Miami Beach, Champlain Towers South apartment building collapse, Part 16 24

[dik]

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

-Dik

 

[IanCA]

Are we talking about sheet pile still?

I'm not sure about the damping. Yes, I was thinking about sheet pile installation. I'm pretty sure there is a large difference in the vertical stiffness between the wall and the deck. I can imagine the deck bouncing more or more likely to resonate. The figure of 0.5 inches per second came from the class action complaint and has no further detail from what I can see. I don't think the original documents have been released. Perhaps the 0.5 inches per second figure already includes an allowance for vibration on the other two axis, I don't know. I thought it was interesting that 100 linear feet of the sheet piles on the north of 87 Park were installed deeper. I'm assuming that was the portion adjacent to CTS (as opposed to the pool deck). I would be interested to know if anyone has more information about that aspect.

 

[IanCA]

would those rotating charges affect wireless transmissions

I think you are right, almost certainly why we don't have 5G FR2 yet.

could perhaps a sudden solar eruption have triggered the fall of the building

Well, as you probably know, a solar flair did apparently contribute to the loss of 40 Starlink satellites launched Feb 3, due to increased drag, but they were a bit higher up. Link

 

[IanCA]

the resultant will be sq root (3) units, ie 1.732 units.

Thanks for that, I should have thought about it a bit more. But I'm wondering whether the combined effect of the vibrations at three different frequencies on different axis is more or less likely to cause resonance or damage than vibration concentrated on a single axis. What do you think?

 

[zebraso]

likely to cause resonance or damage

Once again I don't have the answer but I have a quote regarding the British standard or at least a subset of it:

For continuous vibrations, the British
standard states:
The guide values . . . relate predominately to
transient vibration which does not give rise
to resonance response in structures, and to
low-rise buildings. Where the dynamic loading caused by continuous vibration is such as
to give rise to dynamic magnification due to
resonance . . . [highlight #EF2929]then the guide values may need
to be reduced by up to 50%[/highlight]. Note: There are
insufficient cases where continuous vibration
has caused damage to buildings to substantiate
these guide values, but they are based on common practice.

Edit: I have to be careful not to be misleading. For the British standard this still put the threshold for continuous in the 30 hz range at around .8in/sec. BUT it is 1/2 of the USBMRI8507 for the same conditions (with nothing mentioned about resonance), This is different still from the Swiss standard which is about .3 in/sec for continuous at 30 hz for this type of building ("well designed and maintained"- love that). DIN would be .3 in/sec for transient at 30 hz at the base and even lower for continuous but that is at the top of the structure so it's not comparable. The only one that calls out resonance seems to be the British. Don't take my word for it
Link
While that is about historic building preservation it does a really good job of comparing standards, even superimposing them on each other.

 

[zebraso]

if you have three measurements of say .558 longitudinal, .408 transverse, and .583 vertical,

I was looking at a study from Sweden trying to model vibration for sheet pile. They drove 7 piles monitoring 1,2, and 4 while they were all driven in interlocking succession. they have sensors top middle and toe. frequency is 35 hz. Anyway on the 4th pile measured on that pile the top sensor near the end of the drive was hitting around 40 g longitudinal. unless I am mistaken at 35 hz that is 70 ips peak. Is that sort of level going to be attenuated down to .5 in the distance we are talking about?

 

[Red Corona]

> if you have three measurements of say .558 longitudinal, .408 transverse, and .583 vertical, at close to the same frequency, I think you end up with a significantly higher resultant vector that's not aligned with any of the measurements axis

Yes - by nearly double in this case. But in the context of a slab or column with clearly defined primary axes, the primary stress axes (which is what you should be measuring) are likely to line up with the geometry. Perhaps this is not the case at the end of the slab where it meets the wall though.

The idea of airflow inside the garage drying the inside of the walls and encouraging salty water to migrate into and through the concrete by capillary action is an interesting one. Surely though if that was something that could happen on this kind of timescale, we'd know about it and there would be rules about waterproofing the outside of sub-grade concrete lined spaces, because otherwise this would apply to every building near the seaside with underground parking.

 

[Nukeman948]

Please can you check, assuming they are at the same frequency and in phase?

Oh, certainly, I'll get right on that, Victor, err..vector. Unfortunately my batteries couldn't hold up to the strain but just before it died I was looking for an input value that corresponds to the third order harmonics of the pile driver and some kind of assurance that the frequency and amplitude would remain stable throughout the time period in question and also the modulus of elasticity of the soil type at the site of the alleged damage. I'm currently studying up on the works of the great mathamagician Paul Simon and his thesis: "There Must Be Fifty Ways To Shake Your Tower".

[sub]What is the point of presenting facts and data when 30% of the population is convinced the earth is flat?[/sub]​

 

[IanCA]

While that is about historic building preservation it does a really good job of comparing standards, even superimposing them on each other

I found that to be an interesting and helpful document, thank you. Here are the points that stood out for me:

Fig 2 put 30Hz at 0.5in/sec into the intolerable region.
Internally Amplified measurements can be 4 to 8 times higher than at the base of the building.
52,000 cycles at 30Hz is less than half an hour.
Strains in walls caused by thermal expansion are several times higher than those caused by vibration.
Key factors:
1 - Building type and condition
2 - Continuous vibration
3 - Importance

All structures should be evaluated on their own physical condition.
Applies limit reduction 50% for 1,000 to 100,000 cycles. Applicable to CTS and vibratory sheet pile driving.
60% above 100,000 cycles.

Resonance and preexisting weakness can be problematic.

Stipulation of protocols to be followed if recorded vibrations exceed the specified limits. Were any specified for CTS?
Post-construction condition surveys. Were any done?
Surveys should be repeated after any above-limit vibrations. Were any done?
Elevation surveying for settlement, crack-width measurements, and visual surveys of general building conditions.

 

[IanCA]

Unfortunately my batteries couldn't hold up

I'm beginning to wonder whether that calculator of yours is real or imaginary. Don't worry AusTony2046 already came up with the answer to my specific question and Red Corona put things into context:

But in the context of a slab or column with clearly defined primary axes, the primary stress axes (which is what you should be measuring) are likely to line up with the geometry.

I suspect the vertical component is the critical one.

The most important point for me is that if you pay an expert for professional advice on vibration monitoring, and they give you a limit not to exceed, and your on-site measurements, made in accordance with their recommendations show that you are exceeding that limit, then you need to take action to reduce the vibration or seek advice to understand why the data could be erroneous and you need to check whether there was any adverse effect on the structure.

 

[IanCA]

What is the point of presenting facts and data when 30% of the population is convinced the earth is flat?

Taken with the appropriate quantity of NaCl. A pinch.
Because it's possible to gradually inform the skeptics, reducing that percentage, and everyone stands to benefit if we can come to an agreement.

 

[Nukeman948]

I'm beginning to wonder whether that calculator of yours is real or imaginary.

My calculator is just another tool I use in exchange for proper compensation to support myself. I see no reason to allow it to be used by persons who wish to deny proper compensation to the real victims of this tragedy.

With a grain of salt...

[sub]I reject your reality and substitute my own.[/sub]​

 

[FJBnomics]

The only difference between science and screwing around is writing it down.

You might want to rethink that Inspiring thought, as what came to my mind immediately was Jeffery Epstein?

EDIT: But my elevator does not go to top floor.......

 

[IanCA]

I see no reason to allow it to be used by persons who wish to deny proper compensation to the real victims of this tragedy.

Personally, I am fully in favor of the real victims receiving proper compensation. As an engineer, I'm also committed to helping to improve our understanding of the risks involved so we can reduce the chances of events like the collapse of CTS happening again in the future.

Thanks for your advice thermopyle2.1.
Reposted with a clarified signature line.

Insert your favorite MythBusters quote here.​

 

[Nukeman948]

Reposted with a clarified signature line.

I must not understand how signature lines work.
I thought I'd need your password to be able to insert my favorite Mythbusters quote in your signature line.

[sub]That's not how any of this works.[/sub]​

 

[IanCA]

I thought I'd need your password to be able to insert my favorite Mythbusters quote in your signature line.

No need for all that credential nonsense, just make the substitution in your mind.

Suggestions welcome.​

 

[FJBnomics]

Suggestions welcome.

Suggestion: Just Following the Science!

Edit: I can see the vibration damage being a valid complaint against 87 Park, but I am having trouble with the water entry into the wall due to removal of 87 Terrace. The reason I am having a problem with water entry is that CTS was built all the way to the property line, with no provision to prevent water entry from property line side of wall. Anytime you build all the way to a property line, you are inviting trouble from your neighbor. You can not even paint your retaining wall without getting permission to be on the other person's property.

But then I have always thought Condo's and Townhouses were a stupid concept that can make life painful depending on who your neighbor is.....

 

[zebraso]

"neighbor" used to be a street.

 

[FJBnomics]

Right, and street was better neighbor as they sloped drainage away from wall rather than towards it.

On one hand 'neighbor' purposely drained towards wall, which is wrong, but when folks build up to line there is no room for U&D easement. And I agree neighbor's should NOT drain water on to their neighbor's

Again, building to line invites problems

 

[Nukeman948]

Around here the streets are crowned and the water runs to the edge where it is contained by the curb and gutter and diverted to a catch basin or some other drainage method.

[sub]It never rains in California...[/sub]​

 

[IanCA]

but I am having trouble with the water entry into the wall due to removal of 87 Terrace

I agree that building to the property line is problematic, particularly when the other side of the line is a different jurisdiction.

I concur with the valid points about the street / public right of way and the original drainage.

Is it possible that the removal of 87 Terrace also had some impact on the lateral stability of the CTS property line wall? With respect to thermal expansion of the parking deck & pool deck?

Suggestions welcome.​