Can you specify exactly what local failures you would expect to see?
The WTC1 case is described at
http://heiwaco.tripod.com/nist3.htm but let's summarize:
Assumptions:
Upper block weighs m = 33 000 000 kgs and free falls h = 3.7 m due to g = 9.82 m/s² on the lower structure. The force it applies on the lower structure at contact is 0.3241 gN and the available energy is 1.199 GJ. The lower structure applies the same force on the upper block.
The velocity v of the upper block at contact is quite low - 8.52 m/s.
At contact 240 cut off columns of both upper block and lower structure do not contact anything as they are assumed outside the foot print in the air.
Remaining 320 cut off columns of both upper block and lower structure are assumed to contact the top floor of the lower structure and the bottom floor of the upper block.
First group of local failures:
Thus there are 320 contact points columns/floors and the columns will punch holes in the floors at first contact. Local failures and energy absorbation and deceleration (and collapse arrest) have started to take place in both upper block and lower structure. Columns are assumed generally intact after these first contacts.
It is assumed that sections of locally damaged floors hinges down on floors below and contact one another causing friction + more local failures absorbing further energy and causing decelaration. Damaged floors in lower structure do not generally add any energy to the destruction as they are still fixed to lower structure columns (just hinging down).
The energy required to produce the first group of local failures can be calculated and its effects on further destruction (energy still available to produce local failures). Already at this stage the upper block must start to tilt due to the unsymmetrical distribution of contact points. Energy added due to upper block downward displacement must be corrected for.
Note that no shock waves, etc, are produced into the lower structure away from the contact points. In laymen's terms; the intact lower structure away from contact points have not got a clue what's going on above it - it is just local failures.
Note also that the upper block is subject to serious local failures from beginning and cannot be regarded at rigid, intact or indestructible.
Second group of local failures:
They are similar to the first group and are produced when the second floors of the upper block and lower structure are contacted by the columns. Now total four levels of floor sections are subject to local failures, there are more contacts points and further local failures between and in them consuming energy. At this stage the upper block is really tilting and there is contacts between perimeter walls of upper block/lower structure consuming energy.
The energy required to produce the second group of local failures can evidently be calculated and its effects on further destruction (energy still available to produce local failures).
And so on. These failures can go on until there are no more floors left in the upper block, when two of its perimeter walls (120 columns) drop down outside the lower structure. But more likely the destruction will stop earlier.
My gut feeling is that all energy available is consumed after 3 or 4 floors of both upper block and lower structure have been locally damaged and that then the destruction is arrested. The upper block is then stopped. The whole event from first contact until arrest may be 3 - 4 seconds incl. 1000's of local failures.
There are software available to do the above local failure analysises and energy absorbtion calculations. They have been used to simulate ship collisions, where much more energies and local steel structure failures were involved (and destruction was arrested after 8-10 seconds). Same software can be used to simulate ships colliding with icebergs.
