Miami Beach, Champlain Towers South apartment building collapse, Part 06 131

[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

SF Charlie
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[itsmoked]

another-florida-building-evacuated-over-concrete-safety-concerns

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Demented]

Hi Demented

Those depths you mention refer to the pile cap itself.

Pile depths - Given the 'bulb' at the bottom of the pile (shown on the drawing), this would indicate that these are driven, cast in-situ piles (Franki). Crudely explained, a steel tube (more or less 20" dia) is driven down until it reaches a point when the displacement of the tube is minimal (probably down onto the limestone). They then anchor the tube to the piling rig and continue dropping a hammer inside the tube, now displacing a dry concrete mix placed in the tube, to create the bulb. A rebar cage is dropped in and concrete or grout is poured in. The steel tube is then pulled out.

Where they call off 'tension' piles, they ensure that the reinforcing cage is linked into the bulb forming an anchor.

These driven piles are usually quite reliable and shaft stresses are quite low (limited to around 800PSI).
Settlement of piles would show up as differential settlement between columns and be noticed long before a collapse. Safety factors on piles is quite generous.

I fully understand what the piles should be. I also fully understand ground crew's interperitations of those plans.
Two very different things.


If there is a callout for cip franki, please link me. I can only find precast.



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

 

[AutisticBez]

So, take a look at that North video and I notice the garage looks in much better shape. Very little water issues.

But the first row of 12x16 pool deck columns along 11.1 are rotated 90 degrees. Why? The buildings look very similar. Why the rotation?

If you designed both buildings with similar plans, why would you change this? Think about this, maybe m11.1 is knocked over because its rotated? The rest of the punching shears are 16x16 square. M11.1 is rectangle and the pool deck probably is pulling away from the building. The pool deck forms a "v" between the south wall and the building.

Perhaps in the loss of pool deck, you get M11.1 falling apart rather then punching through due to its flat angle with the direction the deck is pulling it?

 

[pellucidar]

Settlement of piles would show up as differential settlement between columns and be noticed long before a collapse. Safety factors on piles is quite generous.

Would the pooling of water in parking spot 78 and the cracked garage floor be evidence of differential settlement?

 

[Penagwin]

@pellucidar I don't think it's much evidence on it's own, that basement is below sea level (at high tide at least), and with all the known water leaks there's plenty of explanation to how water got there.

Could there still be differential settlement sure, but I don't think the pool of water helps clarify it.

 

[pellucidar]

I don't think it's much evidence on it's own, that basement is below sea level (at high tide at least), and with all the known water leaks there's plenty of explanation to how water got there.

Regardless of where the water comes from, it shows the floor is not level. Possibly it was never level, but that would be an odd coincidence (of location).

 

[Jedidad]

I was looking at that photo a few posts above that shows the fire department ladder truck rescuing people from the balconies and I was wondering why it was parked way out in the street. Then I remembered there is a garage under that driveway. Probably a good thing the truck didn't drive over it. I'm wondering if they knew or if this is just SOP.

Are the ceilings of these types of underground parking garages normally rated to handle the weight of these big trucks? Google shows a ladder truck weighing anywhere from 36,000 to 60,000 pounds.

 

[w-streng]

From the outset it seems obvious that the main collapse followed the pool deck collapse which caused instability. What is bothering is that 3 separate reports from 111, 611, 1211 (all above each other) report preceding creaking noises.

• 1211 (below top penthouse) 20 hours prior to collapse Elena Blasser heard creaking which woke her up.
• 111 (Ms Nir) heard banging noises which continued to the point where she believed the wall above her was collapsing. She went to enquire at reception and then only saw the pool deck level collapse. Ran back, got her family and when reaching Collins the main collapse occurred.
• Unit 611 woken by noise, saw cracks appear in wall and got as far as 2 flights down prior to collapse (time line here not really saying much).

Could there even have been a trigger at penthouse roof level? Maybe punching shear at the penthouse roof slab (K8 or K10) which then left the roof resting on the cmu of the apartment 1211 below. After some time this load may have transferred into the cmu below and this deflected and transferred through the very thin 8” slabs until reaching the ground floor slab. This then overloaded the ground floor slab and caused a localised collapse (tik tok), spreading to the podium area. A few minutes elapsed whilst the loads were redistributing to surrounding columns until overload was reached.

There really could be so many scenarios. They may even have the video evidence showing exactly where the failure mechanism started, thus explaining the apparent gung-ho debris removal.

 

[CE3527]

Parking garage floors are typically sloped for drainage. There are drains at the low points to collect water. It's hard to keep water out of them. But they need to be maintained, cracks sealed, toppings replaced, etc. Based on the videos of the garage ceiling showing rust, cracks, and peeling paint, one clear source of water intrusion into the garage was from above, but it could come from groundwater below, openings like the entrance ramp, and through retaining wall cracks. The report shows pictures of cracks at the ramp down to the garage (area is highly exposed to rain and water blown in), but I don't remember seeing much in the way of cracks showing differential settlement at the actual garage floor slab. I think the water on the garage floor was a symptom of the porous ceiling above rather than a cause.

 

[Colostruct]

Jedidad

Underground parking garage roofs should be designed for anticipated loads. The code, in my experience, is a bit vague when it comes to what loads these structures should be capable of supporting when they are outside of buildings.

I was involved in the evaluation and repair of an exterior plaza over a parking structure. Very similar to the situation at Champlaign South. The terrace was showing signs of damage to supporting beams...in this case steel due to de-icing chemicals and a poor membrane flashing install.

Somewhere after the terrace was constructed the fire department decided that this terrace was a “fire lane”. The building adjacent to it was an 8 story hotel/condo. They decided to do a training session and had a fire truck on it. The plaza was not designed for this and by shear luck the loaded outrigger ended up on a beam.

The original designer of the building had no idea this area would be used for rescue operations. I designed additional supports and we built permanent barricades that limited vehicle travel locations.

My long answer to your short question is that sometimes we consider these loads and sometimes we don’t. But we should.

 

[Spartan5]

What is bothering is that 3 separate reports from 111, 611, 1211 (all above each other) report preceding creaking noises.

• 1211 (below top penthouse) 20 hours prior to collapse Elena Blasser heard creaking which woke her up.
• 111 (Ms Nir) heard banging noises which continued to the point where she believed the wall above her was collapsing. She went to enquire at reception and then only saw the pool deck level collapse. Ran back, got her family and when reaching Collins the main collapse occurred.
• Unit 611 woken by noise, saw cracks appear in wall and got as far as 2 flights down prior to collapse (time line here not really saying much).

At the point when 111 and 611 heard creaking noises, the building was already in the process of collapsing; for 611 it was imminent (<1 minute).

For 111, it’s no wonder the noises were coming from above. There was 12 floors of load being redistributed throughout the building surrounding them. Even at the onset of the start of the progressive collapse of the slab outdoors, the mass of the building (columns and beams) is what was transmitting the sounds.

 

[gonefishing2]

w-streng, Along the lines of your theory, the Post Roof Anchors for the Penthouse appear to be located on top of the PH roof slab directly over columns. If this area of slab was under nourished for punch shear as the patio deck to column interface appears to have been. It seems very logical that any activity in this area of PH slab, whether drilling and testing Hilti-Adhesive Anchor bolts, or perhaps repairing damaged concrete, or performing OSHA certification test of installed post anchor assembly in these areas would be very risky, now that we know patio deck was under nourished, and there was lots of water leaking in garage and lots of water under 25 year old build-up roofing. Further could they have damaged rebars in this area installing anchors or core drilling. We see from core samples they were able to center core drill directly over rebars.......

Edit: Plus all the rain that had fallen and was sitting on patio deck slab and roof. Were roof drains clogged?? There does not seem to be lots of non-cosmetic maintenance going on....

???

 

[gonefishing2]

warrenslo, you are up!

 

[Demented]

Yes, drains were clogged and water was pooling on the roof above the collapsed locations, as well as others. ILl find the images later

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

 

[w-streng]

I don't disagree and can't stand conspiracy stuff, just trying to make sense of the time lines and exploring options. When 111 was hearing noises the pool slab seemingly had not collapsed yet. But maybe it had already started elsewhere.

 

[Murph 9000]

Underground parking garage roofs should be designed for anticipated loads. The code, in my experience, is a bit vague when it comes to what loads these structures should be capable of supporting when they are outside of buildings.

They need to be designed for human error as well, including humans being unaware that it's a roof and/or signs being obscured / missing. There was an example in Quincy, MA not so long ago of a loaded dump truck (a big one, probably 60,000 lbs to 80,000 lbs gross) driving across a garage roof at a medical building, and falling through it.

In this collapse, one of my hypothetical triggers is something like a 14,000 lb F-350 backing over the surface parking to the planters. It was a wide enough entrance, and something like 8 or 9 foot headroom. E.g. something associated with the landscaping, ongoing construction, the core cutting, or any other service truck. It doesn't have to be an instant collapse, just do enough damage to start the countdown. I.e. potentially fatally crack it at noon, thermal contraction at midnight finished the job.

If your anticipated loads are passenger cars, but heavy trucks can still physically fit, you have an accident waiting to happen. You also can't rely on the valet or security guard to enforce cars only access, as they can be on a break or the new guy who didn't know.

 

[Colostruct]

Murph 9000

I'm just a one to two man structural engineering firm. In my limited experience, I have seen vehicles on terraces (or almost on them) half a dozen times. Recently, I designed a residential parking garage for a mixed use building that had living space below. I showed up one day and a trailer full of bags of mortar was backing up onto the slab (the structure had yet to be enclosed). My design of the floor system was well above code because parking structures scare me a bit. But, still this vehicle would have tested that system.

I've witnessed, a number of times, fork lifts moving pavers around terraces when pavers are being replaced. The wheel loads of a fork lift can well exceed the code loading for these systems. Looking at the terrace slab design for the Champlaign Tower, I have my doubts that this pool deck was designed for any sort of substantial vehicular loading. And, high end clients HATE yellow painted barriers at entrances to terraces. So, even signage and barricades at the initial construction might not stop theses sorts of loads.

This is a judgement call. Should you assume every access point to a building that COULD have a truck on it be constructed for this loading? And, what sort of truck do we consider? A concrete mixer on a parking structure could be a huge additional expense. I've designed for this when I felt I couldn't keep a truck away from a structure and no one was happy with me with what it cost to do it.

 

[Spartan5]

I don't disagree and can't stand conspiracy stuff, just trying to make sense of the time lines and exploring options. When 111 was hearing noises the pool slab seemingly had not collapsed yet. But maybe it had already started elsewhere.

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.

What 111 didn’t appear to hear was parapet wall and AC units slamming into the concrete at 70 MPH outside of their unit.

 

[w-streng]

I would read nothing sinister into this.
floor drilling: I would suggest that he is trying to build a feel for the concrete strength as well as the make-up of the floor to determine the loads. During construction they would need to have raised the penthouse finished floor level above the roof level to stay out of the water.
Column drilling: These are the least loaded columns, makes sense to test here.

 

[w-streng]

Oh dear, not you too.

Edit: Misunderstanding, my bad.