Quake-Proof Bridge | National Geographic

the unstable ground makes Japan the last
place on earth an engineer would choose
to build the world’s longest suspension
bridge if the ground beneath a
suspension bridge is shaken by an
earthquake we could in the worst case
for example get a tower toppling over
obviously a catastrophic event
the first line of defense against
earthquake is the bridge towers
themselves they’re built from steel to
make them flexible if a tremor hits the
steel towers can move with the earth to
absorb the shock
and inside each tower lies a second
layer protection 20 huge pendulums
called dampers each 10 ton dampener
hangs from a frame if a tremor caused
the tower to lurch one way the huge
hydraulic dampers swing in the opposite
direction counteract the shift and
prevent the tower from falling over
to test the dampers in the absence of an
earthquake engineers resort to a novel
approach they carefully choreographed
more than 100 workers to sway in perfect
harmony to mimic a tremor during this
man-made quake the dampers react to keep
the tower steady but on January the 17th
1995 nature tests the technology for
real
a magnitude 7 earthquake devastates Kobe
the city on the Akashi bridges north
bank
it kills over 6,000 people and destroys
more than 100,000 buildings but the
Akashi bridge survives saved by its
dampers it still bears the scars of that
fateful day the earthquake opens a fault
line in the seabed directly under the
bridge
this causes the ground and bridge towers
to shift apart and stretches the bridge
by over three feet engineers must fill
this space with extra decking to join it
to the shoreline as a result of this
earthquake the longest bridge in the
world became a little bit longer
the Akashi bridge proves the strength of
its record-breaking design in the most
challenging environment
it is the culmination of over two
centuries of innovation and engineering
breakthroughs
after more than a decade of operation it
remains the longest and tallest
suspension bridge in the world