Friday, April 17, 2009

Earthquakes in Italy

Italy is a country where earthquakes are a constant threat. The main problem is that the old buildings have very little resistance to them. If you want to understand what happens in an earthquake try this. Take a piece of cardboard and build a little house of blocks just staked one on top of the other on the cardboard. Now grab an edge of the cardboard and pull it back and forth horizontally. As you move the cardboard the blocks will start to separate and eventually fall down. This is basically the way the old Italian buildings, and buildings in many other countries are built. They are made of stones or masonry blocks/bricks just stacked up and held lightly together with cement mortar.

Earthquakes generally move the earth horizontally, with some vertical movement as well. If you imagine the house of blocks model several floors tall with heavy concrete slabs for floors and a heavy roof on top you can imagine what happens. The inertia of the mass of the floors and roofs make them want to stay where they are. The earth moves under them and the walls start to separate and or tilt. Then they can't support the mass above and the whole thing comes falling down.

More on this to follow.

1 comment:

  1. Born and raised in San Francisco, I can really appreciate the educational value of your work here. Let's hope some Italian civil engineers do, too.