Planning and Implementation of a Seismic Monitoring System for the Bill Emerson Memorial Bridge in Cape Girardeau, MO

Abstract

The Bill Emerson Memorial Bridge is a new cable-stayed Mississippi River crossing in Cape Girardeau, Missouri that opened on December 13, 2003. The site is known for its proximity to the New Madrid Fault, necessitating a design for a M7.5 event. It is the first major bridge structure in the Central and Eastern United States (CEUS) where seismic (and wind) monitoring was considered from the early stages of design. A multi-agency team effort was used to design a system, acquire the sensors and other instrumentation, provide for installation and performance testing, and establish a suitable protocol for operation and data dissemination. The instrumentation of the bridge including two free-field arrays with downholes was completed in March 2005. Data is now being streamed in real-time and transmitted via the internet to the user community for analyses and conducting structural health monitoring. The purpose of this paper is to describe the entire process so the experience can be studied and used as a guide for future bridge projects, especially those in the CEUS. The Bill Emerson Memorial Bridge consists of a three span cable-stay river crossing and an eleven span steel plate girder Illinois approach. The total bridge length is 3,965 feet (1210 m) with a 1,150-foot (350 m) main river span. Cape Girardeau is approximately 50 miles due north of the New Madrid Seismic Zone (NMSZ), the location of three large (M > 7.5) and numerous smaller earthquakes during the winter of 1811–1812. A Federal Highway Administration (FHWA) geotechnical engineer, Chris Dumas, originally conceived seismic instrumentation of the Bill Emerson Memorial Bridge in 1996. Several meetings were conducted in 1996 and 1997 between various stakeholders associated with the bridge and seismic instrumentation networks. As an outcome of this series of meetings, a seismic instrumentation plan for the structure was developed by the United States Geological Survey (USGS) and authored by Mehmet Celebi. However, at the time no funding source for the project existed so acquisition of the system did not proceed. In the subsequent Transportation Efficiency for the 21st Century (TEA-21) Federal Highway Bill, the FHWA sponsored a 6-year seismic research program with the Multidisciplinary Center for Earthquake Engineering Research (MCEER) at the State University of New York - Buffalo. The program included funding for the final design and hardware acquisition of the seismic instrumentation system for the Bill Emerson Memorial Bridge. Total funding set aside for the purchase of the hardware including 84 channels of accelerometers and data acquisition and transmission systems, as part of this program, was $375,000.