Effect of spatial variability of seismic strong motions on long regular and irregular slab-girder RC bridges

Abstract

Long bridges and other lifeline systems are particularly susceptible to the spatial variability of earthquake actions. Even though it is a matter that has been substantially studied in the past decades, there are still plenty of issues with the engineering application of earthquake spatial variability. One of the difficulties is generating displacement time-histories with zero initial and small residual displacement values. This is essential to obtain results that have good quality in terms of the pseudo-static effects. Another difficulty is the uncertainty associated with the simulation of the spatial variability of the seismic ground motions in engineering applications (Zerva et al. in: 16th European conference on earthquake engineering, Thessaloniki, 2018). In this study, the conditional method for simulation of spatially variable ground motions is used and the respective displacement time-histories are generated. These time-histories are then applied to perform seismic analysis of a set of long irregular RC bridges, with different irregularity layouts and different total lengths. The goal of this study is to ascertain the impact of spatial variability on the seismic behaviour of these structures, according to their length, irregularity and to the coherency model of the strong motions and comparing the results with the case without spatial variability. The relative importance between dynamic and pseudo-static effects is also ascertained for each case-study. Finally, the definition of the cases for whom the effects of the spatially variable seismic ground motions are more detrimental than those of the uniform ground motions.