Updating the Assessment of Resistance and Reliability of Existing Aging Bridges with Prior Service Loads

Abstract

The successful past performance of an existing bridge is evidence of its resistance, which reduces the uncertainty associated with the resistance and so increases the bridge reliability. However, the resistance deterioration and increases in traffic load may negate this effect. In this paper, statistical techniques are used to combine the prior estimate of time-dependent resistance with new information from the service load history, thereby obtaining an updated estimate of bridge resistance, as well as an updated reliability for subsequent years. The application of the method is illustrated using an existing bridge. The influences of the intensity and nonstationarity of service load history and the shape and variance of deterioration function on updated estimates of bridge resistance and reliability are examined using parametric examples. It is found that the updated resistance of an existing bridge with ever-increasing traffic load is close to that of the same bridge with a stationary traffic load process if the load intensities at the latest stage of the two-load process are identical; however, the updated reliability of the bridge is greatly reduced considering the increase of traffic load with time. The statistics of the deterioration function has a significant effect on both the updated resistance and reliability of the bridge, while the shape of the deterioration function has a significant effect on the updated reliability only. The estimate of initial bridge resistance can also be updated by the proposed method, but the updating effect is insignificant compared with the updating of current resistance.