting into NFPA is about the dumbest thing I can think of in this instance, I was trying to steer the conversation in a different

The building failed because of stupidity, and alot of people lost their lives due to the same. Single point analysis is a waste of time and energy. What we need to do is make the general cause of the failure understandable to the general population, and more importantly how to economically remediate poor conditions. Why waste your time doing complex analysis of a failure moment that is entirely preventable? It happened, it was preventable, what do we do to improve the future of other structures that are in a similar condition, because there are alot of them out there.

 

[Demented]

Keith_1, absurdity was 7 threads ago. This has since toned down.

We still don't know why the building failed. Despite the poor state of the maintenance of the building, there could have been other contributing factors that had caused it to collapse. There are some very egregious flaws from the original construction that may or may not have contributed, such as a majority of the missing rebar. The maintenance issues may very well have been futile in preventing continued damage to specific areas due to that reason, and as shoddy as some of the remediation work was, may have been one of the only things that kept the building standing for as long as it did. After seeing some of the very corroded rebar at the base of columns, as crazy as it seemed months ago, a car for all we know really could have taken out a column. With uneven subsidence being evident in the building, there could be an unknown pile failure or failures that we've yet to see. FIU research was showing that this building was gradually subsidizing more than it's surrounding buildings over time, which could come down to various causes. We still have no information on the piles, or much of the actual as-built of the building. We still don't know if the original construction stretched out the concrete mix with beach sand and salt water, nor do we even know if even the proper grades of concrete and rebar were used. We have little indication of if certain non-load bearing walls in the original design did indeed carry some of the building's load and their removal could have carried some consequences. Many documents related to the building are still missing, or so we're lead to believe from the town of Surfside. We have no idea what backfill was used to level the grade on the site, or if it was ever even compacted, let alone laid properly to avoid erosion as this grade was under mean sea level. The original construction had work stoppages for accidents and plan deviation/permit violations, which raises all sorts of questions on what set of plans the building was even constructed under. I for the most part do agree with you that this came down to a maintenance issue, but for the reasons stated above, we just don't know and the maintenance issues could very well just be blinders on us. There appear to be many single points of failure possible. I feel it's worth digging into it all, which can ultimately help in preventing future occurrences.

Precision guess work based on information provided by those of questionable knowledge

 

[Optical98]

Demented

I think we were onto something regarding the elevator shear wall area. If I can figure out how to share things on here from twitter...

Here is one image -

This is more from Dawn Lehman and the Miami Herald. I can see snippets on twitter but links are behind a paywall.

 

[Optical98]

Lehman said the witnesses’ collective memory suggests that the collapse likely began when steel reinforcement fractured at or near the southern edge of the first-floor slab, in the valet parking area at the western edge of the pool deck.

The tower’s night security guard, Shamoka Furman, provided the framework for the Herald’s investigation when she described a sequence of three distinct failures:

One small, the next large, and the final unspeakably brutal.

The Herald identified six people who heard the first –– boom, boom –– but saw nothing. Engineers said that’s indicative of steel reinforcement inside the concrete fracturing.

A minute later, 10 people heard the pool deck collapse in one thunderous crash.

Seven minutes later, the tower fell.

Lehman worked with a team at the University of Washington to build a complex computer model to identify pre-existing stresses in the structure and test various collapse scenarios.

It was a process of trial and error.

Collapse scenarios were rejected if they contradicted the timeline of events. They were also rejected if the model produced a different damage pattern than what was visible in images of the collapse.

Lehman zeroed in on the connection between the pool deck slab and the southern perimeter wall, where post-collapse photos showed pre-existing problems in the area.

The rusty rebar fracturing could have made the “boom, boom” sound, engineers said.

A computer simulation of the corrosion and missing reinforcement along the wall showed rebar fracturing down the line –– “boom, boom” –– before cracks spread across the deck and into the tower, following similar patterns seen in post-collapse photos.

The Herald’s forensic investigation was based on observable conditions in photographs and videos from before and after the collapse, more than two dozen interviews with people familiar with the building, and the review of thousands of records.

In addition to Lehman, who worked as a consultant to the Herald on this project, nine other engineers reviewed the results of the Herald’s reporting and model.

“If the slab lost support on the southern edge where it was sitting on the wall ... then there could be an unzipping effect because you get more force on the nearby rebar,” said Shankar Nair, an engineer with 50 years of experience with large structures.

Credits: Miami Herald, Sarah Blaskey and Nick Nehamas

 

[MaudSTL]

This is more from Dawn Lehman and the Miami Herald. I can see snippets on twitter but links are behind a paywall.

The archived version of this piece, which anyone can access, was provided earlier in this part. Although some of the images don’t make it into the archive, many do.

The tower’s night security guard, Shamoka Furman, provided the framework for the Herald’s investigation when she described a sequence of three distinct failures:

One small, the next large, and the final unspeakably brutal.

This is the same thing that Gabe Nir earlier described as Collapse 1 through 3. The Witness Statement Timeline uses his nomenclature.

 

[Optical98]

Maud,

It's weird, because the pics are different in the twitter version, for me anyway...
And in the link you posted, I saw what the survivors were saying etc, but nothing about Lehman. o.o