Japan is a nation that has grown rapidly in the last few
decades, both economically and socially. During its development Japan invested
well in technology and is now one of the biggest technology exporting countries
in the world today. Moreover it has managed to achieve this despite being in an
area of the world that is riddled with environmental hazards.
One of the most hazardous
is the threat of a major earthquake. Tokyo, is one of the three most densely
populated cities on the planet where seismologists expect major earthquakes to
occur. However it is one of the few places on the planet where such seismic
activity doesn’t usually cause catastrophic damage. Why is this? It is because
of the adaptation techniques that Japan have installed.
Adaptation is the process by which a country prepares
itself for the inevitable hazard, in this case earthquakes and their side
effects. One way in which Japan has done this is by changing the way in which
modern buildings are designed. It is possible these days the design buildings
to sustain the effects of the ground shaking caused by earthquakes because we
now know far more about how buildings behave in different scenarios.
One way in which buildings are being
designed to sustain the effects of an earthquake is by putting in dampeners.
This is far cheaper to do than using building techniques that make the
structure far stronger. A dampener is a mechanism that absorbs the energy of
the vibrations caused by the quake and makes the movement die away over time.
One type of dampener is called
a tuned mass damper (TMD). This involves installing a huge mass,
either mounted on springs or as a pendulum, which is tuned to have a natural
frequency close to that of the building. In the event of an earthquake at close
to that resonant frequency, the TMD oscillates in the opposite direction to the
building, counteracting its motion.
The natural frequency of the building can
be calculated by using the formula:
where K is the stiffness constant of the
building and M is the mass of the building. Structures can be both reinforced horizontally and
vertically, by using: diaphragms, trussing, braced frames, shear walls and
moment resisting frames.
However structural reinforcing and engineering is not the
only way in which Japan is reducing the damaged caused by earthquakes. They
have installed my pre-earthquake warning systems such as sirens that allow
people such as school children to prepare for the imminent tremors by doing
things such as hiding under desks or gathering in areas that should be safest
from falling debris and collapsing buildings.
Another way in which Japan try
and prevent catastrophes during earthquakes is by shutting down core reactors
in nuclear power plants to avoid meltdowns and radiation related
disasters.
The way in which Japan is now prepared for the threat of
earthquakes has not always been the case and much of the planning and building
regulations for “earthquake safe” buildings only came in after the Kobe
earthquake in 1995. During which over 6,400 people lost their lives and
thousands of homes were destroyed.
No comments :
Post a Comment