How did the Twin Towers collapse?

Due to sagging floors denting surrounding tubes.

What was the unique design feature of the Twin Towers?

Perimeter tube design for spacious office layouts.

Kangaroo crane climbing and securing frames.

High temperatures softening the steel.

The unique perimeter tube design of the Twin Towers, chosen for spacious office layouts, ultimately led to their collapse as the sagging floors weakened the structure, causing a chain reaction.
Despite withstanding the initial impact for over an hour, the collapse of the Twin Towers was swift and catastrophic due to high temperatures softening the steel, leading to the failure of core support and a rapid chain reaction collapse.

How did the Twin Towers collapse?
Due to sagging floors denting surrounding tubes.
What was the unique design feature of the Twin Towers?
Perimeter tube design for spacious office layouts.
How did engineers stabilize the construction of the World Trade Center?
Kangaroo crane climbing and securing frames.
What protected the trusses of the Twin Towers?
Spray foam insulation.
What caused the swift collapse of the Twin Towers?
High temperatures softening the steel.

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The Twin Towers withstood the impact of the terrorist planes for over an hour before collapsing due to the structural design.
The towers' unique perimeter tube design supported the concrete floors, with trusses sagging from the jet fuel fire during the crash.
Engineers chose the perimeter tube design for spacious office layouts without interior columns, unlike the Empire State Building.
A kangaroo crane aided in the construction of the World Trade Center, climbing and securing frames to stabilize the towers.
Spray foam insulation protected trusses, while the core carried the tower's gravity load with welded columns and i-beam girders.
The towers collapsed due to the sagging floors denting the surrounding tubes, weakening the structure and leading to a chain reaction collapse.
The towers stood strong for over an hour post-impact, thanks to viscoelastic dampers and the remaining columns supporting the weight.
The towers collapsed due to the high temperatures softening the steel, causing the trusses to sag and the core support to break away.
The collapse was swift, with the North Tower falling in 13 seconds and the South Tower in 11 seconds, due to the impact's damage and buckling of columns.