Status reports from Chief Hayden and engineers with at at least one transit advising Hayden?
Stephen Gregory says that multiple FDNY "collapse units" were on on the scene. FDNY deals with unstable buildings on a regular basis and maybe Tri can describe in detail what these people do. I expect the brought the transit and know how to use it.
Reports from the unit commanders for the 100+ firemen named in this index?
Mark Roberts indexed all the statements of the firemen. Maybe you've never seen this before. All the names are in the spreadsheet, below and the full transcripts are at the URL, below. The transcripts give lits of context and additional information. They make good reading. Many of the 36 people that said "pull" were tallking about collapse. I think you can start there.
- 41 firemen mention severity of fire in WTC7
- 29 firemen mention damage to WTC7
- 104 firemen mention pullback from WTC7
- 36 firemen mention "Pull" to mean withdraw from the building
Summary spreadsheet names & statements:
Yes, BigAl, I can tell you what they do.
If we (FDNY) suspect that a building may be in danger, we caall the collapse unit in.
Once the collapse unit arrives, they set the collapse zone up around the building. Some of the guys who command that unit are engineers, some are experts in survey equipment. (Transits and the like)
Now, for the most part, they sit over there, and do calculations, look at the building, look at the blueprints of said building, then make an educated guess on if it will fall, or when it will fall.
Now, once they have done that, they decide what to do about the building. Sometimes we bring in heavy equipment, sometimes we would use cribbing and shore the building till someone more qualified can decide what to do. These guys are usually engineers or architects from local firms, or from the department itself.
The other job of the collapse unit is post-collapse. Deciding what to move, how to move it, where to place air bags, rams, spreaders, and the like. They also dictate where we need to shore up something, and how to do it.
Hope that helps.