Implementing Displacement-Based Seismic Design and Streamlining Low Seismic Zone Design Requirements in the AASHTO LRFD Bridge Design Specifications

Seismic design for roadway bridges has evolved over the past several decades, moving away from traditional force-based approaches toward displacement-based and performance-based methodologies. The current force-based provisions in the AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications (BDS) rely on approximate relationships between force reduction factors and expected structural performance, which have been shown to be conservative in some cases but not others. In contrast, displacement-based seismic design provides a more direct and reliable relationship between design methods and expected bridge performance. The American Association of State Highway and Transportation Officials (AASHTO) allows both force-based and displacement-based approaches, potentially resulting in different design outcomes depending on the method selected. Additionally, recent advancements in performance-based seismic design and seismic isolation have not been fully integrated into the BDS. For example, current performance-based guidelines reference outdated ground motion models, while the Seismic Guide Specifications lack sufficient detail in areas such as steel substructures and emerging design approaches for bridge pier walls. Additionally, the seismic provisions are distributed across multiple sections of the BDS and related guide specifications, making it difficult for practitioners to identify pertinent requirements. There is a need for research to develop a streamlined framework for seismic bridge design for all seismic regions that reflects current research and practice, and to update current guidance. The objectives of this research are to (1) develop a guide suitable for practitioners in all seismic regions that synthesizes recent advances in seismic analysis and design, and consolidates seismic design requirements; (2) provide a streamlined framework for a performance-based approach to seismic bridge design and seismic isolation; and (3) prepare a standalone memorandum with language suitable for AASHTO’s consideration in evaluating potential updates to the AASHTO Guide Specifications for LRFD Seismic Bridge Design and a new seismic design section within the BDS.

• Record URL:
  • http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=6048
• Supplemental Notes:
  • Contract to a Performing Organization has not yet been awarded.

Language

• English

Project

• Status: Proposed
• Funding: $800,000.00
• Contract Numbers:

  Project 12-136

• Sponsor Organizations:

  National Cooperative Highway Research Program

  Transportation Research Board
  500 Fifth Street, NW
  Washington, DC  United States  20001

  American Association of State Highway and Transportation Officials (AASHTO)

  444 North Capitol Street, NW
  Washington, DC  United States  20001

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Project Managers:

  Crichton-Sumners, Camille

• Start Date: 20260608
• Expected Completion Date: 0
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Bridge design; Earthquake resistant design
• Identifier Terms: AASHTO LRFD Bridge Design Specifications
• Subject Areas: Bridges and other structures; Design; Highways;

Filing Info

• Accession Number: 01992134
• Record Type: Research project
• Source Agency: Transportation Research Board
• Contract Numbers: Project 12-136
• Files: TRB, RIP
• Created Date: Jun 9 2026 12:36PM