SEISMIC VULNERABILITY ASSESSMENT OF A FAMILY OF HORIZONTALLY CURVED STEEL BRIDGES USING RESPONSE SURFACE METAMODELS
Open Access
- Author:
- Seo, Junwon
- Graduate Program:
- Civil Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 08, 2009
- Committee Members:
- Dr Linzell, Dissertation Advisor/Co-Advisor
Daniel G Linzell, Committee Chair/Co-Chair
Jeffrey A Laman, Committee Member
Andrew Scanlon, Committee Member
Linda Morley Hanagan, Committee Member
Peggy Ann Johnson, Committee Member - Keywords:
- Bridge
Metamodels
Fragility Curves
Seismic Vulnerability Assessment - Abstract:
- Civil infrastructure systems must be designed and constructed to resist the effects of natural and manmade hazards to ensure public safety and to support the socio-economic goals and needs of society. In recent decades, earthquake hazards have been viewed as extremely important among the natural hazards impacting civil infrastructure systems across certain regions in the United States. The occurrence of three major earthquakes during that period (San Fernando in 1971, Loma Prieta in 1989, and Northridge in 1994) demonstrated the possible seismic vulnerabilities that existing bridges may contain. These major seismic events also have provided the impetus for significant improvements in engineering practices for bridge seismic design, analysis, and vulnerability assessment. Bridge seismic risk assessment tools have been proposed and utilized by many engineers and researchers since the inception of earthquake engineering in the 1970’s. These tools have predominately used fragility curves, which are conditional probability statements that give the probability of a bridge reaching or exceeding a particular damage level for an earthquake of a given intensity level, for examining straight bridge structures. Fragility curves for the bridge components and system are essential inputs into the final damage estimation algorithm for a given earthquake event. Since these tools were developed for evaluating the seismic vulnerability of straight bridges, they cannot be applied to curved bridges. There has been a steady growth in the use of horizontally curved steel bridges since approximately 1970, which coincides with the initiation period of the earthquake engineering field. Effects of various curved bridge parameters, including radius of curvature, on the fragility of bridges across geographic regions must be investigated for their seismic assessment. In this study the characteristics of structures in a target inventory were used to estimate fragilities for a family of horizontally curved steel bridges. Consideration was restricted to the class of bridge structures consisting of horizontally curved steel I-girder bridges. Statistically significant predictors for seismic vulnerability assessment were identified using Design of Experiments (DOE) and other statistical tools, and appropriate seismic response surface metamodels (RSMs) were developed to rapidly predict seismic response for a family of horizontally curved steel bridges. Fragility curves for horizontally curved steel I-girder bridges were estimated using the metamodels with Monte Carlo simulation. The use of metamodels reduced the required computations and made it practical to carry out probabilistic response calculations in an efficient manner. Various sources of structural uncertainty were considered and tracked throughout the study, including radius of curvature, number of spans, cross-frame spacing, girder spacing, span length. This approach allowed for the direct implementation of findings into existing seismic risk assessment packages (e.g., FEMA Hazards U.S. Multi-Hazard loss assessment package, etc.). Findings from the study show that this approach provides reliable fragility curves for a family of horizontally curved steel I-girder bridges in the target region.