21-10-2012, 05:12 PM
Albert we can only speculate at the cause but we can be more certain of the mechanism of collapse because we can measure and study the movement of the building. As I have proposed the collapse appears to have been the result of a weakened structure below the core in the 6&7th floors where the transfer trusses spanned over the sub station.
When the aggregage strength was less than the actual loads.. the tower collapsed. The weakening was likey a process where one failure in one member of the structure which could no longer carry the loads it was designed to carry and its load was distributed to other parts of the structure (colums and transfer trusses). This eroded the reserve strength of those members. The structure remained standing as long as the aggregate strength exceed the loads... but when it no longer could support the loads the entire structure collapsed.
However, before that... it's possible to have local failures and collapses... the columns or members which for whatever reason lost the ability to carry their design loads. We saw the east penthouse come down AS the rest of the tower stood. But this was the beginning of the end. So it is MORE than likely that there was local interior destruction/collapse of parts of the building and this WOULD send dust out (from the lower floors) where the collapse took place... stuff fall down!
The collapse was a process... a progression and it was only the easily visible parts at the end of the process that we refer to when we call use the term collapse or destruction (or CD). All of it took place behind the facade...in the lowest floors obscurred from camera view. But when the strength was gone we saw it collapse before our eyes.
When the aggregage strength was less than the actual loads.. the tower collapsed. The weakening was likey a process where one failure in one member of the structure which could no longer carry the loads it was designed to carry and its load was distributed to other parts of the structure (colums and transfer trusses). This eroded the reserve strength of those members. The structure remained standing as long as the aggregate strength exceed the loads... but when it no longer could support the loads the entire structure collapsed.
However, before that... it's possible to have local failures and collapses... the columns or members which for whatever reason lost the ability to carry their design loads. We saw the east penthouse come down AS the rest of the tower stood. But this was the beginning of the end. So it is MORE than likely that there was local interior destruction/collapse of parts of the building and this WOULD send dust out (from the lower floors) where the collapse took place... stuff fall down!
The collapse was a process... a progression and it was only the easily visible parts at the end of the process that we refer to when we call use the term collapse or destruction (or CD). All of it took place behind the facade...in the lowest floors obscurred from camera view. But when the strength was gone we saw it collapse before our eyes.