Analytical Development and Practical Application of Fragility Curves for Retrofitted Bridges

Recent developments in bridge vulnerability assessment have provided insight on likely vulnerable classes of bridges. However, there is a lack of understanding of the impact of retrofit on the vulnerability, or fragility, of these classes of bridges in order to support decision making and risk reduction efforts. This paper presents a general methodology for the development of retrofitted bridge fragility curves considering the impact of various retrofit measures (elastomeric bearings, restrainer cables, seat extenders, steel jackets, and shear keys) on the performance of the overall bridge system. The implementation and practical application of the retrofitted bridge fragility curves is highlighted. These curves offer valuable insight to decision makers and bridge owners seeking to reduce the risk of damage to bridges and consequences of bridge damage on the performance of the transportation network. Analysis of the fragilities provides guidance as to the most effective retrofit for a given bridge type and performance objective. In addition to this performance-based retrofit assessment, the fragilities are incorporated in cost-benefit studies as well as a seismic risk assessment, which exemplify their importance in supporting effective investment of funds and evaluation of the impact of retrofit on regional consequences.