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Enhancing Seismic Design Strategies for Bridges: Leveraging Data-Driven Decision Making through Shear Wave Velocity Testing and Site-Specific Ground Motion Response Analysis

Seismic hazards play a crucial role in the design of transportation infrastructure, particularly bridges, across the southern plains and various regions of the United States. The recent introduction of risk-targeted ground motions and the updated seismic site classification scheme in the 2023 American Association of State Highway and Transportation Officials (AASHTO) guide specifications for Load and Resistance Factor Design (LRFD) seismic bridge design has introduced considerable uncertainty regarding their impact on commonly used design approaches. This project aims to investigate the following: (1) How changes in seismic site classification can influence the seismic design category, thus affecting bridge design and construction costs; (2) The drawbacks of continued use of the standard penetration test (SPT) for seismic site classification versus the advantages of employing shear wave velocity; (3) The benefits of conducting a Site-Specific Ground Motion Response Analysis (SSGMRA) on the seismic design category and the design response spectrum, consequently influencing bridge design and construction costs. As demonstrated in the Arkansas Department of Transportation (ARDOT) research project TRC1603, significant cost savings of up to 7% of the total bridge construction cost, or approximately $200,000, are achievable at certain sites where SSGMRA is performed (with the cost of SSGMRA being substantially lower (5% to 10%) than the potential savings). However, it remains uncertain whether these savings can be replicated across sites throughout the southern plains and the broader U.S. Consequently, there is a pressing need to determine the circumstances and locations where such analyses can yield substantial cost benefits for projects. Furthermore, these analyses are not limited to regions with very high seismic activity but can also provide notable advantages in areas with relatively lower seismic requirements by potentially reducing the seismic design category (e.g., transitioning from a "C" to a "B" seismic design category). This bears significant implications for the seismic design standards applicable to bridges and other transportation infrastructure projects. Moreover, with the updated seismic site classification scheme in the AASHTO 2023 guidelines, the use of SPT N values for seismic site classification is heavily penalized when determining the seismic site class. Given that many DOTs and transportation designers still rely on SPT for seismic site classification, there is a crucial need for designers to comprehend the consequences of continuing this practice and to identify locations where substantial benefits can be derived from conducting shear wave velocity testing, as advocated by the 2023 AASHTO guidelines. The project comprises two main components. Initially, seismic hazard maps derived from the 2023 AASHTO code will be analyzed to identify regions where improving the seismic design category through either shear wave velocity testing or SSGMRA could result in cost-saving advantages. These regions typically exhibit ground motions near the boundary limits for the seismic design category or possess soils with sufficient stiffness or shallow bedrock, allowing for a transition from the default seismic site class D to a more favorable class, such as CD, C, BC, or B. Such transitions have the potential to significantly reduce design ground motions for various projects. Subsequently, SSGMRA will be conducted across different sections of the southern plains and central and eastern US to assess whether similar benefits to those observed in the TRC1603 project can be realized in other regions of the country. This endeavor entails utilizing previously gathered Vs profiles and conducting SSGMRA in various locations within the designated area of interest. Through this process, we aim to identify specific scenarios and locations where conducting SSGMRA can offer tangible benefits for transportation projects. The study will be carried out through the following detailed tasks. Task 1: Develop maps of seismic design category for Region 6 to determine where changes in seismic site class would result in changes in seismic design category. These maps would be based on the available seismic design maps and national hazard maps available from USGS and AASHTO. These estimates will be maps at the resolution level of the current hazard maps. Task 2: Develop scenarios comparing the site classification from SPT and that from Vs to determine the impact of continuing to use SPT for site classification. Approximately 50 example SPT and Vs profiles will be used and placed in different locations to assess the impact of using both for site classification. Task 3: Conduct SSGMRA for scenario sites (approximately 20) in Region 6 to compare with the code based generic approach and assess potential cost savings associated with conducting these measurements in the future. Task 4: A final project report will be developed to convey the findings from the project.

Language

  • English

Project

  • Status: Active
  • Funding: $135,115.00
  • Contract Numbers:

    CY2-UARK-02

    69A3552348306

  • Sponsor Organizations:

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Managing Organizations:

    Southern Plains Transportation Center

    University of Oklahoma
    202 W Boyd St, Room 213A
    Norman, OK  United States  73019
  • Project Managers:

    Dunn, Denise

  • Performing Organizations:

    University of Arkansas, Fayetteville

    4190 Bell Engineering
    Civil Engineering
    Fayetteville, Arkansas  United States  72701
  • Principal Investigators:

    Wood, Clint

  • Start Date: 20241001
  • Expected Completion Date: 20250930
  • Actual Completion Date: 0
  • USDOT Program: University Transportation Centers

Subject/Index Terms

Filing Info

  • Accession Number: 01941686
  • Record Type: Research project
  • Source Agency: Southern Plains Transportation Center
  • Contract Numbers: CY2-UARK-02, 69A3552348306
  • Files: UTC, RIP
  • Created Date: Jan 1 2025 4:39PM