Probabilistic seismic assessment of RC box-girder highway bridges with unequal-height piers subjected to earthquake-induced pounding

Abstract

This paper uses the probabilistic seismic assessment to study the effects of pounding and irregularity on the seismic behavior of typical concrete box-girder bridges with four levels of altitudinal irregularity. To extend the results for all bridges in the same class, uncertainty related to the earthquake, structural geometries, and materials are considered. Pounding is likely to take place in two cases: the first one concerns the seat-type abutments, and the second is at the in-span hinge of multi-frame bridges. Accordingly, the present study is an attempt to investigate the behavior of irregular bridges considering the effects of pounding in both cases. In the first case, the effects of changes in the gap size on engineering demand parameters (EDPs) were investigated. Then, correlations between earthquake parameters and the pounding force were evaluated. Furthermore, the pounding force exerted on the abutment was compared for different bridge irregularity levels. In the second part of the paper, the effects of pounding of adjacent bridge segments in the decks of non-continuous bridges were studied for equivalent Two-Degree-of-Freedom structures, for which the probability of non-occurrence was estimated. In the end, the relationship between structural or seismic parameters and the pounding force was evaluated in case of pounding. The results of the study show that the gap size between the abutment and the deck has the highest effect on the abutment passive deformation, pounding force, and base shear. Also, the substructure irregularity of bridges reduces the correlation between the gap size and the EDPs, except for the column ductility. Moreover, decreasing the ratio of periods of the adjacent frames diminishes the effect of the type of the earthquake but increases the probability of pounding.