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Seismic performance evaluation of circular reinforced concrete bridge piers retrofitted with fibre reinforced polymer Parghi, Anantray M.


A large number of researchers around the globe are currently conducting investigations on the use of fibre-reinforced polymer (FRP) for strengthening of reinforced concrete (RC) bridge piers. It has been observed that such strengthening technique can be a cost-effective method for restoring and increasing the strength and ductility of piers damaged during catastrophic events, like earthquakes. Material properties, amount of longitudinal and transverse steel, external confinement, axial load and shear span-depth ratio affect the lateral load capacity, ductility and failure mode of retrofitted bridge piers under seismic load. These parameters are considerably different in the pre-1970 code designed RC bridge piers compared to the current seismically designed bridges. This research investigates the effect of different factors and their interactions on the limit states of FRP-confined seismically deficient RC circular bridge piers using factorial design method. Nonlinear static pushover analyses of the non-seismically designed FRP retrofitted circular bridge piers are conducted in order to determine the sequence of different limit states such as yielding of reinforcement, and concrete crushing along with ductility capacity of the piers. In addition, nonlinear reverse cyclic, and dynamic time-history analyses are carried out in order to determine the lateral load carrying capacity, flexural ductility, and hysteretic behavior of such retrofitted piers. Fragility curves are developed for the FRP retrofitted RC bridge piers considering different limit states of displacement ductility as the demand parameter. The incremental dynamic analysis is conducted by considering 20 ground motion records to investigate the nonlinear dynamic behavior of the retrofitted piers. The fragility curves are described using lognormal distribution functions with two parameters developed as a function of peak ground acceleration. The impact of various parameters is evaluated on the bridge pier fragility curve based on the theory of probability. This study shows that the shear span-depth ratio, the yield strength of reinforcement, longitudinal reinforcement ratio, axial load and FRP confinement significantly affect the lateral load capacity, ductility and the failure mode of the retrofitted bridge piers under seismic load.

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