The earthquake stresses in a structure are generally greater than those which would be produced by a constant acceleration equal to the maximum value reached during the earthquake; there is an amplification due to resonance. This effect depends on the period of the structure and is measured by a function of the period, designated here as the spectrum of the earthquake. A mechanical analyzer is described by which the spectrum curves for several strong-motion earthquakes have been plotted. It is shown how the spectrum can be used for the evaluation of earthquake stresses in complicated structures, and the particular example is treated of a multistory building with an elastic first story.

You do not currently have access to this article.