Bridge built with traffic safety in mind

Case Studies
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Population growth and development in Sioux Falls, S.D.’s, southeast quadrant is forcing city officials to upgrade what were previously rural farm-to-market roads. The plan calls for new roundabouts and bridges to efficiently address increasing traffic demands and allow the traveling public to safely cross the BNSF Railway lines.

The city is in the midst of a two-year construction project on 69th Street to upgrade approximately 1 mile of rural roadway. Gone is the gravel road, replaced by a modern 4-lane paved road with curbs and gutters and a raised median. “There is a new school and planned development for the area, so the upgrades will improve traffic safety,” said Brad Ludens, P.E., project manager for the city of Sioux Falls.

The BNSF Railway bisects 69th Street in the construction zone. Rather than building the road to cross the rail line at grade level, city officials decided to build a bridge overpass. “This will help to reduce or eliminate the potential for accidents at the crossing,” added Ludens.

The 69th Street Bridge deck measures less than 100 ft long and 70 ft wide. However, it did pose some construction challenges for bridge contractor Grangaard Construction Inc. of Watertown, S.D. Extremely poor sub-grade conditions required the excavation of 8 to 10 ft of soil and construction of embankments for the bridge approaches. A Geopier rammed aggregate pier was constructed to support the embankment.

One phase of bridge construction that did not pose a challenge for Grangaard was deck paving. To match the 4-lane road approaches, bridge design included four traffic lanes and 6-ft pedestrian walkways on the north and south sides of the deck. “The entire deck measured 68 ft wide with a 2% crown,” said Jerry Chaon, service engineer for Terex® Bid-Well , who was on site to assist with the pour.

Grangaard set its Terex® Bid-Well 4800 paver to a 73-ft width, allowing the crews to pave the entire deck width at once. The company’s standard paver features a robust, 48-in. truss depth, which allowed crews to pave the entire width without deflection.

When equipped with available 66-in. truss inserts, the 4800 is capable of delivering paving widths reaching 196 ft, providing machine flexibility to pave a wide variety of bridge designs. It rides on the rails via four machine travel bogies and four heavy-duty, 6-in. tubular legs with hydraulically adjustable height. To increase paving versatility, the 4800 provides up to 15 ft of leg travel to each side, allowing for on-the-fly width changes.

Specifications called for an 8.25-in.-thick bridge deck, using Class A45 concrete. To reduce hand work, the 4800’s paving carriage included dual double-flighted augers to effectively meter the concrete in front of the carriage. Two, 5-ft-long paving rollers finished the concrete, while a trailing pan system sealed and textured the deck surface.

The paving carriage’s patented Rota-Vibe® system sets the 4800 apart from other bridge pavers. This exclusive 11.5-in.-long, ribbed roller uniformly consolidates the top 2.5 in. of concrete to facilitate difficult-to-finish designs.

Grangaard’s crews paved the bridge deck in less than a day. With the bridge completed on time, attention is now focused on reconstructing the rest of 69th Street and adding a roundabout at the S. Southeastern Avenue intersection so the entire two-year project can be completed by early fall 2011.

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