Shaky Buildings

Raymond Neal, St. Patrick’s College, Kilbirnie, Wellington

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Science in the New Zealand Curriculum:

Making Sense of Planet Earth and Beyond. Level 5 A.O. 1&2 ‘investigate and describe processes which change the Earth’s surface over time at local and global levels, eg., erosion, weathering, earthquakes, volcanoes, continental drift, plate tectonics;

 Background: How much will this building shake in an Earthquake? The answer to this is, of course, very complicated but we can look at it bit by bit. Here we consider the size and mass distribution of the building.

In a city, there are building of many different sizes; some low, some tall, some wide, some thin.

We will model buildings with pieces of pipe cleaner and paper clips and we will supply the ‘earthquake’.

The general set up:

Test 1. Short and Tall buildings.

Predict which ‘building’ will shake the most.

Shake the polystyrene blocks slowly and note which ‘building’ shakes most.

Now shake the block quickly and note which building shakes most.

Was your prediction correct?

Write a conclusion stating how the height of a building affects the frequency of it’s shaking.

Note: frequency is a measure of how fast or slow the shaking is.

In the 1985 Mexico Earthquake, medium height buildings were severely damaged but low buildings and tall buildings were less damaged.

Test 2. Position of Mass in the Building

Shake the polystyrene blocks slowly and note which ‘building’ shakes most.

Now shake the block quickly and note which building shakes most.

Write a conclusion stating how the position of the mass affects the frequency of the building's shaking.

An example of a building with its mass at the top is an apartment block with a swimming pool on the top storey.