ABOUT STRUCTURAL DESIGN: All modern high-rise buildings and most bridges feature something called redundant design: when one section fails, the entire structure should still be able to stand. It's a bit like a net: lose one string and the net will be weakened, but as a whole, the net still functions. Most high-rise buildings and bridges also are designed to sway in the breeze, because if the structure is too rigid it can snap under too large an impact. The World Trade Center was designed to withstand strong winds striking it from the side, and was even able to absorb the initial impact of an airplane colliding with it on 9/11, although the Twin Towers ultimately collapsed.
DIFFERENT DEFORMATIONS: Different materials can withstand different amounts of deformation, a property known as elasticity. Most materials are elastic to some degree: when they are deformed or bent, they will bounce back to their original shape. But elastic materials all have their limits. Metal springs and rubber bands are very elastic. Plaster and glass are not; instead, they are brittle and snap even with a small deformation.
The American Society of Civil Engineers and the Institute of Electrical and Electronics Engineers, Inc.-USA, contributed to the information contained in the TV portion of this report.
