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dont foget fire fighters reach the 79 th floor reporting small fires and people stood in the impact hole awaiting rescueWhat you wont see is the steel structure was manufactured to take a static load bearing in a downwards direction of the calculated maximum weight plus a safety factor of 10%. This was calculated across the whole area even though the main support structure was in the central column of lift shafts. If any one of those central columns was to give the whole weighjt of the building would exceed the safety margin for the rest of the buildings central structure. This combined with the heat from the aviation fuel fires would compound the problem and the steel would explode as it reached critical temperature.
I have seen nothing of exploded steel but plenty about the collapse of heat-weakened supports.
That is what happens when the steel is weakened with heat, the maths and science is very complex but imagine a forest fire and all the animals running away from the fire. Well that is what happens to the inclusions in the steel when they run away from the source of the heat. This leaves a very brittle poor quality cast iron that cant take the weight, so it explodes as a closed can of soup does when heated. It is not an explosion as in dynamite or plastic, but the sound and effects are the same. I saw a stainless steel plate explode into millions of needles when the water cooling was not set right, we were collecting them for 6 months afterKey findings include:
- Floor sagging and exposure to high temperatures caused the perimeter columns to bow inward and buckle—a process that spread across the faces of the buildings.
- Even though the jet fuel on the planes burned off in the first few minutes after impact, there was enough office furniture to sustain intense fires for at least an hour.
- The original builders of the twin towers and those who later renovated the structures did not have a clear technical standard for deciding on how much insulation to use around the structural beams, many of which gave way in the intense heat.
Don't forget the effect of the lift shafts acting as venturi's and drawing air under pressure from the ground levels which acted as a blast furnace acts. This created a high pressure air current that added more and more oxygen to the fire, increasing the temperature. Remember the bunsen burner used in the labs at school, and how you could control the heat by opening ports at the bottom.
And no one reported seeing any sign of explosive being attached to the central core, so your point being what ?