The newly opened White River Bridge uses four interlocking 114-ft. high pylon legs and two rows of massive cables that suspend the structure. The design is the work of J. Muller International, a Chicago architecture firm that specializes in complex bridges.

The 465-ft.-long structure is suspended from a center-locking quadripod pylon and two radiating rows of cable stays. Engineers went to great lengths to guarantee the structural stability of the unusual design.

The bridge is anchored by four permanent concrete-filled steel casings that are socketed below the water and into bedrock. Milestone Contractors, the general contractor, chose to pump concrete into the 6.5-ft.-diameter caissons, even though it was a challenge due to the harsh mix and engineering design.

"The 90-ft. caissons were unusual in that they had to be filled with concrete under water on a 64-degree slope," said Neil Comstock, senior construction manager for Milestone Contractors. "This slope made it very difficult to maintain contact with the mix and keep head pressures to a minimum."

To place the concrete, Milestone used a crane to lower a retractable 110-ft. pipe into the caisson. Once lowered, George’s Concrete Pumping attached a 42X-Meter Putzmeister boom pump hose to the pipe.

The pipe was positioned 7 ft. below the concrete level throughout each 80-cu. yd. caisson pour. Tremendous line pressure had to be maintained to prevent water from coming in contact with the Class A modified mix. Later, George’s also used the truck-mounted pump to place concrete in each of the attached pylons.

Measuring 120-ft. long by 4.5 ft. in diameter, four hollow steel pylons extend up from the caissons and connect above the bridge deck. By placing the pump hose in a hole located 60 ft. above the base of the pylons, George’s filled the bottom half of the pylon with concrete, too. At the end of the pour, George’s placed a total of 470 cu. yd. of concrete in the caissons and pylons.

The deck

At the top of the pylons is one of the most intricate components of the bridge, the structural steel quadripod pylon head that anchors the 40 cable stays. Locked in the pylon head, these cables suspend the entire bridge deck.

George’s used a pair of Putzmeister 42X-meter pumps to place 775 cu. yd. of corrosion-inhibiting microsilica-modified concrete for the bridge deck. The pour took 14 hrs., while the deck was pre-loaded in front of the screed machine — and testing was performed at the end of the boom.

Post-tension cables in plastic tubing run throughout the deck Superplastizer was added to the mix to make it free flowing and to help alleviate voids.

Post-tensioning

Seven days after the deck pour, the post-tension cables were tightened, giving the deck a crowning effect and producing a longitudinal arch.

"We had some access difficulty due to the location of the pylon legs and head section," says Comstock. "Air entrapment requirements were very tight, but maintained throughout the pour at the pump discharge line."

George’s used a 5-in. to 4-in. reducer with two 4-in., 90-degree elbows clamped at the end to help maintain air content.

"The placement of concrete for the caissons, pylon legs, and bridge deck was discussed many times by the contractor, designer, supplier, and Indiana Department of Transportation," said Comstock.

"Each operation had its own set of challenges such as access, mix design requirements, and volume of cubic yards needed to maintain a good, consistent mix.