Miami Beach, Champlain Towers South apartment building collapse, Part 03 148

[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

Thank you

SF Charlie
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[1503-44]

In fact, the codes seem to be moving to reducing redundancy if anything. Or is that just my impression?

 

[Mark R]

In fact, the codes seem to be moving to reducing redundancy if anything. Or is that just my impression?

It's definitely not just your impression. They are using the term "Value Engineering" to reduce the redundancy and strength of designs. As long as it stands or states together until it's paid for that's good enough is the prevailing attitude these days in many disciplines.

 

[1503-44]

Back in the day, we'd design for lateral using X brace and moment frame. If we had a "shear wall" we would not consider that it actually resisted anything. It was an entirely redundant element.
Now it seems to be the only thing keeping the rest of the things upright.

 

[FacEngrPE]

It used to be that design techniques were built assuming our knowledge of material properties and physical behavior were limited, this caused engineers to use large safety factors in design codes. Prior to design codes many things were marginally designed, with the result that boiler explosions were frequent, and bridges made with less well understood materials fell down. After looking at the bridge list I think there is some work to do here, most of the recent bridge failures seem to include some sort of human factors problem. The dramatic reduction in boiler explosions coincides nicely with the creation of the ASME Boiler code.

In any case as we have better design techniques, there has been a temptation to "optimize" the designs to remove "un needed" material. IE design margins have been reduced. Much of this reduction of design margin is valid, but in some cases reducing safety factors also create a requirement to add material (or perhaps a design property) where previously we did not know it was required, the design margin took care of it.

The discussion of the need for designing for ductile failure of reinforced concrete may be one of the cases that now more important, as the design margin no longer provides as much extra meat to the structure.

 

[SFCharlie]

Thanks for your reply

SF Charlie
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[Awestruc]

Its interesting to see that the columns punched through the slab and what is left of them look like half sharpened pencils. Punching shear theory assumes that the crack will form at the face of the column and radiate at a 45deg angle up and out, leaving an upside down cone shaped piece of slab atop the column. This did not appear to happen as it looks like the slab took some of the column concrete with it on the way down instead.

 

[Vance Wiley]

Mark - it was your post that prompted mine - and I did look for your source but it was farther back than I thought so I grabbed the youtube address. {was it a tiktok?} The comments by the condo manager are quite interesting.
I apologize for not crediting you. From your post :

https://www.youtube.com/watch?v=uGYZIEQxf1I

What is your opinion about the condition addressed in that video?
It has since been described as an expansion joint. It probably acts as one today, but is it intentionally random and ugly? Without exploring and investigating it I would call it very serious until proved otherwise.

 

[Vance Wiley]

and it looks like the slab took some of the column concrete with it on the way down

I would suspect weak concrete, demonstrating a failure in compression rather than diagonal tension.
Or perhaps simply crumbling.
I hope they investigate the quality of concrete in the slab and columns and compare the findings in the pool deck/courtyard with that in the building areas.

 

[Spartan5]

Awestruc, details of some of the column tops:

 

[lucky555]

The middle part of the building's history is not considered. Major 2002-2003 work by A.T. Designs had a bunch of structural repairs, mostly balconies. Then again they were doing more repairs 2009. Column spall repair pg.172 chipping out concrete at columns was part of it and who knows if they did more bad than good. I'm not sure what stacks 01,02,03,04,12,14 and poolside 09,10,11 mean but they worked on those as well. pg. 17/218 many observations.
Link permit-09
Link permit-02
Can't find third permit link.

If a building is improperly maintained, there is water and saltwater ingress - at what point are the engineer's no longer responsible?
I'm reminded of people who don't maintain their vehicles, nothing left for brake pads and they refuse to pay for that repair and the mechanic lets them roll out of the shop.

 

[zebraso]

nothing left for brake pads and they refuse to pay for that repair and the mechanic lets them roll out of the shop.

True in Florida where there is no state inspection requirement for sure. But it's not true everywhere.

 

[Js5180]

Here is a video tour of the north tower, which I found by accident:

https://m.youtube.com/watch?v=arUOCTDRnCc

 

[RobertHale]

I have been thinking about this collapse for a bit now; I think there are several items that we (the construction community and the building structural engineering community) have to look at and potentially address. My observation is that these items can be broken down into four areas: 1) the initiating event for the collapse, 2) the progressive/disproportionate collapse, 3) design review/construction inspection, and 4) Post-CO inspection.
[ol 1]
[li]Initiating Event:
To my mind, the initiating event for this is really only of primary interest if it wasn't extraordinary. Once the reports are written and that initial domino is determined, it may well be appropriate to modify the design codes to account for some type of additional "loading" or some type of additional member resiliency.[/li]
[li]Progressive/disproportionate collapse:
The progressive/disproportionate collapse is the scariest part of this unfortunate event. As a community, we have come a long way in addressing progressive collapse, but it has been accrued through tragic events like this collapse (Ronan Point, Oklahoma City, WTC). Most in the SE community would use the prescriptive requirements for continuity spattered throughout the various design codes for buildings like this. The more direct and robust design solutions are time-consuming and computationally intensive, not to mention they require substantial knowledge of the reinforcing and connections in the members.
I was gobsmacked by the reinforcing of the columns where the parking slab punched. As best as I can tell, there was a minimal amount of top reinforcing over the columns and any bottom reinforcing over the columns was not sufficiently developed or lapped to form the catenary action that would enable the structure to "span over" localized column failures. I have not taken the time to scrutinize the construction documents, but I expect this bottom reinforcing condition would be typical for the building. I would be interested to see how a building with the same concrete strength and the same reinforcing ratios as the condo tower, but with the reinforcing detailing we currently use, would perform for a loss of column scenario. To return to the first point, if the initiating event was a vehicle striking a column in the garage area, perhaps we should explicitly design the structure above for a loss of column scenario or mandating the columns in these areas be robustly reinforced to handle a vehicle strike.
Overall I think the UFC design approach for progressive collapse is a good approach, but I would like to see it developed into more of a standalone document that doesn't rely on ASCE 41 as much. Eventually, I would like to see ASCE produce a standard for progressive collapse that offers the use of the 4 analysis procedures listed in the UFC and mandates under what conditions the more rigorous procedures are used.[/li]
[li]Design Review/Construction Inspection:
Design Review in a lot of jurisdictions is depressing. I have dealt with major jurisdictions where code reviewers have requested information that is patently obvious on my design documents. To the point, my colleagues and I have questioned the ability of the reviewer to truly digest any important structural information. In many places, design review is merely a proforma check of loading parameters mandated by the Code. I know there are many jurisdictions that mandate some form of peer review, and by and large, I think that is a good thing, although these reviews can sometimes devolve into petty and esoteric comments. We need real review that validates the structure loading and identifies complete and robust load paths, both gravity and lateral. This also means we need building officials with a structural knowledge base and meaningful experience in design.
In my first few years of practice, I attended a SEA meeting that looked at the renovation of the Georgia Dome. One thing from that case study that stuck with me was that the main tension ring in the structure was built with half the shear stirrups called for in the construction documents. This was a major marquee, public project, and the inspection scheme missed critical reinforcing on a primary design element. The more experience I have gained, the more troubling I found this incident. I think special inspections as implemented by the IBC have gone a long way toward making the actual structure reflect the design documents. That being said, it wasn't until the mid-2000's that a lot of jurisdictions got on board with the special inspection process. I have had limited experience with the Florida Threshold inspection process, and to be quite frank, I still cannot tell you specific items required by threshold inspections. A few years ago, I attempted to compare the Threshold Inspections with the standard IBC inspections, but I hit a brick wall and didn't find real answers. All this being said above, there is still a real disconnect between structures constructed before the implementation of a rigorous inspection process and those constructed after. I also think that all buildings constructed should have a repository of all the final construction documents and submittals, along with documents related to post-construction renovation/modification.[/li]
[li]Post-CO Inspections:
While a properly designed, constructed, and inspected structure is a good way to ensure a resilient structure with a reasonable lifespan, maintenance has a significant impact on structural performance over the long run. I know many of you in the SE community have run across your share of structures that did not have the upkeep to keep them performing as intended, just like this structure appears to have suffered from. I was not aware of Miami/Dade's post-CO inspection requirements. I think that is a good start, but I agree with some other posters that 40 years is likely too long a period to wait, given that most designs are geared toward a 50-year lifespan. I also like some other's comments that there should be some type of tiered inspection. I jumped into thinking about the ASCE 41 tiered evaluation. Perhaps we should be using an increasing level of scrutiny on a 20, 30, 40-year schedule. I think this is also important for more substantial structures that were likely designed and constructed in accordance with the state of practice at the time of construction but do not include considerations for phenomena (like progressive collapse) that have become increasingly important. For some structures, it seems unreasonable to wait for some potential future event (like a significant renovation) to trigger a review of the design and constructed condition[/li]
[/ol]
This was a little longer than I intended, and it may have rambled on, but I think it needs to be considered by the community, and it looks to the future for issues we can already identify and begin addressing.


Robert Hale, PE, SE

 

[Mark R]

Quote (lucky555)
nothing left for brake pads and they refuse to pay for that repair and the mechanic lets them roll out of the shop.

True in Florida where there is no state inspection requirement for sure. But it's not true everywhere.

Actually these days there are more states that do not require vehicle inspections than states that do. Even in a number of states requiring pollution control inspections is diminishing.

 

[Mark R]

Here is a video tour of the north tower, which I found by accident:

https://m.youtube.com/watch?v=arUOCTDRnCc

Great Find, I wish it was an online translator for the audio portion! Has anybody seen any place how much the North building have spent on repairs vs. the South building?

 

[Awestruc]

Thanks for the close ups Spartan5.
The brownish slab concrete definitely looks badly deteriorated compared to the Grey column concrete.

 

[zebraso]

Actually these days there are more states that do not require vehicle inspections than states that do. Even in a number of states requiring pollution control inspections is diminishing.

My understanding is that in Florida even when they had vehicle inspection you could sit in your car while they did it. I don't know how they inspect the brakes without pulling the tires. Where I am the car must be put on a lift. Which begs the question of how superficial are the requirements. Without inspections you don't have to have bumpers or working headlights. Well ok. No brakes is another story. I think this is on topic and the subject has been covered, but it's just another illustration of how these things are neglected. I never saw as many cars on fire by the side of the road as I did in Florida (small sample size).

 

[SFCharlie]

I wish it was an online translator for the audio portion!

If the video is captioned(it is), YouTube should allow you to turn a transcript on(3 dots under the right edge of the video, "open transcript". you can then copy and paste the transcript into google translate

A twin building that collapsed in Miami, an X-ray from the inside
[Music] [Music]
we are in the metro building but here one arrives with ice cream is entering by collins heading north and had than leave the car here look how good it looks it seems very safe very well maintained now we're climbing the ladder These are the entrance doors to the departments that work in this part which is the door entered your Department this department, I think there would be cut in the middle of the building and I think this department is like the rooms in this apartment the shear wall so yes we were in the other department to starting from this line taking a step further towards the area not only the sea I'd be moving the mountain of rubble so were the balconies of the collapsed building because it is the same architectural design the same company the same style for you to see when you see this progressive collapse how the balconies were stacked one above the other there is no one thesis there will be very few people takes account of 80% television went into exile this would be the first part of collapse because the one on the pool deck and down the pool the arms whatever the parking sector how many are we talking to here square a block say 100 160 meters approximately ah in the collapsed building is all this is what's missing [Music] the people who except play against skin soul sides and delivered to carrió is the pool already they say that he also lost a lot of water seemed to give better maintained than they showed the truth from the other building [Music]
Ah! I love google translate, it seems particularly bad at Spanish (specially weird since google is in silicon valley, which is full of fluent Spanish speakers).

SF Charlie
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[aggualaqisaaq]

This simulated view of the vantage point of the TikTok video comes from the Miami Herald. They also have a 3D rendering thing there too:

https://amp.miamiherald.com/news/local/community/miami-dade/miami-beach/article252487373.html

 

[BlakeStr]

Looking at the column photos, the pool deck patio slab looks to have failed in negative moment bending.