Effective duration of seismic acceleration and occurrence of maximum responses

Abstract

The maximum response of structures due to a seismic excitation is generally obtained through dynamic analysis, using the entire history of the accelerogram. However, due to the damping effect of structures, only a certain portion of the accelerogram is effective and contributes significantly to the peak response. This paper introduces an efficient procedure for separately 1) selecting the effective duration from a seismic excitation, and 2) predicting the occurrence time of the response maxima. An analytical procedure is developed to determine the effective duration for a seismic excitation, based on the study of the structural responses and the control on error bound. Three multi-degree-of-freedom structures are subjected to several accelerograms, results obtained prove the accuracy of the procedure. The occurrence of the response maxima is derived analytically for the two extreme cases of structural rigidity, namely very flexible (e.g. tall stacks), and very rigid (e.g. power reactors). For structures with intermediate rigidity, the response due to various actual accelerogram indicates the correlation between the response maxima and the arrival frequency of seismic waves.