Load-Carrying Capacity Assessment of an Existing Highway Bridge Based on Hybrid Finite-Element Model Updating

The load-carrying assessment of existing and aging bridges has been a critical challenge in Australia and elsewhere. The reversed capacity of these bridges is under investigation because of increasing traffic loads, deterioration of materials, and accumulated damage during operations. In this study, a hybrid finite-element (FE) model updating approach is developed to identify the current condition of a nearly 50-year-old highway bridge. The reserved capacity of the bridge subjected to the current traffic loadings in design specifications is evaluated. An initial FE model of the bridge is built based on the design documents. Strain data obtained from static load testing of the bridge and modal information identified from the measured acceleration responses of the bridge under operational traffic are simultaneously used to update the material properties and dynamic characteristics of the bridge model. The updated model can simultaneously match the recorded static response and identified modal information of the bridge, which can reflect the present operational condition of the bridge better than the original model constructed by design drawings. Based on the updated bridge model, the load rating factor (RF) is calculated to evaluate the performance of the bridge under the present design traffic loading specified in Australian bridge design standards. The calculated results indicate that the reserved capacity of the bridge for traffic and dead load effects can satisfy the requirements of the current bridge design specifications.