The author is a naval architect with 40 years of steel structural design experience including structural damage analysis. He has investigated the structural damage from many ship collisions. The destruction of WTC1 is in many respects similar to a collision between two steel ships!
At the moment of contact of A) the 'WTC upper part and lower structure' or B) 'two ships in collision', a certain momentum (mass times velocity), energy (momentum times velocity divided by 2) and force (energy divided by displacement) are involved. Acceleration does not come into the picture! Local failures occur, energy is absorbed, friction between failed parts in contact develops, forces and loads are re-distributed and the destruction is always arrested after a while as will be shown below. Or the ships just bounce against each other!
It is quite simple to learn what happens in collisions or impacts! Gravity alone will not suffice to crush anything.
Just drop Anything on Something
Start with a solid rubber ball, mass m (kg) and drop it on the floor from height h = 3.7 meters height = the height that WTC1 upper part is assumed to drop. The ball free falls with acceleration g (9.81 m/s²) due to gravity, makes contact with the floor and normally bounces. The ball was not rigid and deformed upon contact with the floor. Why? The floor applied a force on the solid rubber ball, so that it deformed, absorbed some of the kinetic energy E involved (E = m*h*g) and then released it and bounced up. Evidently the ball also applied a force on the floor that also deformed, absorbed the remainder of the energy involved; maybe the floor vibrated a little. This is Newton's third law at work.
Then do the same thing with a solid sphere of steel. Drop it on the floor. If the floor is strong enough, the same thing will happen as with a rubber ball! The steel sphere bounces. If the floor is not strong enough, i.e. it cannot produce a force big enough to deform the steel sphere, so that it bounces back, the floor will be damaged - maybe a hole is formed in it, and the steel sphere drops through the hole at reduced speed and contacts something else below, or the floor is just partially damaged ... and catches the steel ball, i.e. arrests it.
Finally drop anything weak (an egg or a lemon?) on something strong! PLAFSH! The weak anything (the egg or lemon!) is crushed against the strong something!
Don't forget that!
Try to compress a lemon with another lemon. What happens? Both lemons compress.
Now you have learnt a little what can happen when you drop anything on something and try to compress something. This basic knowledge is used in this paper.
And then you have to work from there. Do the analysis step by step! In A) a vertical drop, gravity is always at work and produces forces acting on the various damaged parts and you have to include that, in B) a horizontal collision, the propulsion force of the ship may still be active and you have to consider that.
| When two bodies of similar steel structure but different size collide, both bodies are evidently deformed at the common contact area. Stronger structural sub-parts will affect weaker structural sub-parts in both bodies, i.e. the weaker steel parts fail before the stronger ones. No rubble of steel parts is generally produced as all parts, even broken ones, are still connected to other parts. Only rubble is damaged furniture and similar inside the steel structure and is of no importance. |
What is a Drop?
If the upper, 53 meters tall, 13-15 storeys upper part of WTC 1 actually dropped on the structure below is a matter of semantics. Drop suggests that it was not being held at all. I prefer that it came into contact after local structural failures and downward displacement and that it was prevented from dropping by the connections between the two parts. Anyway, only the velocity at contact is of interest and it was not high in the WTC 1 case. Assuming a 'drop' of 3.7 metres, it does not produce a big velocity; it is around 8 m/s. If the 'drop' is dampened by intermediate connections the velocity is much less. All will be explained below.
Assuming in A) above (WTC 1 upper part drops on the lower structure with perfect alignment columns/columns) that the two parts act as springs (disregarding local failures), the upper part would just bounce as described in one of my other articles. No global collapse would ensue! This article is a follow-up of this conclusion.
In B) above (ships colliding) the contact velocity may be up to 10 m/s and the masses up to 200 000 tons, so it should be clear that in B) 8 times bigger momentums and 10 times more energies may be involved compared with A).
Dr Bazant (described below) and NIST suggest that the energy initiating or released at the WTC 1 destruction was enormous but in a serious ships collision it can be up to 10 times bigger!! NIST should learn from ship collisions! Bazant also assumes that the WTC 1 upper part was rigid (!). A rigid object is indestructible and will destroy anything non-rigid. But ships and WTC 1 upper part are not rigid.
The structural damage analysis are quite similar for A) and B). Very few mechanical, civil or building engineers have studied the subject (99.9% concentrate on design of new, intact structures) but there is nothing new about structural damage analysis. No need to write scientific papers about it, as it was a new event that had never happened before and needed explanation. Structural damages (ships collisions) occur every day. Steel structure tower collapses are much more rarer.
The Bazant papers described below are therefore very suspect. Enjoy this article. Comments are always welcome. And thanks for comments already given.
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North and West (right) walls of WTC 1 just prior destruction. According basic structural analysis no failed parts of the upper part can damage the solid columns below the initiation zone. This is the beauty of steel structure design. If a part fails and loads are displaced by gravity, only secondary, weaker parts may fail (mostly floors) as a consequence. The intact primary structure below cannot fail! | The official Explanation(s) The official explanation(s) of the WTC 1 (photo left) global collapse (sic) is that the alleged release of potential energy (PE), of the mass of an upper part C above all supporting columns after sudden, local deformation and buckling, due to downward, alleged near free fall movement in an initiation zone (indicated by red) and impact of a structure below, exceeds the strain energy (SE) that can be absorbed by the same columns below and above and that all this was due to gravity only. It is suggested that the upper part C is rigid and remains intact during the complete crush down of the WTC 1 structure below, i.e. the global collapse (sic) is not a collapse but a 'crush down'. The crush down is suggested to take place as follows: WTC 1 is assumed to consist of three parts: |
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| Part A - the lower structure (97 stories before crush down). Part C - the upper part (13-15 stories). Part B - rubble that is formed of part A, when part C crushes the stories one after the other. Each storey is 3.6 meters tall with density 0.255 and becomes a 0.9 meter thick layer or rubble with density 1.025, when crushed, e.g. [2]. At time t = 0 sec part C is alleged to drop on part A - crush down starts. At, say, time t = 8 seconds about 60 stories have been crushed and there are still 37 stories remaining of part A. A 54 meters thick layer of rubble - part B - has been formed of what was 60 stories! The upper part C remains on top. At time t = 10 seconds part A is completely crushed and only a 87.3 meters thick - very tall! - layer of rubble on the ground - part B - remains of part A. The upper part C still remains on top. At time t = 15 seconds nothing remains! Part C has been destroyed in a crush up and the rubble - part B - is spread out on the ground. |
What you would expect to happen
The following would happen, if the upper part C actually drops; two of its thin walls slide and drop outside and do not damage anything. The other two thin walls slide and fall inside the structure - part A - below and punch holes in or slices the floors there locally. No rubble is really formed.
The thin floors of the upper part C are in turn locally punched or sliced by the part A walls/columns below and will soon be jammed inside the part A walls/columns below. No walls or columns are dropping on other walls or columns producing an impact! Do not believe that the upper part C is solid, rigid, strong or anything like that! It is quite weak. Local failures - floors punched and sliced - will be produced at contacts. No crush down will ever start!
| Local gravity failures above cannot destroy the columns of the intact structure below! All the energy released by dropping upper part C is absorbed by the deformations, failures and fractures of floors in the initiation zone and locally in the upper part C and top of lower structure part A and by friction between locally failed floor parts rubbing against each other after initiation and by any loose parts dropping down outside. The crush down should be arrested inside the initiation zone! Or maybe upper part C would slip off and drop beside the structure below. |
NIST explains Something else
From NIST report - NIST NCSTAR 1-6D chapter 5.2:
"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 (PE) due to downward movement of the building mass above the buckled columns exceeded the strain energy (SE) that could be absorbed by the structure. Global collapse ensued."
The global collapse (sic!) that ensued can be seen here!
Rigid Blocks, Boxes or Sponges
NIST speaks of the core of WTC 1 as consisting of three sections - NIST NCSTAR 1, p. 79: "At this point, the core of WTC 1 could be imagined (sic) to be in three sections. There was a bottom section below the impact floors (i.e. below floor 93) that could be thought of as a strong, rigid box, structurally undamaged and at almost normal temperatures. There was a top section (the upper part above floor 98) above the impact and fire floors that was also a heavy, rigid box. In the middle was the third section, partially damaged by the aircraft and weakened by heat from the fires."
The section of the building above the damage zone, the upper part, NIST calls a "rigid box."
This rigid box first manifests its independent movement, when it tilts to the south - NIST NCSTAR 1, p. 201: "The section of the building above the impact zone (near the 98th floor), acting as a rigid block, tilted…".
NIST also refers to this rigid block or box with terms such as "upper section," "building section above the impact zone," "building mass," "upper building section" and "structural block." - NIST NCSTAR 1, pp. 83, 195, 196, 201.
However, you have to treat the upper part structure/stiffness in 3-D and then it becomes very springy - like a sponge; light structure of elastic material full of holes able to absorb water. It is quite difficult to destroy a sponge dropping another sponge on it. The other sponge bounces.
NIST acknowledges that this rigid block or box, upper part, then falls. NIST says that "the building section began to fall downward," "the building section began to fall vertically."
It is suggested that this falling rigid block goes through all or part of the damaged area or initiation zone "essentially in free fall." : "Since the stories below the level of collapse initiation provided little resistance to the tremendous (sic) energy released by the falling building mass, the building section above came down essentially in free fall, as seen in videos." - NIST NCSTAR 1-6, pp. 416, 238; NIST NCSTAR 1, p. 196.
Seen in videos? Where?
After falling through all or part of the damaged area of WTC 1, the rigid block or falling building mass - the upper part - encounters "intact structure." And, no surprise: "The potential energy released by the downward movement of the large building mass far exceeded (sic) the capacity of the intact structure below to absorb that through energy of deformation." - NIST NCSTAR 1, p. 196. This is very strange! The intact structure was previously described as a rigid box!
Energy of deformation is the same as strain energy!
What is Strain Energy and can you calculate it?
Strain energy (SE) is simply speaking a measure of the strength of the structure that holds it together. Apply outside energy on the structure that exceeds the strain energy that can be absorbed and the structure deforms or fails locally. Evidently the strain energy of the structure at every floor above, the upper part, and in the structure below the initiation zone was about the same. However, in all official explanations of the collapses it is assumed that the upper part is rigid with infinite strain energy from start and therefore will not deform and will absorb no amounts of extra strain energy at all! All free energy at impact is therefore assumed being directed down into the lower non-rigid structure by NIST and its supporting experts.
The upper part is, however not rigid and can only absorb very limited strain energy during a crush down prior it self-destructs and the destruction is arrested. To assume the opposite in various papers described below and indirectly by NIST is simply to mislead the public. The upper part has a very limited capability to absorb strain energy and that is the main reason why it cannot crush down the structure below and produce rubble. On the contrary - the upper part structure should be subject to serious structural failures at impact and absorb the energy released and arrest further destruction. Not so difficult to grasp. That's why steel buildings of any type are not crushed down by gravity acting on a loose top part due to local failures.
| Every time you break a piece of structure, strain energy is consumed. The amount of strain energy built into a structure thus depends on how many times you break the pieces. The amount of potential energy, PE, due to downward movement of the WTC 1 upper part mass was definitely too small to destroy the lower structure in 100 000's of pieces and dust. There is 1000 times more strain energy, SE, built into the structure below than any PE applied from above! Calculations are given below and here. |
Controlled Demolition
One way of demolishing a structure is to horizontally cut off vital connections of primary structure holding the structure together at the bottom, i.e. to reduce its strain energy in its strongest area. The structure will then collapse straight down due to gravity. It is called Controlled Demolition! You can try the same thing starting from the top, cutting structure horizontally!, but then you will create a fountain of rubble when blowing broken structure sideways. See figure 10. Gravity only failures without further assistance do not produce rubble. Controlled demolition on the contrary produces plenty of rubble in the process of destruction.
The major Problem - Lack of Evidence!
The major problems with the NIST cause - a crush down - are that fires normally only cause visible, local structural failures, deformations, fractures and displacements of steel structures that are soon arrested, when any energy released is absorbed by intact structure above and below the contact points and local failures - no global collapse or rubble . There is
(1) no evidence that the core structure displaced downward, as it could not be seen,
(2) no evidence of any simultaneously buckled visible, outside wall columns in the fire zone - no such damaged, buckled, columns have been retrieved from the rubble;
(3) no sign (evidence) of drop of the building mass above the buckled columns - the upper part - at near free fall acceleration a certain height and time as a rigid, solid mass and associated release of potential energy, PE, and
(4) no indication (evidence) of an impact (the PE is now kinetic energy, KE) between the rigid, upper part and the non-rigid structure below at which perfect alignment is necessary, which would be seen as a bump/deceleration on any video.
These four conditions are according NIST required for the upper part to commence destroying, crushing down, the structure below, but there is no evidence for them. Evidence to the contrary will be produced below.
The upper part is not really one part. It is a steel structure and an assembly of columns and floors.
There is further
(5) no calculations by NIST of the potential energy, PE, released and the strain energy, SE, or lack of it, of the structure below (and above!) that could be absorbed proving it was less than the PE or KE transmitted to it by the upper part permitting a gravity only driven global collapse/crush down to progress or ensue,
(6) no mention or calculation of deformations, fractures in and friction between locally and partly damaged floors and other parts that would absorb further energy after initiation,
(7) no explanation how the solid, intact columns below were overloaded by gravity only, what loads were actually applied on the columns after initiation and why the columns would rupture/fracture horizontally in 1000's of pieces about 10-12 meters long,
(8) no explanation (or evidence) why the upper part would remain intact at the (4) impact (except that it is rigid, which it is not), and
(9) no explanation why so much rubble (broken, fractured pieces) and dust were produced.
Evidently the potential energy released is transmitted to both the upper part structure and the structure below - always as walls/columns punching/slicing floors - a fact that NIST conveniently forgets or ignores or intentionally censors. Actually 50% of any energy released should be absorbed by the smaller upper part floors at impact and following destruction.
Evidence contradicting the NIST Cause
All videos of the WTC 1 destruction show that the upper part telescopes into or shortens itself or implodes for about 3-4 seconds (like the bottom structure below floor 16 of WTC 7 10 hours later), while the steel columns of the structure below are still intact prior any invisible impact! Gordon Ross has described this clearly 2007. The deformation of the upper part cannot be produced by gravity alone. The upper part is not very strong and you wonder how it can crush down anything - except itself - later? David Chandler explains clearly what happens in his video analysis 2009.
It would appear that the WTC 1 roof line drops about 35 meters in 3.1 seconds at an average velocity of 11.3 m/s prior any destruction of structure below is initiated (by an alleged impact). The acceleration associated with such a drop of the upper part is of the order 7.3 m/s² or 0.75 g, and this displacement of the roof line is not associated with any destruction of structure or floors below floor 93! The only conclusion is that the upper part, undamaged by any real fire, is compressed/implodes vertically >50% during the 3.1 seconds ... and there is no impact! This vertical compression is however not associated with any horizontal expansion of the structure of the upper part, so how can it take place? At least 8-10 floors of the upper part including the initiation zone seem to disappear prior any destruction of the structure below. One explanation is that the columns between a fair number of floors inside the upper part are locally destroyed or cut and displaced prior initiation of lower structure destruction. The ejection of smoke from the upper part prior any destruction of structure/floors below suggests that some form local destruction is taking place in the upper part. It has been suggested that the local destruction of the upper part starts on the 105th floor as seen on videos of the South wall of the North Tower/WTC1 - sudden fire, where there was no fire before, and some wall columns buckling.
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| WTC 1 North wall just before upper part shortens itself or implodes. Note intact steel columns below the upper part. No collapse or crush down of structure below has yet started there due to lack of strain energy ... and it will not take place!. | WTC 1 when upper part has shortened itself or imploded 20 meters after about 2.4 seconds of roof line dropping; columns of structure below the upper part still remain intact. The only reason for the shortening of the upper part is that strain energy is consumed in the upper part, i.e. it collapses into itself for unknown reasons in the lower part of the upper part now covered by smoke being ejected. The roof with the mast and the upper part of the upper part appear to be still intact. No collapse/crush down of structure below has started. Soon after the upper part disappers completely in a cloud of smoke and rubble! The lack of strain energy, strength, of the upper part is quite noticeable. |
There are 1000's of photos of the crush down that follows but unfortunately some are missing, e.g. those during the 0.8 - 0.9 seconds, when the alleged indestructible upper part supposedly near free falls 3.7 meters - all columns fail there and disappear at one storey - and then collides/impacts with the structure below transmitting the total upper block KE.
Actually no such photos exist as no free fall or impact took place! And no intact upper part is seen during the crush down destruction of the structure below that follows. The upper part is simply destroyed prior to any impact.
The upper part of WTC 1 is a problem for NIST. Its weight was not massive, only about 33 000 tons and the uniform density was <0.18!>strain energy, strength, to keep the upper part together was exactly the same as for the structure below.
What is a crush down? Ever heard about one?
An American professor Z P Bazant published (13 September 2001) soon (2 days only!) after the WTC collapses an ostensible and passionate theory [1] that was adopted by the authorities, FEMA and NIST, as true. Bazant suggested that there were five stages until the doom/crush down as illustrated in Fig. 1.
| Stage 1: The fire causes the steel of the columns to be exposed to sustained temperatures apparently exceeding 800° C in an initiation zone (500° C according NIST - and in only a few columns at a time). Stage 2: At such temperatures, structural steel suffers a decrease of yield strength and loses its load carrying capacity! (Actually the load carrying capacity is reduced abt 20% at 500°C and with a Factor of Safety >3 no serious decrease of load carrying capacity should happen). Stage 3 (Crush down starts): Once more than half of the columns in the critical floor (floors 94-95 of WTC1) that is heated most suffer buckling so the upper part starts falling down onto the structure below the critical floor (floor 93). At that moment, the upper part has acquired an enormous kinetic energy, KE,(only 1.2 GJ corresponding to 41 kgs of jet fuel - if it actually happened) and a significant downward velocity (less than 8 m/s)! |
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Stage 5 (Compression): This causes failure of an underlying multi-floor segment of the tower, in which the failure of the connections of the floor-carrying trusses to the columns is either accompanied or quickly followed by buckling of the core columns and overall buckling of the wall columns! (Not proven, of course. The upper part should simply bounce on the lower structure, while there are some local failures. Just buckling one column requires; first to deform it elastically vertically and sideways, then to produce three plastic hinges in the column, then to produce fractures in the hinges that must cut through the column; as soon as one fracture cuts off the column, there is no longer any contact and the top part slides off the lower part, etc).
Stage 6 (Crush down): The part of building lying beneath, i.e. the structure below, is then impacted again by an even larger mass falling with a greater velocity and the series of impacts and failures then proceeds all the way down (This is impossible! Each column has now been cut off by one fracture at one plastic hinge and the upper part of a column can no longer impact a lower column. It will therefore contact something else - a floor! - and cause local failure there or just slide against other structure. Friction between loose parts absorbing energy should now start).
This Stage 6 is the famous 'crush down' of a steel structure that nobody in serious structural engineering circles had ever heard of before 911 when it was invented by Bazant. Or after! Compare with the global collapse (sic!) that ensued that can be seen here!
In [5] Bazant (2007) points out errors in his previous paper and develops some new ideas about Stage 6:
"The kinetic energy of the top part of the tower impacting (sic - highlight by AB) the floor below was found to be about 8.4X larger than the plastic energy absorption capability of the underlying storey, and considerably higher than that if fracturing were taken into account. This fact, along with the fact that during the progressive collapse of underlying stories … the loss of gravitational potential per story is much greater than the energy dissipated per story, was sufficient for Bazant and Zhou to conclude, purely on energy grounds, that the tower was doomed once the top part of the tower dropped through the height of one story or even 0.5 m. It was also observed that this conclusion made any calculations of the dynamics of progressive collapse after the first single-story drop of upper part superfluous."
and
"When the upper floor crashes into the lower one, with a layer of rubble between them, the initial height h of the story is reduced to lh, with l denoting the compaction ratio (in finite-strain theory, l is called the stretch). After that, the load can increase without bounds."
Does really the kinetic energy of the upper part after a drop of only 0.5 m exceed the plastic energy absorption capability of the underlying storey by a factor of 8.4 and is it relevant? Well, the upper part is 53 meters tall and an underlying storey is only 3.6 meters tall and if you assume that the upper part is like a solid hammer head and the underlying storey is a nail, then the hammer head will deform the nail. But no rubble will be produced. The hammer head, the upper part will then slip off. Bazant assumes it hits again.
If, one the other hand you assume that the nail consists of 97 storeys, i.e. consider the whole structure below, then the underlying structure can absorb 97 times more energy than just one storey and then the upper part will just bounce on the lower structure. The kinetic energy of the upper part is just 0.086 of the plastic absorption capability of the total structure.
The kinetic energy of the upper part was too small to do any real harm or initiate a crush down. The only result will be lots of local failures up top.
| The upper part of the tower cannot really impact the floor below, because, before that would happen, the columns damage locally both the floor above in the upper part and the floor below (the underlying storey) and the interface changes. No rubble is really created except crushed furniture and lightweight walls (gypsum boards) as the space between the top part and the underlying floor is 95% air - the columns occupying 0.13% of the volume. |
Upper Part is destroyed
It is furthermore not the total kinetic energy of the upper part that is applied to the underlying storey - only the forces applied by upper part columns are locally damaging, fracturing the underlying floor. At the same time the columns below apply forces on and start to destroy the upper part bottom floor in the same manner. To fracture a floor requires energy. Locally damaged floors would then get entangled into one another, huge friction forces would develop and arrest further destruction. No impact! To suggest that the load can increase without bounds due to a layer of rubble is nonsense. Bazant ignores local damages to the floors, all fractures that develop and the huge friction between these locally failed floors as the main factors arresting structural destruction. The loads are actually reduced, mostly by friction! And collapse arrest should soon follow!
Obvious Contradictions
Regardless - Bazant 100% contradicts what NIST says about the system that supports the upper part (repeat from above):
"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., …." (NIST report - NIST NCSTAR 1-6D chapter 5.2).
Imagine an upper part supported by a core and four walls and that the core below it (not seen of course) displaces downwards! Then the core cannot support anything above, unless the upper part starts to deform, but why should it? It is undamaged. So, if the core displaced downwards as suggested by NIST, the core would then carry 100% (!) less load, i.e. nothing at all; actually the core must have been disconnected from the upper part and the load on the core should be transmitted to the walls.
Furthermore, Bazant assumes in [1] that the lower structure can be regarded as an elastic spring (while the upper part is rigid and not a spring at all!) and wonders what its spring constant C can be:
"According to this hypothesis, one may estimate that C =71 GN/m (due to unavailability of precise data, an approximate design of column cross sections had to be carried out for this purpose)".
This results in an extremely stiff spring that does not really compress at all as a spring (more like a solid rod) and is easily locally overloaded, i.e. breaks in one point (at the top) but does not globally collapse. But if a big force, or 4F, would suddenly be applied to a lower tower structure with flexible vertical columns supported by horizontal floors pin joint to the columns by an upper part from above (let's forget that the core has already displaced downwards), you would expect the whole lower tower structure to deform as shown below in figure 2, i.e. bulge in/out between floors, before any failures occur! Simple Finite Element Analysis, FEA, or rather beam analysis shows this.
Fig. 2 Elastic, vertical deformation of of steel beam tower
The WTC towers were in fact very flexible. Apply a wind load sideways and the roof may deflect transversely 4-6 meters relative the ground.
A more realistic value for WTC 1 as a spring is therefore C = 0.5-1.0 GN/m at top and little more further down, the lower structure is quite flexible, and then the upper part will just bounce [6] on the lower structure at hypothetical impact (disregarding local failures). You wonder why Bazant estimates spring constants 140 times bigger than a realistic one and that the upper part remains intact. To prove global collapse? His whole theory seems to be based on this estimate. However, David B. Benson, co-writer of [2] with Bazant has 27 January 2009 explained to the writer:
"That result applies, strictly speaking, only to a one-dimensional homogenous crush down. Since the top portion was tilted and the sturcture (sic) was not homogeneous, no damage to the top portion is only an approximation to reality."
The WTC1 collapse is evidently not a one-dimensional homogeneous crush down and approximations should be avoided.
David B. Benson has also informed he has seen no videos and pictures of WTC1!! His PC is too slow!
If any column would fail and not produce a bounce - Stage 2 in the Bazant theory - you would expect the following to happen to it in 3-D when a compressive load is applied:
A...............................................................;;;B.;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;C.
D................................;;;;;........................E.
Fig. 3 - Five steps of buckling of a column due to vertical, compressive load
First, A, a plastic hinge develops in the middle of the compressed column due to lack of strain energy there, then, B, two more plastic hinges develop above and below the first hinge, then, C and D, the column 'kneels' and finally, E, a severely deformed part of the column may punch a hole in the floor below it. The column will never fracture in any location and it will never rupture due to fractures at the hinges into several pieces, i.e. it will always be connected, albeit very deformed. To suggest that 'buckling' of a column will result in free fall of the load it carries is not correct! The above deformation takes time and would be seen on any video, if it took place! Thus, Stage 3, of Bazant in not possible!
More strange explanations were given by Bazant (2008) in [2] with Frank Greening and David B. Benson joining.
In [2] WTC1 is split into three parts during destruction; part A - lower structure to be crushed, part B - a layer of debris being formed by a part C - the upper part - that remains intact and drives the destruction.
| Mass and Density of Part C Near the top, the linear, 1-D, specific mass (of WTC1) (mass per unit height) µ = 1 020 000 kg/m or 1 020 ton/m according [2]. In [2] the problem is only in 1-D; one dimension! A line that is being shortened! With a storey height 3.6 m, the mass of a storey - or the line representing the storey - is 3 672 ton. Assuming the upper part C is 53 m high (14.7 storeys), total mass of upper part C is 54.060 tons. In my article I suggest 33 000 tons, but the difference is of no importance. Using a floor area of 4 000 m² of the line - to make the model 3-D - the volume of upper part C is 212 000 m3, thus the uniform (which it is not) density of the upper part C is 0.255 ton/m3 or 255 kg/m3 according [2]. It is not very much! Reason is that there is plenty of air inside a storey structure. This clearly shows how Bazant & Co confuse the issue: they treat the three parts A, B and C as lines! Density of Rubble - Part B The known typical (sic) linear, 1-D, density (sic) of rubble, µc = 4 100 000 kg/m or 4 100 ton/m according [2]. The density of this rubble is then exactly 1 025 kg/m3 (as the floor area is 4 000 m²), which is the density of salt water (that ships float in). Imagine a line of salt water! |
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Initiation of Collapse - the first Crush - Formation of Part B
Thus at initiation – upper part C – 54 060 tons – crushes the uppermost floor - say it is floor no. 97 - of part A, the lower structure of WTC 1, and compresses it into a 0.896 m thick layer of debris that becomes part B. This layer is resting on the second uppermost floor of part A. This compression takes place at increasing velocity. Only air/smoke is ejected sideways out between floors 97/96. The mass of the rubble - 3670 tons - is uniformly distributed on the floor no. 96 below - 918 kg/m² - and this floor no. 96 floor should be able to carry that load according NIST FAQ.
Note that part C only compresses the storey floors 97/96 into a rubble layer - part B. It does not accelerate the rubble layer/part B. The compression should be associated with a deceleration of part C. Not seen of course.
What about the part C and its 54 060 tons? Is it acting on the debris layer part B? Not really - part C is intact and only its bottom floor, floor no. 98, is in contact with rubble part B. The columns of part C are now not in contact with the columns of part A below due to this layer of debris, but let's assume that part C columns crushes the columns below as suggested in [2], so that destruction can continue!
The roof line has then dropped 2.704 m! Air/smoke should be ejected from floor no. 97.
The second Crush - Part B doubles in Thickness
Then the upper part C + part B (the layer of debris) crushes the second uppermost floor of part A. This event can hardly be associated with a second impact by part C as it had just compressed floors 97/96. Regardless, now storey floors 96/95 is compressed into another 0.896 m thick layer of debris that is added to part B. Part B rubble is thus 1.792 m high/thick after two floors of part A have been crushed.
The roof line has then dropped 5.408 m! The velocity of the roof line apparently is increasing - but why? It should slow down by so much compression. More air/smoke should be ejected sideways from between floors 96/95, i.e. only from the storey being crushed. Can you see it on any video?
And so on!
The Displacement of the Roof Line of Part C during Destruction of 13 storeys
According careful observations in [6] we know that the roof line of upper part C dropped 35 m in 3.17 seconds at increasing velocity. We also know that upper part C is accelerating at about 0.64-0.7g [6]! This means that upper part C can only apply a force of 0.3 g or 30% of its own weight to crush floors of part A and build up the rubble layer - part B (ignoring the fact that it is upper part C that actually implodes).
Every time a storey is crushed, upper part C drops 2.704 m and an 0.896 m layer of debris is formed according [2] and upper part C is remaining intact.
Thus, when the roof line has dropped 35 m, 12.94 storeys (!!), total height 46.6 m (!) of part A should have been crushed, and should have been replaced by an 11.56 m thick layer of debris – part B.
Writers of [6] believe that only 9 (or 9.72) storeys have been crushed but according [2] it should be 12.94 storeys! Writers of [6] forget that there should be an 11.56 m thick layer of debris below the upper part C, when it has dropped 35 m after 3.17 seconds.
Verification of Parts A and B using Video Recordings of the Destruction of 13 storeys
Regardless – does anybody see an 11.56 m thick layer of compressed debris – part B – on any video after a 35 m drop of the upper part of WTC 1, part C according [2]? And that 46.6 m of part A - floors 97-86 - has been destroyed after 3.17 seconds?
It would appear that at least floors 86-93 are still intact!
And does anybody believe that an upper part C with density 255 kgs/m3 can produce an 11.56 m thick layer of debris during 3.17 seconds and at the same time accelerate at 0.64-0.7g? Only [2] suggests so, but it is just an invention to suit a false model/theory of crush down.
This layer of debris - part B - should then be moving at a velocity of >20 m/s and increasing as acceleration seems to be rather constant 0.64-0.7g. Only air should be ejected from the next storey below being crushed, where more debris is formed. But upper part C cannot possibly both compress and accelerate part B at the same time! Ah, what funny model [2] invents! Don't they see that upper part C is destroyed?
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| Picture left shows the upper part of WTC 1 about 4 or 5 seconds after the roof line started to move. Is it there? Maybe the top of the mast is seen above the corner of the tower just above the plume of smoke and debris. The rest of the upper part is hidden by a fountain of debris ... if it is there? According [2] there should not be any debris outside the tower at all - just a layer of rubble - part B - on top of part A. Crush down! With part C - the upper part riding on part B Video evidence - and this picture - on the other hand show that all parts A (top) , B (doesn't exist!) and C are exploding or have been destroyed and structural pieces of them are thrown out in all directions. You really wonder if the authors of [2] have studied any videos or pictures of the WTC 1 destructions? |
| Situations when Part C Roof Line has dropped 100 m, 200 m and when Part B hits Ground Now – when upper part C has dropped 100 m and 37 storeys have been crushed, the layer of debris – part B – should be 33 m thick on top of which a 53 m high upper part C should still be visible (forgetting the mast). An when upper part C has dropped 200 m and 74 storeys have been crushed, the layer of debris should be an impressive 66 m thick with part C still riding on top of it. Imagine a layer of debris - density 1.025 ton/m3 - 66 m high. Over 4 000 m² floor area it is almost a big cube of 264 000 tons of rubble!! On top of which part C - 54 060 tons float. Part C is 53 m high! Add the rubble - part B - and we have a moving mass of 318 060 tons that is 119 m high when the part C roof line has dropped 200 meters. Below this 119 m high pile, a storey of part A - floor 23 - is just being crushed and air - not smoke - is ejected there. How the columns of part C - 66 m above floor 23 can crush the columns 66 m below is not clear. 266 m of walls should also be gone. There are another 23 storeys still to crush! About 83 m of WTC1 remains to be crushed. |
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| When all 98 floors of WTC 1 - part A - have been crushed, there should be an 83 m thick layer of debris on the ground + upper part C on top - 53 m. This is also confirmed by [2] - see fig. 4 (b) right: just before the end of crush down the 53 m high part C rests on a 92 m thick layer of debris (density 1.025 ton/m3) - the crush down has also penetrated the basement 22 m below ground! The roof line should be 135 m above ground then! And the velocity of part B at the ground or bottom of basement must be 0! As the velocity of the part B in contact with part C above must be the same as part C, you realize that part B cannot be regarded as one 'part'! An instant later upper part C is destroyed in a crush-up according [2] and should form a 13 m thick layer of rubble. The total thickness of rubble should be 92 + 13 = 105 m minus 22 m of rubble in the basement = 83 m of rubble above ground but only 20 m is suggested by [2]. Evidently some rubble is spread outside the 4 000 m² foot print, but it seems the density of the rubble must have increased 3 times - 3.075 ton/m3! But it is not possible - it is too dense. So where did all the rubble go? Actually no rubble could be produced at all by dropping upper part C, as it should have got stuck up top. All energy applied when part C dropped one storey would have been consumed by local failures and friction trying to crush only one storey! |
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After having published above G, Frank Greening, who co-authored [2] asked:
So, Heiwa (that's me), tell me what you see after a 35 m drop!
Again, Heiwa, tell us what you see when there are 36 storeys still to crush.
And I replied:
"Thanks for asking. There is plenty to see on the videos of the WTC1 destruction apart from a 'jolt' that nobody sees. Lately I have concentrated on those features that you postulate in your paper What Did and Did not Cause Collapse of WTC Twin Towers in New York [2] that I found in the Journal of Engineering Mechanics, ASCE, Vol. 134 (2008). And there are plenty features I do not see.
Of course, the title of your paper is misleading. WTC 1 never collapsed! It was crushed down from the top according to you. It - part A/lower structure below floor 97 - was crushed by a layer of rubble - part B - that was created when part C - the upper part floor 98 and above - dropped down. Part A never collapsed - each and anyone of its 97 storeys were crushed, one after the other.
According your paper - as I understand it - part C suddenly dropped (its support were weakened by fire/heat and buckled) and impacted on floor 97 of part A. This impact allegedly destroyed the columns between floor 97/96 and floor 97 dropped down on floor 96. I do not see that on any video.
It is now the crush down of part A starts. When floor 97 drops down it becomes a 0.896 m thick layer of rubble - that you call part B - that contacts floor 96 of part A. This rubble is volume vise about 3 600 m3! The uniform (sic) density of structure floors 97/96 was originally 0.255 according you (plenty of air). The density of the rubble is 1.025 according you so compression takes place. It is part C that compresses structure floors 97/96 75.1%.
I do not see that on any video.
To compress rubble requires energy applied by part C and it seems you do not consider that in your differential equations. To compress rubble you must overcome friction in the rubble. As the solid parts of the rubble have density 7.8 (columns) and 2.5-3.0 (concrete) there must still be plenty of air in part B - the rubble layer.
I do not see this rubble layer on any video. To compress 14 400 m3 of structure with density 0.255 to 3 600 m3 of rubble with density 1.025 requires plenty of energy! I would expect the destruction to stop then. But I do not see that! Instead upper part C soon after accelerates constantly a 0.7g due gravity. Not possible if part C shall compress rubble at the same time.
Anyway, next crush is floors 96/95. Now it is a layer of rubble - part B - with part C on top that damages part A. An impact between parts C and A is impossible with so much rubble in between. You suggest that parts B and C now overloads floor 96 (pancake theory?) so floor 96 drops down.
Fair enough! I don't agree and I do not see it, but this is what you suggest. According videos (and your own paper) acceleration of part C is now 0.65-0.7g.
Part B - the rubble layer doubles in thickness - and the crushing continues another 11 floors of part A at constant acceleration 0.7g.
So after a 35 m drop of part C - it takes 3.17-3.3 seconds according your differential equations and acceleration given above - total 13 floors of part A have been crushed (should be floors 97-84), 46.6 m of perimeter walls have failed in pieces and part B has become 11.56 m thick and part C should remain intact on top of the rubble!
Frankly speaking nobody can see that on any video.
What I see is that part C - the upper part - explodes in its lower part - floors 98-105. Controlled demolition no doubt! That's why the roof line has dropped 35 m. I do not see an 11.56 m thick layer of debris on top of floor 84! Actually I can clearly see that floors 84-96 are undamaged!
So much for your model and theory, G.
So what do I see, when there is 36 floors to crush (61 floors of part A have been crushed)?
| Look right and imagine that it represents when there are 36 floors to crush! Part A is about 130 m tall at this stage. 61 floors have been crushed so part B should be abt 55 m thick and on top of that we should see part C, which is 53 m tall to roof line, and then the 40+ m mast. Thus, when floor 36 is being crushed - and air/smoke is ejected there and only there - at 130 m above ground we should see, according your theory, a 53 m thick layer of rubble - part B - top of which is 183 m above ground. On top of that we should see part C undamaged according your theory, roof line of which is 236 m above ground, and then we should see the mast. There should be no free rubble anywhere ... and no smoke! |
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| So, sorry! I cannot see anything that confirms your model and theory, Dr. G. But I wonder! Why do you invent such a stupid model and theory and publish it in the Journal of Engineering Mechanics? Are you working for the perpetrators of the controlled demolitions of WTC 1, 2, 7 or some agents of those? Do you think you can convince anyone with your unscientific nonsense? Why do you do it? Why not simply shut up like most other poor bastards and don't say anything. I don't expect you to be like me that can do real structural damage analysis and quickly see that WTC 1 destruction is not caused by crush down or PE>SE that NIST suggests. |
It is always nice with reader contacts! I will update this page when G clarifies his motives.
But ...
More funny Explanations
The authors of [2] suggest:
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| The 53 meters high upper part C, intact, rigid and of uniform density at start of crush down remains INTACT after the global crush down ... on top of all rubble that the upper part has produced of the structure below ... and only then finally destroys itself in crush up as illustrated in figure 4 left. The destruction of the upper part is the last event of the gravity driven global crush down. Not seen of course and there is no evidence for it. You wonder then why the upper part C does not continue through the rubble and the soft ground and makes a big hole in the ground! Bazant/Greening/Benson make four basic assumptions of the gravity driven crush down ending in Stage 6 apart from the misleading introduction in [2]: "Abstract: Previous analysis of progressive collapse (sic - crush down!) showed that gravity alone suffices to explain the overall collapse of the World Trade Center towers". That conclusion is as valid as a three dollars bill! Structures are not crushed down from above and rubble is not caused by gravity alone. Further claims by Bazant & Co [2]: |
| (1) The only displacements are vertical and only the mean of vertical displacement over the whole 4 000 m² floor needs to be considered. There is perfect alignment and the upper part columns always hit the lower columns without slipping sideways and the lower structure does not deform. How can a column hit a column through a 33 m thick layer of rubble? (2) Energy is dissipated only at the crushing front! The separate parts of the upper part and structure below of the collapsing tower may be treated as rigid and will not be destroyed(!); the deformations of the structures away from the crushing front may be neglected. |  Fig.5 - Air jets well below the upper part ! |
(3) The upper part therefore remains intact during the crush down including its lowest floor at the crushing front!
But is the upper part C there at all? And how can soft rubble destroy solid columns?
(4) Air jets (sic) displace broken material 200 metres sideways in all directions.
All these assumptions, apart from being ridiculous, are false. A rigid body, an upper part C, does not exist! By definition a rigid body destroys anything non-rigid it touches. But the upper part C is destroyed before the destruction of the lower structure commences.
Note, e.g. the explanation for air jets. The upper part C intact, with an air tight bottom floor (with a thick layer of compressed rubble below it - part B) is supposed to compress the air in the top remaining storey below - part A - and blow out (?) the debris and rubble before the wall columns are affected. The crush down has changed in character. No compression - now it is blow out! To compress this storey takes 0.07 seconds according [2], i.e. the velocity of part B - the rubble - is 51.4 m/s! Ask yourself what produces these air jets, if there is no upper part C or rubble layer part B, and when the air jets can be mistaken for smaller air jets seen preceding the destruction - fig. 5 - by 10 storeys. And where does the rubble being ejected come from? It is ejected horizontally! Local failures due to gravity do not produce the big amount of rubble ejected horizontally as seen on the videos! And according [2] the rubble should just be compressed to form part B.
Unproven Assumptions
There are many unproven assumptions by Bazant & Co. associated with the WTC 1 crush down destruction, i.e. lack of evidence for, e.g:
1. All support columns suddenly disappear/buckle in the fire zone below the upper part C (they should just 'kneel').
2. The upper part C near free falls or drops 3.7 meters (it cannot as it is connected via deformed columns to the structure below - part A).
3. The upper part C impacts the structure below, part A, with perfect alignment (it cannot happen!) and produces a layer of debris, part B.
4. The upper part C and its bottom thin floor are still intact due to massive strain energy in it (it is assumed rigid and remains so for while - compare 7. below).
5. The upper part C (mostly air - uniform density <0.18>
6. Friction between parts, floors, of the upper part C rubbing against parts, floors, of the lower structure does not exist.
7. The upper part C and the rubble part B produce air jets in the structure, part A, below, that blow out the débris and throw out the rubble 200 meters!
8. The upper part C lands intact on a 70-80 m high heap of soft rubble after a successful crush-down of the tower.
9. The upper part C finally self-destructs in a crush-up (sic) of the soft rubble, i.e. suddenly it is not rigid anymore!
As with all real conspiracy theories there are no evidences for them.
Bazant's & Co's crush down theory is based on a rigid, intact upper part C that is not damaged by local failures, when first losing its supports and later, when in contact with the structure below. The upper part C bottom floor (no. 97) remains air tight, flat and solid, etc, like the rest of the upper part C! It thus has massive strain energy built in and is supposed to be much stronger than the structure below (but not stronger than rubble on the ground). But it does not really matter - [2] suggests that a layer of rubble - part B - increasing to 70-80 m thickness destroys WTC 1.
| There is no evidence for all this! It is simple lies transmitted only two days after the destruction to fool the public and hide the real reasons for destruction. |
"I admit my model calculation is very crude, but it shows that a gravity-driven collapse of WTC 1 & 2 was physically possible without the help of explosives! My model may not “see” everything that happened; you, on the other hand, see things that never happened …… ".
Exactly the Bazant model is very crude and has nothing to do with reality! The nine invented events or assumptions listed above cannot be seen and never happened. Local deformations, failures, fractures and friction alone would have stopped the destruction very early. Part C would have got stuck up on top of part A. No rubble layer part B would have been formed. And why say that the structure below collapsed, when it was just crushed down by the upper part C producing a rubble layer, part B, and throwing out loose parts sideways according a new phenomenon never seen before? Nobody has ever heard of steel structures being crushed down by an upper part above with equivalent strength as the structure below, but everything must happen a first time. Twice - within an hour. More!
| Seriously speaking - the Bazant 1-D theory treating the WTC 1 as a line that becomes shorter is complete and utter nonsense! |
Over-loading!
Another 'expert', K. A. Seffen, in a paper [3] suggests that the potential energy released by the mass above - the upper part - resulted in dynamical "over-loading" of the undamaged columns of the structure below by a factor of 30 compared to their static load capacity at impact and transmits it to the complete structure below and shakes it into pieces. Seffen also treats the problem in 1-D: a line that becomes shorter!
Seffen assumes that during a gravity driven collapse (or crush down or over-loading) a tower of height L and uniform density ro consists of three parts, when it has lost aL of its height:
| 1. A solid upper part lL (actually a line) that is rigid and intact and perfectly aligned with the columns below all the time during crush down. It does not slide off! 2. A moving intermediate block bL (another piece of line) between the upper part and a crush front that apparently consist of semi-broken parts, rubble, and produces a crush front, actually 280+ crush fronts that are perfectly applied to the 280+ columns at every stage of the crush down. 3. A static lower, intact part (1-a-b-l), a third piece of line, below the crush front that produces resistance to motion as per fig. 6. It is in fact the 280+ columns of the structure below that produce resistance ... if a load is actually applied on them from above. l is constant during the crush down, which is not observed during the WTC 1 collapse. Actually l becomes 0 very early! |
Fig. 6 (from [3]) |
These are the false assumptions of K.A. Seffen:
(1) the tower has uniform (<0.18)> ro, while it is not uniform at all; it consists of solid columns 0.13% of the floor area (with density 7.8), weak floors 99.87% of the floor area (with density about 3 but spaced 3.7 meters apart) and air (density <0.02)>
(2) the lL upper part begins to accelerate downwards as a rigid undamaged body with uniform density ro, while it is seen to self-destruct,
(3) the initial load imposed onto the structure below was exceptionally high, while is not established how and when it contacts the structure,
(4) the damage, no new failures seen of course in the smoke, was bound to propagate, and
(5) fractures in and friction between locally damaged parts in contact with one another can be ignored.
Alignment of upper part with columns below is conveniently forgotten. According to Seffen the rigid upper part drives the crush down. And the upper part is not slipping off the structure below.
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Fig. 7 | You need kinetic energy, KE, for that and it can only be provided by an intact, rigid, uniform density upper part that remains intact, rigid, with uniform density during the whole destruction of the structure below. No such object exists anywhere! The upper part is the only part that can provide KE during the alleged global push down. The structure below does not add any extra KE to the destruction or contribute to it - it is being destroyed due to lack of strain energy and lack of friction between parts in contact according NIST. The upper part, intact, rigid and of uniform density at start of crush down, should according to Seffen remain INTACT after the global destruction ... on top of all rubble the upper part has produced of the structure below as per figure 7 left and should then also destroy the rubble. Nothing could destroy a rigid upper part of uniform density - not even the final impact with the ground forgetting that the rubble is there to dampen the final impact. |
| The Seffen theory is another completely nonsensical theory about the WTC1 collapse. |
Collapse Arrest - Happens all the Time!
Bazant, Greening, Benson and Seffen incorrectly assume that the upper part can absorb massive amounts of strain energy to remain intact during any local failures, i.e. the upper part is indestructible. That is a puerile assumption and apparently intended to fool people.
What a reasonable person using clear thinking would expect after local failures of supporting structure in the initiation zone - even very serious ones - is that the forces in the structure of the upper part would be redistributed and cause failures there and that gravity would just slowly (no free fall, no sudden release of PE) pull the upper part assembly down, i.w.o. local failures. The upper part is always connected to the structure below albeit by deformed columns. Some parts may then contact the structure below and cause further damages or get damaged like in a soft collision (no impact!), and after that primary and secondary structural parts of the upper part and the structure below would get entangled into one another and friction develops.
No Rubble would be produced!
Evidently the structure below will cause serious damages to the upper part structure above at once, when the upper part displaces downwards and makes contact with the static structure below. It means that the Bazant, Seffen, NIST assumption of an undamaged upper part during the whole destruction or crush down is proven wrong ... at once. This strange misty assumption - that the upper part remains intact - is suspicious. Very suspicious. Has nothing to do with reality.
| The fact that local failures occur but are arrested by deformation of intact structure and friction between loose parts is the basic reason why a multiple-parts steel structure does not ever globally collapse like a house of cards! |
There are many structural parts that may fail, deform, fracture, be punched and displace - connected to one another one way or another forming the upper part. You cannot simplify and say the upper part is only one solid, rigid mass of uniform density that remains intact. There are four outer walls and core columns - all primary structure, many floors - all secondary structure -, a roof, and plenty of air!
If the upper part masses drop or move, their PEs become KEs. Each part mass has its own PE/KE due to gravity. And each part mass starts at a different location and will drop on a different location by gravity on the structure below.
The structure below of WTC1 is fairly complex - 280+ columns, 94 floors, etc. The columns only occupy 0.13% of the total cross area of the tower. What loads are applied on them at an impact? Probably none as they are small and any load will slip off.
The uppermost floor of the structure below thus occupy 99.87% of the cross area. What loads are put on it and where and when? There are different masses dropping down or moving. And what parts will rub against each other and what are the frictional forces?
In order to analyze the damage initiation you evidently apply the loads to the structure below and see what happens! Does global collapse or crush down or whatever starts and is rubble produced or is it just local failures that are arrested and no rubble? [4] The analysis is based on experience from ships' collisions.
No Rubble is produced by local Failures!
So let's assume (see figure 8 below) that the upper part gets lose (A). It means that the potential energy available in a one-story drop was greater than the local strain energy to be overcome in the initiation zone, i.e. crushing all columns there. It is furthermore assumed that the compressive force, necessary for a descent was available; otherwise the motion would not start, i.e. no initiation. If these assumptions are not fulfilled, the conclusion is that the motion will be arrested already during the damage of the initiation zone and the building will stand.
What happens then? Let's assume that the upper part gets misaligned (exaggerated in figure 8 below) and is shifted outside the lower structure on two wall sides and inside on the two other wall sides of the lower structure (B) and goes down (C). Similar misalignment takes place at the core. The original interface between upper part and lower structure changes. Before the primary load bearing solid steel columns were connected. Now they are only in contact with secondary structure; the thin, mainly concrete floors or with nothing outside the building! It is now the 'impact' or collision or contact starts.
If the upper part columns are not misaligned with the lower structure columns and there is perfect contact of all columns of upper part and lower structure at collision/impact, the upper part would be subject to a visible jolt and deceleration [6] at contact. As such perfect contact is impossible to take place under any circumstances - the columns will slide off - here it is thus assumed that the solid columns contact the thin floors or air outside the structure.
The upper part walls steel columns (right in C above), misaligned on the inside of the lower structure, will now punch or slice through the first red floor below the initiation zone - the red floor hinges down on the red floor below as it is only bolted to the core column/beam - while the upper part walls steel columns (left in picture C above) misaligned on the outside will drop in the air and hit nothing! Actually only half the mass/walls of the upper part carried by the walls participate in the local failures/crashes that follow and results in tilting of the upper part. 
;;;;;;;;;;;;;;;;;;;A ;;;;;;;;;;;;;;;;;;;;;;;;;;B ::::::::::::::::::::::;;;;;;C:::::::::::::::::::::::::::::D xxxxxxxxxxxxxxxxxxE
Fig. 8
On the other hand the steel columns of the structure below (left in C above) on the inside of the upper part will slice/punch through the first, lowest green floor of the upper part - and it hinges down too on the red floor below! You do not need much energy for that. And the walls steel columns of the structure below on the outside of the upper part (right in picture C above) will remain ... intact, as they are not contacted by anything!
Similar floor failures occur at the core but there the steel columns are fewer and spread around and interconnected by horizontal beams to which the floors are bolted. These latter connections will shear off and the floors will hinge down around the opposite edge.
Does anyone believe that the upper part will fall vertically - at near free fall speed - under these circumstances of local floor failures - and crush down parts below - which is the fundamental assumption of Bazant, Greening and Seffen? No free rubble (lose structural parts) can be produced that would provide extra energy and drive the destruction further!
What a free fall drop is, is explained at web site http://uk.youtube.com/watch?v=gC44L0-2zL8 . Or try to click here! The WTC 1 collapse can be seen at web site http://www.youtube.com/watch?v=dtx_GcFCs6c&feature=channel_page . Or try to click here here! Internet is funny. Sometimes the link doesn't work! I wonder why?
Progressive local failures of structural parts have however started in the little example due to the original energy input and local failures! Thus we have to see what happens at the next floors above and below applying all the relevant contact loads there in proper order as per [4].
The upper part is thus assumed to continue moving down due to gravity, but there is no free fall, only local failures and fractures in the floors and friction between bent and punctured parts in contact producing friction and absorbing energy and slowing the downward movement. No rubble is produced! No air jets are produced! And no débris can be ejected as there is no loose débris produced!
In D the upper part right wall solid steel columns inside the structure below are assumed to have sliced three red floors in the structure below and these floors have hinged down below the green floors of the upper part that have also been cut by the strong wall columns of the structure below inside the upper part. Similar failures take place at the core.
Massive frictional Forces develop
Evidently this asymmetric destruction pattern of local failures will tip the upper part against the intact (right in D above) steel wall of the structure below held together by spandrels and the upper part will soon be jammed, e.g. in E when outside walls of the upper part (left in E above) has been sliced off by the columns below and dropped to the ground. All the floors of the upper part however remain jammed in the top of the structure below.
If the upper part drops and accelerates at 0.75 g [6] and the punching of holes in the floors by the columns and hinging down of the locally failed floors take no time, the upper and lower floors themselves, spaced 12 feet apart, will contact each other after about 1.0, 1.4, 1.75, 2.08, 2.3, 2.53, 2.75,2.88, 3.17 and 3.3 seconds, i.e. after 3.3 seconds 10 floors of the upper part would be entangled in 10 floors of the lower structure ... and the WTC1 would be 120 feet shorter as per above diagram. It is very likely that the destruction would be stopped earlier.
| The progressive local failures of secondary structural parts are thus arrested. No rubble has been produced. The main reason for this is that the failed floors are in contact with each other and rub against one another and huge frictional forces develop that absorb the released potential energy much more effective than any built in strain energy of intact structure that deforms. NIST, Bazant and Seffen do not even consider that friction between locally damaged parts exists! This logical local pattern of destruction is not considered by NIST, Bazant or Seffen. |
Other Possibilities
There are other possibilities of serious local structural failures and what may happen. In fig. 9 below it is assumed that three green floors in the upper part fail in their bolted connections to the wall columns (B) due to fire/heat in the initiation zone and that the green floors hinge down on the red top floor of the structure below. The green floors are still connected/bolted to the core acting as a hinge.
Fig. 9 xxxxxxxxxxxx A xxxxxxxxxxxxxxxxxxxx B xxxxxxxxxxxxxxxxxxxx C xxxxxxxxxxxxxxxxxxxx D
The result would be that the walls in the fire zone buckle inwards on top of the green floors that dropped down previously (C). The walls of the upper part are then hanging on the hat truss in the roof that is assumed to deform downwards. The walls above do not transmit any forces to the walls of the structure below!
The outside floors in the upper part are thus pulled down by the unsupported walls of the upper block. The extra load in the hat truss is transmitted to the core columns at the top that buckle locally at the weakest areas just below the hat truss due to overload. The roof and the mast on top displace downwards (C) a couple of meters. Due to these deformations and displacements of the upper block parts the floor bolts shear off at the walls (it is assumed they remain intact at the core), the walls of the upper block gets loose and falls down (D) and slips off on parts off the walls previously buckled inwards acting as a damper on top of the damaged green floors in the initiation area and drops to the ground ... and the collapse is arrested. Or the green floors hanging on the upper part core pull down the upper block core more until they contacts the inwards buckled wall below and are diverted outside the tower ... when further destruction or collapse is arrested. No crush down will occur! No free rubble is produced.
It should be noted that in this second example, fig. 9, the local failures at the fire zone - the green floors dropping down and the walls buckle bending inwards - result in further local failures 58 metres higher up due to local forces in the upper part structure being transferred there due to the first failures below. The upper part is evidently not just one 'parts' but consists of many parts, and the weakest ones will fail, when any supports below fail. Thus the upper part will be part destroyed prior anything can happen to the structure below! This is a fundamental part of collapse arrest analysis of steel structures.
| You have to keep an eye on where the forces are transferred after local, initial failures and what really happens to the upper part. Bazant, Seffen, Greening, Benson and others fail miserably in their one dimensional analysis in this respect and therefore make insane conclusions. NIST is worse. |
| NIST in its 10 000 pages report does not mention or analyse the destruction of the upper part or collapse arrest as a logical result of local structural failures in the initiation zone and the report is thus incomplete. |
Dangerous Sect at work
In the struggle against great, organized, sectarian forces of intolerance and insane self-assertion it is important that scientific reports, papers and analysis of damaged and destroyed steel structures are done by honest people using correct thinking, right feeling and proper estimating of facts. Confused thinking, bad passions, dishonesty, corrupt manners, erroneous assumptions and haste do not contribute to a better understanding of the world around us. They are only normal parts of dangerous sects that threathen us.
References
[1] Why Did the World Trade Center Collapse? - Simple Analysis
Zdenek P. Bazant, F.ASCE, and Yong Zhou (2001)
[2] What Did and Did not Cause Collapse of WTC Twin Towers in New York
Zdenek P. Bazant, Jia-Liang Le, Frank R. Greening and David B. Benson (2008)
[3] Progressive Collapse of the World Trade Centre: a Simple Analysis
K. A. Seffen, Cambridge University
[4] Development of progressive Collapse Analysis Procedure and Condition Assessment for Structures
Professor Ted Krauthammer, Protective Technology Center, The Pennsylvania State University, Robert L. Hall, PhD, Stanley C. Woodson, PhD, James T. Baylot, PhD, John R. Hayes, PhD, US Army Engineer Research and Development Center, Young Sohn, PhD, Defense Threat Reduction Agency
[5] Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions
Zdenek P. Bazant, F.ASCE, and Mathieu Verdure (2007)
[6] The Missing Jolt: A Simple Refutation of the NIST-Bazant Collapse Hypothesis
Graeme MacQueen, Tony Szamboti, January 14, 2009
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