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Importance of Survival Skills

How We Design Buildings To Survive Earthquakes

DNews is based in grand old San Francisco.
Known for it’s culture, or counterculture, giant reddish orange bridge, and earthquakes. Earthquakes happen when tectonic plates shift.
This sudden burst of energy sends seismic waves shooting in all directions. These waves
can violently shake buildings both up and down and side to side with enormous force.
It’s this forceful shifting that actually causes stress on the buildings to the point
of collapse. As we live in an Earthquake prone area, we
realize a fundamental truth. Earthquakes don’t kill people. Buildings do. So researchers
have spent a lot of time wondering how to make buildings safer. When an engineer is first planning a new building
they have to take into account where the building will be built. Earthquake guidelines are different
in say Kansas than in California. The intensity of forces from Earthquakes varies from place
to place. The goal when building in high intensity earthquake
areas is to make a building earthquake resistant. Earthquake proof is doable, but extremely
expensive. Now, to be considered “Earthquake resistant” a building can suffer damaging,
but it can’t collapse on the people trying to get out. And there’s two main ways to
do that, by designing a building so it’s stronger or more flexible. One way engineers
can make buildings stronger is by reinforcing concrete with steel. But in high risk areas
like California, that’s often not enough. One of the most effective ways to protect
a building from such disasters is to keep them from moving by detaching it from the
ground. Base isolation is when engineers design a structure to be built on top of a separate
base, instead of attached to a foundation, so that when an earthquake hits, the base
moves, but the building only ways slightly. For instance San Francisco’s City Hall was
retrofitted with a base isolation system. And this concept isn’t new. We see these
examples as early as the 4th century. They utilized isolation bases made of smooth rocks
that could slide against each other. In modern times these bases are usually made out of
a combination of a flexible material like rubber and steel. The rubber also acts like
a shock absorber. But a cool piece of shocking tech comes Taiwan.
The supertall skyscraper, Taipei 101, combats earthquakes with a giant 728 ton ball. Well
it’s technically called a “tuned mass damper” but it’s basically a giant ball
that’s suspended near the top of the building. If the building sways because of an earthquake
or a typhoon, the damper swings in the opposite direction. During a particularly strong gust
in 2015, the ball in Taipei 101, swung a meter from it’s center position. And technology is getting even more advanced.
According to one study published in the journal Applied Physics Letters researchers are working
on a way to make a building invisible to shock waves using a shield. This shield of concrete
and plastic buried at least 3 feet down, looks like two rainbows surrounding the building
with a gap between them. Each strip, or “color” is more stiff the farther out they are from
the core. The waves have an easier time traveling through a stiff and hard layer. So the waves,
once they hit a softer layer, deflect and head back to the easier path. The way these
plates curve, essentially channels the shock waves around the building. As they move around
the building they hit a gap in the plate which allows some of the force to dissipate. So
the plate kind of hides the building from the Earthquake. Like an invisibility cloak
for earthquakes! When earthquakes hit, their intensity is measured
in a point system called the richter scale. Trace takes a look at the different ways seismologists
measure earthquakes and what do these ratings mean in this episode right here. Have you lived through an earthquake? Tell
me your experience down in the comments below

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