Why It Should Be Obvious That the WTC Towers Were Brought Down by Demolition
(modified and updated from an older post)
This essay is based strictly on structural concerns, and doesn't take into account more dramatic evidence of demolition, such as near free-fall time for fall, complete pulverization of interior contents, complete destruction of the structure, absence of a significant percentage of the massive structural steel columns in the debris, molten steel in the debris, elevated radiation at Ground Zero -- and all the other factors point to 9/11 being an "inside job", including lies about the plane crashes themselves.
But here we will focus purely on physics and engineering:
The official argument is that plane damage and fire weakened the structure enough at one point to cause the upper section of building to essentially break free, causing this upper section to drop down with tremendous force, enough to not only break through the next floor down, but with enough force to initiate a chain-reaction of cascading global collapse. The argument is that once this reaction started, there was no way the lower structure had enough strength to resist this force, and so the whole building collapsed in a pile of steel beams. The complete official mechanism for initiation of the global collapse is detailed here.
There are two basic questions about this argument.
1) First, is it even possible for the upper section of a building to break off precipitously such that it generates large downward momentum?
The answer would seem to be NO, based on he following logic:
The most amount of dropping momentum would be obtained if EVERY supporting column on that floor (say floor 97 for WTC1) gave way at the same time and gave way equally. But we can safely assume that the chances of this are so improbable as to be infinitesimal. So, let's say that half of the supporting columns that are fire weakened give way at the same time (this is probably too many than realistic, but let's go with it). This will require the other 50% of the columns to carry the additional load. Now these remaining columns will have more stress put on them. Realistically, the head-failed beams would be located on one side or one corner of the building. So, only that side would fail -- and the top of the building will rotate over and eventually fall off or at minimum lead to an asymmetric collapse on one side of the tower. Thus, an initial collapse leading to symmetrical collapse leading to global collapse violates basic physical laws. Right here, we can see that global collapse induced by this sort of column failure mechanism is extremely unlikely. This is of course why NIST admitted they were unable to model the global collapses!
But, to continue the argument, let's assume that every other column failed, all around the floor-- so 50% column failure. But there is yet another problem -- if half of the columns fail, the remaining columns will have to carry two-times the load they were designed to carry. But the safety factor had to be greater than TWO for a safe structure.
So for a section of building to break off, a full 75% of the supporting columns had to fail AT THE SAME TIME. But now, the probability of this is approaching zero, making it so unlikely we can discount it as an explanation.
2) Second, once a section of building drops down onto the lower section, will it automatically destroy the structure below it by sheer force of the huge mass being propelled downward by gravity?
The answer would seem to be NO, based on two lines of evidence:
a) For the 110 story WTC towers, the bottom layers of construction need to be far stronger than the upper floors, since the 10th floor would be required to support the weight of 100 floors above it, while the 90th floor would only need to support the weight of 20 floors. WTC1 was hit about floor 97, and thus the upper 13 floors (98 - 110) represent at most 12% of the building's total weight, but it is more likely they represented less than 10% of the total weight due to the strength issue. For the collapse of the WTC1 tower, common sense would say that a proportionally small mass of falling debris (9 - 12% of the buildings total mass) which only initially fell approximately 1 story (from 98th to 97th floor), could not crush the intact structure below, especially at the remarkable speed of collapse seen with the WTC1 collapse.
b) The failed demolition of the South Dakota feed mill showed how 80% of a tower dropping straight down several stories (because of the the failed demolition) was not enough to crush the lowest floor, much less start a progressive collapse.
3) Here are some other considerations:
a. If a large number of columns are going to all fail at the same time, they need to be evenly distributed if the collapse goes straight down.
b. The proportion of failed columns must be greater than 1/SF (SF =
safety factor). Typically, for large structures, the SF's are from 4 to 10.
c. Assuming “N” number of columns fail because of heat, they will essentially wilt. Heat does not cause brittle failure of steel. As the hot columns wilt, they will do so gradually, say within a minute -- not rapidly. This gradual wilting will not produce impact loading. As a result, the load carried by the remaining columns is gradually increased (even if over a 1-minute duration). So, now we have a heavy building sitting on fewer columns. There is no rapid initial collapse that will start the chain reaction going.
d. The columns will only buckle if the cross bracing as also been removed. If the column buckles, it can buckle outward or inward, somewhat like an archery bow. That's what the buckled column should be like, as structural steel is a ductile material. So, the buckling column would bend and lower the floor down, gradually (again, over several seconds to a minute time frame).
These factors all STRONGLY indicate that a precipitous progressive collapse of an upper section of the WTC can not occur simply from plane damage and fire. The only explanation for the collapses, therefore, is some form of powerful explosive demolition.
Similar logic holds for WTC7, except we take away the much of the structural damage seen for the twin towers, making the fire-induced collapsed explanation essentially impossible.
Finally, apart from 9/11, there are NO real world examples of top-down symmetrical and global collapses of towers!
This essay is based strictly on structural concerns, and doesn't take into account more dramatic evidence of demolition, such as near free-fall time for fall, complete pulverization of interior contents, complete destruction of the structure, absence of a significant percentage of the massive structural steel columns in the debris, molten steel in the debris, elevated radiation at Ground Zero -- and all the other factors point to 9/11 being an "inside job", including lies about the plane crashes themselves.
But here we will focus purely on physics and engineering:
The official argument is that plane damage and fire weakened the structure enough at one point to cause the upper section of building to essentially break free, causing this upper section to drop down with tremendous force, enough to not only break through the next floor down, but with enough force to initiate a chain-reaction of cascading global collapse. The argument is that once this reaction started, there was no way the lower structure had enough strength to resist this force, and so the whole building collapsed in a pile of steel beams. The complete official mechanism for initiation of the global collapse is detailed here.
There are two basic questions about this argument.
1) First, is it even possible for the upper section of a building to break off precipitously such that it generates large downward momentum?
The answer would seem to be NO, based on he following logic:
The most amount of dropping momentum would be obtained if EVERY supporting column on that floor (say floor 97 for WTC1) gave way at the same time and gave way equally. But we can safely assume that the chances of this are so improbable as to be infinitesimal. So, let's say that half of the supporting columns that are fire weakened give way at the same time (this is probably too many than realistic, but let's go with it). This will require the other 50% of the columns to carry the additional load. Now these remaining columns will have more stress put on them. Realistically, the head-failed beams would be located on one side or one corner of the building. So, only that side would fail -- and the top of the building will rotate over and eventually fall off or at minimum lead to an asymmetric collapse on one side of the tower. Thus, an initial collapse leading to symmetrical collapse leading to global collapse violates basic physical laws. Right here, we can see that global collapse induced by this sort of column failure mechanism is extremely unlikely. This is of course why NIST admitted they were unable to model the global collapses!
But, to continue the argument, let's assume that every other column failed, all around the floor-- so 50% column failure. But there is yet another problem -- if half of the columns fail, the remaining columns will have to carry two-times the load they were designed to carry. But the safety factor had to be greater than TWO for a safe structure.
So for a section of building to break off, a full 75% of the supporting columns had to fail AT THE SAME TIME. But now, the probability of this is approaching zero, making it so unlikely we can discount it as an explanation.
2) Second, once a section of building drops down onto the lower section, will it automatically destroy the structure below it by sheer force of the huge mass being propelled downward by gravity?
The answer would seem to be NO, based on two lines of evidence:
a) For the 110 story WTC towers, the bottom layers of construction need to be far stronger than the upper floors, since the 10th floor would be required to support the weight of 100 floors above it, while the 90th floor would only need to support the weight of 20 floors. WTC1 was hit about floor 97, and thus the upper 13 floors (98 - 110) represent at most 12% of the building's total weight, but it is more likely they represented less than 10% of the total weight due to the strength issue. For the collapse of the WTC1 tower, common sense would say that a proportionally small mass of falling debris (9 - 12% of the buildings total mass) which only initially fell approximately 1 story (from 98th to 97th floor), could not crush the intact structure below, especially at the remarkable speed of collapse seen with the WTC1 collapse.
b) The failed demolition of the South Dakota feed mill showed how 80% of a tower dropping straight down several stories (because of the the failed demolition) was not enough to crush the lowest floor, much less start a progressive collapse.
3) Here are some other considerations:
a. If a large number of columns are going to all fail at the same time, they need to be evenly distributed if the collapse goes straight down.
b. The proportion of failed columns must be greater than 1/SF (SF =
safety factor). Typically, for large structures, the SF's are from 4 to 10.
c. Assuming “N” number of columns fail because of heat, they will essentially wilt. Heat does not cause brittle failure of steel. As the hot columns wilt, they will do so gradually, say within a minute -- not rapidly. This gradual wilting will not produce impact loading. As a result, the load carried by the remaining columns is gradually increased (even if over a 1-minute duration). So, now we have a heavy building sitting on fewer columns. There is no rapid initial collapse that will start the chain reaction going.
d. The columns will only buckle if the cross bracing as also been removed. If the column buckles, it can buckle outward or inward, somewhat like an archery bow. That's what the buckled column should be like, as structural steel is a ductile material. So, the buckling column would bend and lower the floor down, gradually (again, over several seconds to a minute time frame).
These factors all STRONGLY indicate that a precipitous progressive collapse of an upper section of the WTC can not occur simply from plane damage and fire. The only explanation for the collapses, therefore, is some form of powerful explosive demolition.
Similar logic holds for WTC7, except we take away the much of the structural damage seen for the twin towers, making the fire-induced collapsed explanation essentially impossible.
Finally, apart from 9/11, there are NO real world examples of top-down symmetrical and global collapses of towers!
posted by spooked at 10:09 AM
2 Comments:
totally obvious!
Thanks, Spooked. That's one of the few explanations that this non-technical person can understand.
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