The virtually free fall speed

[beachnut]

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

??? - nonsense.
Got some equations to go with your nonsense? Some numbers, math, physics? You never explained which plane hit horizontally, or specified the pitch angle it hit at. You are all talk, nonsensically talk and you never present your point. You are one reason 10 years of failure are in the bag for 911 truth.

As soon as you say "free-fall", I prepare for idiotic claims and anti-intellectual claptrap to follow. Is being science challenged a prerequisite for supporting the lies of 911 truth?

 

[GrimFandango]

“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.”

But – NIST does not call this 2.5 seconds “Virtually free fall” they call it FREE FALL –in its purest form, which can occur only when there is NO resistance to the falling object. Get the NO RESISTANCE part?

Where did NIST say this? Glad you asked, it was in the NIST NCSTAR1 report from page 602, the following 3 paragraphs are excerpted verbatim.

In Stage 1, the descent was slow and the acceleration was less than that of gravity. This stage corresponds to the initial buckling of the exterior columns in the lower stories of the north face, as seen in Figure 12-62. By 1.75 s, the north face had descended 7 ft. In Stage 2, the north face descended at gravitational acceleration, as exterior column buckling progressed and the columns provided negligible support to the upper portion of the north face. This free fall drop continued for approximately 8 stories (105 ft), the distance travelled between times t = 1.75 and t = 4.0s. In Stage 3, the acceleration decreased somewhat as the upper portion of the north face encountered resistance from the collapsed structure and the debris pile below(3). Between 4.0 s and 5.4 s, the northwest corner fell an additional 130 ft.
As you can see, NIST has admitted to real, honest to goodness free fall of the massive WTC7 to the tune of 8 full stories, an incredible amount equal to over 17% of the total height of the 47 story structure. You can read it for yourself at - whoops I can't post links yet, training wheels and all that, maybe you can Google NCSTAR1 1-9 Vol 2.pdf


“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.”

Once again, I’m glad you asked – how about the following Structural Engineers and their comments about the amazing colossal collapsing steel structures of 9/11? (All members of Architects and Engineers for 9/11 Truth, over 1,400 members strong to date)


Alfred Lee Lopez, Structural Engineer
Lic: 6201016289
B.S. Arch. Eng. Lawrence Tech Univ
Holly, MI


Steven Merritt, P.E.
Lic: C70334
MS, Structural Engineering, UC San Diego
San Diego, CA


Steven Francis Dusterwald, Structural Engineer
Lic: Nevada Civil & Structural #4925
B.S.C.E. Cooper Union, NY, NY 5/73
Las Vegas, NV


Ronald H. Brookman, Structural Engineer
Lic: Structural Engineer 3653 CA Civil Engineer 44654 C
B.S. & M.S. Engineering, U.C. Davis
Novato, CA


Robert F. Marceau, P.E.Structural
Lic: P.E.16996,Colorado,C.E. 7587Nevada retired
M.S. Un.Las Vega, B.S. Un. of Conn.
Kalispell, MT


Paul A. Thomas, P.E.
Lic: 22650-006 WI
M.Architecture/Structural Engineering
Tucson, AZ

Patricia Lyn Seitz, P.E.
Lic: 19559
Architectrual Engineering – Structural
Lititz, PA


Michael T. Donly, P.E., Structural/Civil Engineer
Lic: New Jersey 24GE04422400
B.S.C.E. N.J. Institute of Technology
Hackensack, NJ


Lester Jay Germanio, Structural Engineer
Lic: TX 54239
BS Civil Eng, LSU & B of Arch, LSU
Austin, TX


Obeid, SE, PE
Lic: Structural Engineer 2826 CA, Civil Engineer 35214
MSCE, UC Berkeley
Fremont, CA


Hantz N. Elalami, P.E.
Lic: Colorado
BS, Research as structural analyst
Denver, CO


Dennis J. Kollar, P.E., Structural Engineer
Lic: 34422-6 professional engineer exp 2008
B.S. + Graduate Coursework
West Bend, WI


Christopher Michael Bradbury, Licensed Structural Engineer
Lic: S 5329 CA, C 63919 CA
BSCE & MEng CivEng, Clarkson University
San Jose, CA


Antonio Arthay, P.E.
Lic: 57912
M.S., Structural Engineering, Illinois
West Palm Beach, FL


Arthur Nelson, P.E.
Lic: MA PE 32785
M.Sc., Structural Eng, Northeastern
Seekonk, MA

Notice that I selected all Structural Engineers, not simply Engineers, or even just Architects, in the hope of satisfying your stringent demands from the Truth community. The following is an example of what these people have to say regarding 9/11, and the foolish Official Conspiracy Theory. I would be happy to post each and every comment for each, please feel free to ask for them

“One of our primary responsibilities as architects and engineers is to ensure public safety in and around our structures, and we take this seriously. It is also our responsibility as concerned American citizens to ask questions and seek honest answers. I encourage everyone to read the numerous books, technical reports and papers about the WTC; look closely at the photographs and videos; listen to the speakers with an open mind. Decide for yourself, and take a stand for what you believe. As a structural engineer I believe in the laws of physics and rely on them every day.

After much reading and studying it is obvious that NIST, FEMA and the 9/11 Commission have all fallen short of a detailed accounting of the catastrophic collapses of the three World Trade Center buildings in Manhattan on 9/11/01. A few examples of unexplained details include the "severe high temperature corrosion attack on the steel" as described in Appendix C of the FEMA Building Performance Study, the complete symmetrical collapses following asymmetric structural damage and short-term fires, and the chemical signature of incendiary compounds found in the toxic WTC dust.

I would really like to know why complete collapse of the twin towers "became inevitable" as expressed by NIST without any scientific analysis to substantiate it. Why would all 110 stories drop straight down to the ground in about 10 seconds, pulverizing most of the contents into dust and ash - twice? Why would WTC 7 fall straight down to the ground in about seven seconds the same day? It was not struck by any aircraft or engulfed in any fire. An independent investigation is justified - and necessary - for all three collapses.”

 

[beachnut]

...
I would really like to know why complete collapse of the twin towers "became inevitable" as expressed by NIST without any scientific analysis to substantiate it. Why would all 110 stories drop straight down to the ground in about 10 seconds, pulverizing most of the contents into dust and ash - twice? Why would WTC 7 fall straight down to the ground in about seven seconds the same day? It was not struck by any aircraft or engulfed in any fire. An independent investigation is justified - and necessary - for all three collapses.”

Steven Merritt, P.E ...
There seem to be a lot of unanswered questions and it would serve the greater good to re-open the investigation and do a more thorough job to remove any doubt.

WOW! He wants to re-open the investigation. What is his problem? He offers no evidence, but for him it seems to be a lot of unanswered questions. ... he failed to list them! ... a lazy engineer.

You got delusions on 911. AE911T signers of the Petition of Woo are not using engineering skills, and they have delusions too.

Antonio Arthay -
Buildings collapsed all by "controlled demolition" methods. Fire and impact were insignificant in all three buildings. Impossible for the three to collapse at free-fall speed. Laws of physics were not suspended on 9/11, unless proven otherwise.

A liar! There was no controlled demolition. He has delusions of CD backed with nothing. Fire was insignificant is a lie! This is the best 911 truth, you and AE911T can do. Free-fall, is a lie too. Laws of physics are never suspended, this makes him an idiot~!

I am afraid to see how moronic the comments are.

Michael T. Donly -
Experts agree that the fires caused by the burning jet fuel, building materials and contents of buildings were not hot enough to melt steel. Yet molten liquid steel was found in the debris of WTC1, WTC2 and WTC7 by FEMA investigators.

No melted steel found. Another lie based on no evidence. Do you have or know anyone who is not delusional on 911?

Kamal S. Obeid -
Only recently have I begun to examine the structural collapse of the buildings. Photos of the steel, evidence about how the buildings collapsed, the unexplainable collapse of WTC 7, evidence of thermite in the debris as well as several other red flags, are quite troubling indications of well planned and controlled demolition.

9 years and now he fails. No thermite was found, that is a lie. If thermite was used there would be thermite products, some evidence of iron fused to steel in the WTC; it was not found. You support losers, 9 years of failure, with no end in sight. Do any of your heroes have evidence? NO


Do you read what the people you posted say? They are morons on 911 issues. They have no clue.

Hantz N. Elalami -
The building collapse seems a result of other explosions that was places at the lowest part of the buildings, and at some other locations located on the main bearing points of the structures. no lateral forces applied at the upper level of such huge structures would cause the sudden collapse of the entire structures.

Another evidence free, "seems like" failed highway engineer. Total nonsense based on nothing. "Seems"??? Is that an engineering term?

Steven Francis Dusterwald -
There was not enough energy delivered to the buildings by the impacting aircraft to destroy all the structural materials.
The absence of any major components after the destruction is proof that massive amounts of energy were delivered to the buildings by planted explosive devices at the critical sections of the structure.
The symmetrical "collapse" due to asymmetrical damage is at odds with the principles of structural mechanics.

This retired "expert" has no clue what happen on 911 based on his comment at AE911T. BTW, the energy released by each tower due to gravity was over 130 TONS of TNT, this means your "expert" can't do physics, that is a shame. The collapse was not symmetrical, he need help in geometry, math, and physics. He gives us retired "experts" a bad name.

Did you read and comprehend these people you presented, as they offer nothing to back their failed opinions?

Welcome to JREF, your claims were debunked on 911 by events. Next time read the nonsense your "experts" posted before presenting them as having something related to what happen on 911.

over 1,400 members strong to date

If you change the strong to wrong, you would be right.

 

[atecom]

I would really like to know why complete collapse of the twin towers "became inevitable" as expressed by NIST without any scientific analysis to substantiate it. Why would all 110 stories drop straight down to the ground in about 10 seconds, pulverizing most of the contents into dust and ash - twice? Why would WTC 7 fall straight down to the ground in about seven seconds the same day? It was not struck by any aircraft or engulfed in any fire. An independent investigation is justified - and necessary - for all three collapses.”

Why even quote a paragraph that can easily shown to be so wrong. Just look at a video of the WTC collapses, and you can see they take longer than 10 seconds, Just look at the video of WTC7 collapsing and the total collapse (Starting from the internal collapse to the full collapse) took longer than 7 seconds, and just looking at any video of WTC at all will show that it was engulfed in fire. The quoted text tells everyone to carefully study the videos from the day, yet it is obvious, This person has not done so. Probably just saw what Richard Gage wanted him to see.

 

[TJM]

<snip>

Is it any wonder you cannot comprehend The NIST Report? You don't even get the OP.

 

[tempesta29]

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.

It doesn't need to be significant to be measurable.

 

[Dragon37]

<snip>

More drones have been released from the hive.

 

[tempesta29]

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

Buckling isn't akin to a knife cutting rope at all. Only after the rope is severed will the load fall, similar to a steel beam being severed, for instance. That's a much better analogy.

 

[GlennB]

It doesn't need to be significant to be measurable.

But being insignificant can make it unmeasurable, depending on the measurement system. For example counting the pixels of a video.

 

[Quad4_72]

Buckling isn't akin to a knife cutting rope at all. Only after the rope is severed will the load fall, similar to a steel beam being severed, for instance. That's a much better analogy.

Has this rope you speak of also been hit by a fully fueled jet liner traveling at the speed of a bullet and then been subjected to a raging inferno of unfought office fires at temperatures of 1800+ degrees Fahrenheit?

 

[tempesta29]

Has this rope you speak of also been hit by a fully fueled jet liner traveling at the speed of a bullet and then been subjected to a raging inferno of unfought office fires at temperatures of 1800+ degrees Fahrenheit?

Uh... wha? Please tell me this isn't what you meant to write.

 

[Quad4_72]

Uh... wha? Please tell me this isn't what you meant to write.

Why would that not be what I meant to write? It is a reference to what the towers went through and a cause for the steel beams to fail. You ARE aware that is what caused the towers to collapse correct?

 

[Oystein]

Buckling isn't akin to a knife cutting rope at all. Only after the rope is severed will the load fall, similar to a steel beam being severed, for instance. That's a much better analogy.

You answered your own, implicit question:
The short free-fall episode on part of the north wall of WTC7 did start only after all support columns below it, and lateral support, were severed and rendered incapable of holding any loads.
Free-fall occurred only after the relevant buckling, just as, in the rope analogy, free-fall occurs only after the rope is cut.

 

[Quad4_72]

Uh... wha? Please tell me this isn't what you meant to write.

Or, if you prefer the reference to WTC7, was said rope subjected to a building falling on top of it and then unfought fires for 6 hours?

 

[Carlos]

It doesn't need to be significant to be measurable.

Measurable or not, the effect remains insignificant.

 

[Carlos]

Buckling isn't akin to a knife cutting rope at all. Only after the rope is severed will the load fall, similar to a steel beam being severed, for instance. That's a much better analogy.

And at WTC 7 the freefall only occurs when the structure become unable to offer any significant resistance. That's the OP point.

 

[Craig4]

Ooooooookay, let's try this again. The Law of Conservation of Matter says that matter can neither be created or destroyed. If an explosive was detonated it would have released a large amount of energy. This energy, in addition to damaging the building, would have dispersed the remnants of the explosive over a wide area. Don't believe me, watch video of Manhattan being covered in dust from the collapse. In this dust there HAS TO BE residue from the explosives. This is an insurmountable problem for the explosive hypotheses (note I did not say theory). When I say insurmountable I mean no way around it. If an explosive was used then the bits (very small bits mind you) have to go somewhere. No list of engineers is ever going to change that.

 

[tempesta29]

And at WTC 7 the freefall only occurs when the structure become unable to offer any significant resistance. That's the OP point.

Doesn't even make sense.

 

[triforcharity]

“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.”

But – NIST does not call this 2.5 seconds “Virtually free fall” they call it FREE FALL –in its purest form, which can occur only when there is NO resistance to the falling object. Get the NO RESISTANCE part?

Where did NIST say this? Glad you asked, it was in the NIST NCSTAR1 report from page 602, the following 3 paragraphs are excerpted verbatim.

In Stage 1, the descent was slow and the acceleration was less than that of gravity. This stage corresponds to the initial buckling of the exterior columns in the lower stories of the north face, as seen in Figure 12-62. By 1.75 s, the north face had descended 7 ft. In Stage 2, the north face descended at gravitational acceleration, as exterior column buckling progressed and the columns provided negligible support to the upper portion of the north face. This free fall drop continued for approximately 8 stories (105 ft), the distance travelled between times t = 1.75 and t = 4.0s. In Stage 3, the acceleration decreased somewhat as the upper portion of the north face encountered resistance from the collapsed structure and the debris pile below(3). Between 4.0 s and 5.4 s, the northwest corner fell an additional 130 ft.
As you can see, NIST has admitted to real, honest to goodness free fall of the massive WTC7 to the tune of 8 full stories, an incredible amount equal to over 17% of the total height of the 47 story structure. You can read it for yourself at - whoops I can't post links yet, training wheels and all that, maybe you can Google NCSTAR1 1-9 Vol 2.pdf

Wonderful.

Here is another tidbit of info you missed.
http://www.nist.gov/public_affairs/factsheet/wtc_qa_082108.cfm

The ENTIRE building did not fall at FFA. This is a lie.

Only a PORTION of the North Face did.

About 1/3rd the way down the page.

“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.”

Once again, I’m glad you asked – how about the following Structural Engineers and their comments about the amazing colossal collapsing steel structures of 9/11? (All members of Architects and Engineers for 9/11 Truth, over 1,400 members strong to date)

<Snipped for length>

And yet, not a single one of them has published a paper proving NIST wrong with math, or physics, or anything.

Yes, I am asking for a paper that is published in something other than bentham, or JONES.

Notice that I selected all Structural Engineers, not simply Engineers, or even just Architects, in the hope of satisfying your stringent demands from the Truth community. The following is an example of what these people have to say regarding 9/11, and the foolish Official Conspiracy Theory. I would be happy to post each and every comment for each, please feel free to ask for them.

Wonderful. Got papers?

“One of our primary responsibilities as architects and engineers is to ensure public safety in and around our structures, and we take this seriously. It is also our responsibility as concerned American citizens to ask questions and seek honest answers. I encourage everyone to read the numerous books, technical reports and papers about the WTC;

Yes, read the technical papers. Here are a few that support the conclusions of the NIST.

Performance based structural fire engineering for modern building design
Rini, D., Lamont, S. 2008 Proceedings of the 2008 Structures Congress - Structures Congress 2008: Crossing the Borders 314

Engineering perspective of the collapse of WTC-I
Irfanoglu, A., Hoffmann, C.M. 2008 Journal of Performance of Constructed Facilities 22 (1),

Collapse of towers as applied to September 11 events
Cherepanov, G.P. 2008 Materials Science 44 (4), pp. 489-499

Modeling pre-evacuation delay by occupants in World Trade Center Towers 1 and 2 on September 11, 2001
Kuligowski, E.D., Mileti, D.S. 2008 Fire Safety Journal

World Trade Center building disaster: Stimulus for innovations
Kodur, V.K.R. 2008 Indian Concrete Journal 82 (1), pp. 23-31

A collective undergraduate class project reconstructing the September 11, 2001 world trade center fire
Marshall, A., Quintiere, J. 2007 ASEE Annual Conference and Exposition, Conference Proceedings

"A new era": The limits of engineering expertise in a post-9/11 world
Pfatteicher, S.K.A. 2007 International Symposium on Technology and Society, Proceedings, art. no. 4362228

Progressive collapse of the World Trade Center: Simple analysis
Seffen, K.A. 2008 Journal of Engineering Mechanics 134 (2), pp. 125-132

Scale modeling of the 96th floor of world trade center tower 1
Wang, M., Chang, P., Quintiere, J., Marshall, A. 2007 Journal of Performance of Constructed Facilities 21 (6), pp. 414-421

Failure of welded floor truss connections from the exterior wall during collapse of the world trade center towers
Banovic, S.W., Siewert, T.A. 2007 Welding Journal (Miami, Fla) 86 (9), pp. 263-s-272-s

The collapse of the world trade center towers: A metallurgist's view
Gayle, F.W. 2007 MRS Bulletin 32 (9), pp. 710-716

Building code changes reflect world trade center investigation
Hansen, B. 2007 Civil Engineering 77 (9), pp. 22+24-25

Fire load in a steel building design
Razdolsky, L. 2008 Proceedings of the 4th International Structural Engineering and Construction Conference, ISEC-4 - Innovations in Structural Engineering and Construction 2, pp. 1163-1167

The structural steel of the World Trade Center towers
Gayle, F.W., Banovic, S.W., Foecke, T., Fields, R.J., Luecke, W.E., McColskey, J.D., McCown, C., Siewert, T.A. 2006 Journal of Failure Analysis and Prevention 6 (5), pp. 5-8

Progressive collapse of structures: Annotated bibliography and comparison of codes and standards
Mohamed, O.A. 2006 Journal of Performance of Constructed Facilities 20 (4), art. no. 001604QCF, pp. 418-425

A simple model of the World Trade Center fireball dynamics
Baum, H.R., Rehm, R.G., Quintiere, J.G. 2005 Proceedings of the Combustion Institute 30 II, pp. 2247-2254

Impact of the Boeing 767 Aircraft into the World Trade Center
Karim, M.R., Hoo Fatt, M.S. 2005 Journal of Engineering Mechanics 131 (10), pp. 1066-1072

High-fidelity simulation of large-scale structures
Hoffmann, C., Sameh, A., Grama, A. 2005 Lecture Notes in Computer Science 3515 (II), pp. 664-671

More can be found here.
http://www.internationalskeptics.com/forums/showthread.php?t=154475

look closely at the photographs and videos;

Yep, we've seen them.

listen to the speakers with an open mind. Decide for yourself, and take a stand for what you believe. As a structural engineer I believe in the laws of physics and rely on them every day.

And I believe that the TM is a bunch of bumbling morons who have yet to prove anything.

After much reading and studying it is obvious that NIST, FEMA and the 9/11 Commission have all fallen short of a detailed accounting of the catastrophic collapses of the three World Trade Center buildings in Manhattan on 9/11/01.

Why would the 9/11 COmmission do an engineering report?

You don't consider 10,000 plus pages detailed?

A few examples of unexplained details include the "severe high temperature corrosion attack on the steel" as described in Appendix C of the FEMA Building Performance Study,

Explained by WPI.

http://www.georgevandervoort.com/fa_lit_papers/WTC_Talk.pdf

Happened over a very long period AFTER the collapse. Pay special attention to page 41 and 62

the complete symmetrical collapses following asymmetric structural damage and short-term fires,

What building collapse was symmetrical?

and the chemical signature of incendiary compounds found in the toxic WTC dust.

Which yeilded more energy than thermite of any flavor does.

Conclusion? Not thermite.

I would really like to know why complete collapse of the twin towers "became
inevitable" as expressed by NIST without any scientific analysis to substantiate it.

See Bazant et al's paper "Why the WTC Towers collapsed"

Why would all 110 stories drop straight down to the ground in about 10 seconds, pulverizing most of the contents into dust and ash - twice?

Gravity.

Why would WTC 7 fall straight down to the ground in about seven seconds the same day?

Didn't fall straight at all. Hit two other buildings.

It was not struck by any aircraft or engulfed in any fire.

No aircraft, correct. However, the fires that burned more than 3.5 times the rating of the SFRM. It also showed signs of structural instability earlier in the day.

An independent investigation is justified - and necessary - for all three collapses.”

Well, get on it!!

 

[tempesta29]

"Didn't fall straight at all. Hit two other buildings."

That's because a 47 story building was reduced to 3 or 4 stories. What do you think happens to mass in that sort of situation? It's dispersed.