Assessment of the seismic vulnerability of wall pier supported highway bridges on priority emergency routes in southern Illinois

Multi-column pier supported and wall pier supported bridge structures comprise approximately 86% of the bridges that carry or cross over southern Illinois highway priority emergency routes. The Illinois Department of Transportation (IDOT) would like these routes to remain functional following a New Madrid Seismic Zone (NMSZ) earthquake. Therefore, to assess their vulnerability to such an event, IDOT has undertaken several research projects that have initiated the assessment by investigating the vulnerability of these two most common bridge types. An earlier project determined the vulnerability of the more prevalent (58% of the total) multi-column pier supported bridges. Presented herein are the findings from the second research project, which has investigated the vulnerability of the wall pier structures (28% of the total) through pushover analyses and the production of structural and site liquefaction fragility curves.; Typical structural characteristics were determined from a sample of 22 southern Illinois priority emergency route wall pier supported bridges. A summary of these characteristics is given. These structural details were used to construct two sets of three-dimensional nonlinear numerical models, one to perform nearly 200 pushover analyses, and one two perform nearly 100 dynamic time-history analyses (required for fragility curve construction). Details concerning the analytical sub-models used for representing the various bridge components in these models are given, as is information concerning the structural limit states that were considered in the analyses. Results and conclusions stemming from the pushover and fragility analyses are presented, including details about how wall pier bridge structural variations affect those failures that are critical and those bridge categories that are most vulnerable. The theoretical underpinnings of the fragility procedure implemented are highlighted. In addition, the liquefaction fragility analysis conducted is detailed, with results and conclusions presented. Finally, implications of these findings for the southern Illinois priority route network are discussed.