Free Fall thread

Cheerful Spring2 wrote: »

No building can collapse in seconds, naturally,. there too many elements would have to buckle and break first and fall away. There long span of floor space, from one corner to the next.

What you see on video is the Penthouse (went first first sign of failure) seconds later about 5 the entire building lost support.

Freefall explains why it was so fast- controlled demolition took out 8 floors of steel columns below and full collapse began.

Cheerful Spring2 wrote: »

Plasco was in Iran- one of the worst places on earth for maintaining building standards. They made it of concrete and steel, no fireproofing, the Iranians declared the building unsafe before the collapse. Gas canisters were stored inside the building ( temps above normal) plus it collapsed with four corners toppling inwards (another clue its natural)

Cheerful Spring2 wrote: »

This is their model- no free fall. You see it at one minute 15 seconds! notice that half still there below (crumbling and twisting) That buckling of floors and columns still taking place even when the building falling.

Overheal wrote: »

The paper (Computer Simulation for Building Implosion Using LS-DYNA) involved here is especially enlightening about the nature of performing these types of computer simulations - and they cut corners:

"The experience gained from these [preliminary simulation] examples showed firstly that the element erosion-algorithm in the case of non vertical collapse scenarios, in which failure occurs mostly due to strong bending of elements and not due to high pressures, can provide reliable results, at least for the initial collapse kinematics. On the other hand, the erosion scheme should not be applied in the case of a vertical collapse, since as a result of removing elements it does not deliver reliable results. The node-split-algorithm, however, is more time consuming and imposes several changes in the discretization, but is a better alternative which delivers realistic results even in the case of vertical collapse with high pressures and material failure due to strong compression."

[...]

"The finite element model consists of 392481 8-node hexahedral solid elements. At first, the CAD geometry was created from the building drawings.
Then, using the preprocessor Hypermesh [14], the finite element mesh was constructed and imported into LS-DYNA. At this final stage, all the numerical algorithms were applied, such as material model, element formulation etc. In the computations to be presented a rather simple, piecewise linear, plasticity model is used (LS-DYNA MAT24) for efficiency reasons. However, some limitations have to be mentioned resulting from the fairly simple failure criterion. In addition to that, it must be noted that also in the case when Node-Split is applied, a rather high resolution of the model is necessary in order to capture sufficiently the entire cracking process. Furthermore, by using continua for the modelling of reinforced concrete the effect of the steel bars is “smeared” in the continuum. E.g. the presence of steel bars, after the mechanical failure of the concrete, would in reality prevent structural parts from flying away from the structure. However, in the simulations when the continua fail, a complete dissolution is obtained. This results in general in an overly brittle behaviour and some elements are flying away from the structure, In the simulations we try to damp this motion which is not a perfect solution. The ground plate is simulated as a rigid body and the building collapses under the effect of gravity."


The compute time for the final model was over 716 hours (29 days). Not including the time spent generating the CAD, mesh, and all the necessary modifications to stop the simulation from crashing out (and the time wasted on simulations that ultimately crashed out):

"New contact interfaces are created and included in the search contact algorithm which is very time consuming and as a consequence slows down the entire computation. In order to remove the major part of the artificial energy which was added to the model during the application of the initial gravitation with explicit time integration, the system had to be damped for 0.1 second, otherwise large vibrations were leading to error terminations.

It proved to be particularly important to avoid the “inversion” of solid elements leading to negative volumes and finally to error terminations, as a result of large element deformations. In order to handle this problem additional contact checks were added which consider contacts between interior surfaces of the hexahedral elements to avoid an inversion. Nevertheless, in the results the limitation in the applicability of the Node Split algorithm is observed from the very strong dissolution of element connections due to material failure, which creates for some parts unrealistic phenomena (structural parts flying e.t.c). The latter would not be possible with reinforcing steel which mostly prevents a complete dissolution of parts."

(ie. they had no way to truly computationally model the destruction mode for reinforced concrete, so it was approximated heavily). Basically, these simulations are incredibly resource and time intensive, and difficult to work with even when you are reverse-engineering an implosion with all your conditions known with regard to explosives used and behavior during the collapse ex post facto. Note also this is a 2011 paper, and the simulation produced was not anything used to control the implosion of the building when it went down in 2004.

Cheerful Spring2 wrote: »

Have you read this? It's the most detailed explanation of freefall you find online. He goes over every aspect why its impossible by natural means.
https://medium.com/@davidchandler_61838/free-fall-131a94a1be7e

Cheerful Spring2 wrote: »

Thier entire study is fake including the models.
They're no freefall here, end of story.


Truthers have done the real science here, NIST should be in court facing criminal charges.