Examination of the Number of Middle Spans on the Number of Required Effective Modes in Seismic Assessment of Bridges

Nonlinear static (pushover) analysis has become a popular tool during the last decade for the seismic assessment of buildings. Nevertheless, its main advantage of lower computational cost compared to nonlinear dynamic time-history analysis (THA) is counter-balanced by its inherent restriction to structures wherein the fundamental mode dominates the response. Extension of the pushover approach to consider higher modes effects has attracted attention of many researchers nowadays, but such work has focused mainly on buildings, while corresponding work on bridges has been very limited. Hence, the aim of this study is to adopt the modal pushover analysis procedure for the seismic assessment of bridges, and investigates its applicability in the case of three bridges with different spans and irregular and long piles. These bridges are assessed using nonlinear static analysis method and examined the effect of number of middle spans on the number of effective modes in the seismic assessment of bridges. Comparative evaluation of the calculated response of the bridges illustrates that by increased numbers of middle spans in bridges, the numbers of effective modes in the seismic assessment of bridges will also be increased.