Tuesday, June 21, 2005

Why could the Skyscraper collapse? How to prevent it?

Location: Los Angeles, California
Building Description: 75-story steel-reinforced concrete skyscraper
Problem: The building is in danger of collapsing from poor design
Task: Recommend a new structural design
Budget: $500 million

Special Notes: "This is going to be a state-of-the-art building. We're planning to have 100 deluxe apartments, two swimming pools, 50 shops, and one movie theater in this skyscraper. We want lots of open space and large, unobstructed windows on each floor. Can you do this for us?"
-- Building Owners

The pressure is on. You want to make the owners of the skyscraper happy, but you also have to decide which design is strong enough to support the tall and heavy structure.

Which structural design will you choose?

 Columns Throughout:
 Stiff Core
 Hollow Tube
A B C

Answer: A
Columns Throughout

Your skyscraper is standing tall -- but there are way too many columns inside!

 3-D Grid: beams and columns evenly spaced throughout skyscraper = Caution

This design is not ideal for this particular skyscraper because the owners want lots of open space on each floor. With this design, there will be too many columns in the way!

Engineers used this structural design to build one of the earliest American skyscrapers, the Empire State Building in New York City, which is also one of the heaviest buildings in the world. Builders used 60,000 tons of steel to construct the Empire State Building! Luckily, engineers have developed newer, more inexpensive designs that require less material and time to build.


Answer: B
Stiff Core

You've given the owners what they want. Congratulations!

Stiff Core: beams, columns and diagonal braces form a rigid backbone up the center of the skyscraper = Right

The stiff core forms a rigid backbone up the center of the skyscraper. This design gives the owners plenty of space to arrange apartments, movie theaters, and shops on each floor. Plus, the stiff inner core acts like the spine of the human body and provides extra structural support for the skyscraper against heavy winds. It also creates space for an elevator shaft. After all, who wants to climb 1,000 feet of stairs?

One of the world's tallest skyscrapers, the Chrysler Building in New York City, is strengthened by a stiff inner core. Super job!

Answer: C
Hollow Tube

You've just designed a good, strong building -- but the columns around the perimeter block the view!

 Hollow Tube: beams, columns and diagonal braces stiffen the outside walls and form a stiff, hollow tube = Caution

The hollow tube design is an inexpensive and very effective skyscraper structure. The fifth and sixth tallest buildings in the world, the World Trade Centre Towers in New York City, are supported by this hollow tube structural design.

Unfortunately, the columns around the perimeter significantly reduce the size of the windows on each floor. This design simply won't work for your skyscraper because the owners specifically asked for large, unobstructed windows.






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