Pushover Analysis of Reinforced Concrete Bridges under Chloride-Induced Corrosion

Long-term seismic performance determination of reinforced concrete bridges is one of the effective factors in service life estimation of these structures. Chloride induced corrosion results in deterioration of critical members in the service life of reinforced concrete bridges and therefore leads to degradation of long-term seismic performance of the bridge. Due to seismicity and high rate of corrosion in reinforced concrete structures due to the corrosive environmental condition in Persian Gulf region, evaluation of corrosion-induced degradation on the long-term seismic performance of existing bridges in this region has a high importance. In order to evaluate this problem, at first based on studies done related to Persian Gulf region, corrosion initiation time of columns as critical seismic members of the bridge has been determined. Then effects of corrosion on the reinforced concrete column at specific time intervals (0, 15, 30, 45, 60, 75, 90 years) in bridge service life have been calculated. Effects of corrosion include degradation of cover and core concrete, steel, and bonding between concrete and steel that result in modification of stress-strain relationship of materials. In the next step, at each time interval based on the modified stress-strain relationship of materials, moment-curvature analysis of bridge column conducted and characteristics of plastic hinge have been determined. Finally, based on plastic hinge characteristic at each time interval, pushover analysis of bridge in longitudinal and transverse directions conducted and bridge capacity curves at mentioned time intervals have been compared. Results indicate the time-dependent degradation of bridge capacity under corrosion. According to the obtained results, in order to ensure the long-term seismic performance of reinforced concrete bridges in corrosive environments, value for an increase of design base shear has been proposed.