Seismic Instrumentation of the I-40 Mississippi River Bridge in Memphis, Tennessee

Abstract

The purpose of this paper is to describe installation of a seismic instrumentation system which is proposed to be deployed on and in the vicinity of the I-40 Hernando DeSoto Mississippi River Bridge in Memphis, Tennessee. This bridge is planned to be retrofitted to withstand a magnitude (mb) 7 event at 65 km distance from the site with 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™ Isolation Bearings will be used to insure the integrity of the main spans of the bridge.The I-40 bridge is scheduled to be retrofitted in several phases. The first phase of the retrofit is scheduled to begin in year 2000. Therefore, there is a window of opportunity to install an integrated system of seismic strong-motion instruments on and around the vicinity of the bridge during the retrofit construction phase. A strong-motion instrumentation with 65 data channels at 25 different locations on the bridge and at the free-field in the vicinity of the bridge is proposed to be installed. This will provide needed data to better understand the ground motion and ground failure and the response of the retrofitted bridge in a strong earthquake. In addition. the instrumentation will strengthen the free-field strong-motion network in the metropolitan Memphis area.