Reliability assessment of RC bridges considering cumulative damage due to seismic loads

A probabilistic estimation to calculate both the expected mean annual failure rate and the confidence factor based on closed-form expressions that consider cumulative damage due to environmental loads over time is proposed. Reliability indicators are estimated under the assumption of normalization between demand and capacity by means of I-DC index, calculated considering different instants of time, and compared with previous works. The mean annual failure rate indicator estimated with the numerical procedure is compared with both closed-form expressions at the time at which the structural system is newly constructed. The structural reliability is estimated for two continuous reinforced concrete bridges with superstructure based on AASHTO-type beams, and substructure with circular columns. The bridges are 110 m and 80 m long with four-lane roadway and twolane roadway, respectively. The systems are designed to comply with a pre-established drift ratio of 0.002, and situated in Mexico City. Variability in mechanical properties, geometric properties, and environmental loads are taken into account. It is concluded that it is possible to design continuous reinforced concrete bridges associated to a pre-established drift ratio. The incorporation of cumulative damage over time indicates that the systems present an undesirable safety level after 90 and 120 years for the case studies associated to the four-lane and twolane roadway, respectively.