From NIST report - NISTNCSTAR1-6D chapter 5.2 - we learn:
"The aircraft impacted the north wall of WTC 1 at 8:46 a.m. … between Floor 93 and Floor 98. … The subsequent fires weakened structural subsystems, including the core columns, floors and exterior walls. The core displaced downward … At 100 min (at 10:28:18), the north, east, and west walls at Floor 98 carried 7 percent, 35 percent and 30 percent more gravity load loads … and the south wall and the core carried about 7 percent and 20 percent less loads, respectively., … At 10.28 a.m., 102 min after the aircraft impact, WTC1 began to collapse. … The release of potential energy due to downward movement of the building mass above the buckled columns exceeded the strain energy that could be absorbed by the structure. Global collapse ensued."
The highlighted items are not proven.
Hi Heiwa. The quote from NCSTAR above is oddly redacted, with text from a later paragraph inserted out of sequence and some important points removed. Here's the original, with the text pasted in from a later paragraph struck out, and the blanks filled in in blue:
"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 100 min (at 10:28:18), the north, east, and west walls at Floor 98 carried 7 percent, 35 percent and 30 percent more gravity load loads than the state after impact and the south wall and the core carried about 7 percent and 20 percent less loads, respectively. At 10.28 a.m., 102 min after the aircraft impact, WTC1 began to collapse.
The sentence at the end, that you bolded, is actually from two pages later in the report.
This strange editing appears designed to convey several false ideas about what NIST actually said in the paragraph.
- It omitted all mention of the damage caused by the airplane impact, creating the false impression that NIST is attributing the effects that follow solely to "the subsequent fires."
- It omits the sagging of the floor and the buckling of the wall, creating the false impression that the downward displacement of the core was the individual initiating event, instead of occurring along with other changes in the structure. Actually, the report is quite clear that the instability that initiated the collapse "started at the center of the south wall and rapidly progressed horizontally to the sides." (Pg. 314)
- It omits the phrase "than the state after impact" from the section pasted in from a later paragraph, creating the false impression that the figures given from increased loads were increases over the original building loads, instead of increases over the already increased and unbalanced loads experienced as a result of the impact damage.
- It inserts and appends sentences from later paragraphs, out of sequence, obfuscating the five-stage sequence that the report actually delineates very clearly.
NIST suggests that the potential energy of the mass above was released when all columns in the initiation zone simultaneosuly failed. No evidence for that. It is clear from all evidence that the mass above moved when all visible columns below were intact!
The edited version you posted suggests that, yes. But the original report says:
Instability started at the center of the south wall and rapidly progessed horizontally toward the sides. As a result of the buckling of the south wall, the south wall was 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 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 inn increased gravity load on the core columns.
That is not a simultaneous failure, though it was a rapidly progressing one. Why was the paragraph edited to suggest something that the original report did not suggest?
It is then assumed that all the potential energy thus released and transformed into kinetic energy then IMPACTED other structure. No evidence for that.
And it is only if there is an IMPACT that strain energy of structure is of interest.
Kinetic energy and strain energy are relevant factors as long as there is movement, which there was, specifically an 8° tilt, in NIST's Event 5. "Impact" is not mentioned in the NCSTAR chapter being referenced here, so no "assumption" of impact was made. It's not NIST's fault that the edited paragraph you posted rearranged the text to juxtapose a statement regarding movement of the structure, and consequent kinetic and strain energies, with the fire-weakening effects they describe in Events 3 and 4.
The above error on one page of the NIST report disqualifies the 10 000 other pages.
Who edited the report to introduce those errors, and why? I'd say that disqualifies the person who moved the words around, rather than the actual report.
Respectfully,
Myriad
).
