Seismic behavior of deficient reinforced concrete bridge piers confined with FRP - A fractional factorial analysis

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 old reinforced concrete (RC) bridge piers compared to the seismically designed bridges. This research investigates the effects of these factors and their interactions on the limit states of carbon fiber reinforced polymer (CFRP) confined seismically deficient RC circular bridge piers using fractional factorial design method. CFRP-confined bridge piers are modelled using a fiber modelling approach and nonlinear static pushover analyses of the bridge piers are conducted in order to determine the sequence of different limit states such as yielding, buckling and fracture of reinforcement, and concrete crushing along with ductility capacity of the piers. This study shows that the shear span-depth ratio, yield strength and longitudinal reinforcement ratio, axial load and CFRP confinement significantly affect the lateral load capacity, ductility and the failure mode of retrofitted bridge piers under seismic load.