SYNTHESIS OF BI-DIRECTIONAL SESIMIC GROUND MOTION BY STANDARD AND COMPLEMENTARY WAVES FOR SEISEMIC DESIGN OF BRIDGES

Abstract

 For the purpose of seimic performance vertification of bridges in the process of seismic design, it is desirable to use spectrum-compatible bi-directional accelerograms with well-established multi-dimentional characteristics. In this paper, a method of generating spectrum-compatible bi-directional accelerograms by means of the complementary normal component wave computed by application of the Hilbert transform to standard accelerograms often provided by design specifications. It is shown that the intensity of the bi-directional input generated by this method is equivlent to that of the comventional unidirectional input with respect to the elastic response spectrum. Particular features of the effect of bi-directional input to structural model is examined with numerical dynamic response analysis of a simplified bridge model consisting of a superstructure, a seismic isolator and a seismic damper, and the difference of the evaluated structural responses between the bi-directional and unidirectional input cases appears, for which the degree of the effect depends on the type of standard earthquake accelerograms.