I was trying to make it easy to speak and listen in the most part. Using too much of the industrial terminology might not be so much entertaining to watch, so sometimes i just let it slip and flow like a casual conversation.

Path of most resistance is UP. Gravity works down. Path of least resistance is down.

Thanks for the sub!

Gravitational Potential Energy. Planes impact Towers, causing massive structural damage, starting multiple floor-wide fires that spread rapidly due to the destruction of fire protection systems during the impact. Serious fires were largely confined to the impact damaged floors and those immediately adjacent to them. Fires were started by the impacts and fuel aboard the aircraft, which acted as an accelerant. No shortage of other consumables inside the tower to continue the fires. Collapse was initiated (started) at the impact and fire damaged floors when floor trusses exposed to heat over time sagged, in turn pulling on and causing the inward bowing of perimeter columns by up to 5 feet until they buckled. No steel melted or needed to. Structural steel will bend and fail at less than half its melting temperature. Once the perimeter columns buckled the formerly static load above became a dynamic load 30 times greater, easily overwhelming the structure below. Thousands of tons of now loose debris fell through the open off space - through the inside of the building - dropping 12 feet onto the first intact floor it comes across. The massive instantly overload causes the floor to fail, adding its mass to the falling mass which continues to accelerate for another 12 feet until it impacts the next floor, rinse and repeat all the way down. *Rate of collapse increases* as momentum increases. As each floor fails, air inside the building (the Towers were 95% air by volume) is compressed, then blows out the sides _in reaction to the Tower falling, not the cause of the Tower falling. No fire required at all on floors below the impact points for them to fail. The mechanisms that _started_ the collapse are different to the mechanisms which _continued_ the collapse. That will be a difficult concept for some. As the floors fail the perimeter columns are left literally hanging in the breeze, no longer attached to the rest of the structure. They peel away and fall in great sheets (think banana) out to more than 600 feet from the base on the 4 points of the compass. Core columns failed last. Each 110-story tower had a 1-acre footprint. The debris pile was up to 14 stories deep and spread out over 16 acres, destroying 8 surrounding buildings and damaging more than 100 others.

You're welcome

​@@TheCriticalStinker-jw4flet, vous avez la même explication pour la tour 7 ?

@@momodesfas4356 - I have a different explanation for Buildng 7 because it is a different event. The unknown and unimportant Building 7 was the 6th building to collapse of 10 lost on 9/11. Though extensively studied, it still confuses many people. Not famous, or a terror target, and no casualties, thus it did not get a lot of attention and few know much about it, creating a void rapidly filled with garbage from the internet. Because _everything seems like a conspiracy if you don’t understand how it works_ I prepared this brief summary explanation of my own analysis. No politics, just engineering. The North Tower collapse at 10:28am bombarded Building 7 with tons of burning debris, causing heavy damage and starting raging fires burning out of control for 7 hours. Half the responding FDNY firefighters having been killed, others injured, units in disarray, equipment destroyed, no water pressure, and the greater urgency of Search & Rescue efforts, firefighting at 7 was pulled as futile. The building couldn’t be saved and was left to its fate. kzbin.info/www/bejne/nZC2p6Otrqhkba8&ab_channel=MFitz Collapse of a burning structure is always a concern for firefighters. Steel buildings subject to fire _rely on active fighting of the fires_ to survive. Buildings are designed around 1 to 3 hours of fire resistance, allowing time for occupants to escape and _ACTIVE firefighting_ to get started, after which all bets are off. Left to their own devices they will exceed their design envelope and collapse. In B7 the occupants escaped, passive and active fire protections were compromised and *active firefighting was abandoned* which left the building to take its chances. It lost. Odds on Building 7 would eventually collapse, and it did. No big deal in logic. That is the sort of choice firefighters make every day in brush fire situations - which houses to save and which ones to let go. Only real difference here is moving the decimal on the size and cost. kzbin.info/www/bejne/jZ-8c4tshrljiJY *FDNY Chief Daniel Nigro* ; _The biggest decision we had to make on the first day was to clear the area and create a collapse zone around the severely damaged 7 World Trade Center, a 47-story building heavily involved in fire. A number of fire officers and companies assessed the damage to the building. The appraisals indicated that the buildings structural integrity was in serious doubt. I issued orders to PULL BACK the firefighters and define the collapse zone. It was a critical decision; We could not lose any more firefighters. It took a lot of time to PULL EVERYONE OUT, given the emotionalism of the day, communications difficulties and the collapse terrain_ *FDNY Deputy Chief Peter Hayden* ; _We had our special operations people set up surveying instruments to monitor and see if there was any movement in the building. We were concerned of the possibility of collapse in the building. And we had a discussion with one particular engineer there, and we asked him if we allowed it to burn could we anticipate a collapse and if so, how soon? And it turned out that he was pretty much right on the money, that he said 'In its current state you have about 5 hours_ The collapse of Building 7 was anticipated all afternoon and widely reported in the media with at least 24 video cameras recording some or all of the collapse. Everyone at the time knew what was coming and why. kzbin.info/www/bejne/hYqYhGihaNmAfqs Building 7’s collapse was totally different to the Twin Towers, harder to understand and most of the details difficult to see. But we can sort out what happened through careful analysis and observation. What follows is *MY EXPLANATION* of the collapse sequence using the best available information and relying on no authority. B7 was complex structure, a 47-story steel framed building built on top of a smaller existing 3-story building, requiring several lower floors dedicated to complex load transfer structures instead of usable office space. Of trapezoidal shape and all-steel tube-in-tube construction, B7 (above the 7th floor) consisted of a central core of steel columns carrying most of the gravity load, perimeter steel columns around the outside of the structure carrying the remainder of the gravity loads and long span beams and girders to tie those elements together and form the floors. On the outside of the building hung a moment frame - the last part of B7 to fall. *Phase 1* : Collapse initiation for B7 is *notably quiet* with observers not realizing the building was collapsing! There was no audible warning in the form of say hundreds of ear drum busting 180-190dB explosive bangs preceding the collapse. The first externally visible signs of collapse initiation occurred at 5:20:28 pm. Here at 12:00 a local CBS affiliate reporter is talking 10 blocks from B7 when collapse begins. People don’t start to notice the collapse until 12:11. Then at 12:45 is the famous CBS fixed camera clip of Building 7’s collapse Again, note how quiet it is. kzbin.info/www/bejne/qmbXdqxsor2Ge5o&ab_channel=fresnosean379 Collapse initiation was due to multiple lower floor failures above the load transfer region (7th floor) in the NE corner of the building. In this video at 0:45 you can see the NW corner from inside the building while under construction, Column 79 just out of frame on the left. That big, angled steel beam across the top of the frame connects to C79 at one end. The girders connect to the beam. That beam and all those girders _depend on just one connection_ kzbin.info/www/bejne/pIGWhYF-hah8jLc&ab_channel=EdwardCurrent *Phase 2* : Lower floor failures caused a loss of critical lateral support over an excessive length of core Column 79 and it buckled. If you look at a floor diagram of Building 7 (see above) and look at all the structures that depend on C79 you quickly realize *this one column was a relatively isolated structural element on which a disproportionately greater fraction of the structure depended* . Externally we see a vertical progression of window breakage along the 44-46 line and a kink in the roof of the East Mechanical Penthouse at the top of the building, consistent with C79 failure. The transition from full capacity to almost no capacity occurs in virtually an instant. *Once the buckling failure occurs there is almost no resistance* Normally with a buckling column, the load could very well be redistributed to other columns, meaning the buckling could stop after a while. With C79 that is not the case - the failure did not redistribute the load, so the collapse rapidly progressed to the roofline, sinking the rooftop penthouse. *Phase 3* : With C79 gone, B7’s progressive, non-symmetrical collapse continues with C80 and C81 at the east end of the core left laterally unsupported and quickly buckled and failed as well, sending the EMP down through the building. C79-81 all have no diagonal bracing, which I believe is a major reason why they could not redistribute a lot of vertical loads among one another. From there *collapse progressed from east to west through the central core until the core was gone* taking all of the interior floors and structures and probably most of the perimeter columns with it. You can see the horizontal progression of window failures low in the building and the dropping of the remaining rooftop structures into the building. One of the big takeaways from the NIST Building 7 study (that gets completely ignored) was their modeling which determined C79 failing under _ANY circumstances_ would have initiated the same collapse sequence. *Phase 4* : After some 10 seconds all that remains of Building 7 is just a hollow empty outer shell - the exterior moment frame - creating the illusion the building is still standing since little has changed externally. But it’s *just a hollow empty shell* like an empty cereal box *supported by only a few remaining columns* and quite unable to remain standing. With all the internal framing gone. the north face leans inward, forming a V in the roofline, the last perimeter columns buckle under the strain and with nothing left keeping it up the moment frame free falls, landing _on top_ of the 7-story high debris pile. It is only at the very end that a single measurement of alleged _free fall acceleration_ is taken. Note this is not _the building but just its outer shell, and only one corner at that, at the very end of the collapse. Start to finish the entire collapse took 18-20 seconds, or _*_less than 1/3 of true free fall_*_ and we have to look at the whole thing, not cherry-pick little bits to fit a particular narrative. Worth noting _how fast something falls cannot tell you what started it falling_ in the first place. The debris spread out, blocking surrounding streets, heavily damaging the Verizon Building and destroyed Fiterman Hall, all well outside of Building 7’s “footprint”. Building 7’s progressive, non-symmetrical collapse was incidental and unintended collateral damage from the combined effects of fire + time + gravity started by the collapsing North Tower. That is *true no matter who planned and carried out the 9/11 attacks or why* . The collapse was of so little consequence it barely even registered at the time, a mere footnote. Anything can seem like a conspiracy if you don’t understand how it works. Now you should. I hope you found this helpful and informative, not adversarial and it solicits informed critical comment. If I made any errors of fact, logic or reason or left anything critical out, please let me know so I can fix it. IF you can offer a more plausible alternative please do. Be the first. Please start any reply with the words “Tits McGee” or I will know you didn’t read it and are wasting my time.

@DrJQureshi thanks for watching, I'm working to improve the video quality everyday.

Which people?

Why?

@TheCriticalStinker-jw4fl It is a firefighters perspective of the 911 attack and buildings collapse. Very educational.