Fragility Analysis of Highway Bridges Based on Long-Term Monitoring Data

Abstract

In the probabilistic seismic risk assessment of highway transportation networks, fragility curves are used to represent the vulnerability of a bridge. Because these networks have hundreds or thousands of bridges, it is not possible to study each bridge individually. Instead, bridges with similar properties are grouped together and are represented by the same fragility curve. However, this approach may be inadequate at times for different reasons. For instance, bridges with similar geometrical and material properties could have different age and/or could deteriorate at a different rate. Moreover, certain bridges are unique such as a cable stayed bridge or a suspension bridge. In this study, fragility curves are calculated based not only on the geometry and material properties but also on vibration data recorded by a structural health monitoring system. The fragility curves are used to track changes of the structural parameters of a bridge throughout its service life. Based on vibration data the fragility curves are updated reflecting a change in structural parameters. Fragility curves based on vibration data, whenever these are available, represent the vulnerability of a bridge with greater accuracy than fragility curves based only on the geometry and material properties. This article demonstrates the applicability of structural health monitoring to generate more reliable fragility curves. This is useful not only for bridges that are unique, which are usually the first to be instrumented, but for every instrumented bridge as well.