Miami Beach, Champlain Towers South apartment building collapse, Part 04 49

[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

SF Charlie
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[tmwaits1]

Towers S.6 Second Floor Framing Plan (Pg.28 of 336) & (Pg.110 of 336) Typical Notes #5 at least 25% of all column strip reinf. shall be centered over the column as explained in typ. flat plate det. - see sheet S.11]

What I would say about this is that the original plans are so sloppy that its impossible to be certain of the slab reinforcement that was required at each of the columns. 25% of the "column strip reinforcement" is a very poor way to call this out in the plans and highly prone to an incorrect interpretation by the contractor. I'm sure someone will comment that this is common practice, however it is not best practice.

 

[bones206]

What I see in this photo is that one of the top bars was installed just outside the column cage. So when the slab yanked down on that side of the column, the bar acted like a wire cutter and helped shear the slab off at the column face, rather than remaining within the column cage and providing some catenary support.

The image resolution isn't great, so I could be wrong about the column tie.

 

[GPR_Tech]

What I think we are missing is, we do not have a copy of the "SHOP Drawings" and those are what would have been used by the contractor to fabricate the building.
We only have a mixed up copy of the Design Drawings.

 

[GPR_Tech]

OK why two different length top bars .30 L1/L2 & .25 L1/L2... or WHAT IS THIS TELLING US?
(I just do not know what this detail would look like)
S.11 (Pg. 38 of 336)

 

[tmwaits1]

The reinforcement we are talking about should be fully detailed in the plans. For this reason, shop drawings would not be required unless this submittal to the EOR is specifically noted as required in the general notes. I don't see any note to this effect in the original plans. The building is not "fabricated" this is the term you would use to describe specific custom components (typically metal or architectural) that for one reason or another, cannot be fully detailed in the plans.

 

[HouTxMechPE]

Has anyone mentioned the fact that a crane collapse on site in 1980 during construction may have doomed the foundation from the beginning?

Link

 

[Mark R]

Quote (GPR_Tech (Civil/Environmental) 7 Jul 21 16:55 Quote (tmwaits1 (Structural)7 Jul 21 15:42) What I think we are missing is, we do not have a copy of the "SHOP Drawings" and those are what would have been used by the contractor to fabricate the building. We only have a mixed up copy of the Design Drawings. )

The reinforcement we are talking about should be fully detailed in the plans. For this reason, shop drawings would not be required unless this submittal to the EOR is specifically noted as required in the general notes. I don't see any note to this effect in the original plans. The building is not "fabricated" this is the term you would use to describe specific custom components (typically metal or architectural) that for one reason or another, cannot be fully detailed in the plans.

Maybe it's different where you are but anyplace I've been detailed shop drawings for the reinforcing as well as other portions of the project are required and reviewed by the appropriate engineers before a project proceeds. However, other than updating the engineering drawings to an "as built" version, shop drawings are not normally archived for the project.

 

[SFCharlie]

"Is there some other transcript, not Geezer's, that you refer to?

Yes, it is the YouTube auto-caption (for what it is worth).

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

As I said at the end of my post

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).

(maybe YouTube auto-caption is as bad at Spanish as google translate?)

SF Charlie
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[GPR_Tech]

Maybe I should have used a better term than "SHOP Drawings" it should have been Placing Drawings
[The Detail Drawings for Reinforcing Bars in Site-Cast Reinforced Concrete Construction]
I know these types of drawings are not always required by contract but they are many time used in this type of construction, if for nothing more than the supplier of the rebar to be able to deliver the correct material for the job.

 

[1503-44]

Apparently Geezer and myself heard and saw the same words on the video and arrived at the exact same translation, so let's vote Google's mash up out. There's no ice cream under the rubble. The other... maybe.

 

[tmwaits1]

As we go forward, it will be critical to look at ways to improve the design, construction, maintenance, and rehab process to try and prevent similar tragedies from happening in the future. This is where my interest in this lies as I do structural design projects (bridges and buildings) in South Florida where the process is obviously less than ideal. It may be that "where you come from" is doing it better and we should be emulating it so I appreciate your perspective on how things are done elsewhere.

 

[Vance Wiley]

Different lengths just to save money.
The practice is (was) to provide reinforcing where moment stresses require, and extend that reinforcing beyond the point of requirement to develop (anchor) the steel. The negative moment rises sharply near the supports, if continuity is present, and the need for steel reinforcing rises also.
Then there is the issue of not beginning or ending ALL the reinforcing at one point and "feathering" out the amount to ease the loads resisted by reinforcing as they may transfer into the concrete.

 

[SFCharlie]

let's vote Google's mash up out.

Yes! Thank you both! I'm sorry for the confusion that I and Google introduced. Perdóname


SF Charlie
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[Vance Wiley]

This is part and parcel to the note from the drawings that 25% of the column strip reinforcing is to be centered over the column. That requirement could be interpreted as 25% PASSING OVER the column or, conversely, as a symmetrical and balanced placement located on the center of the column - even if the strip of reinforcing were 20 feet wide.

A comment if I may about maximum reinforcing to prevent a brittle and sudden failure. While that may be the intent, the 'balance' can change if the concrete deteriorates and the point of over-reinforcing changes. If the concrete cannot do its part, the ductility is lost. On the other hand, if the reinforcing corrodes at a similar rate, the ductility may remain. I see that part as a bit of a chore to program and control.

 

[RickyTickyTavi]

The reinforcement we are talking about should be fully detailed in the plans. For this reason, shop drawings would not be required unless this submittal to the EOR is specifically noted as required in the general notes. I don't see any note to this effect in the original plans. The building is not "fabricated" this is the term you would use to describe specific custom components (typically metal or architectural) that for one reason or another, cannot be fully detailed in the plans.

I get shop drawings for rebar for just about every new construction project I work on. Houston, TX, for what its worth. I would not anticipate this to differ much in the 70s or 80s.

 

[IEGeezer]

There's

http://www.almadepiel.com,

but otherwise I am not aware of it as an idiom.

Machine captioning is still primitive. As for translation, the one I had trouble with was "muro de corte", which was translated as "shear wall." That's too technical a term for machine translation. As a general rule, technical terms turn into something interesting. I came up with "plane of cut" based on context, as in: this is where the two halves of the buildings separated.

What YouTube autocaptions did was interpret "más de aquel" as "alma de piel." They are actually phonetically more similar than one would think by looking at the written word.

 

[dik]

Typical Flat Slab reinforcing, I've used for decades...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Vance Wiley]

The requirement for shop drawings was the practice in our office in the 60s thru 2000s. Shop drawings can tell the engineer if his drawings were interpreted to meet his intent. If something does not fit the drawings can request further information or suggest a resolution. And shop drawings are the last opportunity for the engineer to review his design before there is a lot of material cut and labor expended. After that, changes or corrections become very costly.

 

[oldrunner]

Reinforcing shop drawings sequence:
1. Engineer's design drawings - submitted to the building department for review and approval. (Maybe after a number of re-submittals) (City may send out project to private plan check firm)
2. General contractor selects rebar sub-contractor
3. Rebar sub-contractor prepares rebar details which includes layout drawings with mark numbers of every rebar. Separate drawing(s) for every bar - straight and bent with bill of materials coordinated with the layout drawing by mark number.
3A: Rebar sub-contractor has the set of rebar drawings checked in-house by the another person.
4. General contractor receives rebar shop drawings and layout sheets.
4A: General contractor also reviews rebar drawings and if ok, then submits them to the EOR.
5. EOR reviews shop drawings and layout sheets for final approval - possible a number of re-submittals.
6. After final approval, rebar is fabricated and delivered to the job site.
7. Rebar installers - using the shop drawings and layout sheets- install the rebar.
8. Inspection - maybe both the city and the EOR's inspector inspects the placement using the layout sheets as well as the EOR's design drawings before signing off on the pour.

Some place in this sequence, rebar mill certificates are submitted for approval. The inspector's are the last line of protection - and sometimes they get bad-mouthed - but I like good inspectors.
It is the rebar detailer that solves the placement problems - this shouldn't be done in the field.