[darbymcgill]

I spent many many hours inside the perimeter in the days following the bombing, working with the USAR and FEMA teams. The details they gave us as far as how the explosion destroyed the building were as follows.

The truck bomb explosion lifted up the front of the Murrah building, compromising one or two of the main horizontal supports on the north side. When the weight of the upper floors came back down, the supports failed and the upper floors crashed through the remaining lower floors. Hence the huge rubble pile in the front middle of the building.

The hole was not blown out of the building, essentially, the hole was created when the unsupported north side of the building collapsed on itself.

I don't know if this explanation helps or hurts anyone's theory, it's just one we were given from the architectural / engineering teams working the site.

[DBrow]

darbymcgill, I seem to remember that there was a first floor transfer beam, that verticals from higher floors rested on- the vertical columns did not go to ground level but terminated on the transfer beam. This allowed for larger open spaces on the ground floor.

When the transfer beam failed, the columns collapsed and a huge chunk fell in.

If you then looked at pictures of the wreckage there was an area where it looked like there should have been columns sticking up from the floor but there were none.

Is my memory correct? is what I'm remembering as transfer beams the main horizontal supports you mention?

And, you were inside the perimeter post blast? What an experience that must have been. I'm sure not a pleasant one, but still, you were a firsthand witness to a really major event.