Bridge Seismic Retrofit Measures Considering Subduction Zone Earthquakes

Peter Dusicka, Portland State University


Seismic retrofit implementation in the state has been minimal due to a lack of funding, and when retrofitshave occurred, the scopewas typically limited to phase I retrofit by providing restrainers for keeping the superstructure from sliding from the supports. Such retrofit measures are effective for their intended purpose, but shift the displacement demands onto the supporting substructure. Designs for strengthening substructure elements for earthquake resistance are typically based on conditions in 1 California, which typically has round bridge columns exposed to crustal seismic events. Oregon has many bridges with reinforced concrete bents and slender rectangular columns with inadequate reinforcement. In addition, Western Oregon experiences subduction zone earthquakes, which can be more intense, longer lasting, and contain different frequency content than crustal earthquakes. Consequently, there is uncertainty with regard to the effectiveness of conventional retrofit measures as applied to Oregon type bridges and uncertainty in the seismic fragility. A research project underway at Portland State University (PSU) funded primarily by the Oregon Transportation Research and Education Consortium (OTREC) is investigating the seismic performance of a representative column with and without a conventional column retrofit measure. This is a good first step, but the research is limited to one repair method of a column exposed to a simulated crustal earthquake. The research described in this work plan will extend the PSU work by investigating the entire bent as a system for retrofits and by simulating a subduction zone earthquake as the input seismic event. Analytical and experimental methods will be used to study typical vulnerable bents and quantify their performance with fragility curves. The research will focus on better understanding the effects of subduction zone earthquakes and on retrofit measures of bridge bents.

Project Details

Project Type:
Project Status:
End Date:
December 31,2014
UTC Grant Cycle:
non-UTC research