After the World Trade Center's twin towers collapsed in the 9/11 attacks, engineers started paying a lot more attention to the materials used to construct skyscrapers. Today, those overseeing the construction of new buildings at Ground Zero are especially conscious of their stability and resistance to fire.
Designers of One World Trade Center, currently under construction, are using a special, super-reinforced concrete mix for the building's core. This reinforced design along with wider staircases and a difference in pressure between the outside and the inside of the building are meant to guard against fire and keep the people inside safe.
Architects say all buildings aren't built in this ultra-safe and reinforced way anymore because people want airier, glass buildings and because the cost can be more than twice as much as using other materials. Today, many engineers are working on ways to make buildings ultra-safe and aesthetically pleasing, all at a lower cost.
"Because of the nature of the destruction that was here before, you don't want to give the impression that this is a place of refuge and of fear. You want it to be a sense of openness to it. This building needs to appear open." - David Childs, designer, One World Trade Center
"This is a concrete specimen that will be used for tower one at the World Trade Center. If you could set this cylinder and put a platform on it, you can accommodate 1,000 Americans standing on this cylinder, you know, normal people 175 pounds in weight; 1,000 people can be supported by this four-inch-diameter cylinder." - Cas Bognacki, Port Authority of New York and New Jersey
1. Name some famous buildings. What makes them famous?
2. Why did humans start building skyscrapers? What purpose do they serve?
3. What do you think the most important design elements would be when building a skyscraper?
1. According to the video, why aren't all skyscrapers built like One World Trade Center?
2. How do you think the outcome of 9/11 would have been different if the buildings had been built like the Ninety West building described in this video?
3. If you were to design a replacement skyscraper for the World Trade Center towers, what elements would it have? Why?