Citat:
Ursprungligen postat av
SnakePlisssken
Ja det står i NISTs rapport att kolumnerna fortsatte under våning 1 genom en grusfylld grund innesluten under betongplattor, många kolonner var dessutom ingjutna i cement, och gick sedan ner i kassunerna.
Nist ncstar 1-9 sid 12:
The caissons extended through the soil, and were socketed (seated) in the bedrock, approximately 60 ft below the surface. There were vertical caissons as well as battered (or sloped) caissons to carry the lateral load. Above the caissons were heavy grillages composed of built up steel girders. Grillages transferred loads between the building columns and the caissons.
The distance between the caisson grillages and the first floor varied between 8 ft and 30 ft.
This region was braced by reinforced concrete walls with thicknesses varying from 1 ft to 2.5 ft. Many of the WTC 7 steel columns were embedded in these walls, and supporting steel braces were made composite by the addition of shear studs along the height of the embedment.
Areas between the concrete walls were backfilled with compacted gravel fill and then covered with a concrete slab on grade or framed slab to form closed cells and bring the structure up to the required elevation. In some cases, the area was left unfilled and used to house fuel tanks.
Grillage: A foundation of crisscrossing timber or steel beams, usually for spreading heavy loads over large areas.
Det verkar således som att det fanns ett utrymme på mellan ca 2,5 - 9 meter mellan floor 1 och den här ”grillage’-konstruktionen.
Var det utrymmet oåtkomligt menar du?