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• 1. [Article] Probabilistic analysis and mapping of seismically induced landslide deformation in Oregon

  Landslides are ubiquitous within the state of Oregon, imposing an annual estimated cost of more than $10 million. Weak, saturated soils at steep slopes combined with persistent rainfall throughout most ...

  Citation × Citation Citation Abstract Copy Title: Probabilistic analysis and mapping of seismically induced landslide deformation in Oregon Author: Sharifi Mood, Mahyar Landslides are ubiquitous within the state of Oregon, imposing an annual estimated cost of more than $10 million. Weak, saturated soils at steep slopes combined with persistent rainfall throughout most of the year provide a dangerous environment for this natural disaster, particularly in western Oregon. This grim situation is intensified by the presence of the Cascadia Subduction Zone, which is capable of generating large and powerful earthquakes. This thesis presents a fully probabilistic method for regional seismically-induced landslide hazard analysis and mapping, which considers the most current predictions for strong ground motions and seismic sources through deaggregation of the USGS next generation attenuation (NGA) seismic hazard curves in conjunction with topographic, geologic, and other geospatial information. The landslide triggering analysis is integrated into the probability chain and performed using Newmark's sliding block method. In order to estimate strength parameters for each lithological unit, which are difficult to obtain in detail for such a large area, estimated friction angle histograms were derived for each unit based on the terrain slope at locations of previously mapped landslides within the unit. Next, predictive displacement regression models suitable for regional assessment were integrated into the probability chain to calculate the probability of exceedance for specific displacement thresholds (0.1, 0.3, 1.0, 10, 100 m) relevant to engineering and planning purposes. The landslide triggering probability map was validated by previously reported landslides (The Statewide Landslide Inventory Database of Oregon, SLIDO), where more than 99.8% of these landslides fall in "very high" category of hazard level on the landslide triggering map. The created maps are suitable for regional resilience and planning studies by various agencies as well as integration with other hazard maps for risk assessment. The maps can also be used to guide geotechnical investigation, but they should not be used in place of a site-specific analysis. Title: Probabilistic analysis and mapping of seismically induced landslide deformation in Oregon Author: Sharifi Mood, Mahyar Landslides are ubiquitous within the state of Oregon, imposing an annual estimated cost of more than $10 million. Weak, saturated soils at steep slopes combined with persistent rainfall throughout most of the year provide a dangerous environment for this natural disaster, particularly in western Oregon. This grim situation is intensified by the presence of the Cascadia Subduction Zone, which is capable of generating large and powerful earthquakes. This thesis presents a fully probabilistic method for regional seismically-induced landslide hazard analysis and mapping, which considers the most current predictions for strong ground motions and seismic sources through deaggregation of the USGS next generation attenuation (NGA) seismic hazard curves in conjunction with topographic, geologic, and other geospatial information. The landslide triggering analysis is integrated into the probability chain and performed using Newmark's sliding block method. In order to estimate strength parameters for each lithological unit, which are difficult to obtain in detail for such a large area, estimated friction angle histograms were derived for each unit based on the terrain slope at locations of previously mapped landslides within the unit. Next, predictive displacement regression models suitable for regional assessment were integrated into the probability chain to calculate the probability of exceedance for specific displacement thresholds (0.1, 0.3, 1.0, 10, 100 m) relevant to engineering and planning purposes. The landslide triggering probability map was validated by previously reported landslides (The Statewide Landslide Inventory Database of Oregon, SLIDO), where more than 99.8% of these landslides fall in "very high" category of hazard level on the landslide triggering map. The created maps are suitable for regional resilience and planning studies by various agencies as well as integration with other hazard maps for risk assessment. The maps can also be used to guide geotechnical investigation, but they should not be used in place of a site-specific analysis. Close

• 2. [Article] Seismic Retrofit Benefit Considering Statewide Transportation Assessment

  The purpose of this study was to identify and demonstrate a methodology to prioritize bridges for retrofit in the State of Oregon. Given the limited resources available, retrofitting all vulnerable bridges ...

  Citation × Citation Citation Abstract Copy Title: Seismic Retrofit Benefit Considering Statewide Transportation Assessment Author: Mehary, Selamawit Tesfayesus, Dusicka, Peter Year: 2015 The purpose of this study was to identify and demonstrate a methodology to prioritize bridges for retrofit in the State of Oregon. Given the limited resources available, retrofitting all vulnerable bridges in the foreseeable future would not be practical. Instead, a retrofit strategy needs to be developed to prioritize the inventory and enumerate the retrofit cost. In this study, a prioritization methodology used a holistic assessment of overall roadway system to consider highway route segments, rather than individual bridges. The overall assessment was based on a cost-benefit analysis including retrofit cost, expected economic loss (with or without retrofit) and social loss caused by system wide travel time delays. A review of 2010 ODOT bridge inventory suggested that a continuous concrete girder bridge (CCGS) with three spans could be utilized to represent a sizeable portion of vulnerable inventory for Oregon highways bridges. After reviewing several potential retrofit measures, carbon fiber composite material was selected for retrofit of vulnerable columns representing those built from the 1950s to mid-1970s. Four full-scale typical square columns were tested to failure. The results showed that despite the intentionally selected square geometry of the reinforced concrete columns, the CFRP composite material showed to be an effective retrofit measure and could be deployed for to address this deficiency. The software package REDARS2 was used for seismic risk analysis (SRA) of the highway network in this study. This platform was adopted to simulate the impact of scenario earthquakes in an effort to assess the expected benefit considering direct bridge costs as well as social costs from traffic induced delays resulting from seismic retrofitting of a particular bridge type. The assessment considered three scenario Cascadia Subsection Zone earthquakes of magnitudes 9.0, 8.5 North, and, 8.5 South. The study area included all highway routes west of the I-5 corridor, highway routes in the Portland area, the entire length of US-101 and extending partially east on I-84 Columbia River Highway. Due to the considerations of a single bridge type and other limitations identified in the seismic analysis software (REDARS2), the retrofit assessment outcomes should be regarded as a first order estimate. Title: Seismic Retrofit Benefit Considering Statewide Transportation Assessment Author: Mehary, Selamawit Tesfayesus, Dusicka, Peter Year: 2015 The purpose of this study was to identify and demonstrate a methodology to prioritize bridges for retrofit in the State of Oregon. Given the limited resources available, retrofitting all vulnerable bridges in the foreseeable future would not be practical. Instead, a retrofit strategy needs to be developed to prioritize the inventory and enumerate the retrofit cost. In this study, a prioritization methodology used a holistic assessment of overall roadway system to consider highway route segments, rather than individual bridges. The overall assessment was based on a cost-benefit analysis including retrofit cost, expected economic loss (with or without retrofit) and social loss caused by system wide travel time delays. A review of 2010 ODOT bridge inventory suggested that a continuous concrete girder bridge (CCGS) with three spans could be utilized to represent a sizeable portion of vulnerable inventory for Oregon highways bridges. After reviewing several potential retrofit measures, carbon fiber composite material was selected for retrofit of vulnerable columns representing those built from the 1950s to mid-1970s. Four full-scale typical square columns were tested to failure. The results showed that despite the intentionally selected square geometry of the reinforced concrete columns, the CFRP composite material showed to be an effective retrofit measure and could be deployed for to address this deficiency. The software package REDARS2 was used for seismic risk analysis (SRA) of the highway network in this study. This platform was adopted to simulate the impact of scenario earthquakes in an effort to assess the expected benefit considering direct bridge costs as well as social costs from traffic induced delays resulting from seismic retrofitting of a particular bridge type. The assessment considered three scenario Cascadia Subsection Zone earthquakes of magnitudes 9.0, 8.5 North, and, 8.5 South. The study area included all highway routes west of the I-5 corridor, highway routes in the Portland area, the entire length of US-101 and extending partially east on I-84 Columbia River Highway. Due to the considerations of a single bridge type and other limitations identified in the seismic analysis software (REDARS2), the retrofit assessment outcomes should be regarded as a first order estimate. Close