Remembering 9/11

[Promo]

It's called Newtons 3rd law of motion - A force is a push or a pull that acts upon an object as a results of its interaction with another object. For every action there is an equal and opposite reaction. Forces come in pairs.

C'mon supercharge, use your brain. I highlighted the words in red in the original post and only commented on those words.

What nutz was trying to say is; as the weight of the collapsing floors was pushing down, the "block building" is pushing up with equal force (because the block is in contact with the ground). But the WTC is not a block building, it's structure failed and he's ignoring the 2nd law.

Good example:
- If I very gently place a 10 ton weight on solid ground nothing will happen
- If I drop a 10 ton weight from 20 feet off the ground onto solid ground, it may ever so slightly compress the ground and stop.
- If I very gently place a 10 ton weight on the roof of a typical wooden house (assume a flat roof), very good chance nothing will happen.
- If I drop a 10 ton weight from 20 feet off the ground on the roof, the weight will smash it's way through the house and may or may-not get to the basement. The outside walls may stay intact, because the internal walls helped distribute and dissipate the forces.
- A proper comparison to the WTC - if that house had no internal walls whatsoever, the weight will definitely smash it's way through the house all the way to the basement. Because the floors will pull on the outside walls as they fail, the walls will likely be pulled down too. <-- even this isn't the best comparison; a house's floor is placed on top of it's frame whereas the WTC floors are hung from the perimeter walls.

Why? Because of Newton's second law.

Again, because of the 2nd law and the failure of the pins, the motion would not stop, but instead very slightly slow down compared to the initial speed of impact. however, mass and speed of collapse overall would continue to increase, because the total force is enough to cause the floor pins to shear.

If the pins were much stronger, the collapse may have been arrested, but the designers couldn't financially design for so many simultaneous failure conditions. The pins on each floor would have to be strong enough to support approximately the gravitational force converted to kinetic force of every floor above it.

The key point here is that the construction of the WTC was unique. It had no columns throughout the floors. Therefore all collapse load is on the pins that hold the floors to the perimeter and core structure. If those planes crashed into a normal built building, we probably wouldn't be having this conversation.

have a look here: https://www.quora.com/How-does-Newt...lapse-of-the-World-Trade-Center’s-Twin-Towers

 

[SuperCharge]

C'mon supercharge, use your brain. I highlighted the words in red in the original post and only commented on those words.

What nutz was trying to say is; as the weight of the collapsing floors was pushing down, the "block building" is pushing up with equal force (because the block is in contact with the ground). But the WTC is not a block building, it's structure failed and he's ignoring the 2nd law.

Good example:
- If I very gently place a 10 ton weight on solid ground nothing will happen
- If I drop a 10 ton weight from 20 feet off the ground onto solid ground, it may ever so slightly compress the ground and stop.
- If I very gently place a 10 ton weight on the roof of a typical wooden house (assume a flat roof), very good chance nothing will happen.
- If I drop a 10 ton weight from 20 feet off the ground on the roof, the weight will smash it's way through the house and may or may-not get to the basement. The outside walls may stay intact, because the internal walls helped distribute and dissipate the forces.
- A proper comparison to the WTC - if that house had no internal walls whatsoever, the weight will definitely smash it's way through the house all the way to the basement. Because the floors will pull on the outside walls as they fail, the walls will likely be pulled down too. <-- even this isn't the best comparison; a house's floor is placed on top of it's frame whereas the WTC floors are hung from the perimeter walls.

Why? Because of Newton's second law.

Again, because of the 2nd law and the failure of the pins, the motion would not stop, but instead very slightly slow down compared to the initial speed of impact. however, mass and speed of collapse overall would continue to increase, because the total force is enough to cause the floor pins to shear.

If the pins were much stronger, the collapse may have been arrested, but the designers couldn't financially design for so many simultaneous failure conditions. The pins on each floor would have to be strong enough to support approximately the gravitational force converted to kinetic force of every floor above it.

The key point here is that the construction of the WTC was unique. It had no columns throughout the floors. Therefore all collapse load is on the pins that hold the floors to the perimeter and core structure. If those planes crashed into a normal built building, we probably wouldn't be having this conversation.

have a look here: https://www.quora.com/How-does-Newt...lapse-of-the-World-Trade-Center’s-Twin-Towers

The top section pushing on the bottom section is going to meet equal forces as it goes, both sections are going to be demolished at the same rate so by the time you've crush up 15 stories below it, the top 15 stories are also going to be crushed and so there is nothing left now to crush the rest of the building. A little tiny chunk of a building cant possibly fall and crush the entire structure below it.

But even if we assume that the top section of the tower had enough potential energy to destroy the rest of the structure below, it could not have done so at the speed it did, which was near free fall speed.

Free fall happens when the only force applied on an object is gravity, as soon as the falling object hits an obstacle and breakage occurs this speed must decrease because some of it's energy needs now to convert into physical breakage. It took each tower between 10-12 sec to collapse to the ground, while an absolute freefall time would have been 9.2 sec. IOW both upper sections of the towers found enough energy to destroy 80,000 tons of healthy structure below at nearly freefall speed?

 

[fuji]

The top section pushing on the bottom section

This is wrong. The top section was not pushing on the bottom section. That is not how the WTC was constructed. Your fundamental misunderstanding of this crucial point results in the rest of your post being irrelevant.

Reread promo's post again in light of understanding that the bottom floors were not pushing up on the top floors, they were ALL hanging from the frame.

Promo described it very well.

 

[SuperCharge]

This is wrong. The top section was not pushing on the bottom section. That is not how the WTC was constructed. Your fundamental misunderstanding of this crucial point results in the rest of your post being irrelevant.

Reread promo's post again in light of understanding that the bottom floors were not pushing up on the top floors, they were ALL hanging from the frame.

Promo described it very well.

Okay put it this way, the upper sections fell at an acceleration close to freefall speed, as if the path had been free of any obstacles. But what about the center core?

 

[fuji]

Okay put it this way, the upper sections fell at an acceleration close to freefall speed, as if the path had been free of any obstacles. But what about the center core?

Center core was not visible to us due to the dust cloud created by the collapse of the floors, but it's likely it did fall a bit slower than the floors. There's some evidence that the bottom of it briefly did stand a few seconds longer.

Note that unlike in a conventional building the center core wasn't supporting the floors..

 

[Promo]

The top section pushing on the bottom section is going to meet equal forces as it goes, both sections are going to be demolished at the same rate so by the time you've crush up 15 stories below it, the top 15 stories are also going to be crushed and so there is nothing left now to crush the rest of the building. A little tiny chunk of a building cant possibly fall and crush the entire structure below it.

LMFAO! Are you stoned bro? So where did the 30 floors of mass go? Black hole? Alternate universe? If E=MC2, the mass to energy conversion would erase most of NY state from the map.

No, the crushing mass increased as the floors pancaked. I sincerely hope you just have a really dry sense of humour.

But even if we assume that the top section of the tower had enough potential energy to destroy the rest of the structure below, it could not have done so at the speed it did, which was near free fall speed.

Free fall happens when the only force applied on an object is gravity, as soon as the falling object hits an obstacle and breakage occurs this speed must decrease because some of it's energy needs now to convert into physical breakage. It took each tower between 10-12 sec to collapse to the ground, while an absolute freefall time would have been 9.2 sec.

You quote a 9.2 second number for free fall, but that number is based on the full height of WTC1 (the collapse started many floors below that). Also the formula assumes a vacuum. Actual FF time is closer to 8 seconds (most experts say 7.8 to 8.4). The tower fell in ~12-15 seconds. Math and computer models confirm these estimates. So where's the problem?

IOW both upper sections of the towers found enough energy to destroy 80,000 tons of healthy structure below at nearly freefall speed?

The steel in the WTC weighed allot more than that and it took 150% of free fall time. You are over-simplifying, but yeah, that's what happened.

 

[Promo]

Okay put it this way, the upper sections fell at an acceleration close to freefall speed, as if the path had been free of any obstacles. But what about the center core?

Correction, 150% of free fall speed. Exact time the mathematical and computer models predict.

No, the path was NOT free of "obstacles". LOL, very transparent attempt at manipulation there Super.

Parts of the Center core stood for an estimate 20-25 seconds after the collapse. - "The lower portions of both buildings' cores (60 stories of WTC 1 and 40 stories of WTC 2) remained standing for up to 25 seconds after the start of the initial collapse before they too collapsed" https://en.wikipedia.org/wiki/Collapse_of_the_World_Trade_Center

 

[huckfinn]

Okay put it this way, the upper sections fell at an acceleration close to freefall speed, as if the path had been free of any obstacles. But what about the center core?

The building was built using the center core and the exterior walls as the two bearing points for any floor systems.

They used steel open web joists with a metal pan on top, then about 2-3 inches of concrete in the metal pan.

The floor system would most likely have looked like this;

When attached to steel, like the outer shell of WTC, they weld the joints. On the end sitting on masonry, they either create pockets, put the joist 'shoe' in, then fill it with concrete, or attach an angle iron to the concrete and weld the joist shoe to the angle iron. The welds couldn't possibly be strong enough to hold the building together. As soon as the joists started warping downward, the welds would give away, or the shoe would pull out of the masonry, possibly creating a bigger hole in the masonry or concrete.

When people speak of melting or softening steel beams, the actual steel being softened were open web steel joists, and they are far, far thinner than steel beams, and will fail much quicker.

You see in one video the outer walls are pulled in just before the building starts coming down, which tells me the core failed first pulling everything inward. That would explain why it looked like controlled demolition, and the building didn't actually tip over. The core would have been concrete that was poured in the 60's, meaning it was 30+ years old and probably not as strong as the original install. It would disintegrate from all the accumulated weight coming down from above.

 

[huckfinn]

This was basically how it was put together. Note around the shaft, there would be open web steel joists spanning 35 feet, and 60 feet with no intermediate support.

Those joists would have been attached at 2 points - the outer wall and the core. All you need is to have them start to soften, warp downward, and they would collapse onto the floor below. The floor below couldn't take the additional weight, as it was only designed to carry its own weight and furniture, occupants etc. So, it would then fail too.......and so on.

Given the airplanes that hit are more than 60' long, and the entire plane disappeared into the building on impact, plus the only resistance was the outer wall, large parts of the airplane would hit the core, and weaken it or break through it. In addition, the floor was not designed to carry the weight of a plane, especially when the structure was weakened by heat.

In addition, many of the X's you see that are not elevators, are mechanical shafts - many would lead to the basement which is where the hot air would have been forced to the basement, causing 'explosions' or banging noises especially on impact.

 

[basketcase]

The top section pushing on the bottom section is going to meet equal forces as it goes,...

Except the structure would cause most of the connecting pins to fail or at least be highly stressed before the upper debris would hit it. There would essentially be nothing to hit. It is also not an application of conservation of momentum (which Newton's 3 is based on) since the entire system is accelerating due to gravity.

 

[basketcase]

Okay put it this way, the upper sections fell at an acceleration close to freefall speed, as if the path had been free of any obstacles. But what about the center core?
...

And another person claiming this 'melting' farce. According to the study I posted several times, by that temperature the steel would have lost the vast majority of its strength.

 

[Insidious Von]

That is correct, the angle pins to the place of rivets in high rise construction, when one fails the load expands to the adjacent pins. But an even bigger factor is that the internal steel beams were not insulated from within.

On a side note; President Bush had his John Holmes moment when he gave his "Mission Accomplished" speech on the USS Abraham Lincoln. He looked resplendent in his blue jump suit showing off his package - what a man! But while that was happening, ISIS was forming under the leadership Abu Musad el Zarqawi. But everyone knows ISIS was founded by President Obama and HIllary Clinton.

And the question remains, who gave the cease and desist order at Tora Bora?

What a Sexy Beast!

 

[Insidious Von]

I left out the best part...what a man!

 

[Insidious Von]

For the sake of objectivity.

President Obama just ripped a huge fart. The class action lawsuit that the families of the 9/11 victims against Saudi Arabia should have been allowed to proceed. He sided on behalf of the tax evading 0.1% over long suffering citizens. Vergonia! (for shame)

 

[SuperCharge]

LMFAO! Are you stoned bro? So where did the 30 floors of mass go? Black hole? Alternate universe? If E=MC2, the mass to energy conversion would erase most of NY state from the map..

Actually I was, it was me and my bong last night lol, but im pretty sure alot of the mass got ejected out of the towers, still doesn't explain how it collapsed at near free fall speed, and tower 7 is even more perplexing.

You quote a 9.2 second number for free fall, but that number is based on the full height of WTC1 (the collapse started many floors below that). Also the formula assumes a vacuum. Actual FF time is closer to 8 seconds (most experts say 7.8 to 8.4). The tower fell in ~12-15 seconds. Math and computer models confirm these estimates. So where's the problem? .

NIST has the calculation at 10 secs, they still have not released their
data so computer models mean nothing unless we have all the data. Where did you get your data from, since NIST did the investigation and has not released it? Your guessing is what you are doing.

The steel in the WTC weighed allot more than that and it took 150% of free fall time. You are over-simplifying, but yeah, that's what happened.

Seriously highly doubt that

 

[SuperCharge]

And another person claiming this 'melting' farce. According to the study I posted several times, by that temperature the steel would have lost the vast majority of its strength.

I race with alcohol and my aluminum pistons get up to 1200 degrees and nothing happens to them. Your 'meltin' is a farce. Not to mention witnesses who had walked down the stairwell that was directly under the impact and they were able to make it out just in time, if the temperature was that hot they would have been vaporized

 

[SuperCharge]

President Obama just ripped a huge fart. The class action lawsuit that the families of the 9/11 victims against Saudi Arabia should have been allowed to proceed. He sided on behalf of the tax evading 0.1% over long suffering citizens. Vergonia! (for shame)

Yes he vetoed the bill. How's that for a slap in the victim's face. This is gonna piss some people off.

 

[basketcase]

I race with alcohol and my aluminum pistons get up to 1200 degrees and nothing happens to them. Your 'meltin' is a farce....

Are you aware that aluminum pistons are not made of structural steel?

I gave you a scientific study about tensile strength of structural steel at temperatures. Instead of pretending to be an expert why don't you try reading it?



BTW. It is your source that identified the fire inside as being at 800 C. If you think that didn't happen then you need to start using better sources.

 

[huckfinn]

I race with alcohol and my aluminum pistons get up to 1200 degrees and nothing happens to them. Your 'meltin' is a farce. Not to mention witnesses who had walked down the stairwell that was directly under the impact and they were able to make it out just in time, if the temperature was that hot they would have been vaporized

I appreciate there would have been excessive heat but it does rise. There may have still been some protection on lower floor stairwells.

Also, recall there was at least one survivor from an impact floor.

Check out this study.

http://s.b5z.net/i/u/10090719/f/stu...ature_on_creep_in_ASTM_A572_high-strength.pdf

Excerpt;
Steel structures exhibit low fire resistance due to faster loss of strength and stiffness properties of steel and also due to rapid rise in temperatures resulting from high thermal conductivity and low specific heat of steel.......However, at high temperatures, creep deformations can become predominant within a short duration of fire exposure and can influence the failure mode and fire resistance of steel structures. The extent of high temperature creep in steel structures primarily depend on properties of steel, exposure temperature, stress level on the member, and time of exposure.....

In the same study, car gasoline fires can make a bridge collapse, jet fuel is a lot hotter, and they carry a lot of fuel, so the jet fuel causing the collapse is very realistic.

In recent years there have been numerous fires in bridges and some of these fires resulted in the collapse or damage of steel girders. Bridge fire incidents generally occur due to crashing of vehicles in the vicinity of a bridge and burning of gasoline fuel underneath a bridge. These gasoline fires produce severe conditions than that of building fires and are typically characterized by rapid heating rate with peak temperatures reaching to 900–1,100 C in the first few minutes. Under such conditions creep deformation tends to accelerate at a very rapid rate.

 

[Jubee]

A firefighter is not qualified to know the difference between molten steel and molten aluminum. No melted steel was found at the site. You are simply wrong, and you are spamming.

No, of course not, they just pulled "foundry" out of their ass because they're just a bunch of idiotic grunts who only know how to turn on a hose, turn it off, climb a ladder and that's about it.

What are they supposed to know about STRUCTURES? pfff idiots.

Btw, most anyone with half a brain knows the difference in how molten steel and molten aluminum looks like.

and

next post, aluminum?

Or is it the other way around?