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Site-specific Ground Motion Response Analysis for Bridges in Western Tennessee

Description: 

The AASHTO LRFD Bridge Design Specifications and the AASHTO Guide Specifications for LRFD Seismic Bridge Design generally provide adequate methods for determining seismic hazards and site response. However, site-specific hazard analyses may be necessary for unique scenarios, such as long-duration earthquakes, critical infrastructure, specific soil types, or near-fault conditions. These analyses can justify reductions in spectral acceleration compared to the uniform seismic hazard values derived from standard procedures, potentially reducing construction costs for bridges.

This study focuses on site-specific ground motion response analysis (SSGMRA) for 32 sites in Western Tennessee. Field tests, including Multi-channel Analysis of Surface Waves (MASW) and Refraction Microtremor (ReMi), were conducted at 12 sites, while data from a prior Tennessee Department of Transportation (TDOT) project was utilized for the remaining locations. Sites were selected based on the locations of existing TDOT bridges, ensuring the availability of at least one borehole dataset per site. To ensure comprehensive spatial coverage of the study area, a maximum Euclidean distance of 20 km between sites was maintained.

The seismic wave data process combines dispersion curves obtained from MASW and ReMi surveys. In some cases, low-frequency ReMi data is combined with MASW measurements to provide deeper subsurface insights. The combined dispersion curves are then inverted to derive detailed shear-wave velocity profiles for each tested site.

This phase of the project focuses on deriving accurate shear-wave velocity profiles through MASW and ReMi data integration, forming the foundation for subsequent phases, such as site response analysis and seismic hazard evaluation.

By incorporating the outcomes of SSGMRA into Geographic Information System (GIS) maps, engineers at TDOT will have access to cost-effective design tools that account for local site conditions, potentially reducing construction costs while enhancing seismic resilience.

Session: Station Installations and Site Conditions, a Quest for Improved Strong Motion Database - I

Type: Oral

Date: 4/16/2025

Presentation Time: 02:15 PM (local time)

Presenting Author: Najme

Student Presenter: Yes

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