UTC 2022 Funding - Cycle 2 Research Projects

Project Number: CY2-UARK-02
Project Title: Enhancing Seismic Design Strategies for Bridges: Leveraging Data-Driven Decision-Making through Shear Wave Velocity Testing and Site-Specific Ground Motion Response Analysis
Performing Institution: University of Arkansas
Principal Investigator: Clinton Wood
Proposed Start and End Date: 10/01/2024 to 09/30/2025
Project Description: 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 AASHTO guide specifications for 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 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.
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