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The construction of a 30-m (100-ft) single-span, arch pedestrian bridge is underway in Aurora, Nebraska, over the Lincoln Creek located approximately 105 km (65 miles) west of Lincoln. The circular arch has a radius of 22 m (72.5 ft) and a rise of 6.1 m (20 ft). The bridge measures 5.5 m (18 ft) in height from the walkway to the crown of the arch. The walking and bicycling deck surface is 3 m (10 ft) wide with 1.4 m (54 in.) timber railings. The bridge takes advantage of the best attributes of concrete, steel, and fiber-reinforced polymer (FRP) for constructability, durability and strength. The bridge was designed in accordance with the AASHTO Highway Bridge Specifications and the 1997 AASHTO Guide Specifications for Pedestrian Bridges. A unique aspect of the bridge is the use of confined concrete to enhance the strength and ductility of the top and bottom chords of the bridge. A novel application of concrete confinement to tension members has been patented by Tadros and Tuan. A high-strength prestressing tendon with a polyethylene (PE) sheath is inserted inside a steel pipe, and positioned at the center by spacers along the length of a bottom chord. Expansive concrete using Type K cement is pumped into the steel pipe. After the concrete is hardened, the tendon is post-tensioned to a specified force to exert pre-compression on the concrete inside the pipe. When the concrete inside is subjected to compressive loading, the steel pipe provides lateral confinement pressure on the concrete very effectively in the form of tensile “hoop stress.” As a result, the bottom chords can carry much higher tensile forces without causing tensile stresses in the concrete. The steel pipe is used solely to provide lateral confinement for the concrete, and not intended to carry external loading. A 20-ft bridge segment was proof-tested at the test site of Wilson Concrete at LaPlatte, Nebraska. More than twice the design load has been reached without any signs of distress.
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