ASPIRE Spring 08 - Aspire - The Concrete Bridge Magazine

Each side of the bridgehas six beam lines.Two cranes prepare to place adrop-in segment. A strong-backis located at the right-hand endof the beam being lifted.the following March, the contractorhad begun drilling foundation caissons.Meanwhile, Janssen & Spaans finishedsuperstructure design. The DPRV Bridgespans over two canals, several railroadlines, two local roads, the Des PlainesRiver, and forest preserve land.The spliced girder design minimizedthe impact on the wetlands.The bridge has a total of 34 piersand 35 spans. The bridge features 18pretensioned concrete spans and 17post-tensioned spans. The tallest piercap is 82 ft above grade, with the bridgedeck rising to 90 ft at the highest point.The simple spans at the DPRV Bridge aremade continuous with closure pours overtheir pier caps. “Over the piers, there’sabout a 1-ft-wide gap between the ends ofthe bulb-tee girders,” says Brian Slagle, VicePresident at Janssen & Spaans. “Reinforcingsteel protrudes from the ends of the beamsinto the gap. And when you cast the deckand make the closure you lock the beamsin at that point, establishing continuity.There are no joints at the piers.”A typical simple-span prestressedconcrete girder is a 90-in.-deep bulbtee, with a top flange width of 4 ft 11in., a web width of 6 in., and a bottomflange width of 24 in. The typical posttensionedbulb-tee girder is 102 in. deepwith a top flange width of 5 ft 1 in. anda bottom flange width of 26 in.“We haunched the girders on the270-ft-long spans,” Slagle explains. “We30 | ASPIRE, Spring 2008