Computation of response spectra from adjusted strong motion accelerograms

Abstract

Because of the complicated nature of earthquake induced ground motions and the corresponding transient response of structures to such motions, the use of response spectrum has achieved wide acceptance, in the field of earthquake engineering, as a meaningful measure of the intensity of an earthquake. Thus, it is useful to investigate the application of the digital computer to characterise real earthquake motion (in the form of digitised acceleration time histories) by means of response spectra. The conceptual development of the response spectrum (which should not be confused with the ground motion spectrum) and its application to the analysis of transient oscillations in elastic systems is attributed to Benioff (1934), Neuman (1936), and Biot (1943). Its engineering significance lies in the fact that once the spectrum is known for a one-degree-of-freedom system, it is possible to compute the value of the maximum shear produced by an earthquake. Further, extension of this concept of response spectra to multidegree of freedom systems can be done using the modal superposition method of dynamic analysis. The mathematical formulation for performing response analyses of a single-degree-of-freedom system is explained.