Earthquake-proof buildings
One wonders, after the huge earthquake that struck near Japan, if an earthquake-proof structure can be built. There are two answers. Engineers can use a variety of techniques to design a sturdy structure that will survive a small or strong quake. Even the most well-engineered buildings can suffer serious damage during an earthquake. Engineers design building to resist sideways movement to minimise damage to structure and give occupants the time they need to leave safely. Buildings are designed to support vertical loads to support walls, roofs and everything inside.
Earthquakes have a sideways or lateral load that can be difficult to take into account. In order to increase the resistance of a simple building to lateral forces during earthquakes, it is possible to bind together walls, floors and roofs in a rigid structure. This construction type is characterized by walls made from bricks stacked atop each other, and then mortared. The roof will be laid on top. The roof is supported by the wall. This type construction collapses or tips over when subjected to an earthquake’s lateral force.
The way in which construction is done can make a big difference to the death toll of earthquakes. In 2010, an earthquake with a magnitude of 8.8 in Chile killed over 700 people. A less powerful 7.0-magnitude earthquake struck Haiti on January 12, 2010. The difference between the death tolls is due to building construction and technological advances. Buildings in Haiti were built rapidly and at a low cost. Chile is a more industrialized, richer country that adheres to stricter building codes. These systems are similar to shock absorbers found in automobiles. They allow buildings to decouple from ground vibrations. They aren’t directly on the earth, so they can be protected from some shocks. If there is a large earthquake, the buildings may move a couple of feet. The buffer zones are “moats,” which surround the buildings to keep them from hitting other structures.
A large mass (several tonnes) can be built at the top of a building to counteract the building’s sway. As “tuned bulk dampers”, this device can reduce a buildings sway up 30 to 40%. Taipei 101 was previously known as Taipei World Financial Center and has a giant swaying pendulum that is mounted between floors 88-92. It is the largest and heaviest damper in the world, weighing 730 tons. It’s so heavy it couldn’t be lifted by cranes.
