Spectrum Intensities of Strong-Motion Earthquakes

[Introduction] The design of structures to resist earthquakes should be based upon a set of rules and procedures which give building designs having the following properties. Each part of the building should have approximately the same factor of safety, buildings of different types should all have approximately the same factors of safety, and the factor of safety should be of such a magnitude that buildings will not be seriously damaged by the strongest earthquake to which they are likely to be subjected. To establish rules which will give such designs, it is necessary to know the stresses that will be produced in structures when they are subjected to earthquakes. This requires a knowledge of the characteristics and intensities of earthquakes and a knowledge of how structures behave during an earthquake. Since no two earthquakes are identical and since there is a wide variation in the size, proportions, mass, rigidity and foundation conditions of structures, it is a difficult problem to determine precisely what happens to buildings during an earthquake.