It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
originally posted by: LaBTop
You really don't understand at all what a REAL thermobaric explosive is..... You just can't understand it.
originally posted by: neutronflux
a reply to: LaBTop
The more you post with out addressing simple questions just shows how lacking you are in understanding science and you lack the comprehension to create elegant and precise answers. If steel looses enough stiffness and drops, no matter how much it expansion and grows, it lost it's ability to expert force and resist strain. What happens when you push a heated bar of steel that lost its ability to resist strain in to an anvil. It buckles and expands out in diameter. The steel holding the floors lost it's ability to hold a load and resist gravity from its straight down pull.
This piece by "professor" Eagar and student Musso has to be some sort of record for the greatest number of lies, and points of misdirection, ever strung together in an "engineering" article. Comment is highlighted in red.
A fatal flaw in Eagar's theory, is that the tops of the trusses were embedded in the concrete slab, so even if a truss was heated to the point of failure, even if it was dripping molten steel, the concrete slab would still hold the truss up and it could not possibly fall as indicated in the animation. If one truss failed, its load was redistributed to the concrete slab and all the remaining trusses associated with that slab. So the failure of one, or even many trusses, does not lead to overall failure. There is absolutely no way that the trusses could collapse one after the other, as claimed by Eagar. Here is a quote from (a section on the WTC in) Multi-Storey Buildings in Steel , by Godfrey :
"Composite action between the concrete and the steelwork is ensured by extending the diagonal web members of the joists (trusses) through the steel decking and embedding them in the (concrete) slab."
Above is a photo of a number of 45 feet (13.5m) long trusses and a buckled steel column after the Broadgate Phase 8 fire (the WTC towers had 35 and 60 foot trusses). The fire occurred while the 14-story high-rise was under construction. Little of the steel was fire protected and the sprinkler system and other active measures were not yet operational. Even though a number of trusses and columns buckled, due to thermal expansion, no collapse was observed at Broadgate.
The system of design of the World Trade Center Towers is called tubular framing, since the perimeter frames of the building are designed to act as a cantilevered tube in resisting lateral forces. This design concept (the so-called tube within a tube architecture) has been employed in the construction of many of the world's tallest buildings. These include the John Hancock Center (1105 ft), the Standard Oil of Indiana Building (1125 ft) and the Sears Tower (1450 ft). In fact, it is the standard design for tall buildings. Vital to the structural integrity of these buildings are the composite floor slabs. In fact, if the floors were not composite, the buildings would eventually collapse.
Eagar totally ignores the fact that the floor slabs were composite (that is, studs or projections from the steel beams were embedded in the concrete slab) preferring to believe the fiction that the floors just rested upon the beams supporting them.
Eagar : ""That's essentially how the World Trade Center absorbed an airplane coming into it. It was somewhat like the way a net absorbs a baseball being thrown against it.""
This is deliberate misdirection. It would be more accurate to say that the towers absorbed the impact of the planes as a sheet of glass absorbs the impact of a bullet. Note that a baseball does more damage to a window than a bullet (even if we arrange that both have the exactly the same momentum). As we all know, the bullet will make a neat little bullet hole while a baseball will smash most of the glass out.
It is the speed (and shape) of the projectile that determines whether the impact damage is localized or spread across a large area. The faster the projectile, the more localized the damage. Other common examples illustrating this effect are, the driving of a nail through a piece of wood, and the firing a bullet through a fence-post. Both are done at speed and thus do only local damage. In both of these examples, the wood just a centimeter or two from the impact point, is essentially undamaged. Similarly, the aircraft impacts were at great speed and severe damage localized to a few floors.
These critical temperatures are only part of the picture. If individual components are exposed to temperatures in excess of those quoted, then they may fail. However, these same components when incorporated in larger structures can be heated to much greater temperatures before failure occurs. The June 1990 Broadgate fire occurred in a high-rise while under construction. Consequently, little of the steel was fire protected. Even though the fire blazed for 4.5 hours, the building did not collapse and runaway type failures did not occur. To investigate the implications of the Broadgate fire on fire standards, the British Steel and the Building Research Establishment performed a series of six experiments at Cardington on a simulated, eight-story building. Here is a quote from one of the research reports from these experiments.
Steel beams in standard fire tests reach a state of deflections and runaway well below temperatures achieved in real fires. In a composite steel frame structure these beams are designed to support the composite deck slab. It is therefore quite understandable that they are fire protected to avoid runaway failures. The fire at Broadgate showed that this (runaway failure) didn't actually happen in a real structure. Subsequently, six full-scale fire tests on a real composite frame structure at Cardington showed that despite large deflections of structural members affected by fire, runaway type failures did not occur in real frame structures when subjected to realistic fires in a variety of compartments. 
And here is a quote from the FEMA report into the WTC collapse (Appendix A).
In the mid-1990s British Steel and the Building Research Establishment performed a series of six experiments at Cardington to investigate the behavior of steel frame buildings. These experiments were conducted in a simulated, eight-story building. Secondary steel beams were not (fire) protected. Despite the temperature of the steel beams reaching 1,500-1,700°F (800-900°C) in three of the tests (well above the traditionally assumed critical temperature of 1,100°F (600°C), no collapse was observed in any of the six experiments.
To get a feeling for how amazingly fire-resistant composite steel structures really are, consider this:
Test 6: The office demonstration test fire at Cardington:
A compartment 18m wide and up to 10m deep with a floor area of 135m2, was constructed on the second floor, using concrete blockwork. The compartment represented an open plan office and contained a series of work-stations consisting of modern day furnishings, computers and filing systems. The test conditions were set to create a very severe fire by incorporating additional wood/plastic cribs to create a total fire load of 9.4 pounds per square foot (46kg per square meter). Less than 5% of offices would exceed this level (mainly office libraries). The fire load was made up of 69% wood, 20% plastic and 11% paper.
The steel columns were fire protected but the primary and secondary beams (and their connections) were not. The maximum atmosphere temperature was 2215°F (1213°C) and the maximum average temperature was approximately 1650°F (900°C). The maximum temperature of the unprotected steel was 2100°F (1150°C) with a maximum average temperature of about 1750°F (950°C). The steel beams would have only have had 3% of their strength at 2000°F (1100°C), with such little remaining strength left in the steel, the beams could only contribute as catenary tension members. It is also clear that the concrete floors were supplying strength to the structural system by membrane action.
The structure showed no signs of collapse.
One of the conclusions derived from the Cardington tests, was that fire protection for the beams (trusses) was not necessary (in a composite steel structure).
NOVA: You've pointed out that structural steel loses about half its strength at 1,200°F, yet even a 50 percent loss of strength is insufficient, by itself, to explain the collapse.
Eagar: Well, normally the biggest load on this building was the wind load (Author comment : actually the biggest load was the gravity load), trying to push it sideways and make it vibrate like a flag in the breeze. The World Trade Center building was designed to withstand a hurricane of about 140 miles an hour, but September 11th wasn't a windy day, so the major loads it was designed for were not on it at the time.
As a result, the World Trade Center, at the time each airplane hit it, was only loaded to about 20 percent of its capacity. That means it had to lose five times its capacity either due to temperature or buckling -- the temperature weakening the steel, the buckling changing the strength of a member because it's bent rather than straight. You can't explain the collapse just in terms of temperature, and you can't explain it just in terms of buckling. It was a combination.
Eagar claims that the exterior columns buckled. The exterior columns were visible from outside the building. There was no visible evidence that these columns buckled before the collapse. There is also no visible evidence that these columns were very hot. Photographs of these columns in the debris heap, showed no indications of thermal buckling (I guess the conspirators will claim that the reason no photographs showed thermal buckling of the exterior columns, was that they made sure that such columns were the first to hauled away and melted down). Eagar jumps from buckled columns to buckled beams in a few more lines, mixing up the two as if they are essentially the same.
Eagar: Exactly. If there was one part of the building in which a beam had a temperature difference of 300°F, then that beam would have become permanently distorted at relatively low temperatures. So instead of being nice and straight, it had a gentle curve. If you press down on a soda straw, you know that if it's perfectly straight, it will support a lot more load than if you start to put a little sideways bend in it. That's what happened in terms of the beams. They were weakened because they were bent by the fire.
(LT : His soda straw argument is again based on a SINGLE straw. Just as that pesky anvil argument. In the WTC floor areas heating situation, we have to include the huge composite steel and concrete floors keeping any axial displacement from happening in that web of 47 core columns. And don't forget the horizontal cross beams under those core area floors.
See the photo of the buckled top of that column in the Broadgate fire :
That goes even much more for the CORE areas, those had much thicker concrete and steel beams inside them. Especially the six (3 double) Maintenance floors, their concrete floors were even 3 times stronger constructed, to hold the extra weight of heavy machinery there.)
Eagar is, as usual, incorrect here. Buckling of beams does not necessarily lead to failure, in fact, in fires it is beneficial. For example, a laterally restrained beam (that will buckle at relatively low temperatures due to the lateral restraint) will not suffer runaway till around 900°C, whereas, a simply supported beam carrying the same loads (that will not buckle) will suffer runaway at around 450°C. So the beam that undergoes buckling is much preferred in a fire situation. Here are two more quotes from research papers examining the Cardington experiments.
In structures such as the composite steel frame at Cardington, the slab strongly restrains the thermal expansion strains and consequently develops large membrane compression and tension forces in the composite steel-concrete floor system. The membrane compressions can be limited by the large downward deflections which occur through thermo-mechanical post-buckling effects and thermal bowing (these are nonlinearly additive). The resulting behavior is then a combination of displacement and force responses. The heated steel part of this composite system, if unprotected, rapidly reaches its axial capacity (through local buckling and strength degradation), and produces a beneficial effect by limiting and then reducing the total membrane compression, so allowing increased expansion of the steel through softening and ductility. This is clearly a desirable behavior here, as it reduces the force imposed on the structure by the expansion forces and allows the damage to be localized. 
In composite floor slabs, buckling of the steel beams as a result of large compressions induced by restrained thermal expansions, is a positive event. The buckle allows the increase in length, as a result of thermal expansion, to be accommodated in downward deflections relieving axial compressions. 
So, in buildings comparable to the World Trade Center, buckling, paradoxically, has a beneficial effect.
But the steel still had plenty of strength, until it reached temperatures of 1,100°F to 1,300°F. In this range, the steel started losing a lot of strength, and the bending became greater. Eventually the steel lost 80 percent of its strength, because of this fire that consumed the whole floor.
If it had only occurred in one little corner, such as a trashcan caught on fire, you might have had to repair that corner, but the whole building wouldn't have come crashing down. The problem was, it was such a widely distributed fire, and then you got this domino effect. Once you started to get angle clips to fail in one area, it put extra load on other angle clips, and then it unzipped around the building on that floor in a matter of seconds.
NOVA: Many other engineers also feel the weak link was these angle clips, which held the floor trusses between the inner core of columns and the exterior columns. Is that simply because they were much smaller pieces of steel?
Eagar: Exactly. That's the easiest way to look at it. If you look at the whole structure, they are the smallest piece of steel. As everything begins to distort, the smallest piece is going to become the weak link in the chain. They were plenty strong for holding up one truss, but when you lost several trusses, the trusses adjacent to those had to hold two or three times what they were expected to hold.
More crap from Eagar. Does he really believe that the towers were only held together with a couple of rivets and duct tape. Here is a quote from the FEMA report into the WTC collapse (Chapter 2).
Pairs of flat bars extended diagonally from the exterior wall to the top chord of adjacent trusses. These diagonal flat bars, which were typically provided with shear studs, provided horizontal shear transfer between the floor slab and exterior wall, as well as out-of-plane bracing for perimeter columns not directly supporting floor trusses.
Eagar claims that the trusses were connected to the perimeter wall only by what he calls, "angle clips". The truth is that every 160 inches, the perimeter wall was solidly attached to a 24 x 18 inch metal plate that was covered with shear studs and set in the concrete slab. In addition a pair of 6 foot long, flat, steel bars lined with shear studs were welded to the plate and to the top chord of the adjacent trusses. These bars were also set in the concrete slab. Between these plates similar pairs of 6 foot long, flat, steel bars connected directly to tabs on the perimeter columns. So these features, as well as the angle clips, connected the perimeter wall to the concrete slab and hence to the rest of the building. Below, is a picture of these plates and steel bars before the concrete slab was poured. The plates are the dark rectangular objects along the perimeter wall. The steel bars are the V-like features :
What Can be Done about Trolls?
When you suspect that somebody is a troll, you might try responding with a polite, mild message to see if it's just somebody in a bad mood. Internet users sometimes let their passions get away from them when seated safely behind their keyboard. If you ignore their bluster and respond in a pleasant manner, they usually calm down.
However, if the person persists in being beastly, and seems to enjoy being unpleasant, the only effective position is summed up as follows:
The only way to deal with trolls is to limit your reaction to reminding others not to respond to trolls.
When you try to reason with a troll, he wins. When you insult a troll, he wins. When you scream at a troll, he wins. The only thing that trolls can't handle is being ignored.
What Not to Do
As already stated, it is futile to try to "cure" a troll of his obsession. But perhaps you simply cannot bear the hostile environment that the troll is creating and want to go away for a while.
those towers could STILL NOT COLLAPSE by fire and plane impacts.! "
originally posted by: hellobruce
originally posted by: LaBTop
You really don't understand at all what a REAL thermobaric explosive is..... You just can't understand it.
Actually, you are the one that has no clue at all what they are, if one went off inside a WTC building the noise and blast effects would have been huge, and everyone for km would have seen and heard that effect.
But you think somehow that they were hush a boom silent explosives....
originally posted by: cardinalfan0596
a reply to: LaBTop
"By the way, Charles M. Beck also showed you that even when we delete 50 % of all the steel from his equations, and to top it off, declare that the remaining half of it lost half of its strength, those towers could STILL NOT COLLAPSE by fire and plane impacts.! "
I am sure that is a great comfort to the families who lost loved ones that day. Mr. Beck says it couldn't happen that way....
originally posted by: cardinalfan0596
a reply to: LaBTop
I wonder what several hundred tons of steel, concrete, furniture, office equipment.....would do when it drops straight down onto a weakened structure......
MRFDEV : YouTube Flash Player has been successfully installed, thank you for giving it a try!
Now each time that you will load a YouTube video you will see the message "Playback isn't supported on this device" during one or two seconds, then the default HTML5 player will be replaced by the Flash Player. That's it, you have nothing to do!
If ever the message lasts more than a few seconds, press "ctrl + F5" on your keyboard to reload the page. You can also quickly enable and disable the add-on by clicking the button that has been placed in the main Firefox toolbar.
dlancer2k, 3 months ago (edited) :
You can see the support structure failing on the left side a whole six seconds before it fails on the right side. Right after the top left housing collapses, windows approx 8 floors down pop out. The windows are a result of the collapsed structure inside. If the broken windows were a result of explosives, they would've broken before the top left housing fell. Then after the windows stop popping out on the left side, the entire building is then being supported by the structures on the right side, and they can't handle the full weight, so the right-side structure buckles after six seconds, causing windows on the right side to pop out as the building falls. The whole thing takes about 12 seconds starting from initial left-side structure failure to finished collapse. Sorry, but that is nothing like a controlled demolition.
The left-side internal structures catching fire makes more sense.
Tony Szamboti : I ran a modal analysis for the northeast beam and girder assembly and it shows the assembly (with the five beams attached at the east wall, three support beams attached at the north wall, and the girder just sitting unrestrained on its seat at Column 44) has a natural frequency (Fn) of 0.52 Hz.
Fn = 1/2π * SQRT(K/m)
Stiffness (K) can then be found with the equation
K = (Fn * 2π)2 * m
The weight of the beams and girder is just over 20,000 lbs., so mass (m) = 20,000/32.174 = 622 slugs so
K = (0.52 * 6.28)2 * 622 = 6,633 lbs./inch
Using Nordenson's potential energy of 3,473,000 in-lbs. and the same standard equation he uses to find deflection
P.E. = 1/2K *D2
D = SQRT(2*P.E./K) = 32.4 inches
Now using the standard equation Nordenson uses to find force
F = K * D = 6,633 lbs./inch * 32.4 inches = 214,909 lbs.
This is only about 1/3rd of the 632,000 lb. force needed to shear the girder seat and proves that the falling girder would not have sheared the seat and the northeast corner of floor 12 would not have collapsed if a girder at floor 13 came off its seat at column 79.
Below are views of the FEA results. In case you are wondering : the information on the upper left says 5.1693e-01 Hz, which I rounded up to 0.52 Hz. The vertical mode was the second mode.
The first mode was side to side and it was 2.2661e-01, which would be 0.23 Hz, but isn't germane here.
SOURCE : Natural frequency of WTC 7 northeast corner beam & girder assembly.pdf
originally posted by: [post=20951627]Informer1958
Yes explosions were captured on most News videos on 911, our eyes do not lie to us.
Explosions so powerful that it hurled thousands of tons of steel support beams over 600 feet