Emergency Earthquake Routes for the State of Indiana Part I: Criteria for Selection of Primary Routes: Transportation Aspects; Part II: Route Seismic Vulnerability Aspects

The occurrence of a strong earthquake in Indiana or neighboring states, as has occurred in the past, has serious implications for the State Transportation System with respect to adequate response. The definition of Earthquake Emergency Routes for the State of Indiana became a priority for the Indiana Department of Transportation. These Emergency Routes take into account various aspects related to transportation including coverage of population and area and travel time along these routes, and issues related to structural and geotechnical seismic vulnerability of the roads and bridges along these routes. Part I of the overall study report formulates a multi-commodity maximal covering network design problem (MCNDP) for identifying critical routes, for earthquake response and to seismically retrofit bridges. In the MCNDP, routes are sought that minimize the total travel time over the selected routes and maximize the total population covered, subject to a budget constraint on bridge retrofitting costs on the selected routes. The problem is formulated as a two objective integer programming model and solved using the branch-and-cut module in the CPLEX optimizer. The model performance is analyzed using the transportation network in southwest Indiana. A problem reduction strategy is introduced to reduce computational times by recognizing that the critical routes are not usually circuitous. Thereby, the search for the critical routes for an origin-destination (O-D) pair is confined to a limited geographical region around it. To further reduce computational costs, the formulation is extended to incorporate valid inequalities that exploit the problem structure. Simulation studies are conducted to investigate the effects of varying the budget and the relative weights of the two objectives. Noninferior frontiers that illustrate the trade-offs between the conflicting objectives for different budgets are constructed to provide practical insights to decision-makers. The final selected routes in addition include constraints set by the Study Advisory Committee regarding specific roads to be included in the final set. Part II of the study report covers the structural and geotechnical seismic issues related to the definition of Earthquake Emergency Routes for the State of Indiana. Previous worldwide experience on bridge damage during strong earthquakes has influenced the bridge earthquake design specifications and mitigation procedures. The evolution of the relevant requirements in the American Association of State Highway and Transportation Officials (AASHTO) Specifications and the existence of a proposed draft seismic design specification under development as part of the National Cooperative Highway Research Program (NCHRP) Project 12-49 have significant implications in the assessment of the existing vulnerability, its mitigation, and the design of new bridges along the Emergency Routes. Geographical Information System (GIS) was implemented to assist the evaluation of seismic vulnerability of the proposed Indiana Emergency Routes. Using the available information, the GIS implementation may be used for mitigation of vulnerability, simulation, and response to a strong earthquake in Indiana incorporating information from the Indiana Department of Transportation (INDOT) maintenance database and selected structural and geotechnical information from the relevant bridge drawings. Findings from a vulnerability assessment as well as final calibration performed using selected representative bridge data such as drawings and soil exploration descriptions are also reported. Vulnerability was evaluated for different levels of ground acceleration in order to obtain behavior patterns for selected bridges and to illustrate upgrade needs for the transportation structures on the Emergency Routes. The information contained in this report could be used to assist the engineers in conducting simulations that will help INDOT to devise mitigation policies for different earthquake occurrence scenarios and to evaluate potential alternative routes.