It took a long time for WTC7 to collapse and it resulted from an internal fire that consumed the non-structural elements of the building and weakened the steel far below its margins of safety. Carbonaceous fuels are easily hot enough to melt steel (what do you suppose we use for blast furnaces?). Nuclear sources are simple loony fantasy.
What "thermal expansion" theory? What I have read is that the center of the building collapsed from weakening of the structural members (loss of strength with temperature). It may well be that the heating distorted the structural frame and created stresses that accelerated the process. Upon collapse of the center, the exterior walls followed suit. This is so unremarkable that I wonder how you can avoid it.
Thermal expansion is a concept that NIST came up with and was popularized in a popular mechanics article on the topic. Also total bullshit.
Review the facts;
no plane hit wtc 7.
no additional combustible material was supposed to be there (I.e. contents of an airplane’s gas tanks)
this means the only combustible material would be standard office tower contents. Review all prior office tower fires in history, is there a single one that collapsed into its own foot print? The answer is no.
in the dust of the wtc complex we find micro iron spheres. Operating theory is that they are produced when molten metal (not hear weakened, but steel in liquid state) is forcibley blown out into the atmosphere where is cools while on free fall.
in the dust of the wtc complex unexploded nano thermate is detected. (I forget many of the details, there is a difference between thermate and thermite; the nano bit comes in because commercial grade stuff is made of materials with x particle size; but this unexploded stuff that was found had component bits that were MUCH MUCH smaller. This means highly sophisticated manufacturing techniques and a thermate that is much more expensive than commercial grade stuff and a thermate that is not commercially available was in fact used.
then we get to the free fall speed. Proven using video and known measurements. Wtc 7 collapsed entirely within … 11 seconds? For 6 of those seconds it can be shown (and was demonstrated by analysis performed in university of Alaska) the roof line of wtc 7 falls at free fall speed. That means everything under the roof also was falling at the speed of gravity. No resistance whatsoever. Think of a tower of wood in your camp fire. It falls over. Ok. But it falls over and hits another piece of wood that changes trajectory of the fall or slows the fall to some degree. Now imagine what is required for a roof line to fall at free fall speed. Answer: everything supporting that roof line also collapsed at that same instant.
squibs. Aka lateral ejections of material from the building often seen in controlled demolitions. Squibs are clearly visible in all three buildings pre and during collapse.
No airplane fuel. So what. That was never a point.
Everything that was not steel or aluminum or glass was potentially combustible, including flooring, ceiling materials, wall, partitions, doors, as well as office furniture. The history of other fires does not disprove the existence of this one. There is always a first time for everything. The fire took a while to generate, and if it is confined, the temperatures can get very high.
As mentioned as simple fact, the burning of carbonaceous materials (wood, etc.) results in temperatures higher than the melting point of steel (wood @ 3596 F, iron @ 2800 F). The collapse would compress the air in the floor spaces and eject any molten materials by aspiration.
Nobody describes what is actually found. There would have to be aluminum oxide present. The fact that it is not mentioned is a "tell" for me that the people making the claim do not understand the chemistry of thermite. The presence of iron micro-spheres would only be evidence for the existence of molten steel, which would be resulting from the high temperature. Also, structural failure by compressive shear results in flaking of the steel from the shear surface.
Free fall. Nothing mysterious here. You have a building whose weight is supported by structural columns, based on design levels of compressive stress and safety margins of strength. A fire originates within the building, turning it into a furnace within. The strength of the steel columns will steadily drop with the increasing temperature until the strength at a given floor (it doesn't matter which one) will reach zero margin...and some column will fail in shear, which is essentially instantaneous. The compressive load will be redistributed among all the remaining columns at the speed of sound in the hot steel, taking maybe a millisecond, and then another column (or columns) would fail in shear, leading to a chain reaction that would take maybe a tenth of a second to accomplish across all the columns. And then the supported mass would descend at free fall. As it collides with floors beneath, the whole overload chain reaction would occur again in another tiny fraction of a second. Until it reaches bottom, at which time the now-unsupported walls would collapse inward. The tiny delays for the chain reaction would not be noticeable in an analysis that wouldn't have the timing resolution to notice a difference.
No squibs. Just the compression of air in the collapsing floors and its exhaust through perforations in the building walls. Blowing out dust and smoke. What else would you expect? You have to understand what is going on, in order to understand what you are seeing.
It took a long time for WTC7 to collapse and it resulted from an internal fire that consumed the non-structural elements of the building and weakened the steel far below its margins of safety. Carbonaceous fuels are easily hot enough to melt steel (what do you suppose we use for blast furnaces?). Nuclear sources are simple loony fantasy.
The thermal expansion theory put out by NIST is looney tunes as well. WTC 7 was taken out by preplanted explosives. (Thermate)
What "thermal expansion" theory? What I have read is that the center of the building collapsed from weakening of the structural members (loss of strength with temperature). It may well be that the heating distorted the structural frame and created stresses that accelerated the process. Upon collapse of the center, the exterior walls followed suit. This is so unremarkable that I wonder how you can avoid it.
Because that explanation is total bullshit.
Thermal expansion is a concept that NIST came up with and was popularized in a popular mechanics article on the topic. Also total bullshit.
Review the facts;
No plane. So what. That was never a point.
No airplane fuel. So what. That was never a point.
Everything that was not steel or aluminum or glass was potentially combustible, including flooring, ceiling materials, wall, partitions, doors, as well as office furniture. The history of other fires does not disprove the existence of this one. There is always a first time for everything. The fire took a while to generate, and if it is confined, the temperatures can get very high.
As mentioned as simple fact, the burning of carbonaceous materials (wood, etc.) results in temperatures higher than the melting point of steel (wood @ 3596 F, iron @ 2800 F). The collapse would compress the air in the floor spaces and eject any molten materials by aspiration.
Nobody describes what is actually found. There would have to be aluminum oxide present. The fact that it is not mentioned is a "tell" for me that the people making the claim do not understand the chemistry of thermite. The presence of iron micro-spheres would only be evidence for the existence of molten steel, which would be resulting from the high temperature. Also, structural failure by compressive shear results in flaking of the steel from the shear surface.
Free fall. Nothing mysterious here. You have a building whose weight is supported by structural columns, based on design levels of compressive stress and safety margins of strength. A fire originates within the building, turning it into a furnace within. The strength of the steel columns will steadily drop with the increasing temperature until the strength at a given floor (it doesn't matter which one) will reach zero margin...and some column will fail in shear, which is essentially instantaneous. The compressive load will be redistributed among all the remaining columns at the speed of sound in the hot steel, taking maybe a millisecond, and then another column (or columns) would fail in shear, leading to a chain reaction that would take maybe a tenth of a second to accomplish across all the columns. And then the supported mass would descend at free fall. As it collides with floors beneath, the whole overload chain reaction would occur again in another tiny fraction of a second. Until it reaches bottom, at which time the now-unsupported walls would collapse inward. The tiny delays for the chain reaction would not be noticeable in an analysis that wouldn't have the timing resolution to notice a difference.
No squibs. Just the compression of air in the collapsing floors and its exhaust through perforations in the building walls. Blowing out dust and smoke. What else would you expect? You have to understand what is going on, in order to understand what you are seeing.