**2. Description of The Bridge Structure**

The examined object was a technological suspension bridge over the Odra River (Southern Poland) designed for joining a marl open-pit mine with a cement plant (Figure 1). Generally, the bridge includes five spans, the main span over the river (165 m) and four spans over the floodplain. The steel transport gallery (together with the belt conveyor) is suspended on two sets of carrying cables (six wires in each set) that are supported on two towers (in the form of portals) and anchored to special reinforced concrete blocks. Each wire in the set has a 48 mm diameter. The height of each tower is 26.50 m, and the total bridge length is 285.00 m. The floodplain sections of the bridge consist of self-supporting trusses with a 30.00 m span. To guarantee lateral stability of the bridge in the case of increased lateral wind action, the bottom parts of the bridge deck are also secured by two cables intersecting at one-third of the main bridge span. An orthotropic plate, made of a 5 mm thick flat sheet, and 50 mm channel bar cross stiffeners spaced at 0.50 m are placed directly on the longitudinal beams. The outermost segments of the river span are set on the lowest beam, concentrating the poles of the pylon. Connections between the hangers, the cables, and the structure of the bridge were designed by placing them in proper steel connectors. The bridge towers rest on a reinforced concrete foundation through the steel articulated bearings. The cross-section of the pole consists of two 550 mm I-sections, connected with batten plates and bridging comprising two I-sections, 500 mm each. The sets of wires are joined to the bridge tower using the head and bolted joints in such a way as to allow limited cable movement on the tower top. The greatest lateral movement on the bearings was anticipated at both sides of the bridge entrance, while tangential bearings were applied in the towers.

**Figure 1.** Side view of the bridge from the upper water side.

The examined bridge was designed to carry the belt conveyor situated on the truss gallery (for limestone transport). The mass of the limestone output transported via the bridge was in the 900 to 1100 tons per hour range, and the velocity of the belt conveyor was about 7 km per hour. The bridge was loaded using evenly distributed loads (output of limestone). The quantity of limestone was automatically controlled by the feeder and was approximately constant. The bridge was recently refurbished by building a new composite (carbon fiber reinforced polymer) deck (instead of a steel orthotropic deck), changing a broken hanger, and eliminating tower cracks. Before the tests described here, no bridge damages were observed. Considering the national principles concerning evaluating bridge conditions, the structural rating was satisfactory.
