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Buildings collapse into their own footprint

Óðinn said:
Unless you are a physicist or an engineer, your opinions may lack the necessary foundation. Here is what we know:


(much crap snipped)
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You are not a physicist or an engineer. You have demonstrated here that you have no foundation at all for any of the incorrect opinions you posted.
 
A physicist answers your first 4 points:
(1) Prior to 9/11 no steel framed building had suffered aircraft impacts or unfought fires anywhere near as severe as those suffered by WTC1, 2 and 7. The fact that unique stimuli produced unique results is in no way surprising.
(2) Bare Assertion Fallacy, and as commented elsewhere, demonstrably untrue.
(3) Before embarrassing yourself further, I suggest you find out the difference between static and dynamic loading.
(4) This is not a basic engineering principle, it is an invalid conclusion derived from a set of flawed premises.

The same vacuous reasoning is repeated throughout the remainder of this collection of long-disproven and, quite frankly, blatantly plagiarised assertions. There is simply no valid argument here to address.

Dave Rogers
M. A, D. Phil, C. Phys, M. Inst. P
 
Óðinn said:
Unless you are a physicist or an engineer, your opinions may lack the necessary foundation.
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Dude, we've got a talent pool here that puts anything you have have to utter shame. We've had more engineering degrees move on from the forum because they figured the work of debunking this old nonsense than you can cite.

And for the record, as someone with a physics degree: Ours is not the best degree for structural engineering situations. We have some basics, but honestly all the time spent on optics, cosmology, quantum mech, relativity, etc. is well not suited for this work.
 
According to the NIST Report, Building 7 collapsed at free-fall speed for 2.4 seconds due to a fire that started on the roof. They subsequently drew no conclusions based on that fact because it was inexplicable.
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I want you to provide a page and paragraph number in the NIST report that states these assertions.
When WTC1 collapsed in created fires on multiple floors in WTC7, not the roof, that were not fought due to a lack of water.
 
Dave Rogers said:
A physicist answers your first 4 points:
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Well done. And now an engineer answers them.

1. Same as the physics answer, because it's neither a physics nor an engineering question. It's just a red herring. Prior to Sept. 11, 2001 there were no previous examples of airliners of that size flying into high-rise buildings of that particular construction. There's nothing suspicious about that; it just hadn't happened before. And after Sept. 11, 2001, there have been no subsequent examples. The closest we got was the bomber flying into the Empire State Building by accident decades ago. The singularity of the occurrences on Sept. 11, 2001 is due to the circumstances simply not arising. The fact that it happened multiple times at that time and place was obviously because it was a planned operation that called for multiple suicide collisions. Duh. If, for example, you drop several bombs on a single building at one time, there will be a "suspicious" level of damage compared to other times and places.

If there is an engineering lesson to be learned for this question, it is the corollary that if you subject two identical structures to similar mechanical injury and subsequent similar thermal loading, you should expect similar outcomes. Voilà.

2. Logically, just bare dicta. From the engineering standpoint, "a steel-framed building" is a straw man. Most steel-framed office buildings are made with pre-engineered steel framing. This is especially attractive since in many places you don't need a structural engineer if you use this method. But these "steel-framed buildings" have vastly different structural behavior characteristics from the World Trade Center, which used a novel structural design. The WTC design was far more structurally efficient and relied on far fewer redundancies and failure isolation methods. There is really no One True steel-framed building, so it's not especially helpful to try to compare them blindly.

How fast a structure fails and to what degree it fails depends on a number of factors that differ widely across construction methods. The comparison to controlled demolition is not entirely inapt. Before the application of explosives, the structural redundancies and inefficiencies are removed using ordinary methods. What remains is the structure barely required to maintain its own dead load. This is then failed with explosives. Inasmuch as the WTC was a highly efficient structural design (ratio of live load to dead load) it can be expected to fail in much the same way.

Buildings are mostly empty space. Falling into their own footprints is the norm for a high-efficiency structure. You get major ejections or tipping only when the building's strength-to-mass ratio is very high.

Claiming that controlled demolition is "the only way" to get a rapid, global, more-or-less vertical collapse is just blowing smoke.

3. Yes, the bottom floor of a structure must hold up all the other floors. And it is expected to do that unless the structure is compromised in some way. The structure of the World Trade Center was compromised in several ways.

A major part of why structures succeed is geometry. You can load a structural member axially to an absurd degree before it fails. Its willingness to accept that load is based on Euler's slenderness ratio, which is an inverse-square law function of the unbraced length of the member. Double the free span and you reduce its axial load-bearing capacity by a factor of 4. Similarly the axial loading must remain axial within a very narrow margin. The slightest eccentricity in the load vector will fail the member. Both of these failure modes occurred in the World Trade Center towers.

Before I endorse the answer that pits dynamic loading against static loading, let me note that you don't need dynamic loading to understand the problem.

There's a simple experiment done in classrooms all over the United States in various science classes. You have a student stand on an empty soda can. The can will easily bear her weight because its geometry keeps the thin aluminum walls braced sufficiently to satisfy Euler. But if you dent the side of the can by tapping it with a stick, the can fails immediately and completely; the student falls at "near free-fall speed" to the floor. The can represents a very highly efficient structure. The can is only about 0.02 kg but can easily support a 50 kg student. But once the geometry that achieves that efficiency is defeated, the static load is enough to fail the structure.

Conversely if you have a 65 mm x 120 mm cylinder of concrete (roughly the same dimensions as a soda can), it will easily hold up the student no matter how many times you try to dent it by tapping it with a stick. In fact you'd have to put a garbage truck on it.

But yes, dynamic loading. It's orders of magnitude greater than static loads. The 2nd floor of a building is meant to hold up the 3rd through 47th floors of a standing structure. It can't even remotely absorb the impact of floors 4-47 if the 3rd floor suffers a major structural failure. And after the underlying floors are obliterated under the dynamic load of a falling building, the sudden impact of the falling upper floors on the ground and wreckage underneath isn't going to be suddenly borne by those lower floors.

4. Not at all a "basic engineering principle," but a simplistic conclusion drawn from lay intuition and dressed up with some sort of undeserved expert imprimatur.

Thermal loading is a major concern for structural design. Real engineers very much understand how reducing the strength of material or changing its geometry via thermal loading can fail a structure. A fire combined with massive structural damage from an airliner impact will easily fail a structure that has fewer redundancies than you expect from your experience with pre-engineered structure.

The WTC fires were not especially on "upper" floors. But it's irrelevant. If the structure's geometry is compromised by impact and its strength reduced by heat, what remains can't be expected forever to hold up the weight of several floors. It's meant to do that only with the structure relatively intact. "Basic engineering" requires looking at the mechanics of materials, indeterminate statics (structural statics that includes the elastic properties of the materials), and elementary structural analysis.

And yes, we've been listening to blowhards playing at being engineers for more than two decades. No new arguments here. Just a bunch of naked assertions with the bluff, "If you don't accept these, then you just don't have the proper foundation of engineering knowledge."
 
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Óðinn said:
In conclusion, the evidence presented in the NIST Report indicates that the three WTC buildings collapsed in a manner consistent with controlled demolition, as no steel-framed skyscraper in history has ever collapsed at free-fall speed into its footprint as a result of fire, which is physically implausible. It is important to note that free-fall implies zero resistance. A steel-framed building cannot even experience a pancake collapse, let alone collapse with no resistance. On September 11, we observed three such unprecedented occurrences. While these implications do not necessarily suggest an inside job, they do indicate that the truth has been obscured.
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Care to take a stab at how the controlled demolition could have been achieved? Somehow I don't think elevator maintenance is the answer. Keep in mind that WTC1 was about 3x the size of the prior world record demolition. So was WTC2. WTC7 about twice the size. (JL Hudson Building, Chicago)

If you can't do that, then the only possible explanation is aircraft impact+fire. Exactly what the entire rational world knew.
 
NM156 said:
Care to take a stab at how the controlled demolition could have been achieved? Somehow I don't think elevator maintenance is the answer. Keep in mind that WTC1 was about 3x the size of the prior world record demolition. So was WTC2. WTC7 about twice the size. (JL Hudson Building, Chicago)

If you can't do that, then the only possible explanation is aircraft impact+fire. Exactly what the entire rational world knew.
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Óðinn is not a physicist or an engineer. By his own admission he can explain nothing about the collapse of buildings on Sept 11 2001, or on any other date.​

 
ahhell said:
I am also a licensed engineer, and I agree with JayUtah.
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I am not a licensed engineer, but listen to those that are, especially those who take the time to explain the issues directly and in detail. Organizations like AE911Truth make their case. It is criticized by other engineers, and they show their work, and it is found lacking.
 
I'll join in the parade. I'm not a licensed engineer but have a BS in engineering and retired from my chosen profession. I listen to those licensed when they make sense. I started out attempting to debunk Apollo hoaxes and grew from there. The site had many "engineers" that posted BS and you could tell by their stupidity they weren't using engineer training to post their nonsense.
 
kookbreaker said:
And for the record, as someone with a physics degree: Ours is not the best degree for structural engineering situations. We have some basics, but honestly all the time spent on optics, cosmology, quantum mech, relativity, etc. is well not suited for this work.
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To be sure, structural engineering is applied classical mechanics, which got its start with Newton's basic formulation of forces and motion and the transformative means of expressing those formulations: calculus. And while that was cutting edge physics in 1687, it isn't something that modern physicists spend much of their attention on. It's settled law, as they say in the legal profession. Hence a modern trained physicist is not likely to want to make his living doing classical mechanics.

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still remains true, but is not especially intriguing to professional physicists in 2025. I hire lots of physicists, especially those with PhDs. What I want them for is their particular way of thinking about problems, which is hard to come by in other ways. If they need to learn engineering principles along the way, we teach them. I'm generally not interested in the angular momentum of an electron, but I'm interested in the kind of thinking that can reason about such things.

I think the emphasis on physics and physicists among fringe claimants comes from the mantra found in many conspiracy genres—something they see "violates the laws of physics." Now we understand that by this they mean that they don't understand what they're looking at. Rather than say to themselves, "I don't understand what I'm looking at," they want to afford themselves an appropriate degree of expertise and imagine that what their intuition has told them must be identical to physical law, and therefore there must be something wrong with the observation rather than with their understanding. The appeal to the "laws of physics" has more to do with pinning an impressive-sounding label on their intuition than in invoking what physicists actually do. This is a long-winded way of agreeing that physicists are generally neither interested nor trained in structural analysis.

On the other side of the coin, while structural analysis is firmly rooted in well-understood principles of mechanics, its practice in the public sector is a matter of rigorously demonstrated competence. In my state, structural engineering requires its own special license. Not only is structural analysis not something generally considered within the purview of most people, it's not even considered within the purview of all engineers. It is its own licensed specialty. When I had to strengthen my downtown building in order to accommodate larger rooftop diesel skids for emergency power, we had to hire an outside firm to do the engineering. All the rest of our engineering is done in-house. The takeaway is that this is not just theoretical or generalized handwaving. Hard-won specialized occupational understanding is required when the public's faith is implicated. So when someone waves his hands vaguely at "basic principles of engineering" to answer questions of why and how public structures fail, and can offer only lay comparisons and intuitive guesses, such armchair engineering simply won't rise to the level of challenging a thorough analysis such as that performed by NIST.

This is not to diminish the knowledge and expertise of professions such as physicist or software developer or construction manager or whatever. But absent additional relevant training and experience, those professions are not positions from which one can speak condescendingly about one's allegedly superior understanding of engineering. Intuition does not help here, and therefore it's better to stay in one's lane.
 
I have a saying, " Science is applied Math, engineering is applied science." As Jay says, structural engineering is applied newtonian physics, mostly statics.

Which is why medicine is really just a branch of engineering.
 
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