[FONT="]There are numerous problems with the collapse of the girder between columns 79 and 44 on floor 13.[/FONT]
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[FONT="]1)[/FONT][FONT="] The girder collapses twice.[/FONT]
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[FONT="]2) [/FONT][FONT="] NIST deleted key words from a paragraph in the NIST L report in order to claim the absence of shear studs on the girder between columns 79 and 44. [/FONT]
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[FONT="]3)[/FONT][FONT="] NIST brought the temperatures of the beams and girder up to 600oC and 500oC respectively, over their entire length in less than 3 seconds.[/FONT]
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[FONT="]4) [/FONT][FONT="]NIST did notinclude the expansion of the floor slab in their calculations for the computer model that showed the shear studs on the beams failing. Concrete expands at 85% the rate of steel.[/FONT]
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[FONT="]1) 1-9 Vol.1 pg 353 [/FONT][FONT="][397 on pg counter][/FONT]
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[FONT="]“Axial compression then increased in the floor beams, and at a beam temperature of 436°C, shown in Figure 8-27 (a), leading to the collapse of the floor system, and
rocking the girder off its seat at Column 79 as shown in Figure 8-27 (b)"
[to the east][/FONT]
[FONT="]http://nasathermalimages.s3.amazonaws.com/public/images/NIST_NCSTAR_1-9_Vol1_for_public_comment_unlocked.pdf[/FONT][FONT="][/FONT]
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[FONT="]1-9 Vol.2 pg 487 [/FONT][FONT="][149][/FONT]
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Walk-off failure of beams and girders was defined to occur when (1) the end of the beam or girder moved along the axis of the beam until it was no longer supported by the bearing seat, or (2)
the beam or girder was pushed laterally until its web was no longer supported by the bearing seat. [/FONT]
[FONT="][see pg 33 Tech Brief] [/FONT][FONT="]http://wtc.nist.gov/media/WTC7_Technical_Briefing_082608.pdf[/FONT][FONT="][/FONT]
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[FONT="]1-9 Vol.2 pg 525[/FONT][FONT="] [187][/FONT]
[FONT="]A girder was considered to have lost vertical support when its web was no longer supported by the bearing seat. The bearing seat at Column 79 was 11 in. wide. Thus, when the girder end at Column 79 had been pushed laterally at least 5.5 in.[/FONT][FONT="] [to the west][/FONT][FONT="], it was no longer supported by the bearing seat.[/FONT]
[FONT="]http://nasathermalimages.s3.amazonaws.com/public/images/NIST_NCSTAR_1-9_vol2_for_public_comment_unlocked.pdf[/FONT][FONT="][/FONT]
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2) In their June 2004 report, NIST referred to the use of shear studs in World Trade Center 7. Shear studs are used to keep steel floor beams and girders in place; they impart stability and strength to buildings. But in their August 2008 final report, NIST re-worded their comments on shear studs to make it appear that none were used on the floor girders.
Why would they do this? To know the answer, you need to understand NIST's collapse theory. This is how it goes:
1. The key girder between column 79 and the exterior wall fails at floor 13.
2. Its failure causes the collapse of floors 13 through 6.
3. Column 79, now unsupported laterally by these floors, buckles and brings down the entire building.
This scenario is easier to posit if the key girder isn't being held firmly with shear studs. Thus, in the August 2008 report, NIST did what it had to do to make it more reasonable that the girder would fail: It magically omitted the shear studs.
Compare these two paragraphs. In the excerpted paragraph of the 2004 report, NIST says that studs were used with both beams and girders, although the studs "were not indicated on the design drawings for many of the core girders" (the girder associated with column 79, by the way, was not a core girder). In the 2008 report, however, not only does NIST drop the association of girders with shear studs ( first sentence of excerpted paragraph), but then they go on to imply that studs were not indicated at all on the girders (last sentence of excerpted paragraph):
June 2004 NIST L pg 6 [10 on pg counter]
Most of the
beams and girders were made composite with the slabs through the use of
shear studs. Typically, the shear studs were 0.75 in. in diameter by 5 in. long, spaced
1 ft to 2 ft on center.
Studs were not indicated on the design drawings for many of the core girders.
http://wtc.nist.gov/progress_report_june04/appendixl.pdf
August 2008 NCSTAR 1-9 vol.1 pg 15 [59]
Most of the
beams - - - - - - - - - were made composite with the slabs through the use of
shear studs. Typically, the shear studs were 0.75 in. in diameter by 5 in. long, spaced
- - - - 2 ft on center*.
Studs were not indicated on the design drawings for - - - - - - the - - - - girders.
http://nasathermalimages.s3.amazona...STAR_1-9_Vol1_for_public_comment_unlocked.pdf
Then, in this paragraph of the 2008 report, they use the "absence" of shear studs to help make their case:
August 2008 NCSTAR 1A pg 49 [87]
At Column 79, heating and expansion of the floor beams in the northeast corner caused the loss of connection between the column and the key girder.
Additional factors that contributed to the failure of the critical north-south girder were (1) the absence of shear studs that would have provided lateral restraint and (2) the one-sided framing of the east floor beams that allowed the beams to push laterally on the girders, due to thermal expansion of the beams.
http://nasathermalimages.s3.amazona...IST_NCSTAR_1A_for_public_comment_unlocked.pdf
This deliberate distortion of the evidence can only be called fraud. Even those who have accepted the official story must acknowledge that NIST's isstatements of its own report are not mistakes. They are bending the facts to accommodate a theory that cannot, so to speak, stand up.
* "on center" - a term that means “apart”
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[FONT="]This bit of sophistry seems to be their reasoning:[/FONT]
9-1 pg 15 [59]
"The structural design drawings (Irwin G. Cantor P.C., Structural Engineers 1985) specified design forces for connections and suggested a typical detail, but did not show specific connection designs; this was standard practice on the U.S. east coast. The erection drawings (Frankel Steel Limited 1985) indicated that design shear forces for the typical beam and girder connections were to be taken from the American Institute of Steel Construction (AISC) beam design tables for beams without shear studs, using 1.5 times those forces for beams with shear studs. However, actual connection designs were obtained from fabrication shop drawings (Frankel Steel Limited 1985a), which provided detailed descriptions of the floor connections and column splices in WTC 7."
This paragraph is discussing shear forces for floor beam and girder connections. It does not say there were no shear studs on the floor beams and girders, yet they conclude that there were shear studs on the beams but not the girders.
This paragraph can be interpreted two ways.
1) The designers made the beam and girder connections stronger because they did not use shear studs. [to cut cost]
2) The designers were making the beam and girder connections stronger than the minimum requirements by 50%. [would not add a great deal of cost]
There is no justification for assuming there were no studs on the floor girders.
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[FONT="]3) NCSTAR 1-9 Vol.1 Pg 351[/FONT][FONT="] [/FONT]
[FONT="]To avoid dynamic effects, the gravity loading was ramped up smoothly over a period of 1 s, as shown in Figure 8–24.
Ramping of the temperatures for the beams and the girder then commenced at 1.1 s, as shown in Figure 8–25, leveling off at temperatures of 600 °C for the beams and 500 °C for the girder at
2.6 s. These temperature histories were prescribed uniformly for all nodes of the beams and the girder, respectively. The material model for the steel beams and girders incorporated temperature dependence in the stress-strain behavior and accounted for thermal expansion. [/FONT]
[FONT="]4) [/FONT][FONT="] No thermal expansion or material degradation was considered for the concrete slab.[/FONT]