EVALUATION OF THE DUPONT ACCESS BRIDGE

Abstract

This paper describes the evaluation of an experimental steel connection used on the DuPont Access Bridge in New Johnsonville, Tennessee. The steel rolled section bridge has two spans and is designed to be erected as simple spans and to act continuously under the dead load. The connection, between the spans, consists of a tension plate bolted to the top flange of the girders at the pier and a wedge plate welded to the bottom flange of the girders. The bridge was instrumented with weldable strain gages and tested during the deck pour and under controlled load conditions. This paper describes the measured and predicted lateral load distribution of the bridge. Introduction: On September 2, 2003 the Tennessee Department of Transportation (TDOT) contracted with the Department of Civil and Environmental Engineering at the University of Tennessee to conduct research on the Dupont Access bridge. The bridge is located near the DuPont plant in New Johnsonville, Tennessee, and carries mostly truck traffic into and out of the plant. It allows easy access to the DuPont Access Rd from both the east and west bound lane of US 70. Substructure: The bridge has two spans and is supported by integral abutments at both ends and one pier located between the east and west bound lanes of US 70 as shown in plan view in Figure 1. The bridge's foundation consists of steel piles which support both the abutments and the three pile caps for the three columns at the center pier. All piles are HP 10x42's. The bearings for the girders at the abutments consist only of riser blocks at the abutment, but a thin neoprene pad exists at the pier. Superstructure: The girders of the Dupont access bridge are W33x240s (Grade 50, weathering steel) spaced at 7'-4 13/16 on center as shown in a typical cross section in Figure 2. They are braced against lateral torsional buckling under the dead load by channels (C15x33.9) bolted to web stiffeners. At the intermediate bracing a web stiffener does not exist on the outside of the fascia girders. At the pier, the north and south girders are connected at the top flange by a 1 5/8 thick cover plate that is 11'-3 1/2 long with 40 bolts into the top flange of each girder. The compression forces at the pier are transferred between girders by a plate that consists of two plates wedged together that bear against the bottom flanges at the ends of the girders. After bearing is achieved the wedge plates are welded together and to the girders. A one foot thick reinforced concrete diaphragm exists at the pier. The girders on the north side of the pier have Nelson studs on 6 centers for the first 8' of the span and on 10 centers for the next 59' of the span measured from the centerline of bearing at the abutment. The girders on the south side of the pier have Nelson studs on 6 centers for the first 8' of the span and on 10 centers for the next 47'-6 of the span also measured from the abutment. The deck is 8 1/4 thick, and acts compositely with the girders. The bridge has a .2% slope laterally in both directions from the center line, and has a standard barrier rail on both sides (See Figure 2) of the bridge. Figure 1. Plan view of the Dupont access bridge