Seismic Risk Management / Caltrans
Caltrans initiated its Seismic Safety Retrofit Program in the wake of bridge failures experienced in the 1989 Loma Prieta Earthquake. Through this program Caltrans evaluated the retrofit needs for all of the over 12,400 bridges on the State Highway System (SHS). Retrofit needs were prioritized using a multi-attribute procedure that calculated a score for each bridge considering the likelihood of an earthquake at the bridge site, the vulnerability of the bridge to collapse in the event of an earthquake, and the impact of a collapse considering the traffic using the bridge and detour distance in the event of a collapse. Through 2014 the program resulted in retrofit of 2,202 state highway bridges at a cost of over $12.2 billion.
Sources:
2018 Caltrans TAMP
Practical Lessons from the Loma Prieta Earthquake (1994), p. 174-180 https://www.nap.edu/catalog/2269/ practical-lessons-from-the-loma-prieta-earthquake
Read more in the chapter: 5.1.4 Consideration of Risk in Resource Allocation