Short Duration Analytic Earthquake

by Gordon R. Johnson, (M.ASCE), Principal Development Engineer; Government and Aeronautical Products Div., Honeywell Inc., Minneapolis, Minn.,
Howard I. Epstein, (M.ASCE), Asst. Prof. of Civ. and Mineral Engrg.; Univ. of Minnesota, Minneapolis, Minn.,

Serial Information: Journal of the Structural Division, 1976, Vol. 102, Issue 5, Pg. 993-1001

Document Type: Journal Paper


A time-history analysis of an elastic structure subjected to an earthquake can be computationally expensive due to the complexity and time duration of the earthquake. A response spectrum analysis of the structure can also be complex because the natural frequencies and mode shapes must be obtained and then the modal responses must be added together in some probabilistic manner. Previously generated artificial earthquakes typically consist of random oscillatory motion of significant time duration. In this work, an analytic earthquake consisting of variable frequency sinusoidal motion is used. The short time duration and the smooth response spectrum of the sine sweep lead to computational efficiency. It is demonstrated that the sine sweep earthquake, applied to an elastic structure, gives results that agree with those obtained using an actual earthquake. Furthermore, by varying the parameters of the sine sweep earthquake, various design spectra can be approximated. The sine sweep earthquake is shown to give consistent modal participation and therefore a time-history analysis using this short duration analytic earthquake can be confidently employed.

Subject Headings: Earthquakes | Elastic analysis | Modal analysis | Computing in civil engineering | Ground motion | Natural frequency | Probability | Parameters (statistics)

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