2009

Earthquake-Safe Buildings

It is easy to erect a simple building. Stack a bunch of cinder blocks into a wall. Add three more walls and you have a room. Put engineered lumber over the top and you have a building. This takes no engineering at all. It could stand for many years. But the day an earthquake rumbles, this building becomes a pile.

During the Haiti earthquake in 2010, buildings collapsed on a massive scale. Tens of thousands of people died. In one city, only 10 percent of the buildings remained standing. The concrete they used contained too little cement. The walls were too thin. There was no reinforcing steel. The soil underneath was not stable. Engineers know how to build earthquake-proof buildings, and their knowledge is embodied in building codes. But when no one follows the building codes, disaster is inevitable.

Engineers have designed extremely large earthquake-safe buildings. One technique is called a base isolation system. The idea is to disconnect the base of the building from the ground so that, when the ground shakes, the building does not. But how is it possible to disconnect a building from the ground? A great example can be seen in Istanbul’s airport—the largest earthquake-safe building in the world completed in 2009. In simple terms, every column in the building rests on plate riding atop a giant ball bearing. Now the ground can move back and forth while the building stays largely stationary by riding on top of its ball bearings.

Another system uses pads. The pads sit on the ground and the building sits atop the pads. The pads might allow the ground to move a foot (0.3 meters) or more side to side under the building. So when the ground shakes, the building does not shake nearly as much.

Engineers also strengthen the structure itself. Even a wooden frame house can gain dramatically improved strength with inexpensive additions that tie all the framing members together. Simple metal straps and tees significantly strengthen the frame at low cost. Engineers: Keeping the roof over your head even during earthquakes.

SEE ALSO Concrete (1400 AAA), Engineered Lumber (1905), Tuned Mass Damper (1977).

Earthquake-damaged building, following the Kobe earthquake, Japan, 1995.