Infrastructure9/11 legacy: more resilient skyscrapers

Published 12 September 2011

Following the 9/11 attacks on the Twin Towers in New York, many predicted that the age of the skyscraper was over; there has been no slowdown in skyscraper orders, however — but the skyscrapers being built today are much stronger than the Twin Towers were; new materials, innovative designs, and attention to safety make today’s skyscraper much more resilient to man-made and natural disasters

Skybridge linking two significant buildings in Detroit // Source:

Following the 9/11 attacks on the Twin Towers in New York, many predicted that the age of the skyscraper was over. An examination of building trends in major urban centers around the world shows that that assessment. Made in the immediate aftermath of the attack, was premature.

The reason architects continue to design skyscrapers, and that builders continue to build them, is the engineers have devised many ways, and are now using many new materials, to bolster the strength of these tall buildings and make them more resilient to man-made or natural disasters.

Fox News reports that among these innovations and improvements are:

  • The typical cement sidewalk used to be able to resist a couple thousand pounds per square inch. There are now concretes that resist 25 thousand pounds per square inch
  • Very high-strength cement can help a building resist the type of impacts caused on 9/11 by protecting the steel that holds skyscrapers together — the weak point in the attacked towers. In 7 World Trade Center — the first of the destroyed buildings to be rebuilt, in 2006 — three feet of concrete now surround the steel core.
  • Steel has also been getting stronger as scientists have gradually found better alloys.
  • Modern skyscrapers are also more likely to use explosion-resistant windows, which are made by using several panes of glass and putting a layer of chemicals in between each. The chemicals bond sheets of glass together, making shattering less likely.
  • Bridges linking two or more skyscrapers would allow more avenue for evacuation. Fox News notes that skybridges have been used in many post-9/11 skyscrapers, including the 88-story Petronas Towers in Malaysia. It was also considered among designs for the new World Trade Center.
  • Sensitive measuring devices in the building that would take into account the strength of the elements holding it up at any given time. If there were a sudden change, the sensors would communicate that to a computer, and the building could physically shift its weight accordingly.
  • Modern skyscrapers include more emergency escapes, protect these escapes with more concrete, and place them strategically.

“The past decade has been the most productive 10 years ever when it comes to tall buildings,” a report from the Council on Tall Buildings and Urban Habitat concluded.