Seismic Instrumentation at the I-40 Hernando Desoto Bridge in Memphis, Tennessee
| Author(s): |
Shahram Pezeshk
(The University of Memphis, Memphis)
Mitch Withers (The University of Memphis, Memphis) Greg Steiner (The University of Memphis, Memphis) |
|---|---|
| Medium: | conference paper |
| Language(s): | English |
| Conference: | Structures Congress 2006, May 18-21, 2006, St. Louis, Missouri, United States |
| Published in: | Structures Congress 2006 |
| Page(s): | 1-5 |
| Year: | 2006 |
| DOI: | 10.1061/40889(201)170 |
| Abstract: | Over the past several years, The Hernando Desoto Bridge carrying I-40 across the Mississippi river at Memphis has been the scene of an intensive strong motion monitoring project, involving the installation of numerous traditional and several non-traditional forms of instrumentation designed to characterize the response of the structure to shaking from seismic and induced sources. This bridge is being retrofitted to withstand a magnitude (mb) 7 event at 65 km distance from the site at a depth of 20 km. The goal of the retrofit is to have this bridge fully operational following the maximum probable earthquake (2500 year return period). As part of the I-40 bridge retrofit, Friction Pendulum TM Isolation Bearings have been used to insure the integrity of the main spans of the bridge. The Tennessee Department of Transportations (TDOT) in conjunction with the Federal Highway Administration (FHWA) have provided funding to install strong-motion instrumentation with 108 data channels at 36 different locations on the bridge. The United State Geological Survey (USGS) in 2002 funded the installation of sensors at the foundation levels. In addition, two free field monitoring stations were installed by Center for Earthquake Research and Information (CERI), at the University of Memphis, through funding from the Advanced National Seismic System (ANSS). Currently, in the United States and elsewhere in the world, there are very little data available on the response of long-span bridges during seismic events. Since such data are scarce, our ability to understand the behavior of such structures and to verify dynamic analyses performed on such structures during design/analyses/retrofit phases is limited. In the NMSZ, there are no long-span suspension bridge structures instrumented. Therefore, data collected from instrumentation of the I-40 bridge in Memphis will be an invaluable asset in evaluating the structure. The data will be used to assess the performance of the bridge following the retrofit and in particular for the assessment of the performance of the base-isolation system. In addition, data collected on the behavior of the base-isolation system will be applicable to any structure incorporating the system. Furthermore, lessons that will be learned from instrumentation of a bridge such as the I-40 bridge will provide important and needed information that will be applicable to structures built on similar seismological and geological settings as the 1-40 bridge. One of the goals of the instrumentation system is to develop a rapid warning system. The rapid warning system will be developed in partnership with TDOT, FHWA, the United States Geological Survey (USGS) and the Mid-America Earthquake Center (MAEC) researchers. The system will be triggered when certain acceleration thresholds, at free fields, are exceeded. Key officials at TDOT will be automatically notified of the exceedance of threshold acceleration within minutes over standard communication devices. This information will help determine the forces that the bridge underwent in a large earthquake, or other threatening events such a barge collision, and should allow quick determination whether it should be closed or/and what precautions rescuers and engineers should take. This type of monitoring and the associated rapid response may save lives. |
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