Laypeople and experts of Steemit: WELCOME!
The category #towerchallenge shall henceforth be dedicated to civil, scientific, objective and agnostic debate and discussion about one question:
How to build a tower that completely, symmetrically and progressively collapses straight down through itself from top to bottom.
The tower
- It should have at least 20 (twenty) floors
In nature, a sequential failure may go through three, five, even seven iterations. This criterion makes sure what we are looking at is not just a "freak accident", but a systematic verification of the principle. - It should somewhat fulfill the definition of a tower (in terms of slenderness ratio λ)
Stout things tend to compress, slender things tend to buckle. - It should be somewhat stable
If it faints from being looked at, there's no point, is it? - It must stand up on its own
Do not have it hang from a ceiling or lean against a wall or something. - It may have any scale
We don't have the means to build a 1:1 replica. A 20cm, 2m, 20m model will serve the purpose just fine. A 600 meter model would be welcome, of course, if that proves Size Matters Law states "the bigger the tower, the plumber its fall". - It may be of any material
Size Matters Law says big things are softer, not as strong, more brittle, than their small scale models with the same density (mass per volume). It is thus allowed to build the tower from wet sand and twigs, Jenga bricks, spaghetti and/or chicken wire and toilet paper rolls. - It may have any density
Size Matters Law says big things are softer, not as strong, more brittle, than their small scale models with the same density (mass per volume). It is thus allowed to build the tower as heavy or as lightweight as desired to scale for size. - It may have any structural layout
Be it a classical "stack", a bundled tube, a tube-in-tube, trussed tube... - It may be built on any planet
To make sure we haven't overlooked the role played by gravity.
The collapse
- You may initiate the "collapse" by picking up the top fourth of the tower and let it drop on the lower three fourth. You may drop it from whichever height you like.
In accordance with the model proposed by Bazant/Zhou, the assumption is that one floor totally vanished, allowing the top portion of the tower to free fall down on the bottom of the tower. - BONUS CHALLENGE:
initiate a delayed, sudden total progressive collapse by setting it alight with any amount of Zippo gas, kerosene or Diesel. It must not move (non-negligibly) for at least ten minutes
...the smaller the activation energy in your model, the better! - The "collapse" must be sudden, complete, vertical, roughly symmetric (no falling over, buckling, toppling, leaning, shearing as a whole!) and rapid
The whole point is to produce a model that, in principle, behaves like the Twins. Eulerian buckling, boring falling over, the top breaking off and leaving a stump do not qualify; nor does a model where all floors compress simultaneously or the core remains standing upright. The collapse front should progress at a rate of more than 0.5g. - It must work 100%
Both the official report (NIST NCSTAR 1) and academia (Bazant/Zhou/Verdure) have proven that the collapse was "inevitable". It was not an accident or a freaky coincidence, it was inherent to the nature of the building - as evident from the fact that both Twins behaved essentially, in principle, the same.
NOTE ABOUT COMPUTER MODELS
Computer models are welcome! Note, however, that an animation does not qualify. All relevant data (routines, scripts, input files, libraries) must be open source and the simulation easily be reproducable by other users sufficiently proficient with the software.
What to post to #towerchallenge:
- historical and contemporary videos, reports and images of collapsing/collapsed towers or tall buildings of all sizes
- scientific research, peer-reviewed papers, expert opinion and discussion thereof
- ideas on how to make the tower completely, symmetrically and progressively collapse straight down through itself from top to bottom at more than 50% free fall rate
- energetic/physical analogies/equivalents
- experiments
- models, models, models
so far, THE CHALLENGE MET:
- North Tower of the WTC, Manhattan, 2001
THE best of all sudden, total, vertical, symmetric, progressive top-down collapses so far. SUCCESS! - South Tower of the WTC, Manhattan, 2001
...slightly less impressive, as the top portion is a lot bigger and tilts considerably at first, but still roughly 1/4 and thus a flawless demonstration of the principle #towerchallenge aims for. SUCCESS!
so far, THE CHALLENGE MET NOT:
- Domino Tower World Record Attempt
ALMOST perfect, just a little slow: CLOSE but still, regrettably, FAIL. - Mick West: Offset narrow core progressive collapse
honorable mention for the huge effort and idea with the magnets! Not enough floors, not really symmetrical, only 2.5-dimensional. Project status: on halt. - Vérinage
two equally big portions crush each other and lose all their momentum doing so: FAIL. - Office Building in Utrecht
although impressive, still just a collapse that propagates horizontally: FAIL. - Delft Faculty of Architecture
something falling off of something else doesn't count either: FAIL. - NMSR does the Heiwa Challenge
FAIL (for the same reason, obviously).
Do not feel discouraged to suggest examples like these though, much can be learned from other cases about what we are trying to achieve!
There are answers to your questions.
Is this some kind of conspiracy theory sorta kind of thing?
The term "conspiracy theorists" applies too loosely to those who believe in reptilian overlords, MKUltra, Operation Northwoods and the Manhattan Project.
A skeptic upholds the scientific method and values the principles of
1 - making an observation and formulating a curious question.
The towers fell.
HOW did they fall?
2 - making a conjecture.
They did not undergo a controlled demolition, that claim is preposterous!
3 - making a prediction.
- All towers will do that.
- Only towers built like the twins will do that.
- Only big towers will do that.
4 - testing
All our models buckle, fall over, break off, lean, shear or topple as a whole, and so do big buildings.
5 - analyzing
Why the fvck is it so hard to make a tower behave like the Twins?
6 - replicating
If an experiment cannot be repeated to produce the same results, this implies that the original results might have been in error. As a result, it is common for a single experiment to be performed multiple times, especially when there are uncontrolled variables or other indications of experimental error. For significant or surprising results, other scientists may also attempt to replicate the results for themselves, especially if those results would be important to their own work.
7 - data recording and sharing
Scientists typically are careful in recording their data, a requirement promoted by Ludwik Fleck and others. Though not typically required, they might be requested to supply this data to other scientists who wish to replicate their original results (or parts of their original results), extending to the sharing of any experimental samples that may be difficult to obtain.
8 - scientific inquiry
Scientific inquiry generally aims to obtain knowledge in the form of testable explanations that can be used to predict the results of future experiments. This allows scientists to gain a better understanding of the topic being studied, and later be able to use that understanding to intervene in its causal mechanisms. The better an explanation is at making predictions, the more useful it frequently can be, and the more likely it is to continue explaining a body of evidence better than its alternatives. The most successful explanations, which explain and make accurate predictions in a wide range of circumstances, are often called scientific theories.
Richard Feynman says:
There is one feature I notice that is generally missing in cargo cult science. … It's a kind of scientific integrity, a principle of scientific thought that corresponds to a kind of utter honesty — a kind of leaning over backwards. For example, if you're doing an experiment, you should report everything that you think might make it invalid — not only what you think is right about it; other causes that could possibly explain your results; and things you thought of that you've eliminated by some other experiment, and how they worked — to make sure the other fellow can tell they have been eliminated.
Details that could throw doubt on your interpretation must be given, if you know them. You must do the best you can — if you know anything at all wrong, or possibly wrong — to explain it. If you make a theory, for example, and advertise it, or put it out, then you must also put down all the facts that disagree with it, as well as those that agree with it. There is also a more subtle problem. When you have put a lot of ideas together to make an elaborate theory, you want to make sure, when explaining what it fits, that those things it fits are not just the things that gave you the idea for the theory; but that the finished theory makes something else come out right, in addition.
In summary, the idea is to try to give all of the information to help others to judge the value of your contribution; not just the information that leads to judgement in one particular direction or another.
- "Cargo Cult Science", 1974
Science is the belief in the ignorance of experts.
- "What is Science?", The Physics Teacher, volume 7, issue 6 (1969), p. 313-320
But don't all experts agree that...
It surprises many that there is not one agreed upon explanation for the collapse mechanism of the Twins. In the early days, there was a wide expert consensus that raging fires melted the structure; later investigations found that jet fuel can't melt steel beams and experts are on record blaming the huge amounts of paper. It has been hypothesized that the plane impacts caused all the spray-on fireproofing to fall off the columns, which ultimately doomed the towers. These considerations, though, are relatively irrelevant for our purposes, as the #towerchallenge premises that an initiation of collapse is within the realm of the possible - far more interesting is that it was not stopped!
FEMA championed the pancake collapse, NIST ruled that out. Bažant - saying the kinetic energy of the falling top was greater than the energy lost to deformation of the first floor, hence, the whole tower was doomed - called it a "progressive collapse" (citing Ronan Point, among others), NIST prefers the term "disproportional collapse".
NIST explicitly states in its report (NIST NCSTAR 1) in two footnotes that it only covered the events leading up to the initiation of the collapse, but for brevity (it was already more than 10,000 pages long) did not analyze the collapse mode itself, agreeing, however, with Bažant in calling the subsequent collapse "inevitable".
The specific objectives were:
- Determine why and how WTC 1 and WTC 2 collapsed following the initial impacts of the aircraft and why and how WTC 7 collapsed. [...]
- NIST NCSTAR 1, p. xxxix
The focus of the investigation was on the sequence of events from the instant of aircraft impact to the initiation of collapse for each tower. For brevity in this report, this sequence is referred to as the ‘probable collapse sequence,’ although it includes little analysis of the structural behaviour of the tower after the conditions for collapse initiation were reached and collapse became inevitable.
- NIST NCSTAR 1, p. xxxvii
The focus of the Investigation was on the sequence of events from the instant of aircraft impact to the initiation of collapse for each tower. For brevity in this report, this sequence is referred to as the “probable collapse sequence,” although it does not actually include the structural behavior of the tower after the conditions for collapse initiation were reached and collapse became inevitable.
- NIST NCSTAR 1, p. 82
We are unable to provide a full explanation of the collapse [...] NIST has stated that it did not analyze the collapse of the towers. NIST's analysis was carried to the point of collapse initiation.
The two aircraft hit the towers at high speed and did considerable damage to principal structural components (core columns, perimeter columns, and floors) that were directly impacted by the aircraft or associated debris. However, the towers withstood the impacts and would have remained standing were it not for the dislodged insulation and the subsequent multi-floor fires.
- NIST NCSTAR 1, p. 174
Every expert knew it would happen
This is also a common misunderstanding:
The destruction of the World Trade Center on September 11, 2001 was not only the largest mass murder in U.S. history but also a big surprise for the structural engineering profession, perhaps the biggest since the collapse of the Tacoma Bridge in 1940. No experienced structural engineer watching the attack expected the WTC towers to collapse. No skyscraper has ever before collapsed due to fire. The fact that the WTC towers did, beckons deep examination.
- Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions, Bažant/Verdure, 2007
But the firefighters...
According to the National Institute of Standards and Technology (NIST), the Fire Department command officers who are planning for operations inside the Twin Towers expect that there will “be localized collapse conditions on the damaged fire floors,” but do “not expect that there [will] be any massive collapse conditions or complete building collapse. [...] No one interviewed indicated that they thought that the buildings would completely collapse.” [National Institute of Standards and Technology, 9/2005, pp. 72 and 75-76]
Are all the experts and official investigation wrong?
Not completely. The leading authorities in the field suggest:
It is proposed to monitor the precise time history of displacements in building demolitions — for example, by radio telemetry from sacrificial accelerometers, or high-speed optical camera — and to engineer different modes of collapse [sic!] to be monitored.
- Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions, Bažant/Verdure, 2007
Similar topics:
- An (incomplete) list of building collapses and demolitions
compares many modes of failure of mid- to large-sized structures - showing that slender things tend to fall over, that natural collapses are assymmetrical, that the center of mass usually moves sideways, that the progression of the collapse front usually decelerates in gravitational collapses and how buildings behave in different types of demolition methods. Particularly the botched demolitions attempts demonstrate that square-cube law (IOW, their sheer size) is no explanation for the behaviour of the Twin Towers: not only small Jenga towers, but also big things tend to damp, cushion and eventually arrest collapse. - The scientific consensus on the cause of total progressive collapse
shows, by aggregating most notable and official expert opinion on the topic, that another common myth - namely, that all experts agree on the basic, underlying principle, and that the science is clear on this issue - is easily dispelled. - Laypeople explain the "collapse" of WTC 1 & 2
refutes the idea that there is wide agreement, consensus and understanding on the cause(s) of the "collapses" among laypeople.
So you are still reading. I cannot guarantee Anders Björkmann will really pay 1,000,000.- Euros for a successful attempt to meet his challenge. So far, nobody seriously tried to claim the price.
His rules are a lot stricter than those of #towerchallenge, but the good news is: towerchallenge makes it easy to demonstrate the principle, scaling up is then a mere matter of routine!
Jim Hoffman's challenge is similar in nature.
It seems there is a market for self-disassembling buildings, let's fill that niche!