Civil and Environmental Engineering PhD Dissertation Defense: Selamawit Mehary
Monday, June 11, 2018 - 12:30pm

The Department of Civil and Environmental Engineering is pleased to announce Selamawit's PhD Dissertation Defense: "Assessment of Seismic Retrofit Prioritization Methodology for Oregon's Highway Bridges Based on the Vulnerability of Highway Segments."

Date: Monday, June 11, 2018
Time: 12:30pm
Location: Engineering Building 315
Adviser: Dr. Peter Dusicka

Geologists have indicated that the question is not if a catastrophic earthquake will occur in Oregon but when one will occur. Scientists estimate that there is close to 40 percent conditional probability that a Cascadia subduction zone earthquake of magnitude 8.0 or above will strike Oregon in the next 50 years. In addition, the majority of Oregon’s bridge inventory was built prior to the current understanding of bridge response and prior to current understanding of the expected earthquake demands. In order to minimize potential bridge damage in the case of an earthquake, one approach is to retrofit seismically deficient bridges. However, often times the decision maker is faced with the difficulty of selecting only a few bridges within the inadequate ones. Hence, the issue of prioritizing upgrading naturally arises. 

The goal of this study is to assess and refine bridge prioritization methodology to be utilized for ranking Oregon’s bridge inventory. CFRP retrofit has been experimentally and analytically evaluated to demonstrate the effectiveness of the technique and was found to be an efficient and economical option. A vulnerability assessment estimates that close to 30 percent of Oregon’s highway bridge inventory will sustain moderate damage to collapse. However, retrofitting two most common bridge types in the inventory will reduce the number of damaged bridges by about 70 percent. A cost-benefit assessment that takes into consideration direct and indirect costs associated with damaged bridges and retrofitting of bridges shows that the benefit is up to three times the cost to retrofit. The same principle was applied to rank twelve highway segments for seismic retrofit considered important by Oregon Department of Transportation. The overall highway network vulnerability was assessed by considering retrofit of each segment. The benefit to cost ratios for each assessment were then compared and the highways segments were ranked  accordingly.