OOOOPS typo on the thread title...should read COLLAPSE not collage!!!!!!!!!!!
As the core columns failed the load that each column had been supporting was no long able to follow the path through THAT column to the one below and on to bedrock that it does in its static state. The load above it now was bearing on "nothing" (or something) which could support it...air? or what was structurally "equivalent" to air. The immediately effect was for the column above the failed column above to drop down.. and in so doing it pulled all the bracing and floors bearing on failed column with them (where there were no shafts) downward. I suspect this broke the lateral beam stub connections to the failed column (3 stories of them), shattered the 3 floor areas locally around the failed/dropping column. This was sort of analogous to the ground dropping into a sink hole... and there was a "sink hole" created around (above) each failed column. The take away effect is that the core area ABOVE the failed columns were "sinking" and destroying the integrity of the core around it... freeing the floor mass from the structure whereas the dropping floor mass began to building to threshold driving collapse mass.
Note the descent of the antenna pre release. This appears to be the tell tale sign that the support for the antenna, coupling it to the columns below and on to bedrock had failed... the antenna was falling into a "sink hole". And of course since the sink hole failure was not perfectly symmetrical, (the damage and the axial load support in the column plan wasn't either) ...eccentricities would attend and so the antenna both descended and tilted. Note as well how eccentricities manifest in columns (antenna was a column with a pinned end condition)... as it dropped it tilted.
My hunch is that in the moments just before the observed release of the facade... pretty much most of the core had gone into "sink hole" behavior mode as the *sink holing* was propagating across the core.. not radially from the center of the core.... and since propagation was moving laterally plan asymmetry was created and this resulted in "tilting" as the last non sinking columns were the last paths of the loads to bedrock.
The sinking core's perimeter's columns then pulled down the core side ends of the floors (if connections held... some did and some didn't presumably) in the region adjacent to and above the failure zone (3 story high plane strike region of one core column length). The floors then either remained as cantilevered rectangular doughnut shapes attached to the facade (unlikely) ... or they began to break apart absent core side support and fall/fail independently very rapidly. The latter would contribute to the outside the core ROOSD mass.
I suspect once the core sink hole effect and ultimate bending and buckling of the last core columns engaged to bedrock... the insides of the upper section was like one massive hollowed out sink hole and its mass disorganized and disengaged from the facade dropping inside the outermost perimeter... which had rotated slightly as noted above, but was descending down pretty much as a rigid tube and breaking apart at its bottom upon impact with the rigid tube of the lower still engaged with bedrock facade below.
Note the facade appears to show inward movement locally in its initial failure. Was this buckling or being pulled in locally by falling floors? Perhaps both?
Therefore, I would suggest that the sink holing of the core preceded and was analogous to and enabled the ROOSD effect outside the core. The entire process of the inside of the tower going from static state to a dynamic "flow" of floor mass was the result of the progressive loss of axial support and column engagement with bedrock of the core which rapidly propagated through the core kicking off both tilting and ROOSD.
In my mind the only issue which remains uncertain is if there was sufficient heat to drive the progressive core column failures and how and where did the heat actually act? Did it drive the capacity of a few columns below service load and begin the progression of failures and sink holing? There was no other known mechanism to erode capacity post plane impact. If the heat was sufficient to accomplish this... the above sequence seems to work.
At the heart of the truth movement's belief... is that there was insufficient heat to weaken the steel frame to failure. Once begun all the column failures were mechanical not heat related... at best heat weakened and facilitated by loss of strength.
I think it comes down to a definitive answer of the fire caused heat issue.
No?
As the core columns failed the load that each column had been supporting was no long able to follow the path through THAT column to the one below and on to bedrock that it does in its static state. The load above it now was bearing on "nothing" (or something) which could support it...air? or what was structurally "equivalent" to air. The immediately effect was for the column above the failed column above to drop down.. and in so doing it pulled all the bracing and floors bearing on failed column with them (where there were no shafts) downward. I suspect this broke the lateral beam stub connections to the failed column (3 stories of them), shattered the 3 floor areas locally around the failed/dropping column. This was sort of analogous to the ground dropping into a sink hole... and there was a "sink hole" created around (above) each failed column. The take away effect is that the core area ABOVE the failed columns were "sinking" and destroying the integrity of the core around it... freeing the floor mass from the structure whereas the dropping floor mass began to building to threshold driving collapse mass.
Note the descent of the antenna pre release. This appears to be the tell tale sign that the support for the antenna, coupling it to the columns below and on to bedrock had failed... the antenna was falling into a "sink hole". And of course since the sink hole failure was not perfectly symmetrical, (the damage and the axial load support in the column plan wasn't either) ...eccentricities would attend and so the antenna both descended and tilted. Note as well how eccentricities manifest in columns (antenna was a column with a pinned end condition)... as it dropped it tilted.
My hunch is that in the moments just before the observed release of the facade... pretty much most of the core had gone into "sink hole" behavior mode as the *sink holing* was propagating across the core.. not radially from the center of the core.... and since propagation was moving laterally plan asymmetry was created and this resulted in "tilting" as the last non sinking columns were the last paths of the loads to bedrock.
The sinking core's perimeter's columns then pulled down the core side ends of the floors (if connections held... some did and some didn't presumably) in the region adjacent to and above the failure zone (3 story high plane strike region of one core column length). The floors then either remained as cantilevered rectangular doughnut shapes attached to the facade (unlikely) ... or they began to break apart absent core side support and fall/fail independently very rapidly. The latter would contribute to the outside the core ROOSD mass.
I suspect once the core sink hole effect and ultimate bending and buckling of the last core columns engaged to bedrock... the insides of the upper section was like one massive hollowed out sink hole and its mass disorganized and disengaged from the facade dropping inside the outermost perimeter... which had rotated slightly as noted above, but was descending down pretty much as a rigid tube and breaking apart at its bottom upon impact with the rigid tube of the lower still engaged with bedrock facade below.
Note the facade appears to show inward movement locally in its initial failure. Was this buckling or being pulled in locally by falling floors? Perhaps both?
Therefore, I would suggest that the sink holing of the core preceded and was analogous to and enabled the ROOSD effect outside the core. The entire process of the inside of the tower going from static state to a dynamic "flow" of floor mass was the result of the progressive loss of axial support and column engagement with bedrock of the core which rapidly propagated through the core kicking off both tilting and ROOSD.
In my mind the only issue which remains uncertain is if there was sufficient heat to drive the progressive core column failures and how and where did the heat actually act? Did it drive the capacity of a few columns below service load and begin the progression of failures and sink holing? There was no other known mechanism to erode capacity post plane impact. If the heat was sufficient to accomplish this... the above sequence seems to work.
At the heart of the truth movement's belief... is that there was insufficient heat to weaken the steel frame to failure. Once begun all the column failures were mechanical not heat related... at best heat weakened and facilitated by loss of strength.
I think it comes down to a definitive answer of the fire caused heat issue.
No?
via JREF Forum http://forums.randi.org/showthread.php?t=266004&goto=newpost
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