The time behavior of what Bazant calls zone A and C depend upon the connection strength between individual floors. He states his own assumption of the forces between individual floors in his third assumption listed in the very first paragraph of the BV section reproduced in my last post.
I wrote that I strongly recommend approaching analysis of the BV, BL, and BLGB papers through the following 7 perspectives:
1) Direct comparision between Bazant and Seffen methods and their key equations of motion (Seffen eq 12 compared to Bazant eqs 12 and 17).
2)) A basic study of 1-dimensional stacked system collision interactions with a variety of parameters altered linked here. This gives one a simple, practical sense of 1-dimensional multiple body interactions, like the type described in BV eqs 12 and 17, and the possible varieties of mechanical movements that can result from them.
3) Direct comparison of claims within BV to the actual collapse propagation rates which were recorded after the 2007-2008 Bazant papers were written.
4) Quotes by David Benson demonstrating how he understood the relationship between BV eqs 12, 17 and the actual collapses of WTC1, 2 linked here
5) Statements by Bazant in BL (the closure to BV) and BLGB demonstrating how he understood the relationship between BV eqs 12, 17 and the actual collapses of WTC1, 2.
6) Comparison of statements about WTC1 and 2 made within BV, BL, and BLGB directly with the visual record of events through the lens of the most accurate mappings of the WTC1, 2 collapse behavior (available in parts 2.1, 2.2, 2.3, and 2.4 of my book).
7) Practical comparison of BV eqs 12 and 17 and Seffen eq 12 to video records of Verinage demolitions.
My own suggested approach to the study of crush up, crush down mechanics of stacked systems of masses in 1 dimension is given in the second perspective offered above.
The mathematical approach to the study of ROOSD propagation is given below as 5 clearly marked steps to be taken in order:
Step 1: GAIN AN OVERALL CONCEPTUAL AND VISUAL UNDERSTANDING OF WHAT ONE IS LOOKING AT
Step 2: RESEARCH AVAILABLE LITERATURE ON THE SUBJECT OF FLOORS IMPACTING FLOORS
Step 3: MEASURE THE COLLAPSE PROPAGATION RATE AS ACCURATELY AND COMPLETELY AS POSSIBLE
Step 4: EXAMINE A VARIETY OF PHYSICS-BASED MATHEMATICAL APPROACHES TO THE COLLAPSE OF STACKED SYSTEMS
Step 5: COMPARE MODELS IN STEP 4 TO INFORMATION IN STEPS 1 - 3 to see which models could match propagation behavior or teach something about it.
Step 1 is incredibly important. I approach step 1 by using a descriptive model which some of us have called ROOSD or 'OOS propagation model.'
The OOS model is based on 6 observable physical features of the WTC1, 2 collapses:
1) Observed Behavior of WTC1 Core
2) Observed Motion of WTC1, 2 Perimeter Walls
3) Observed Behavior of the Crush Fronts
4) Observation of core and perimeter columns within the rubble
5) Pieces of flooring remain intact and people survive at the base of WTC 1
6) Appearance at the base of each tower after collapse
Note that in following the simple 5 step process, mappings of the most global features of the collapses are created in step 1. These mappings involve no assumptions of any kind.
Your question: Coversely, what are the assumptions about mass in ROOSD, in both directions?
Unlike both Bazant and Seffen, I do not speculate about collapse front behavior either upward or downward at all. I map it instead.
