It seems like every few years or so there is a major earthquake with catastrophic effects somewhere in the world. Not even considering aftershocks or the potential of tidal waves resulting from these quakes, the damage is often devastating, though thanks to modern engineering the damage can often times be mitigated. This understanding of resulting frequencies is even more important in cities filled with skyscrapers. But how do engineers and architects account for earthquakes when designing a skyscraper?
Not surprisingly, it starts from the ground up. They call this base isolation. The idea here is to make the base of the building absorb as much of the vibration for the earthquake as possible. In the past the base would be created much wider than the rest of the building, often with different layers of stone to try and help with vibration. Today, buildings are designed to “float” on a system of padded cylinders, springs or ball bearings to act as shock absorbers, allowing the rest of the building not to be significantly impacted by the vibrations.
The next technique that is now used is to build the structure out of more lightweight, flexible materials that can withstand the sideways movements from an earthquake better than something like concrete. Most skyscrapers are now created out of steel, or even aluminum. Unlike a house, the weight of the floors and walls of a skyscraper are supported by this steel frame, allowing for taller buildings to be built and for increased flexibility during an earthquake.
Some skyscrapers, such as Burj Khalifa in Dubai (currently the world’s tallest building) use huge mass dampeners for additional vibration projection. This harmonic absorber is integrated inside the building providing additional support for frequencies that might otherwise cause damage to the building. Inside Taipei 101 in Taiwan, there is a large column that acts like a pendulum. As the building sways, the pendulum moves in the opposite direction by as much as 5 feet, not eliminating the vibration but helping to offset it. Other buildings use similar designs, with massive disks connected to actuators inside the building that negate the effects of an earthquake much like the pendulum described above.
Earthquakes will always be a concern, and there is no way to ensure that the precautions used will keep a skyscraper from falling, but with the use of up front simulation and a continually improving understanding of engineering, we can hope reduce damage to a minimal amount. With the increased investment in composite materials and other enhancements, no one knows what improvements the next skyscrapers might see.