[Science Report]:Planning for Safer Buildings


This is the VOA SpecialEnglish Science Report.

Experts are beginning to study ways to secure large buildingsagainst terrorist attacks. They are reacting to the attacks thatdestroyed the World Trade Center buildings in New York Septembereleventh.

The American Institute of Steel Construction has created aworking group of experts to investigate the reasons the buildingsfell. The A-I-S-C is the organization responsible for developing therules for the design of steel buildings in the United States.Information developed by the working group will help A-I-S-C decideif the design rules should be changed.

The south World Trade Center building fell fifty-six minutesafter a passenger plane crashed into it. The north building fellabout one-hundred minutes after a similar crash. Each building wasfour-hundred-ten meters tall. Experts say the buildings could notsurvive the extremely hot fires caused by the airplane fuel.

Engineers think the airplane crashes destroyed part of thestructure of the buildings that kept them standing. The resultingfire weakened the remaining structure. The buildings fell becausethe weight above the area where the planes hit was greater than theremaining structure could hold.

Building experts say it is possible to build a skyscraper thatwould survive such an attack. But they say the cost would be so hugethat no one could pay for it. They also say that materials developedsince the World Trade Center was built may give people more time toescape such a situation.

The building experts say the most important consideration is toslow the destruction caused by the fires. The World Trade Center'ssupport structures were made of a strong metal, steel. The heat ofthe fires caused the steel to expand, weaken, and fail. Today,builders can use concrete that has steel bars inside. Concrete is amix of cement, sand and small stones. Experts say it can survivebetter than steel alone can.

The two tallest buildings in the world are the Petronas Towers inKuala Lampur, Malaysia. Each is four-hundred-fifty-two meters tall.They were built of concrete and steel. Experts say their structurescould provide a better chance of surviving than did the World TradeCenter buildings. They also say the escape areas of the PetronasTowers are treated to keep out smoke and fire.

This VOA Special English Science Report was written by NancySteinbach.

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