NCHRP 20-7 Proposed Research Needs Statement

AASHTO Subcommittee on Bridges and Structures Gregg C. Fredrick, P.E. Date April 29, 2016 TITLE Seismic Design Criteria for Bridge Modifications and Widening BACKGROUND / NEEDS STATEMENT Widening of existing bridges in seismic regions is often challenging, specifically when it comes to determining how to address elements of the existing structure that do not meet current design standards. The Seismic Analysis and Retrofit Policy for Bridge Widening Projects has been established to give bridge design engineers guidance on how and when to address structural deficiencies in existing bridges that are being widened. Seismic retrofit can have a substantial impact on project scope, cost, and schedule. Therefore, it is important that required seismic retrofit for bridge widening projects be identified as early in the project development process as possible, ideally at the Advanced Planning Study phase. RESEARCH OBJECTIVE The objective of this research is to provide design guidance for Widening of Bridges in Seismic Regions. A bridge widening is defined as where substructure bents are modified and new columns or piers are added, or an increase of bridge deck width or widenings to the sidewalk or barrier rails of an existing bridge resulting in significant mass increase or structural component changes. WORK TASKS Tasks anticipated in this project include the following: • Literature study of bridge widening in seismic regions with or without presence of liquefiable soils. • Develop analytical model that to investigate different widening and modification scenarios such as: o Substructure bents are modified and new columns or piers are added. o Change in net superstructure mass as compared the original superstructure mass. o Fixity conditions of the foundations are changed. o Change in live load use of the bridge such as addition of light rail. • Develop final research report encompassing the research results and retrofit options. The report should include design specifications, design procedures, and numerical examples. URGENCY Development of the design specifications and guidelines for bridge widening in seismic regions will provide transportation agencies with a wide range of options for addressing bridge system resiliency in a seismic event, and for lifeline routes. FUNDING REQUESTED AND TIME REQUIRED It is estimated that this research will take 12 months to complete and will require $99,000. CONTACT PERSON Bijan Khaleghi, PhD, PE, SE State Bridge Design Engineer Washington State DOT Olympia Washington Phone: (360) 705-7181 Fax: (360) 705-6814 Email: [email protected]