Development of a methodology for the integration of seismic risk mitigation activities in project and network level bridge management systems

The most widely used bridge management systems (BMS's), at the present time, employ Markovian decision processes for preservation optimization and level of service analysis for assessment of improvement needs. Using this approach, coordinated network and project-level programs are developed using incremental benefit-cost analysis. Retrofitting to mitigate potentially damaging effects of natural hazards and extreme events, such as that from seismic events, are not considered in the existing systems. The development of a methodology to facilitate network and level planning and programming is pursued. The mathematical approaches utilized, assumptions made and constraints imposed by the current BMS paradigms are examined in depth. Predominant prioritization procedures, which form the basis for current seismic retrofitting programs, are examined and evaluated. Data requirements are compared to contributory factors identified through historical damage. Inventory-wide data limitations are identified and additional data collection requirements are outlined. Constraints on the output of seismic retrofitting modules are defined and viable alternative approaches for model development presented. Viable approaches include measure-value procedures and the development of a new risk-based methodology. The measure value approach is examined using constant, linear and categorical estimators. Significant variations were exhibited with the raw indices and the procedures were decomposed to enable a focus on vulnerability specific variables and parameters. Variations persisted in both the project and network-level results. Application of a more rigorous, quantitative approach was thus shown to be a preferred technique. A methodology based on component-level ground motion-damage relationships was developed. The component level damage relationships were defined empirically based on historical damage information and expert opinion. Retrofits were defined as modifiers to the relationship parameters, which enabled quantification of effectiveness, assessment of expected costs, and determination of benefits as expected impacts to the traveling public, bridge owning agency, and general population. The methodology is applicable for the development of budgetary requirements to reduce risks, for the prioritization of structures, and for integration into project and network components of predominant BMS approaches. Application is demonstrated using a sample data set from the California bridge inventory.