Effects of multi-support excitation on isolated bridges

ABSTRACT

Multi-support seismic excitation can affect the response of isolated bridges, and particularly the perfomance of the isolating devices, which are generally designed for synchronous action. Three phenomena are of major interest for bridge structures, denoted as a) incoherence, b)wave-passage, c)site-response, of which the former two, grouped under the term 'nonsynchronism', have been object of an extensive parametric study in the past. Here, the third phenomenon is addressed, which is due to spatially varying local soil profiles, and its effects on the bridge response are evaluated. The technique adopted is that of a random vibration analysis of linear systems, equivalent to the examined bridges equipped with hysteretic-type isolating devices, whose response is represented through linear elements of equivalent stiffness and damping.(AU)