MadSci Network: Engineering |
There are no particular types of materials chosen for earthquake proof structures and highways. The design of the structure must take into the account the extreme vibrations caused by the earthquake. These start out usually as a strong vertical pulse followed by a period of strong side to side motions of the earth. The design of the structure in question must take take into account the stresses and deflections (movements) created by the motion of the earth. This is often done today by modeling the building or highway on a computer as a series of finite elements and watching what happens to each of the elements when the motion is simulated. If the structure is flexible enough and the motions not too extreme, the materials in the structure will bend but not break. This might still be disconcerting for the occupants, but it will not pose a danger. In California, any building over several stories is required to have a ground motion recorder in the building. As a graduate student at Caltech in the 70's, I remember looking up the displacement records for the Alcoa Building in downtown Los Angeles and being amazed that the top of the building swayed several feet in the last strong earthquake there. Stiff buildings, like un-reinforced concrete buildings, seem to fare the worse. Concrete is ok in compressive loading where it is being squeezed together, but develops cracks and falls apart when pulled in tension like what might happen in an earthquake. You might want to pay a visit to the Caltech Mechanical Engineering Department, which specializes in earthquake engineering. You might be able to get more details on their research and what materials are more commonly used or avoided.
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