Hat-Truss Collapse Video
Video of the North Tower hat-truss/antenna falling. By removing the hat truss the exterior walls were free to fall away from the core as it was demolished. Nothing exotic to see here.
Slow-Motion close-up courtesy nineeleven twentyfourseven:
Related videos showing the “spire” falling straight-down in the same manner.
During the cleanup they demonstrated how they make vertical columns fall straight down: