9/11

Pull it..

 

Gravity

 

Storch isnt here right now, please leave a message after the beep

 

NIST NCSTAR 1-6D

5.2 WTC 1 collapse sequence

The aircraft impacted the north wall of WTC 1 at 8:46 a.m. The aircraft severed exterior columns and floors on the north side of the tower and core columns and floor members between Floor 93 and Floor 98.

The subsequent fires weakened structural subsystems, including the core columns, floors, and exterior walls. The core displaced downward, the floors sagged, and the south exterior wall bowed inward.

At 10:28 a.m., about 102 min after the aircraft impact, WTC 1 began to collapse.
The sequence of main structural events that led to the collapse of WTC 1, starting from aircraft impact, and the causes and effects of these structural events along with key observations, are discussed below.

The WTC 1 collapse sequence consists of five main events, listed in Table 5–1, which are discussed below. Actual observations are summarized in Table 5–2, which are based on NIST’s examination of photos and videos (NIST NCSTAR 1-6).

Table 5–1.
Summary of main events that led to the collapse of WTC 1.

Event Number Event

1 Aircraft impact
2 Unloading of core
3 Sagging of floors and floor/wall disconnections
4 Bowing of south wall
5 Buckling of south wall and collapse initiation

Table 5–2. Observations on WTC 1 provided by NIST.
Time Time from Impact (min) Observation

8:46:26 0 Aircraft impact on the north wall of WTC 1 between Floor 93 and Floor 99 and Columns 112 and 151.

9:25:28 39 Fire on west side of south wall.

9:40 54 No bowing of columns was observed between Columns 301 and 323 on the east side of south wall.

10:18:43 92 Smoke suddenly expelled on Floor 92 north wall, Floor 94 east side of north wall, Floor 95 to Floor 98 on west side of north wall, Floor 95 and Floor 98 on north side of west wall, lower floor on south side.

10:22:59 97 Inward bowing from Floor 95 to about Floor 99 between Columns 308 and 326 (maybe to 340) on the south wall,maximum amplitude approximately 55 in. at Floor 97.

10:28:18 102 Smoke puff out of north edge and center of west wall; smoke and debris clouds out of the north, east, and west walls on Floor 98. Fire out of windows on the north, east, west, and south walls between
Floor 92 and Floor 98, and on Floor 104.

10:28:20 102 WTC 1 began to collapse. First exterior sign of collapse was at Floor 98. Rotation of at least 8 degrees to the south occurred before the building section began to fall vertically under gravity.

Aircraft Impact

The aircraft impacted WTC 1 at the north wall. The aircraft severed or heavily damaged Columns 112 to 151 between Floors 94 and 98 on the north wall. After breaching the building’s perimeter, the aircraft continued to penetrate into the building. The north office area floor system sustained severe structural damage between Columns 112 and 145 at Floors 94 to 98. Core Columns 503, 504, 505, 506, 604, 704, 706, 805, and 904 were severed or heavily damaged between Floor 92 and Floor 97.

The aircraft also severed a single exterior panel at the center of the south wall from Columns 329 to 331 between Floor 93 and Floor 96. In summary, 38 of 59 columns of the north wall, three of 59 columns of the south wall, and nine of 47 core columns were severed or heavily damaged. In addition, thermal insulation on floor
framing and columns was also damaged from the impact area to the south perimeter wall, primarily through the center of WTC 1 and over one-third to one-half of the core width.

Figures 2–2, 2–14, and 2–18 summarize aircraft impact damage to exterior and core columns and floors of WTC 1.

Gravity loads in the columns that were severed were redistributed, mostly to the neighboring columns. Due to the severe impact damage to the north wall, the wall section above the impact zone moved
downward as shown in Figs. 4–9 and 4–13.

The hat truss resisted the downward movement of the north wall and rotated about its east-west axis, which reduced the load on the south wall. As a result, the north
and south walls each carried about 7 percent less gravity loads at Floor 98 after impact, the east and west walls each carried about 7 percent more loads, and the core carried about 1 percent more gravity loads at
Floor 98 after impact (Table 5–3).

Column 705 buckled, and Columns 605 and 804 showed minor buckling.

Unloading of Core

Temperatures in the core area rose quickly, and thermal expansion of the core was greater than the thermal expansion of the exterior walls in early stages of the fire.

This increased the gravity loads in the
core columns until 10 min after impact (Table 5–3). The additional gravity loads from adjacent severed columns and high temperatures caused high plastic and creep strains to develop in the core columns in
early stages of the fire.

More columns buckled inelastically due to high temperatures. Creep strain continued to increase to the point of collapse (see Fig. 4–81). By 30 min, the plastic-plus-creep strains
exceeded thermal expansion strains. Due to high plastic and creep strains and inelastic buckling of core columns, the core columns shortened, and the core displaced downward.

At 100 min, the downward displacement of the core at Floor 99 became 2.0 in. on the average, as shown in Fig. 4–37.

The shortening of core columns was resisted by the hat truss, which unloaded the core over time and redistributed the gravity loads from the core to the exterior walls, as can be seen in Table 5–3.

As a result, the north, east, south, and west walls at Floor 98 carried about 12 percent, 27 percent, 10 percent, and 22 percent more gravity loads, respectively, at 80 min than the state after the impact, and the core
carried about 20 percent less loads as shown in Table 5–3.

The net increase in the total column load on
the south wall, where exterior wall failure initiated, was only about 10 percent due to the downward displacement of the core (see Fig. 5–3).

At 80 min, the total core column loads reached their maximum.
As the floor pulled in starting at 80 min on in the south side, the south exterior wall began to shed load to adjacent walls and the core.

Sagging of Floors and Floor/Wall Disconnections

The long-span trusses of Floor 95 through Floor 99 sagged due to high temperatures.

While the fires were on the north side and the floors on the north side sagged first, the fires later reached the south side, and the floors on the south side sagged. Figure 5–4 shows vertical displacements of Floors 95 through 98 determined by the full floor models at 100 min. Full floor models underestimated the extent of sagging because cracking and spalling of concrete and creep in steel under high temperatures were not included in
the floor models, and because the extent of insulation damage was conservatively estimated.

The sagging floors pulled in the south wall columns over Floors 95 to 99. In addition, the exterior seats on the south wall in the hot zone of Floors 97 and 98 began to fail due to their reduced vertical shear capacity at
around 80 min, and by 100 min about 20 percent of the exterior seats on the south wall of Floors 97 and 98 failed, as shown in Figs. 5–4 and 5–5.

Partial collapse of the floor may have occurred at Floors 97 and 98, resulting from the exterior seat failures, as indicated by the observed smoke puff at 92 min (10:19
a.m.) in Table 5–2, but this phenomenon was not modeled.

Bowing of South Wall

The exterior columns on the south wall bowed inward as they were subjected to high temperatures, pull-in forces from the floors beginning at 80 min, and additional gravity loads redistributed from the core.

Figure 5–6 shows the observed and the estimated inward bowing of the south wall at 97 min after impact (10:23 a.m.). Since no bowing was observed on the south wall at 69 min (9:55 a.m.), as shown in Table
5–2, it is estimated that the south wall began to bow inward at around 80 min when the floors on the south side began to substantially sag.

The inward bowing of the south wall increased with time due to continuing floor sagging and increased temperatures on the south wall as shown in Figs. 4–42 and 5–7.
At 97 min (10:23 a.m.), the maximum bowing observed was about 55 in. (see Fig. 5–6).

Buckling of South Wall and Collapse Initiation

With continuously increased bowing, as more columns buckled, the entire width of the south wall buckled inward. Instability started at the center of the south wall and rapidly progressed horizontally toward the
sides. As a result of the buckling of the south wall, the south wall significantly unloaded (Fig. 5–3), redistributing its load to the softened core through the hat truss and to the south side of the east and west walls through the spandrels.

The onset of this load redistribution can be found in the total column loads
in the WTC 1 global model at 100 min in the bottom line of Table 5–3. At 100 min, the north, east, and west walls at Floor 98 carried about 7 percent, 35 percent, and 30 percent more gravity loads than the state after impact, and the south wall and the core carried about 7 percent and 20 percent less loads, respectively.

The section of the building above the impact zone tilted to the south (observed at about 8˚, Table 5–2) as column instability progressed rapidly from the south wall to the adjacent east and west walls (see Fig. 5–8), resulting in increased gravity load on the core columns.

The release of potential
energy due to downward movement of building mass above the buckled columns exceeded the strain energy that could be absorbed by the structure. Global collapse ensued

 

"BEEP".......Hi Storch...It's GLEN Here.....Sorry To Hear That You Are Unwell.....Best Wishes

For A Speedy Recovery.........



Cheers Glen.

 

Gordon Ross's Junior high maths assignment:


Energy Summary:


The energy balance can be summarised as

Energy available;

Kinetic energy 2105MJ

Potential energy Additional downward movement 95MJ

Compression of impacting section 32MJ

Compression of impacted section 24MJ

Total Energy available 2256MJ

Energy required;

Momentum losses 1389MJ

Plastic strain energy in lower impacted storey 244MJ

Plastic strain energy in upper impacted storey 215MJ

Elastic strain energy in lower storeys 64MJ

Elastic strain energy in upper storeys 126MJ

Pulverisation of concrete on impacting floor 304MJ

Pulverisation of concrete on impacted floor 304MJ

Total Energy required 2646MJ


Minimum Energy Deficit -390MJ

 

You're showing how gullible you are by accepting this statement from the NIST even though they offer no evidence to support it. They've even stated that their Report does not include anything that occurred after collapse initiation. But you, with your childlike faith, accepted their baseless conclusion simply because it's what they told you, and it's what you wanted to believe. So even though they've admitted that their version of how the collapse was initiated is speculation, you were hypnotized by the detail with which they outlined their speculation. Hell, they even admitted that they couldn't see inside the Tower to assess the fire.
________________________________________________________________________________________________________

The first of the specific objectives of the NIST study was to "[d]etermine why and how WTC 1 and WTC 2 collapsed following the initial impacts of the aircraft and why and how WTC 7 collapsed." [3] These questions are not answered for simple reasons:

Incredibly, the progressive collapse of the Twin Towers has been left out of the computer models used: "The global models of the towers extended from several stories below the impact area to the top of the structure." [4] Thus the structurally intact floors 1-91 of WTC 1 and floors 1-77 of WTC 2 were excluded from the so called "global" models of the towers.

Correspondingly, the temporal dimension was cut short as well: NIST gave itself the task of finding out "[t]he probable sequence of events from the moment of aircraft impact until the initiation of global building collapse." [5]

In other words, "Even without the modeling of the progressive collapse we had to postpone the publication of the reports four times so we just didn't have time to do that. And besides, the lower parts of the buildings simply did not slow down the collapse, as everyone could see on TV, so why bother?"
__________________________________________________________________________________
Are you getting this?

In summary: The reports by NIST say nothing about how -- and if! -- the collapse was able to progress through dozens and dozens of structurally intact floors without being stopped. If no external energy was available e.g. in the form of explosives, this would have been the opportunity to show that no such energy was needed. On the other hand, if some unaccounted-for energy broke the supporting structures enabling the collapse to progress with the speed it did, there would have been many good reasons not to try to model the impossible, ie. a purely gravitation-driven collapse. Stopping the analysis early enough also saves NIST from trying to explain the symmetricality of the collapses (despite non-symmetrical impact damage and fires), the almost complete pulverization of non-metallic materials as well as the extremely hot spots in the rubble. These remain as inexplicable by the official story as they have ever been.

One appendix of project 6 includes an interesting analysis of a dropping floor. [8] According to the results, however, temperatures of 400 to 700 ºC are needed in order for the collapse to be initiated. Unfortunately, the destruction of evidence at Ground Zero was so complete that NIST can now only say that the steel components recovered demonstrate that there was "limited exposure if any above 250 ºC." [9]

NIST's collapse creed, repeated eleven times with identical wording (and once with a slightly different one) in the report of project 6 dealing with the collapse sequences, is this:

" The change in potential energy due to downward movement of building mass above the buckled columns exceeded the strain energy that could have been absorbed by the structure. Global collapse then ensued." [10]

In other words: "Once the top started coming down, it was so heavy that the damaged columns could not stop it. Neither could the undamaged columns of dozens of floors do that, it seems. But we didn't need to model that for we've all seen that down it came."

Thorough, open, independent?

9-11 Review: NIST's Evasion
________________________________________________________________________


To the best of your ability, tell us what you think this means about the core structure when it comes to the idea of column-weakening fires. Keep in mind that this is part of their Report.

"The core space contained relatively little combustible mass." (NCSTAR 1-5 p49 para7)

"The fuel loading in the core areas of the focus floors was negligible." (NCSTAR 1-5 p51 para2)

Keep in mind that simply repeating this without a response is . . . not a response.

 

Well, what do you want me to tell you, half the people watching that day in 2001 surprised the buildings collapsed....then they went away and thought about it for a couple days, couple weeks months...a year later you probably had 90% of the population getting it, didnt need anyone explaining to them why if part of it collapsed, well then whats going to stop it. Then came tne truthers...who were all one type of person, which didnt really help matters. By the time you get to the NIST report, your were down to 5% of the population that needed it explained to them.

By 2018 we are down to 1% really.

Thats all this thread was ever going to be

 

And this is what this thread has de-evolved down to.

"tell us" who do you think "us" is?

The 1% left that are going to say stuff like duh uh uh errr When a moving body collides with a body of the same composition, two things happen........

 

Really? Could you direct me to the poll that validates that so that I don't have to show everyone that you just made that up?

 

Who is "everyone"?

 

If by "de-evolving" you mean you believing that your complaints are a good substitute for explaining what this:

"The core space contained relatively little combustible mass." (NCSTAR 1-5 p49 para7)

"The fuel loading in the core areas of the focus floors was negligible." (NCSTAR 1-5 p51 para2)

means to you, then yeah, it's de-evolved.

 

I asked you to support your claim that only 1% of the population doesn't "get it." So, support it.

 

Answering what? You didnt ask a question, you asked me about column weakening fires then copy and pasted sentences from a section on office combustibles

 

No only 1% left that dont get it

 

Are you pretending that I didn't ask you to support that claim?

 

Yes I did.

To the best of your ability, tell us what you think the following means about the core structure when it comes to the idea of core column-weakening fires. Keep in mind that this is part of the NIST Report.

"The core space contained relatively little combustible mass." (NCSTAR 1-5 p49 para7)

"The fuel loading in the core areas of the focus floors was negligible." (NCSTAR 1-5 p51 para2)