11/21/2023 0 Comments Fall speed from a demolition buildingThe four sides of each building formed a tube with window slots This tube was designed to carry the weight of the building and its contents directly downward to the foundations. To augment strength, these panels were staggered vertically, like pieces of a puzzle, so that all their tops and bottoms did not align at the same floor level. Three-story-tall by three-column-wide panels of the lattice were fabricated in a factory and transported to downtown Manhattan. Much of the welding was performed off-site. There were also deep beams at the floor levels, forming a tight latticework of steel that covered the surfaces of the buildings. The exterior walls had narrow windows flanked by unusually closely spaced steel columns. You have seen photographs of the towers pre-9/11. The buildings stood, albeit briefly, primarily because their structures had redundant mechanisms to support the weight. Many key structural elements were destroyed instantly, and large fires ignited simultaneously on several floors with ruined sprinklers. Engineers might have assumed that fires in either building likely would be confined to one floor and that sprinkler systems would work properly. At most, when they were designed, there was concern that an errant aircraft might accidently hit one of the towers. The twin towers were not designed to resist the kind of damage they experienced. Shouldn’t that have been enough to cause immediate collapse? Commercial aircraft flying at nearly top speed crashed into the buildings, cutting wide swaths through the exterior walls and inflicting extensive interior damage. Structural engineers asked these questions, too, but they also asked the contrasting question: How did the World Trade Center towers manage to stand up to the attack at all, even for a short while? The damage was extensive. We asked ourselves, “How could this possibly happen? How could they collapse?” These are natural questions that express the scope of the loss we felt on that day. city, gouging and crushing other buildings for hundreds of feet in all directions. We could not imagine that two iconic 110-story skyscrapers would collapse in the middle of a U.S. Before that day, we could not imagine that someone would be bold and cruel enough to enact such violence.
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