Assessment of the Bill Emerson Memorial Bridge - FTP Directory ...

Executive SummaryOpen to traffic on December 13, 2003, the Bill Emerson Memorial Bridge is a 1206 m(3956 ft) long cable-stayed structure. It carries four lanes of vehicular traffic alongMissouri State Highway 34, Missouri State Highway 74 and Illinois Route 146 across theMississippi River between Cape Girardeau, Missouri, and East Cape Girardeau, Illinois.The structure consists of 128 cables, two longitudinal stiffened steel girders, and twotowers in the cable-stayed spans, and 12 additional piers in the Illinois approach span. Inaddition to four pot bearings at two towers, the superstructure of the cable-stayed span isconstrained to the substructure with 16 longitudinal earthquake shock transfer devices attwo towers, four tie-down devices at two ends of the cable-stayed span, and six lateralearthquake restrainers. The approach span is composed of one simply-supported, onefour-span continuous, and two three-span continuous steel girder structures.Seismic instrumentation systemThe Missouri end of the bridge directly rests on rock and the Illinois end is supported ondrilled shaft foundations. Due to its complexity in structure and site geology as well as itsproximity to the New Madrid Seismic Zone, the bridge was instrumented with an 84-accelerometer, real-time, seismic instrumentation system. The monitoring system hasbeen in operation since December 2004 and it continuously records site and structuralresponses due to traffic loading and minor earthquakes. However, only a most recent 16-day worth of recorded data are kept on file unless a sizable earthquake has beenidentified.At 12:37′32″ (Universal Time) of May 1, 2005, an earthquake of M4.1 on a Richter scaleoccurred at four miles SSE (162 o ) from Manila, Arkansas, and 180 kilometers from thebridge. The hypocenter depth was estimated to be about 10 kilometers. This set ofearthquake data will be used to validate a three-dimensional finite element (3-D FE)model of the cable-stayed bridge.Research objectivesThe objectives of this study are to retrieve peak ground and structure accelerations fromthe real-time instrumentation system, assess the condition of the bridge structure under adesign earthquake, develop and validate a 3-D FE model that represents the actualbehavior of the bridge.To achieve the above objectives, several topics are studied in this report, including: (1)automatic retrieval of peak accelerations and measured data analysis, (2) 3-D FE bridgemodel with explicit modeling of all main components, (3) sensitivity study and validationof the 3-D FE bridge model, and (4) seismic behavior and assessment of the bridgestructure.iv