The collapse of the northern half of the building took roughly seven seconds. As the truck exploded, it first destroyed the column next to it, designated as G20, and shattered the entire glass facade of the building. The shockwave of the explosion forced the lower floors upwards, before the fourth and fifth floors collapsed onto the third floor, which housed a transfer beam that ran the length of the building and was being supported by four pillars below, as well as supporting the pillars that hold the upper floors. The added weight meant that the third floor gave way along with the transfer beam, which in turn caused the collapse of the building."The Bomb in Oklahoma City" ("Oklahoma City"). Seconds From Disaster.
The collapse of the northern half of the building took roughly seven seconds. As the truck exploded, it first destroyed the column next to it, designated as G20, and shattered the entire glass facade of the building. The shockwave of the explosion forced the lower floors upwards, before the fourth and fifth floors collapsed onto the third floor which housed a tr,ansfer beam that ran the length of the building and was being supported by four pillars below, as well as supporting the pillars that hold the upper floors. The added weight meant that the third floor gave way along with the transfer beam, which in turn caused the collapse of the building."The Bomb in Oklahoma City" ("Oklahoma City"). Seconds From Disaster.