[Split]Physics of collision and collapse - split from: Offer to the Truth Movement: L

[DC]

What does the relative weight of the levels it penetrated have to do with anything?

Can you show me the physics formula where the weight of a material is more critical in a collision than factors like elasticity, resistance, and velocity? (Not the mass of the moving object, but the weight of the stationary object.)

the mass off steel would directly influence the resistance oc.

 

[aggle-rithm]

The weight of the levels relative to the plane. The NIST report says the south tower oscillated for four minutes after impact. I have not see where they specify how much the building moved laterally at the level of the impact. But elasticity AND MASS would be factors in that.

psik

But were the oscillations a factor in the damage? You've never answered that question.

 

[aggle-rithm]

But knowing the quantity of steel and concrete on every level would provide information on how much stronger.

Unless I'm mistaken, the concrete did not provide any structural strength at all in these buildings. It was there merely to provide flooring for each level.

ETA: And, of course, during collapse, it served to add mass and thus release more potential energy.

 

[psikeyhackr]

But were the oscillations a factor in the damage? You've never answered that question.

Since the buildings had to be designed to sway in the wind I am assuming the oscillaions did not cause damage.

BUT

It was kinetic energy from the impact that caused the oscillation. So the energy that started the oscillation should be subtracted from the total amount of kinetic energy and only the remainder did structural damage, so the oscillation should have reduced damage. I haven't noticed much mention of this in SIX YEARS.

Unless I'm mistaken, the concrete did not provide any structural strength at all in these buildings. It was there merely to provide flooring for each level.

Didn't the core of the building have to sway because of the wind? It could not have remained stationary while the exterior moved. The wind impacted the exterior columns and glass but some of that force was transfered to the core BY THE FLOOR SLABS. The exterior had to apply compressional force to the edge of the slabs which in turn pushed against the core. The floor slabs were not structural in relation to gravitational force but they were in relation to any lateral forces, like the wind and the airliners.

psik

 

[DGM]

The wind impacted the exterior columns and glass but some of that force was transfered to the core BY THE FLOOR SLABS. The exterior had to apply compressional force to the edge of the slabs which in turn pushed against the core.

psik

Why do you refuse to read the report that would give you the information you need to NOT be so wrong?

The edge of the "floor slabs" had no contact with the columns.

 

[aggle-rithm]

Since the buildings had to be designed to sway in the wind I am assuming the oscillaions did not cause damage.

BUT

It was kinetic energy from the impact that caused the oscillation. So the energy that started the oscillation should be subtracted from the total amount of kinetic energy and only the remainder did structural damage, so the oscillation should have reduced damage. I haven't noticed much mention of this in SIX YEARS.

I see what you're saying now.

The problem is this: You have observed yourself that the mass of the plane was only a small percentage of the mass of the building. Therefore, you wouldn't expect it to cause much oscillation unless it bounced off of it, as was shown in the model.

Picture the initial impact of the airliner. As the nose of the plane contacted the facade of the building, it started an oscillation. However, as it penetrated the facade, there would have been a damping effect caused by the fact that the energy needed to "bend" the building has been used in penetrating the facade.

As the plane is destroyed and knocks out the columns, the building would oscillate a bit more as each major source of resistance is breached, but again the energy is being absorbed by the crash, which dampens the oscillation.

Only when the plane comes to a complete stop is the building free to oscillate without any damping forces at work. By then, the damage has been done.

It's like the difference between trying to hammer a nail into a flexible piece of plywood, which is difficult because the wood absorbs the kinetic energy of the hammer, or shooting it into the wood with a nail gun. In the latter case, the plywood doesn't have to chance to absorb any of the energy, because the energy has been used up penetrating the wood.

 

[psikeyhackr]

The edge of the "floor slabs" had no contact with the columns.

I am not going to quibble with you about the trivial detail of the trusses being connected to the columns. The lateral forces created by the wind were transferred to the core by the floor slabs.

psik

 

[aggle-rithm]

I am not going to quibble with you about the trivial detail of the trusses being connected to the columns.

Oh, the irony.

 

[psikeyhackr]

I see what you're saying now.

The problem is this: You have observed yourself that the mass of the plane was only a small percentage of the mass of the building. Therefore, you wouldn't expect it to cause much oscillation unless it bounced off of it, as was shown in the model.

That is a TOTALLY INVALID statement. The only way for oscillation to not occur would be by punching a hole that caused very little resistance to create. You debate by assuming your opponent is stupid, I guess that is an inevitable result of assuming superior intelligence,

It looks like a waste of time to read this silliness just to bother making the effort to refute it because it is so DUMB.

psik

 

[aggle-rithm]

That is a TOTALLY INVALID statement. The only way for oscillation to not occur would be by punching a hole that caused very little resistance to create.

Watch the videos again. Does it LOOK like a lot of resistance?

I'm sure the resistance could be considered formidable in certain situations -- such as, if a pigeon hit the world trade center -- but a fully-fueled airliner at hundreds of miles per hour went through the facade like a knife through butter.

You debate by assuming your opponent is stupid, I guess that is an inevitable result of assuming superior intelligence,

You presume to know what I assume.

Pretty presumptuous.

It looks like a waste of time to read this silliness just to bother making the effort to refute it because it is so DUMB.

psik

How do you know it's dumb if you don't read it?

Don't worry about it, though...I know exactly where you're coming from.

 

[Belz...]

Two levels must break simultaneously. The bottom level of the falling mass and the top level of the stationary mass. Those two levels collapsing had to take energy out of the system. Since the falling mass would have to be moving faster than gravity would accelerate the stationary mass then momentum was lost getting the crushed level going. Then the next level is going to slow things down more. And the next, and the next,...

Good grief, man. Take that physics course.

Are you saying that the CONTINUED effect of gravity has NO impact whatsoever on your scenario ?

 

[Hokulele]

I will second Mackey's suggestion to read Appendix K of NIST NCSTAR 1-5A. If you are having problems finding this appendix, I would note that the PDF file downloaded from NIST had the confusing name of Appendix H, but the document in the PDF file has the appendices starting from H which includes Appendix K. Not only does it take into account the oscillation of the building, but also the induced rotation (which you seem to fail to mention in your work).

 

[rwguinn]

That is a TOTALLY INVALID statement. The only way for oscillation to not occur would be by punching a hole that caused very little resistance to create. You debate by assuming your opponent is stupid, I guess that is an inevitable result of assuming superior intelligence,

It looks like a waste of time to read this silliness just to bother making the effort to refute it because it is so DUMB.

psik

When the duration of the forcing function << the period of the object, you will get little to no oscillation.
The period of the building first mode was 11 seconds, IIRC. The impact took less than a second.
There are lots of neat little tables in Shock and Vibration books (Shock and Vib Hdbk, Ch 8, gives some equations and analysis--you might look at it. It is available in your library)

 

[rwguinn]

When the duration of the forcing function << the period of the object, you will get little to no oscillation.
The period of the building first mode was 11 seconds, IIRC. The impact took less than a second.
There are lots of neat little tables in Shock and Vibration books (Shock and Vib Hdbk, Ch 8, gives some equations and analysis--you might look at it. It is available in your library)

Bump for our resident "Physics expert"
you there, psikeyhackr? Yoo Hoo!

 

[aggle-rithm]

When the duration of the forcing function << the period of the object, you will get little to no oscillation.
The period of the building first mode was 11 seconds, IIRC. The impact took less than a second.
There are lots of neat little tables in Shock and Vibration books (Shock and Vib Hdbk, Ch 8, gives some equations and analysis--you might look at it. It is available in your library)

Do you have a link to this so-called "library"?

Seriously, though, thanks for the confirmation. I knew intuitively that the faster and more destructive the impact, the less momentum is converted to movement of the stationary object, but I didn't have any handy physics formulas to demonstrate it. I figured it may have had something to do with the oscillation period taking longer than the impact, but I didn't want to speak out of turn...

 

[aggle-rithm]

Bump for our resident "Physics expert"
you there, psikeyhackr? Yoo Hoo!

Apparently, I have stunned him with the "dumbness" of my post, which was reportedly so overwhelmingly dumb that the ambient dumbness rendered him incapable of reading it.

Fortunately, I appear to be immune to the effects, for I was able to write it without suffering any loss of cognitive function.

 

[aggle-rithm]

Good grief, man. Take that physics course.

Are you saying that the CONTINUED effect of gravity has NO impact whatsoever on your scenario ?

You know what they say: "Gravity never strikes the same spot twice. Except when it does."

 

[rwguinn]

Do you have a link to this so-called "library"?

Seriously, though, thanks for the confirmation. I knew intuitively that the faster and more destructive the impact, the less momentum is converted to movement of the stationary object, but I didn't have any handy physics formulas to demonstrate it. I figured it may have had something to do with the oscillation period taking longer than the impact, but I didn't want to speak out of turn...

The result will look something like this:
Frequency ratio is Ff (forcing Frequency) divided by Fn (natural frequency of the system).
While this is a transmissibility curve for vibration isolation, the principles are the same--
The % numbers are % of critical damping

 

[psikeyhackr]

JREF << Dumb

When the duration of the forcing function << the period of the object, you will get little to no oscillation.
The period of the building first mode was 11 seconds, IIRC. The impact took less than a second.
There are lots of neat little tables in Shock and Vibration books (Shock and Vib Hdbk, Ch 8, gives some equations and analysis--you might look at it. It is available in your library)

Why don't you tell the NIST that the south tower should have had little or no oscillation.

NIST NCSTAR 1-2
http://wtc.nist.gov/NISTNCSTAR1-2.pdf
Baseline Structural Performance and Aircraft Impact Damage Analysis of
the World Trade Center Towers
pdf page 143

Figure 2–15. Displacement of floor 70 of WTC 2 after impact based on video analysis (NIST NCSTAR 1-5A).

The impact of the aircraft into WTC 2 caused the tower to sway back and forth for almost four minutes. The estimated period of oscillation was found to be nearly equal to the calculated first mode period of the undamaged structure, indicating that the overall lateral stiffness of the tower was not affected appreciably by the impact damage. The maximum deflection at the top of the tower was estimated to be more than 1/3 of the drift resulting from the original design wind loads (about 65 in. in the N–S direction) as calculated from the baseline analysis (see Chapter 4). Since the lateral stiffness of the building before and after impact was essentially the same, it can be concluded that the additional stresses in the columns due to this oscillation were roughly 1/3 of the column stresses resulting from the original design wind loads, assuming linear behavior and assuming that the oscillation mode shape and the static deflected shape under design wind loads were identical. The building demonstrated an ability to carry this additional load and therefore, still had reserve capacity. This was confirmed by the structural analysis of the damaged
towers reported in NIST NCSTAR 1-6.

The plane stopped in 0.6 seconds.

0.6 < 11 == TRUE

0.6 << 11 == FALSE

O.6 in not a LOT LESS than 11.

If it is then explain to the NIST why the building oscillated.

Mathematics is not physics. The moons of Jupiter do not do calculations to figure out how to move from on microsecond to the next. People have to UNDERSTAND PHYSICS to figure out how to correctly apply the mathematics. Of course some people who think they are smart try to use the mathematics to intimidate and confuse others with BS.

Bump for our resident "Physics expert"
you there, psikeyhackr? Yoo Hoo!

I am not coming in here more than once a day to shoot down ever idiotic piece of bu-ls--t that is thrown up.

psik

 

[R.Mackey]

In mathematics, "<<" typically refers to an order of magnitude or so. By that standard, 0.6 << 11 is true.

Read Appendix K of NCSTAR1-5A already. It contains everything that you claim NIST didn't do with respect to oscillation. This is the fourth time you've been told, so you have no excuse at this point.