Seismic Vulnerability of Segmental Bridges with Drop-In Span by Pushover Analysis

Featured Application When evaluating the seismic vulnerability by means of non-linear static analysis of bridges characterized by the presence of drop-in spans, attention must be paid to the choice of the force distribution, which must be able to excite the structure in such a way as to represent the oscillations of all its parts and the possible phase deviation angle.Abstract Insight into the application of pushover analysis to prestressed concrete segmental bridges built in the 1950s-1970s by cantilevering with medium-large span length is provided. Seismic assessment must be carried out considering the whole structural response and, in particular, the task of tall piers, bearings, and drop-in spans with Gerber saddles, which are likely to be subjected to girder pounding and/or unseating. In this paper, the assessment of seismic vulnerability is initially performed by linear modal dynamic analysis; then, the efficiency in assessing the seismic response of different methods of pushover analyses is compared, assuming as a benchmark the results of non-linear time history analysis. The outcomes show that, for the bridge with the drop-in span, criteria for selecting the load pattern considered in pushover analysis, the reliable modeling of the bearings, and tall piers play a dominant role in the assessment of the seismic vulnerability, particularly in longitudinal motion.