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originally posted by: reldra
originally posted by: CALGARIAN
Yes, this was def FINALLY resolved... back in 2001.
The MASSIVE amount of fire debris that crushed the side of the building caused it to collapse.
WHY (or who) would have planted explosives in WTC7? lol.
I had thought the owner of the building made the call, so the building would have been pre-wired for detination.
I imagine there had been multiple different plans like this since the 1993 bombing.
I can't find the videos where either a security head or a designer repeatedly said it would happen again after 1993 and asked for upgrades in security protocols, etc after the1993 bombing, maybe someone can assist in finding that, as I know I saw them.
To calculate the kinetic energy used in the tower destruction takes a moment, after a simple thought experiment, namely considering the tower would fall at G if there were NO resistance, and if it fell so slowly that it consumed ALL its energy, it wouldn’t fall at all. So we can see that the PROPORTION of the energy used up by the collapse must equate with the proportion of G which the collapse was unable to achieve.
As the collapse acceleration was, by truther calculation, established to be about 70% of the acceleration due to gravity, we’ll use that.
Tony Duncan : The energy used up in tower destruction was 30% of 246, or 73.9 tonnes of TNT.
Assuming that 30% of the tower fell outside of the basement, then the energy (Er) available to heat the wreckage base (by elastic energy transfer and crushing) was 0.70 * (246 - 73.9), or 120 tonnes of TNT.
We know that the steel reached at least 1,000 degrees Centigrade because that is the melting point of iron sulfide.
We can therefore calculate the mass (m) of steel that was raised to that temperature.
The specific heat of iron (Fs) is known to be 0.45e6 Joules / tonne / degree Celsius.
The ambient temperature was 20 deg C, so the temperature rise (Tr) was 980 degrees Celsius.
Equation: Er = m * Fs * Tr, so m = Er / Tr * Fs = ( 120 * 4.184e9 ) / 980 * 0.45e6
And so m = 5.02e11 / 4.41e8 = 1,138 tonnes - that is, tonnes of red hot steel at 1,000 degrees Centigrade.
So we can see that there is no need to postulate an extra source of energy, and that the basement wreckage heat is also easily accountable, with the additional corroboration of burning hydrogen at the wreckage surface, and molten iron sulfide at the wreckage base.
And so the underlying 'truther' assumption, that the planes couldn't bring down the towers, is shown to be FALSE, as it is shown by calculation, using the physically-correct values, that the potential energy possessed by the towers numerically accounts for ALL the known consequences, through elastic energy transfer, plastic deformation, and HEAT. These results are EVIDENCE of the event. They have been evident to any REAL scientist or engineer from day 1.
Gourley : The Bažant/Greening paper repeated and expanded upon Dr. Bažant’s theory of crush down/crush up collapse progression. This crush down/crush up theory was first developed by Bažant in 2001, and expanded on by Bažant & Zhou in 2002, and Bažant & Verdure in 2007.
I find the crush down/crush up theory completely unbelievable for the reasons I stated in my paper.
Page 914 JEM, Szuladzinski : The strain energy (as a measure of resistance to be overcome), which is needed to collapse the column, is larger than the potential energy available. The conclusion is that the motion will be arrested during the damaged story collapse and the building will stand.
-- snip --
Equating kinetic and strain energies gives a result of 7.238 x 10^9 ( read it ! )
This means a free fall from 3.69 m ( read it ! )
This is more than one story and is clearly beyond the range of possibilities.
-- snip --
In summary, the postulated failure mode is not a proper explanation of the WTC Towers collapse, as concluded from several criteria used previously. The visual evidence is not favorable to this theory, either. There was an absence of “kinks” or “elbows” from bent columns sticking out and visible in the early phase of the fall
Bažant's Closure article, PDF-page 7/11 (art. p.920) : The fact that some perimeter columns showed gradually increasing lateral deflections, reaching as much as 55 in. (or 1.40 m) [ NIST (2005), part NCSTAR-1, Chapter 2, p. 32 and Fig. 2–12 ], cannot be explained as anything other than creep buckling of heated columns.
--snip--
The visible bowing of columns appears to have spanned about three stories, etc.
Dear Professor Bažant,
This open letter is being sent to you to request that you correct your four papers on the collapse of the WTC Towers, which were published by the Journal of Engineering Mechanics.
In these papers, the values used for the below three items:
* The velocity of the descending upper section of the building
* The mass of the descending upper section of the building
* The column strength of the underlying story at the impact floor
have been shown in the intervening years to be significantly unrepresentative of the actual situation concerning the North Tower (WTC 1) at the time of its collapse.
Tony Szamboti : By your use of free fall through the first story of the collapse it would seem that you had not measured the descent from video. Others have measured it, and the velocity after a fall of one story is approximately 6.13 meters/sec and not the 8.52 meters/sec velocity, resulting from a free fall through one story, used in your papers. This leads to a near doubling of the velocity component in the kinetic energy of the upper section, since it is squared with 6.13^2 = 37.58, while your velocity is squared with 8.52^2 = 72.59.
(LT : I expanded/explained this last line of text only a tad bit, to make things clearer for the casual reader, this is Tony's original text :
- - ,since it is squared with 6.13^2 = 37.58, and 8.52^2 = 72.59.)
Your papers show a mass of either 58 x 10^6 kg or 54.18 x 10^6 kg for the descending upper section, which seem to correspond to 15 or 14 stories at the 3.87 x 10^6 kg per story mass given in two of your papers. The collapse initiation in the North Tower actually occurred at the 98th story and the actual in-service load of the 12 story upper section can be calculated, based on story masses from the NIST report, as 33 x 10^6 kg. This would equate to an average of 2.75 x 10^6 kg per story.
Interestingly, in the second page of the addendum to your first paper (Bažant and Zhou 2002) you used the vibration period of the tower (14s) to estimate the mass of 44% of the 117 stories of the tower as 141 x 10^6 kg. If this partial mass is divided by 0.44 it gives a full mass of 320.45 x 10^6 kg for the whole tower. When this full mass is then divided by 117 stories it gives 2.74 x 10^6 kg per story. This is very close to what can be discerned from the NIST report and thus your own calculations tend to confirm it.
(LT : Each tower consisted of a 110-story above-grade structure and 6-story below-grade structure.)
It is thus confounding as to why you used a 3.87 x 10^6 kg per story mass in your papers. This per story mass seems like a maximum design load and not the actual in-service load. Use of a maximum design load, when that is not what was present during the failure, will prevent any forensic analysis from being accurate.
The overestimates of velocity and mass of the descending upper section in your papers cause it to have a kinetic energy which is several times what it actually would have been. Of course, this would make a collapse propagation more likely.
In your January 2011 paper (Le and Bažant) you show a total cross sectional area, for the 287 columns on the underlying story at the impact floor, of 6.05 m2. This would be for an average 14 inch square box column with a wall thickness of 15.49 mm (0.610 inches). However, you then give an average yield bending moment of 0.32 MNm, which calculations show would be for much thinner, weaker, and less energy dissipative, 14 inch square box columns with a wall thickness of 6.75 mm (0.266 inches) These 6.75 mm wall columns would only give a total cross sectional area of 2.70 m2.
It does not make sense that you would give a total cross sectional area of 6.05 m2 and then give an average yield moment for columns having a total cross sectional area of 2.70 m2.
The actual total column cross sectional area at the 97th floor for the 287 columns is approximately 4.00 m2 and the average yield moment there is approximately 0.75 MNm.
Additionally, in the 2011 paper, the mass of one story, used for the conservation of momentum loss calculation, is shown as 0.627 x 106 kg. However, as mentioned above, in earlier papers you show it as 3.870 x 106 kg. The use of this lower figure in your calculation causes velocity loss due to conservation of momentum to be just 1.1%. With the greater mass it would have been about 7.1% from conservation of momentum alone, without even considering the column resistance losses yet. It seems this 0.627 x 106 kg mass is that of just the concrete slab.
It does not include all of the additional mass on a story, which would bring it to the 2.750 x 106 kg mass that NIST shows, and that you also determined, but did not use, with your vibrational period and a concentrated mass on a massless cantilever analysis.
In the 2011 paper, you claim that the velocity loss would only be about 3% and thus too small to observe with the available video resolution. However, that would be far from the case if you corrected the velocity, mass, and column size to reflect the actual conditions.
A Canadian professor, Richard Johns, and I did submit a Discussion paper to the Journal of Engineering Mechanics in 2011 regarding these errors and they took 27 months before finally telling us our Discussion was “out of scope”, although it only discussed your January 2011 paper and corrected its errors.
I am not sure if you are aware of this and am attaching a letter on our experience, which also includes our Discussion of your paper.
Abstract :
This article elaborates on variables associated with the collapse of the North Tower of the World Trade Center. The previously published quantification of inertia, column capacity, and the assumptions related to the beginning of downward motion, are examined and corrected. The reasons for false conclusions reached in several previous analyses are presented.
ABSTRACT :
We derive discrete and continuous class of mathematical models that describe a progressive collapse in a fictional one-dimensional structure, where we consider plastic and elastic types of collisions.
We examine static (collapse initiation lines, derived from the ultimate yield strength of the structural steel) and dynamic (duration of collapse, computed using mathematical models) features of events that comprised the collapse in WTC 1 and 2.
We show that
(a), the dynamic and static aspects of the collapse are mutually consistent and weakly dependent on the class or type of mathematical model used, and
(b), that the NIST scenario, in which the buildings collapse after a sequence of two damaging events (airplane impact and subsequent ambient fires), is inconsistent with respect to the structural strength of the buildings.
Our analysis shows that the force that resisted the collapse in WTC 1 and 2 came from a single structural element, the weaker perimeter columns, while the second structural element, the stronger core columns, did not contribute.
We discuss two non-obvious inconsistencies between the mathematical models of progressive collapse based on the NIST scenario, and the practical realizations of collapse in WTC 1 and 2 :
(i), the average avalanche pressure is 3 orders of magnitude smaller than the pressure the vertical columns are able to withstand, and
(ii), the intact vertical columns can easily absorb through plastic deformation the energy of the falling top section of the WTCs.
We propose collapse scenario that resolves these inconsistencies, and is in agreement with the observations and with the mathematical models.
ABSTRACT :
We derive a mathematical model of progressive collapse and examine role of compaction.
Contrary to a previous result by Bažant and Verdure, J. Engr. Mech. ASCE 133 (2006) 308, we find that compaction slows down the avalanche by effectively increasing the resistive force.
We compare currently available estimates of the resistive force, that of Bažant and Verdure (2006) corrected for compaction for World Trade Center (WTC) 2, and of Beck, www.arxiv.org:physics/0609105, for WTC 1 and 2.
We concentrate on a damage wave propagating through the building before the avalanche that figures in both models:
* an implicit heat wave that reduces the resistive force of the building by 60% in Bažant and Verdure (2006), or
* a wave of massive destruction that reduces the resistive force by 75% in Beck (2006).
We show that the avalanche cannot supply the energy to the heat wave as this increases the resistive force by two orders of magnitude.
We thus reaffirm the conclusion of Beck (2006) that the avalanche is initiated in the wake of the damage wave.
Abstract :
We examine four WTC 7 descent curves, labeled "C," "E," "N," and "O," either anonymously published, or confidentially communicated to us. Descent curve describes apparent height of a collapsing building as a function of time.
The set "C" suggests that there are three active phases of collapse.
Phase I is a free fall for the first H1 =~ 28m or T1 =~ 2.3s, during which the acceleration a is that of the gravity, a = g = 9.8m/s^2.
In Phase II, which continues until drop H2 =~ 68m, or T2 =~ 3.8s, the acceleration is a =~ 5m/s^2,
while in Phase III which continues for the remaining of the data set, a =~ -1m/s^2.
We propose that the collapse of WTC 7 is initiated by a total and sudden annihilation of the base (section of the building from the ground level to H1), which then allows the top section (building above H1) to free fall during Phase I, and then collide with the ground in Phase II and III.
The total duration of the collapse, assuming that Phase III continues to the end, is in the range 7.8−8.6s.
We derive a physical model for collision of the building with the ground, in which we correct the "crush-up" model of Bažant and Verdure, J. Engr. Mech. ASCE, [bf 133] (2006) 308, and estimate the magnitude of the resistive force in the top section.
We compare our findings to those of NIST investigators and find an agreement with respect to the distribution of damage in the primary zone. We conclude that the building was destroyed in a highly controlled fashion.
Abstract :
In this paper, we study the progressive collapse of 3D framed structures made of reinforced concrete after the sudden loss of a column. The structures are represented by elasto-plastic Euler Bernoulli beams with elongation-rotation failure threshold. We performed simulations using the Discrete Element Method considering inelastic collisions between the structural elements. The results show what collapse initiation and impact-driven propagation mechanisms are activated in structures with different geometric and mechanical features.
Namely, we investigate the influence of the cross sectional size and reinforcement 'alpha' and of the plastic capacity 'beta' of the structural elements. We also study the final collapse extent and the fragment size distribution and their relation to 'alpha', 'beta' and to the observed collapse mechanisms. Finally, we compare the damage response of structures with symmetric and asymmetric reinforcement in the beams.
For instance, we know that the loss of external columns from the facades or the corners of a buildings are the most serious scenarios where, according to the ALPM method, one column is instantaneously removed (see, e.g. (Kaewkulchai and Williamson, 2003)). Moreover, it was shown that beam-column connections are critical points of failure initiation (Khandelwal et al., 2008) and that catenary effects in the floor slabs can remarkably improve robustness (Vlassis et al., 2006).
Even though the final outcome of progressive collapse depends on the collisions between structural elements, most of literature focuses on collapse initiation. Collisions are rarely taken into account either detailed with Finite Elements (Hartmann et al., 2008; Luccioni et al., 2004), or approximated in the framework of Finite Macro-Elements (Kaewkulchai and Williamson, 2006; Grierson et al., 2005). Detailed Finite Elements are too demanding in terms of computational time for extensive parametric studies on large structures. Differently, Finite Macro-Elements are efficient and can be applied to large structures, but they require strong approximations to take into account collisions and catenary effects, especially in 3D (e.g. see (Isobe and Tsuda, 2004)).
The lack of experimental results of progressive collapses suggests an approached based on simulations whose reliability arises from the basic physics incorporated. The results obtained with such algorithms can be used to construct, test and calibrate simpler models. In this work, we use spherical Discrete Elements (DE) to simulate the progressive collapse of typical 3D framed structures made of reinforced concrete with fixed regular overall geometry (see Sec. 2).
The aim is to study the collapse initiation mechanisms due to dynamic stress redistribution, and the subsequent damage propagation mechanisms due to collisions between the structural elements. Understanding the activated mechanisms, depending on the strength, the stiffness and the plastic properties of the structural elements, can help to choose optimal robustness oriented design solutions as well as the most appropriate structural reinforcement of existing buildings. We perform parametric studies scaling the cross sectional size and reinforcement by the cross sectional scale factor 'alpha' and varying the plastic capacity 'beta' of the structural elements (see Sec. 3). In this way, we show the expected collapse mechanisms and the final consequences of progressive collapse in terms of final collapse extent and fragment size distribution for various ( 'alpha', 'beta' ). Finally, in Sec. 4 we compare the damage response of structures with symmetric and asymmetric reinforcement in the beams.
B.M. Chiaia and E. Masoero. Analogies between progressive collapse of structures and fracture of materials. Int. J. Fract., 154(1-2):177-193, 2008.
D. Hartmann, M. Breidt, V. van Nguyen, F. Stangenberg, S. Hoehler, K. Schweizerhof, S. Mattern, G. BlankenHorn, B. Moeller, and M. Liebscher.
Structural collapse simulation under consideration of uncertainty - fundamental concept and results. Comput. Struct., 86(21-22):2064-2078, 2008.
D. Isobe and M. Tsuda. Seismic collapse analysis of reinforced concrete framed structures using the finite element method. Earthq. Eng. Struct. D., 32(13):2027-2046, 2004.
B.M. Luccioni, R.D. Ambrosini, and Danesi R.F. Analysis of building collapse under blast load. Eng. Struct.,26:63-71, 2004.
S. Marjanishvili and E. Agnew. Comparison of various procedure for progressive collapse analysis. J. Perform. Constr. Fac., 20(4):365-374, 2006.
R.S. Nair. Progressive collapse basics. Modern Steel Constr., 44(3):37-44, 2004.
K.A. Seffen. Progressive collapse of the world trade center. J. Eng. Mech.-ASCE,134(2):125-132, 2008.
D.V. Val and E.G. Val. Robustness of framed structures. Struct. Eng. Int., 16(2):108-112, 2006.
A.G. Vlassis. Progressive collapse assessment of tall buildings. PhD thesis, London Imperial College, UK, 2007.
A.G. Vlassis, B.A Izzudin, A.Y. Elghazouli, and D.A. Nethercot. Design oriented approach for progressive collapse assessment of steel framed buildings. Struct. Eng. Int., 16(2):129-136, 2006.
The NIST stopped their analysis at a point where the report says the building was “poised to collapse” when the south exterior wall purportedly buckled. There is no analysis or explanation provided in the report for the horizontal propagation across the building. The NIST report simply moves from a single buckled exterior wall to your analysis for substantiation of vertical propagation. I am not sure if you are aware, but the actual horizontal propagation occurs from the southwest to northeast corners (a distance of nearly 300 ft.) across the 98th floor of the North Tower in less than a second. The measurement of the vertical descent/propagation does not show any deceleration, at any time. Focused ejections can be observed emanating from the corners and the sides of the building during the collapse. None of these three observations can be explained easily as being due to naturally caused occurrences, but can easily be explained by the use of charges.
Unfortunately, the possibility that there were charges in the buildings has not been investigated up to this point and it would appear that your papers, with these errors still intact, have provided some level of umbrage for those who presently insist it is not necessary. It is hard to believe you would approve of that knowing there are errors. It is sincerely hoped that you will correct these errors now that they have been brought to your attention. Once they are corrected your analyses can no longer be used as an argument against a new investigation to look into those things which were missed in the first attempt to investigate these collapses.
Sincerely,
Anthony Szamboti
CC :
Office of the president of Northwestern University.
Dean of the Engineering School at Northwestern University.
Office for Research Integrity at Northwestern University.
Architects & Engineers for 911 Truth.
Journal of 911 Studies.
All of Dr. Bažant’s papers use free-fall acceleration through the first story and the maximum design load mass of the falling upper section. Neither of these are representative of the actual situation, so this causes an embellishment of the upper section’s kinetic energy in his papers. He also significantly under-estimates the energy dissipation due to column deformation during impact. Dr. Bažant has been made aware of these problems with his hypothesis, and in January 2011 he had a paper published by the Journal of Engineering Mechanics where, with a graduate student as his co-author, he tried to claim the deceleration would not be observable. This paper has been shown to use fraudulent values for both inertial and column deformation energy losses.
However, NIST continues to use his work.
Recent research using test results versus the three-hinge method for estimating energy dissipation caused by plastic hinge formation in axially-loaded buckling columns has shown the three-hinge method to significantly underestimate it —and this is without using fraudulently low column plastic moment (Mp) values, as Le and Bažant did in their Jan. 2011 paper.
This research provides even more support for the contention that the lack of deceleration in the descent of WTC 1 is a severe impediment for a natural-collapse scenario.