Influence of ground motion type on nonlinear seismic behaviour and fragility of corrosion-damaged reinforced concrete bridge piers

Two identical reinforced concrete (RC) bridge piers including a rectangular and a circular section are considered. The influence of corrosion damage, non-stationary characteristics of ground motions, and cross-sectional shape on nonlinear dynamic behaviour, failure mechanism and failure probability of these piers is investigated. An advanced modelling technique, capable of modelling coupled influence of inelastic buckling and low-cycle fatigue degradation of reinforcement, is employed to simulate the nonlinear structural behaviour of the piers. The considered bridge piers with various mass loss ratios (as a measure of corrosion) are subjected to a series of static pushover analyses and incremental dynamic analyses under three different suites of ground motions such as, Far-Field (FF), Near-Field With Pulse (NFWP), and Near-Field with No Pulse (NFNP). Furthermore, an advanced matching algorithm is used to investigate the effect of non-stationary content of near-field earthquake records including the presence of large pulses in ground motion time series on the nonlinear dynamic behaviour of the corrosion-damaged RC bridge piers. Finally, fragility curves are developed for each corroded bridge pier with different corrosion ratios subjected to each ground motion suite. Analyses results show that the failure mechanism of the corrosion-damaged bridge piers significantly depends on the cross-sectional shape and ground motion type. It is concluded that while both of the piers with slight corrosion levels are much more vulnerable under NFWP ground motions than those under FF and NFNP ground motions; the probability of failure of the extremely corroded bridge piers is approximately the same regardless of ground motion type