They are not mutually exclusive, test both on this relatively reliable model and tell me whether it contradicts what we witnessed Doubting 'official versions' without offering more credible explanations is not very helpful. A model that goes all the way in predicting what could never have happened should also explain or attempt to explain what happened

You seem confused. The model should first interrogate the dominant or accepted hypothesis with the objective of testing (verifying/falsifying) it. If the hypothesis is falsified (ie the model does not behave as predicted, within reasonable parameters) then alternative hypotheses may be developed, possibly with insights gained from the results of the initial model's tests.

Or, as in the case of many of the models discussed in this thread, the initial prediction should be checked. Especially in terms of scale, and modeling realistic events.

Indeed. And here again femr2's approach is vastly superior to NIST's attempt to model the WTC7 event, at least in terms of method, as every single variable and all input data must be available for independent examination if the suggestion of drylabbing the model to achieve the predicted outcome is to be avoided.

What drylabbing, is that a claim? Is that what you can do with all those variables in Femr2 model? Which is the key variable in femr2's WTC 7 model? Is femr2's model a layperson, model, or engineering? Femr2 model, was it ported to WTC 7? Explain in detail how femr2 model is superior to NIST's engineering model. How many more variables are in femr2's model? Everyone? Does femr2's model support CD, or what? http://femr2.ucoz.com/ why is femr2 able to extimate and get real close to WTC values when Psikeyhackr can't for his model? Where is femr2 WTC 7 model. A hypothesis has to be able to be falsifiable to be valid. Your earlier post make no sense.

@Keith Beachy To be honest, @Cube Radio said femr2 is better than NIST because the data and model are open and available while NIST is not. I am not sure if that is true, but that is what he said. femr2 is repeatable while NIST (apparently) is not.

Well OK, if you HAVE tried it, why didn't you tell us the results? either you found it a useful model so therefore there IS a useful model oryou found it not useful in which case, why the hell even bring it up? Except to say Here's a model but it;s not very useful because X. then offering ways to improve the model. but you didn't do any of that. I am trying to see what your point is.

To my disappointment I discover the visualizer is no longer available to download from the link on femr2's website. The intention was obviously for you to use it to investigate the collapse for yourself and come to your own conclusions as whether or not the collapse could have happened as hypothesised (or criticise the model as Mick and I have discussed upthread). However, here is femr2's YouTube playlist of videos made using the collapse simulator. https://www.youtube.com/view_play_list?p=22FAFC72D202A6D7 Here is one example from the playlist. I think it is fair to say that femr2 does not believe the model supports the gravity-driven collapse hypothesis, although that is not explicitly stated. Whilst searching the net to see if I could find femr2's visualizer archived anywhere in order to be able to post it to the thread, I found this YouTube video that, though old, I had not seen before. Although it is not a model of the collapse, it does demonstrate the degree of detail than can be achieved with 3D modelling software.

How do you know whether the 'visualizer' is really affected by your inputs? We are supposed to supply data to Ms Excel and happily believe a Youtube video? Is this any different from the Unity machines that come with hours of video as the ONLY evidence they work?

The model was designed to take its inputs from a spreadsheet but the visualisation was an application that ran on your pc. I don't have it on my old laptop. Since I can't find it to download elsewhere I don't expect anyone to be impressed by its results or construction, and we may well drop it from the discussion. It remains however an example of the best method by which models should be developed, which is to say, with full transparency: I don't think anyone here would disagree with this principle.

It's a shame that it isn't available then. because at least you could change variables to see if there;s any difference when you run the SIM. You could make the columns infinitely strong or whatever and see if the floors still collapse anyway. The interesting thing with those videos is that the first one, if modelled accurately shows th e building clearly did NOT fall at free fall speed as it finishes collapsing before the real building does. The second one is very pretty and shows how good a VISUAL simulation can be but I am not sure if it can ALSO model the collapse in the same way. Other people earlier in this thread ARE still correct though. Mathematical models have already shown that the gravity driven collapse is not only possibly but most likely, and so these other models are just really to show people who don't understand the concepts how it COULD have happened. The problem is, if you are hardcore believer in one particular collapse scenario, then you will simply believe the model has been "fixed" just so it shows you the "opposite" story.

Did he intend to make the model and its inputs available for the public to fool around with it. I doubt it very much. A model of something very complicated isn't meant for the public so they can fool around on it and in the end this could have a negative impact on his "model's" effectiveness, if it were available..

Yes, the inputs at least were accessible and could be changed. Whatever you may say about complicated models, this had an open design precisely because that is the method by which accusations of "fixing" results are avoided. But really, unless I can find femr2's model for download, I don't think the discussion here should focus on it. It gave rise to a great deal of forum discussion at the time, which remains easy to find online.

Cube, I went on the site for femr2 that you provided and the page looks like it was created in 2009, and there's only been 1 comment, with 0 traffic in god knows how long. Could this be an indication that his simulations might not be acceptable? And I agree, without the simulation we probably shouldn't discuss the "what if's" of it

In general terms femr2 is pretty well known for video analysis work relating to 9/11 and that model did generate a lot of discussion when it first appeared. However, there's no question that there's been little activity from femr2 for a long time, which was not something I was fully aware of when I mentioned the collapse simulator.

I'm sensing you're trying to distance yourself from femr2, but you still believe other factors are at work in the collapse of the twin towers

I think the spreadsheet IS the model. You can change values in the spreadsheet and get different tins. The visualizer just makes a video of the result.

I'm disappointed I can't find the visualiser, but I'm not "distancing" myself from anything: I mentioned femr2's collapse simulator because it's (somewhat) on topic, given that the discussion expanded to include computer models. As far as your senses are concerned: you're not a Jedi yet, Jai-son.

True, and it's a safe bet that I will never be one. lol.. At any rate, do you think the towers could've came down without the use of explosives based on the models you've seen Mick and dee submit.

I know femr2. While I can't speak for him, I know that his program was available for download so that people could play around with different values and see the results. There's nothing wrong with it (i.e., it is acceptable), though it can let you change the parameters to something quite unphysical if desired. femr2 originally didn't think that the collapses were natural, but eventually came to see that collapse, once initiated, would continue. The matter of whether the initiation was natural is much more difficult to ascertain from external evidence, and that was left in a gray area. I don't know what his current thinking is regarding artificial assistance; we made a point of not going there for several years. "Belief" did not come to the analysis table. He has lost interest in the subject. My opinion is, if it's not available, build your own. It's not too difficult, and you'll learn a lot in the process.

found an hour to post. I was wondering.... If a group were to build an exact full scal model of ONE floor of the towers, supported on columns 12 feet long, details as seen fit, and then dropped 10 times the dead + live load onto it from a height of 6 feet, to be conservative with impact velocity, and the floor connections failed. Would truthers accept this as validating the progressive floor failure scenario as very probable (ie. true)?

Do you happen to have a link for this program so we can download it, because the old link keeps giving me a 404 page not found error. I would like to try it it out if possible.

The performance of materials and assemblies have been tested in full scale real world experiments. These tests are what is used in load design tables for various materials and assemblies. The collapse of the twin towers was the result of the floor assemblies failing from dynamic loading as materials from above (other floors and contents) descended down upon them. If a floor system is designed to support Xpsf and 5X or 10X is dropped onto it... the floor system will fail, safety factor notwithstanding. The twin tower collapse was a runaway...or domino effect of the initial floor failure repeating all the way down to the ground... leaving the columns without sufficient lateral support to remain standing. They collapsed from Euler forces and this too has been modeled in real world testing. There is no need to model the performance of ALL the systems in the towers as the individual systems have been modeled and their limits known. One floor fail leads to the next and that leads to the columns loss of bracing and they fail. Perhaps the naysayers will accept proof by taking a single column and see how tall it can be before it topples from instability. But of course you can see what happens in the vids of the "spire" .. full scale real word. Why do we need models when one's observations of the event should suffice?

So how could they have built the towers to take a direct hit from a plane, granted not a fully fueled plane and traveling at the speeds they were on 911, but considering the mass of an individual plane, wouldn't the plane's mass be enough to cause floor failure

You should do the math there. What's the weight of plane? How much can a floor support? How concentrated is the mass of a plane? Where will the plane mass end up?

http://www.airliners.net/aircraft-data/stats.main?id=103 So empty the aircraft weighed about 165,000 lbs. What size plane or impact were the towers designed to withstand? Edit: http://www.boeing.com/boeing/commercial/707family/product.page. Towers were designed to take an impact from a 707 which has similar mass to the 767. Empty it's around 160,000lbs.

Looking randomly upthread, I see a figure of 29,000,000 pounds for the weight a floor could support. So the simple fact of plane being in there is not going to trigger progressive collapse. The actual events are much more complex - but buildings (and building floors) weigh a lot more than planes.

Thanks I was trying to find that. If each floor was designed to support 29,000,000 lbs, what would happen if you dropped 11,000,000 lbs onto it from 10 feat above. I found this chart which broke the mass down for each floor in the towers, and as the tower got higher the mass of each floor dropped, because it was designed with wind loads in mind. Here is the chart. Maybe I'm doing the math wrong, but I simply added the mass of each floor above the 86th floor and multiplied it by 2000lbs (1 ton) to get the total weight in lbs.. So what would nearly 11,000,000 lbs feel like when it accels at nearly free fall velocity after 10 feet of falling. I don't know, I was hoping someone with a math background could answer this.

Compare it to holding a hammer in your hand, vs. dropping a hammer on your hand from ten feet up. It's the old static vs. dynamic load thing. Weight is a a force (mass*gravity). In an impact the situation is more complicated, but essentially it's still the same thing (force) - just now instead of gravity, you multiply it by the "g-force" of it hitting the concrete. The actual force depends on the materials (and how rigid they are) but it's vastly higher than gravity alone.

Which also helps explain why the 2nd tower that was hit fell first, since the impact was lower, the mass above was easily tripled.

160,000 lbs is equivalent to about 800 men. My non-engineer gut feeling is that, yes you could have 800 people on the floor without it collapsing.

There's no indication that there was ever a design goal or specification that the Twin Towers be able to take a direct hit from an airliner. It was more a question, "Given this design, could these buildings withstand an impact?" With the limited computing power of the time, the answer would be more of a "back of the envelope" calculation, than a sophisticated study.

Yes, your right but that was an empty plane, when fueld up and loaded with passengers the weight is over 350,000 lbs, which still wouldn't matter since I learned earlier today that these floors were designed to hold 29,000,000 lbs. One last question though, was each floor designed to have a max load capacity that was independant of the floor above or below it. Since the floors steel, and concrete were constructed differently as the towers increased in height... as evident in the chart I attached above in post #232

The issue of whether the towers were designed to take an impact from a plane has been discussed on other threads. This is drifting into being off topic. New topics in new threads. Old topics can be researched using the search function.

Seriously? I don't buy that for a second. How could any engineer designing the construction of a sky scraper not seriously discuss a plane hitting it, or a bomb going off in the basement or on a floor. I'm sure there was also serious discussion between the company insuring the Towers and the structural engineers. OT: whats also become obvious to me, and I don't know if anyone else has considered this. If someone decided to bomb the towers on lets say the 75th floor, and used enough explosives to cause the structure to fail (in the way 911 happened) then the towers probably would've come down in a similar fashion. Right? How much explosives do you think it would've taken to create the same damage, and would it have been possible.

Now that's definately getting off topic. Have a look at https://www.metabunk.org/threads/the-plausibility-of-demolishing-wtc7-with-explosives-on-9-11.2518/ Which has similar discussions.