15-05-2011, 01:26 AM
I don't have present a hypothesis. I present accepted engineering principles applied to the situation at the twin towers.
Every floor is designed to support a live load in addition to carrying its own weight. In the case of office uses in NYC the code stipulates the floor must be designed to support 100 psf (pounds per square foot). At the time when the towers we being design the PANYNJ requested and were granted a load reduction to 58 psf.
Regardless any floor will fail when over loaded. This is not at the safe working load because the floor and its components have a safety factor. A 5/8" Ø grade 5 coarse threaded bolt has a safe working load (tensile strength) of 27,000 pounds. But with a safety factor it will take more to "fail" the bolt. Safety factors in steel designs are up to 1.5 typically. It's also hard ... and not done in practice to engineer each component to have the same working design load and safety factor in a composite floor system, for example. So in the case of the twin tower floors there were many components, each with their own design performance specs, but each selected to support their part of the assumed design load.
What occurred in the collapse of the WTC composite floors is that they were "assaulted"... by imposed loads far in excess of their safety factor.. whether it was 2, 4, or 6. The design load was 58 psf and floors themselves weighed 120 psf... this includes to 4" light weight slab, the trusses, ceiling tiles and steel to hang them... 22ga metal decking. So each floor itself weighed 2x the design live load. If you simply placed floor 87 on top of floor 86 it would be then carrying 2x its design load... likely less than the margin of safety (design safety factor) it would not fail or fracture. But if you dropped floor 87 on floor 86 it would be a DYNAMIC load and this could be as much as 10x the static load. This is the difference between resting a hammer on your head and letting one drop from 2 feet onto your head. Both cases the hammer weighs 20 oz. But the load experienced by your skull is perhaps 10 times in the dropping case then it is in the resting case.
What you had in the towers was an assault of many dynamic loads from the destroyed floors above the crash zone. We don't know how those floors were destroyed, fractured and broken apart. But once they were... they provided the sufficient over loads to fail any undamaged tenant composite floor.
This did not involve the crushing of any columns as others seem to be focused on to claim that the floors could not possibly collapse. Witness Jim Fetzer's hard head on this as well as those of Gage, Boldwyn, Woods and numerous others who simply haven't looked at the structure or considered the most basic engineering principles at work. I am 100% certain the Dr. Bazant would agree with all of the above as would any qualified civil engineer.
The official story re the twin towers did NOT discuss the actual collapse. They tried (and failed) to (weave a tale) explain what caused the collapse to begin... the sagging truss rubbish. No one accepts that and it has been proven by computer modeling to be impossible. The fact that the official story didn't explain the "collapse" phase... post initiation does not mean it "defied physics" or engineering or simply could not be explained.
By not explaining the basic engineering as I have above, they have left fertile ground for all sorts of speculation and "theories" about what happened as the towers came down.
The task before us is to figure out what initiated this gravity driven collapse. THAT is fertile ground for research, hypothesis and speculation. Arguing about the collapse phase is a waste of time and is making a mockery of the "science" of the 911 truth movement. Send in the clowns.. or send them away I say.
Understanding begins with observations informed by technical experience in structural engineering, physics, material science and the specific design of the structure observed collapsing / or being destroyed. If you aren't up to snuff on these discplines you can't possibly understand what you think you are seeing and your observations are no more informed than a child or naive adult... or armchair "expert" such as Jim Fetzer.
Every floor is designed to support a live load in addition to carrying its own weight. In the case of office uses in NYC the code stipulates the floor must be designed to support 100 psf (pounds per square foot). At the time when the towers we being design the PANYNJ requested and were granted a load reduction to 58 psf.
Regardless any floor will fail when over loaded. This is not at the safe working load because the floor and its components have a safety factor. A 5/8" Ø grade 5 coarse threaded bolt has a safe working load (tensile strength) of 27,000 pounds. But with a safety factor it will take more to "fail" the bolt. Safety factors in steel designs are up to 1.5 typically. It's also hard ... and not done in practice to engineer each component to have the same working design load and safety factor in a composite floor system, for example. So in the case of the twin tower floors there were many components, each with their own design performance specs, but each selected to support their part of the assumed design load.
What occurred in the collapse of the WTC composite floors is that they were "assaulted"... by imposed loads far in excess of their safety factor.. whether it was 2, 4, or 6. The design load was 58 psf and floors themselves weighed 120 psf... this includes to 4" light weight slab, the trusses, ceiling tiles and steel to hang them... 22ga metal decking. So each floor itself weighed 2x the design live load. If you simply placed floor 87 on top of floor 86 it would be then carrying 2x its design load... likely less than the margin of safety (design safety factor) it would not fail or fracture. But if you dropped floor 87 on floor 86 it would be a DYNAMIC load and this could be as much as 10x the static load. This is the difference between resting a hammer on your head and letting one drop from 2 feet onto your head. Both cases the hammer weighs 20 oz. But the load experienced by your skull is perhaps 10 times in the dropping case then it is in the resting case.
What you had in the towers was an assault of many dynamic loads from the destroyed floors above the crash zone. We don't know how those floors were destroyed, fractured and broken apart. But once they were... they provided the sufficient over loads to fail any undamaged tenant composite floor.
This did not involve the crushing of any columns as others seem to be focused on to claim that the floors could not possibly collapse. Witness Jim Fetzer's hard head on this as well as those of Gage, Boldwyn, Woods and numerous others who simply haven't looked at the structure or considered the most basic engineering principles at work. I am 100% certain the Dr. Bazant would agree with all of the above as would any qualified civil engineer.
The official story re the twin towers did NOT discuss the actual collapse. They tried (and failed) to (weave a tale) explain what caused the collapse to begin... the sagging truss rubbish. No one accepts that and it has been proven by computer modeling to be impossible. The fact that the official story didn't explain the "collapse" phase... post initiation does not mean it "defied physics" or engineering or simply could not be explained.
By not explaining the basic engineering as I have above, they have left fertile ground for all sorts of speculation and "theories" about what happened as the towers came down.
The task before us is to figure out what initiated this gravity driven collapse. THAT is fertile ground for research, hypothesis and speculation. Arguing about the collapse phase is a waste of time and is making a mockery of the "science" of the 911 truth movement. Send in the clowns.. or send them away I say.
Understanding begins with observations informed by technical experience in structural engineering, physics, material science and the specific design of the structure observed collapsing / or being destroyed. If you aren't up to snuff on these discplines you can't possibly understand what you think you are seeing and your observations are no more informed than a child or naive adult... or armchair "expert" such as Jim Fetzer.