Performance-Based Decision-Making in Post-Earthquake Highway Bridge Repair
- Author(s): Gordin, Eugene
- Advisor(s): Stojadinovic, Bozidar
- et al.
Post-earthquake highway bridge repair is an ever-present part of the lifecycle of transportation systems in seismic regions. These repairs require multi-level decisions involving various stakeholders with differing values. The improvement of the repair decision process, repair decision itself, and repair decision outcomes, requires an evaluation of current practices in post-earthquake repair decision-making.
This dissertation assesses these current practices within the California Department of Transportation (Caltrans), outlines areas where the current process is ineffective, and highlights areas for improvement. Current repair decision-making practice is focused on the repair of individual bridges given a limited set of established repair methods.
To improve upon these practices, this dissertation presents the Bridge Repair Decision Framework (BRDF), a new and unique methodology that allows for simultaneous consideration of all earthquake-damaged bridges as individual elements of a larger regional transportation system. This systematic approach enables the achievement of short- and long-term transportation system performance objectives while accounting for engineering, construction, financing, and public policy constraints. Furthermore, the BRDF allows for continuous refinement of the decision-making process to incorporate engineering and construction innovations, changes in the financial and public policy environment and, most importantly, changes in transportation system performance goals. While existing methodologies allow the incorporation of some of these changes, the BRDF provides a flexible structure that can account for all of these changes simultaneously.
This is accomplished through a rigorous, performance-based, and risk-informed decision-making approach that presents repair decisions using a traditional engineering demand-capacity inequality. As a result, the BRDF empowers decision-makers with a holistic understanding of the transportation network condition on a microscopic (bridge) as well as macroscopic (overall system) level.
The BRDF also accounts for the probabilistic nature of the earthquake hazard, bridge seismic capacity, and subsequent repair decisions, providing decision-makers with transparency regarding the uncertainties of system condition, repair method reliability, construction workforce availability, and public and business risks. BRDF decision-outcomes are technology-neutral as a result, greatly expanding the range of repair method alternatives that a decision-maker may consider while allowing for tradeoffs to be made between performance, cost, and time in light of transportation system condition and constraints.
The BRDF is validated using a simulated bridge system case study that requires post-earthquake repair. This study was designed to demonstrate the functionality of the framework and to examine two alternate decision-making strategies: one with complete and the other with incomplete post-earthquake bridge damage state information. This case study led to refinements in the framework and insights about the benefits of additional information on the damage state of bridges in terms of overall repair time and cost of the regional transportation system. Additionally, the validation revealed areas where the current BRDF can be improved in future studies.
The BRDF was created for large public transportation organizations such as the California Department of Transportation (Caltrans), where implementation of the BRDF requires several important prerequisites, including new database creation and additional training for engineers. Once implemented however, the BRDF allows decision-makers to potentially reduce repair costs and times, minimize system downtime, make better investments, and account for transportation system performance goals given current financial and public policy constraints.