Search

Search Results

• 1. [Article] Bridge Seismic Retrofit Measures Considering Subduction Zone Earthquakes

  Over the years, earthquakes have exposed the vulnerability of reinforced concrete structures under seismic loads. The recent occurrence of highly devastating earthquakes near instrumented regions, e.g. ...

  Citation × Citation Citation Abstract Copy Title: Bridge Seismic Retrofit Measures Considering Subduction Zone Earthquakes Author: Dusicka, Peter, Bazaez, Ramiro, Knoles, Sarah Year: 2015 Over the years, earthquakes have exposed the vulnerability of reinforced concrete structures under seismic loads. The recent occurrence of highly devastating earthquakes near instrumented regions, e.g. 2010 Maule, Chile and 2011 Tohoku, Japan, has demonstrated the catastrophic impact of such natural force upon reinforced concrete structures. Research was conducted to investigate the effect of subduction zone earthquakes on structural damage. The study suggests that large magnitude ground motions of long duration have the potential of significantly increasing the number of inelastic excursions and consequently incur more extensive structural damage as compared to ground motions with similar elastic spectral demands but of shorter duration. This increase in demand plays a crucial role in the Pacific Northwest where a mega subduction zone earthquake is impending. Typical reinforced concrete bridge bents constructed in the 1950 to mid-1970 in the State of Oregon were designed and built with minimum seismic considerations. This resulted in inadequate detailing within plastic hinge zones, leaving numerous RC bents highly susceptible to damage following an earthquake. In this study, the cyclic performance of an as-built RC square column and a reinforced concrete bridge bent retrofitted using buckling restrained braces (BRBs) was experimentally evaluated using quasi-static cyclic loading protocols aiming to reflect subduction zone earthquake demands up to displacement ductility. The buckling restrained braces were designed as replaceable elements in order to take the earthquake-induced energy and dissipate it through nonlinear hysteretic behavior. Two BRB designs were considered in the study in an effort to assess the influence of BRB stiffness on the overall structural performance. The results of these large-scale experiments successfully demonstrated the effectiveness of utilizing buckling restrained braces for achieving high displacement ductility of the retrofitted structure, while also controlling the damage of the existing vulnerable reinforced concrete bent up to the design performance levels. The potential of improving the overall seismic behavior and the design performance levels with BRBs offers structural design professionals a viable method for performance driven retrofit of reinforced concrete bents. Title: Bridge Seismic Retrofit Measures Considering Subduction Zone Earthquakes Author: Dusicka, Peter, Bazaez, Ramiro, Knoles, Sarah Year: 2015 Over the years, earthquakes have exposed the vulnerability of reinforced concrete structures under seismic loads. The recent occurrence of highly devastating earthquakes near instrumented regions, e.g. 2010 Maule, Chile and 2011 Tohoku, Japan, has demonstrated the catastrophic impact of such natural force upon reinforced concrete structures. Research was conducted to investigate the effect of subduction zone earthquakes on structural damage. The study suggests that large magnitude ground motions of long duration have the potential of significantly increasing the number of inelastic excursions and consequently incur more extensive structural damage as compared to ground motions with similar elastic spectral demands but of shorter duration. This increase in demand plays a crucial role in the Pacific Northwest where a mega subduction zone earthquake is impending. Typical reinforced concrete bridge bents constructed in the 1950 to mid-1970 in the State of Oregon were designed and built with minimum seismic considerations. This resulted in inadequate detailing within plastic hinge zones, leaving numerous RC bents highly susceptible to damage following an earthquake. In this study, the cyclic performance of an as-built RC square column and a reinforced concrete bridge bent retrofitted using buckling restrained braces (BRBs) was experimentally evaluated using quasi-static cyclic loading protocols aiming to reflect subduction zone earthquake demands up to displacement ductility. The buckling restrained braces were designed as replaceable elements in order to take the earthquake-induced energy and dissipate it through nonlinear hysteretic behavior. Two BRB designs were considered in the study in an effort to assess the influence of BRB stiffness on the overall structural performance. The results of these large-scale experiments successfully demonstrated the effectiveness of utilizing buckling restrained braces for achieving high displacement ductility of the retrofitted structure, while also controlling the damage of the existing vulnerable reinforced concrete bent up to the design performance levels. The potential of improving the overall seismic behavior and the design performance levels with BRBs offers structural design professionals a viable method for performance driven retrofit of reinforced concrete bents. 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