Seismic fragility analysis of nonuniformly corroded irregular RC bridges

Reinforced Concrete (RC) bridges in over crossings are typically constructed with unequal-height piers. The resulting substructure irregularity triggers an unbalanced seismic behaviour of these bridges, which increases their seismic vulnerability. The seismic irregularity of such bridge structures might be further intensified if the piers of varying heights expose to unsymmetrical chloride-induced corrosion damage. To accurately evaluate the seismic vulnerability of corroded irregular RC bridges, this paper studies the seismic fragility of a benchmark multi-span irregular RC bridge with five different corrosion damage scenarios, including unsymmetrical corrosion of piers. Toward this objective, first, monotonic nonlinear pushover analysis is used to quantify the time-dependent seismic capacity limit states by employing an advanced three-dimensional nonlinear finite element model. Then, Incremental Dynamic Analysis (IDA) and seismic fragility analysis are carried out to investigate the nonlinear dynamic behaviour and vulnerability of selected corroded bridges. The results show that, depending on the corrosion scenario, the distribution of seismic ductility demands can be varied in unequal-height bents, which can change the critical bent within a bridge system. Furthermore, results indicate that severe unsymmetrical corrosion damage can cause a synchronised failure of unequal-height piers.