Bad news: You just built this skyscraper in a major earthquake zone. If you don't strengthen this skyscraper before the next earthquake hits, it will whip back and forth and snap in pieces! You need to further brace this tall building before the earth moves or you're in deep trouble.
How will you strengthen your skyscraper?
|Rigid backbone with diagonal braces (A) ||Long, supporting arms (B) ||Rigid backbone, with solid concrete walls (C)|
Build a rigid backbone through the core of the building with diagonal steel braces
You're on the right track!
A rigid core made of diagonal steel braces would do a good job holding the tall, wobbly building together while the ground shakes during an earthquake. But there is another material that you should add to the core of the building. It tends to be cheaper than steel, and it has great stiffness in the horizontal direction -- a great characteristic to have in an earthquake.
Build long, supporting arms
Watch out -- buttresses aren't very sturdy in an earthquake!
Long, supporting arms, called buttresses, would be useless during an earthquake. They'd snap and break right off the tall building as soon as the earth started shifting back and forth. Besides, downtown Los Angeles is pretty crowded. There's not enough room for the humungous buttresses you'd need to brace a skyscraper this tall!
Build a rigid backbone through the core of the building with solid, concrete walls
Congratulations! Your skyscraper is ready for the next big earthquake!
Solid concrete walls, also called shear-walls, have great stiffness in the horizontal direction. This means that when the ground moves back and forth during an earthquake, the shear backbone of your skyscraper will keep it standing strong and firm.
The First Interstate World Centre in Los Angeles, the tallest building in the world in a major earthquake zone, has a solid concrete core right up the center of the building. This design allows it to withstand an earthquake with a magnitude of 8.3 on the Richter scale! Great job!