Earthquake damage of recent decades has revealed that bridges are the most vulnerable components of the transportation system. Damage to these nodes can cause significant disruption to the transportation network, posing a threat to emergency response and recovery as well as resulting in severe economic losses for the region. The transportation system of the Central and Southeastern United States (CSUS) is particularly at risk because many of its bridges were designed with little or no seismic consideration. In an effort to mitigate potential damage to existing bridges, those bridges with inadequate seismic detailing may be seismically retrofit.

In recent years, awareness of the potential hazard to the CSUS has increased. This is now coupled with the recommendation of a design spectrum based on a longer return period characteristic earthquake. Such developments have initiated seismic retrofit activities and evaluations in some CSUS states, well as prompted concern over the cost of the large number of bridges that may be required to be retrofit. There is a strong need for a comparative assessment of the viability of various retrofit strategies for CSUS type bridges and a need for effective prioritization and selection of bridges retrofits.

This research aims to provide enhanced understanding of the impact of various retrofit strategies on the seismic performance of typical CSUS bridges. The effect of retrofit on multiple bridge components' response will be illustrated and key considerations for retrofit of CSUS type bridges will be presented through deterministic study. Probabilistic assessment of general classes of bridges retrofit with different strategies will allow for relative comparison of the effectiveness of the retrofits for CSUS bridges. A primary objective is the development of a methodology for generation of retrofitted bridge fragility curves that would facilitate such a comparison of bridge retrofits and would permit a network assessment for effective retrofit selection and prioritization based on transportation network performance.

Selected Publications and Presentations
Padgett, J. E., DesRoches, R., Nielson, B. G. (2004) "Seismic Retrofit of Bridges in Moderate Seismic Zones." US-Turkey Workshop on Seismic Design, Retrofit and Post-Earthquake Evaluation of Highway Bridges , Ankara , Turkey , September, 2004.