Fragility assessment of bridge superstructures under hydrodynamic forces
Date
2015
Authors
Turner, David, author
van de Lindt, John, advisor
Senior, Bolivar, committee member
Atadero, Rebecca, committee member
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Abstract
On September 11-17, 2013, Colorado suffered devastating and widespread flash flooding which spread 150 miles, from Colorado Springs north to Fort Collins impacting 24 counties. The flood damaged several bridges as well as over 400 miles of state roads. As a result of the transportation damage, residents of Drake, Colorado were isolated and had to be evacuated via helicopter. This thesis aims to determine the failure risk associated with the inundation of bridge superstructures. A linear network of eight bridges near Drake, Colorado is selected for analysis which includes three unique structural configurations. Flood analysis is performed using the design equations presented by Kerenyi et al. (2009) which follows the same equation format that is listed in AASHTO. Fragilities are developed for the most critical internal and external composite girders for each bridge. The results obtained from fragility analysis are then used to determine the elevation adjustments needed to reach a target beta value of 3.5. Based on the analysis conducted in this thesis, it was found that the forces associated with bridge deck inundation, more specifically, in fast-moving mountain rivers is substantial and needs to be considered in design. Currently, bridge superstructures are designed based on the 100 year flood, which in the case of the bridges in this study, would not have resulted in any inundation of the bridge deck at the time of construction based on the knowledge at that time. To counter this, bridge superstructures should be designed based on the 500 year flood which would incorporate inundation forces in the initial design. The methodology presented in this thesis can be used to assess and improve the flood vulnerability for any communities' bridge network.
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Subject
bridge
fragility
hydrodynamic
superstructure