A SIMPLIFIED SEISMIC ASSESSMENT PROCEDURE FOR BRIDGES IN INDIANA
The potential for damaging earthquakes in Indiana from the New Madrid Seismic Zone (NMSZ) has been known for 200 years. However, the identification of the Wabash Valley Seismic Zone (WVSZ) has increased the awareness of the seismic risk in Indiana. The Indiana Department of Transportation (INDOT) has been preparing for the occurrence of a large event by reducing the vulnerability of its bridge network, specifically in the Vincennes district. To facilitate the work of the State of Indiana, in this thesis the development of a simplified assessment procedure for the bridges typical in Indiana is presented. The thesis also includes a proposed simplified assessment tool, Indiana Seismic Assessment Tool (INSAT) to rapidly assess the vulnerability of INDOT’s bridges. To understand the behavior and vulnerabilities typical to bridges in Indiana, a set of 100 representative bridges was chosen for a detailed seismic assessment. The assessment is completed using information from the bridge drawings and 100 synthetic ground motion time-histories. The results of the detailed assessment, found in the SPR 4222 final report, are used to develop trends in mass and stiffness across bridge types, to identify vulnerability thresholds for application in the simplified assessment, and to validate the simplified assessment procedure.
The simplified seismic assessment procedure presented in this thesis and INSAT leverage information found in BIAS. However, in its current state, BIAS does not contain enough information to perform a robust seismic assessment. Eight data items are recommended for implementation into BIAS in order to carry out a simplified assessment. These eight data items are the substructure type, the abutment type, the number of elements, the element height, length, and width, the deck thickness, and a height ratio flag. While some of these items can be estimated, the best version of the simplified assessment utilizes all of the recommended data items and leads to an 87% agreement between the vulnerability classifications of the simplified assessment and the detailed assessment.