Seismic Retrofit Guidelines for Utah Highway Bridges

Much of Utah’s population dwells in a seismically active region, and many of the bridges connecting transportation lifelines predate the rigorous seismic design standards that have been developed in the past 10-20 years. Seismic retrofitting methods used in the United States have been investigated for applicability in the state of Utah. The guidelines developed here are based on the Federal Highway Administration’s (FHWA'S) "Seismic Retrofitting Manual for Highway Structures: Part 1 – Bridges," which presents the most current advances in retrofitting and earthquake engineering techniques. As a key difference from FHWA’s guidelines, criteria for selecting earthquake ground motions are based on bridge anticipated service life. Bridges with 30 or more remaining years are analyzed for the 2500 and 500-year return periods, and bridges with less than 30 remaining years are analyzed for the 1000 and 100-year return periods. Flowcharts are provided to assist decision making in retrofit evaluation. The FHWA’s indices method is recommended for screening and prioritizing bridges.