Half an apartment building collapsed in Miami last night.

brandonsmash said:

In reply to SV reX :

Surely they meant "weaker than specified by engineering" rather than code. 2500psi is rather low for major load-bearing structures; even here in Arizona, stem walls are 3k minimum.

All that said, of course concrete is strongest in compression. That's all good and well until you get into tension or ductility concerns, which it sounds like may have played a part here (if, in fact, the rebar was corroded).

What was code in 1980-whenever when this was built?

You cant compare what you see now with something 40 years ago.

Also, if its weaker than code it is almost by definition weaker than the engineering design.  

In reply to Mr_Asa :

I've been building for over 45 years. I never remember anything less than 2500 psi (and that was for residential).

Although, there are lots of things I never remember... 😂

In reply to Mr_Asa :

Also.. I disagree. Read the article I linked. We absolutely CAN recognize  poor construction practices that are 40 years old. 
 

It wasn't built right. Has nothing to do with current code. 

In reply to Mr_Asa :

Reading the article, it seems the investigators are saying the building was not compliant with code when it was built. Add in the shoddy maintenance and excess loads, and you have what the Barenaked Ladies would call "A recipe for disaster"

"Investigators detailed numerous areas in which the design and construction of Champlain Towers South failed to comply with building codes when it was constructed in 1981."  (Emphasis mine. -Recon)

You brought up 2500, I have no clue what AIC says and being I'm mechanical I dont need to go reading it.  I'm responding to what you are saying.

[I][b]If the building did not even meet code, whatever the code was, whenever the code was, it wouldnt meet engineering design which would be more rigorous. [/i][/b]

I didn't say you can't recognize poor building practices. I said you cant compare code.  And you cant, not beyond an intellectual exercise. Generally codes are not retroactive.  Once a building is built thats it.  Completely different matter if a building is not up to code.

Recon1342 said:

In reply to Mr_Asa :

Reading the article, it seems the investigators are saying the building was not compliant with code when it was built. Add in the shoddy maintenance and excess loads, and you have what the Barenaked Ladies would call "A recipe for disaster"

"Investigators detailed numerous areas in which the design and construction of Champlain Towers South failed to comply with building codes when it was constructed in 1981."  (Emphasis mine. -Recon)

Yes.  I have been following that.

The National Institute of Standards and Technology has spent $30 million gathering evidence and testing materials.
 

I'm pretty sure those guys know which year code book they are supposed to be reading. 🙄

Lets try a different way of looking at it.

You have to be 18 to vote.  You have to be 21 to drink.  You have to be 25 to rent a car.

This building wasnt even able to vote and was trying to rent a car.  It did not meet the bare minimums, so of course it would not meet the more rigorous standards.

In reply to SV reX :

Brother, I wish you would actually read what I wrote instead of thinking you understand what I said.

If there is something I did not say clearly, please point it out.

In reply to Mr_Asa :

There is absolutely nothing you wrote which is unclear. I haven't disagreed once. No need to repeat it. 

In reply to SV reX :

Your rolling eyes emoji comes off negatively above.  Gives that entire comment a condescending vibe like I dont know what I'm talking about. If nothing I wrote was unclear, I have no clue what the purpose of that post is except to try to put me down.

Text alone is an inherently difficult manner to convey meaning.  We should all attempt to be as clear as possible. 

In reply to Mr_Asa :

Engineering requirements are very often more stringent than codes. 2500psi is not a very high bar to clear and I can't think of a cementitious materials supplier that would even risk supplying anything below that.

It's easy to see how a specific project might meet code but not engineering: This I see all the time, hence why I suggested that it may have been weaker than specified by engineering.

I could certainly be wrong and the concrete supplied may not have met code standards; that would be truly shocking. Even in 1980s Miami I have to imagine that there were city P&P engineers and inspectors who weren't wacked out of their nuggets on coke and who would have caught an error (or subversion) that significant. Rebar crowding would also be an odd failure catalyst as that would actually have involved MORE expense and work to create that flaw.

In reply to brandonsmash :

I couldn't agree more. 

In reply to Mr_Asa :

I think you are massively overthinking what an emoji may mean. 
 

SV reX said:

In reply to Mr_Asa :

I think you are massively overthinking what an emoji may mean. 
 

I told you how you came off in that interaction. You want to take that away from it you are free to.

You two realize that you will get this thread locked if you keep this up. It is kind of going in circles at this point. 

In reply to dean1484 :

👍

dean1484 said:

You two realize that you will get this thread locked if you keep this up. It is kind of going in circles at this point. 

Blessed are the peacemakers.

I think the understanding from both reports is that some of the concrete wasn't correct strength to support the building over its life. 

I have received concrete mix tickets on jobs that say everything was mixed per design but after 1 hour of placement we all know something is wrong. Then find that something went wrong with the mix and the tickets are lies. Last year we had some of this situation and found it was way below 2000psi break at 7days when previous placements were already over the min 5000psi at that duration. The only time my test engineering company called me instead of just emailing reports. 1st cylinder didn't break it "mushed" like a slow motion slump test.  I am surprised when it happened across several trucks.

In this situation it may very well be that the mix came bad plus they only took cylinders from this or that truck. 

No matter how the concrete got that way the investigation is pointing to low strength. 

Yeah, reading a 1/2 dozen links from that NPR story and some others, it's very much told that the strength of the concrete was fudged or overlooked when it was built. The wiki page has been updated that "Corruption during construction has been cited by multiple local media sources as a potential contributing cause of the collapse."

dean1484 said:

You two realize that you will get this thread locked if you keep this up. It is kind of going in circles at this point. 

The main reason I rarely come here much anymore.  

CrustyRedXpress said:

dean1484 said:

You two realize that you will get this thread locked if you keep this up. It is kind of going in circles at this point. 

Blessed are the peacemakers.

Blessed are the cheese makers?

(Wait... cheesemakers! Is that who did the concrete?)

I have been in this field for a long time and it is almost always a trifecta of things that align to cause a problem.. Seems like this is the case again.   I am just glad that it seems like they have figured it out. We can't change the past but hopefully this will make things better for the future. 

Advan046 said:

I think the understanding from both reports is that some of the concrete wasn't correct strength to support the building over its life. 

I have received concrete mix tickets on jobs that say everything was mixed per design but after 1 hour of placement we all know something is wrong. Then find that something went wrong with the mix and the tickets are lies. Last year we had some of this situation and found it was way below 2000psi break at 7days when previous placements were already over the min 5000psi at that duration. The only time my test engineering company called me instead of just emailing reports. 1st cylinder didn't break it "mushed" like a slow motion slump test.  I am surprised when it happened across several trucks.

In this situation it may very well be that the mix came bad plus they only took cylinders from this or that truck. 

No matter how the concrete got that way the investigation is pointing to low strength. 

Had a parking deck project 2 years ago where a full day worth of trucks from one batch plant got a bad admix dosage. My project and several others around town bought the same mix and ALL were berkeleyed. Engineer rescued our weak concrete with carbon fiber.  E36 M3 happens. 

Today, the Florida building code (based on IBC but modified specifically for stuff like hurricanes) requires rigorous "threshold inspection" of all structural elements. Shoddy buildings like this fallen condo might just be exactly why those structural inspections became the norm. 

This one that I'm working on now is seven stories and almost 1,000' long. 120,000 cubic yards of concrete. Testing every batch. 
 

In reply to OHSCrifle :

Every batch?  Like every truckload?

We usually test every 4th truckload