The virtually free fall speed

[Carlos]

Conspiracy theorists claim that the 2.5 seconds of "virtually free fall speed" is the definitive proof that explosives caused the collapse of WTC7. According to them, it would only be possible if eight floors of the building suddenly disappeared.

I totally disagree. To me it's consistent with the scenario of a structural collapse due to instability of the structure (in this case, 7 / 8 floors) caused by successive failures of connections and formation of plastic hinges (at beams an buckling columns). In other words, a structure initially hyperstatic (i.e. redundant, as every building is) has become a mechanism, i.e. a structure that's unable to keep itself in static balance.

Obviously all this didn't happen suddenly as the conspiracy theorists claim. The process of structural failures began early, during the fire, and it aggravated with the collapse of the west penthouse and the first 1.8 seconds of total collapse.

So, I would like truthers with some technical knowledge of structural engineering proved me wrong.


PS.: Answers like "should have offered some resistance" are obviously not welcome in this thread.

First, we are talking about frame structures, ie structures formed by bars and connected by fasteners, not "solid structures" as a block or a tree. Further, remember that more than 90% of the volume of a building structure is occupied by nothing but air.

Second, we are talking about frame structures that are no longer able to keep in static balance, due to successive structural failures.

 

[HatRack]

So, I would like truthers with some technical knowledge of structural engineering proved me wrong.

You might find a handful of people who fit into that category, if even.

 

[Lenbrazil]

They also ignore that the building had already started collaping, and had lost the core collumns and probablly some of the south facade perimiter columns

 

[twinstead]

Well, I don't know anything about engineering or physics, but I know what I know, and the building's collapse was suspicious.....

 

[tsig]

Well, I don't know anything about engineering or physics, but I know what I know, and the building's collapse was suspicious.....

Utterly unfounded suspicions Rock!!

 

[tempesta29]

PS.: Answers like "should have offered some resistance" are obviously not welcome in this thread.

Of course not, because that's the answer. Steel does not buckle at free fall acceleration. Buckling involves resistance.

 

[twinstead]

Of course not, because that's the answer. Steel does not buckle at free fall acceleration. Buckling involves resistance.

I think you missed the part where he said "truthers with some technical knowledge of structural engineering". You don't fall under that category.

Must of been a simple oversight on your part. You're welcome.

 

[DGM]

I think you missed the part where he said "truthers with some technical knowledge of structural engineering". You don't fall under that category.

Must of been a simple oversight on your part. You're welcome.

Somehow I get the feeling that the combination of "plastic hinges" and "structural steel" confuses him.

 

[Dog Town]

Of course not, because that's the answer.

Well, there's your problem!

 

[tempesta29]

I think you missed the part where he said "truthers with some technical knowledge of structural engineering". You don't fall under that category.

That's ironic. Neither do you.

Must of been a simple oversight on your part. You're welcome.

No. I simply don't care.

 

[Craig4]

That's ironic. Neither do you.



No. I simply don't care.

How's it coming with the explosive residue? No explosive residue, no explosives. Conservation of Matter, not just a good idea, it's the law.

 

[Oystein]

...Steel does not buckle at free fall acceleration...

That sentence makes no sense. ETA: It is a bit like saying "knifes don't cut ropes at free fall acceleration". They don't have to. After the knife cut the rope, the alpinist will fall at free fall acceleration

 

[GlennB]

How's it coming with the explosive residue? No explosive residue, no explosives. Conservation of Matter, not just a good idea, it's the law.

Then there's the hundreds (if not thousands) of 130+db bangs and flashes required for demolition by explosives.

Cameras? check
Audio? check

Bangs+flashes? no check. Checkless. Absence of checkiness. Houston, we do not check.

 

[Craig4]

If I hear that the NWO or the Illuminati or the Rotary Club International came and recovered it all I'm going to be merciless in my sarcasm.

 

[BasqueArch]

Originally Posted by twinstead View Post
I think you missed the part where he said "truthers with some technical knowledge of structural engineering". You don't fall under that category.

That's ironic. Neither do you.

There is an important difference.

The difference is that when non-engineers agree with NIST, they are right because there is a large bank of evidence and analysis by the top , most experienced engineers corroborating that opinion, as well as worldwide confirmation by other top tier engineers, that fire caused the collapse of the three Towers.

However, when non-engineers like you disagree with NIST, the burden to prove you are right is impossible to carry because as an amateur, you have none of the required knowledge to understand or competently rebut their findings.

Not knowing what you are talking about is a serious handicap in persuading others you are right and the top professionals wrong.

 

[Julio]

The "free fall speed" is just a strawman. So to keep debating about collapse times, buckling resistance, etc... is just going round the unsupported, unproved assertion "Free Fall=CD".There's nothing to make such assertion. No law, no principle, nothing implies that "Free fall=CD"

And the fallacy becomes totally apparent when some people like Chandler or Szamboti do measure the acceleration of WTC1 to be 0.7g or so but concluding it was also CD. And think on verinage: it is a CD, but there's no "free fall" there.

The only point to debate "free fall" is to show it is a strawman. It is pointless debating on buckling, resistance, stiffness, collapse times, plastic deformations, etc...

 

[Thunder]

fact: the videos show steel falling off the towers faster than the collapse progression.

 

[adkinsjr]

Of course not, because that's the answer. Steel does not buckle at free fall acceleration.

How do you measure the acceleration of buckling?

Buckling involves resistance.

How much do you think?

http://www.internationalskeptics.com/forums/showthread.php?t=123033&page=13

 

[Julio]

fact: the videos show steel falling off the towers faster than the collapse progression.

Which proves that the building did not fall at free fall speed. Using CT reasoning, it would discard a CD. But they don't. Fallacy. Full stop.

 

[Carlos]

Of course not, because that's the answer. Steel does not buckle at free fall acceleration. Buckling involves resistance.

Everything involves resistance. The process of buckling of a column also involves some resistance, drop a rock from the top of the Tower of Pisa involves some resistance, drop an anvil on a sand castle involves some resistance and even controlled demolition involves some resistance. However, having some resistance does not necessarily mean that resistance will be great enough to, for example, changing the trajectory of a moving body or cause a significant delay on it.