The Ohio River Bridges project consists of two new bridges over the Ohio River between Louisville, Ky., and southern Indiana. The Downtown Crossing bridge will add capacity to Interstate 65 in downtown Louisville; the East End Crossing, 8 miles upriver, provides a new crossing. In addition to major congestion relief, the East End Crossing will be a catalyst for economic growth on both sides of the river, completing the I-265 loop connecting Jefferson County in Kentucky with southern Indiana.
The East End Crossing bridge features two convex diamond-shaped reinforced concrete towers, or pylons, that rise 300 feet above the water to support a 1,200-foot main span. The joint venture design-build contractor, Walsh-Vinci, chose PERI technology to meet the numerous forming challenges: lower legs that lean outward on a radius and taper in both dimensions, a hollow lower cross strut at road level, hollow upper legs on a radius leaning inward and tapering in one dimension, and innovative anchor boxes for the cable stays topped off with a hollow upper cross strut.
The contractor is using two large tower cranes (one at each tower) next to the pylon foundations in the river channel. The foundations themselves began as precast footing boxes, each about 100 feet long, 50 feet wide, and 16 feet tall. “We precast the footing boxes, or footing tubs, in a dry dock, then floated each one into position,” says Jeff St. John, Walsh-Vinci’s section 5 manager for the cable-stayed bridge.
At that point, crews removed the 8-foot 6-inch diameter plugs that had been cast into the tub floor where 12 drilled shaft caissons would go to support the pylon foundation. Removing the plugs allowed the tub to settle onto temporary steel framework about 10 feet below water level. “Then we used the footing box as a template to do all the drilled shafts,” St. John says. After connecting the box to the caissons, it was filled with No. 14 rebar and 3,000 yards of concrete, completing the pylon foundation.
Building the towers depended heavily on several sets of formwork. “We broke the pylon up into five main sections, or phases, treating each one like a brand new structure,” says Mark Henning, sales engineer with PERI Formwork Systems Inc. The lower legs, lower strut, upper legs, the stay anchors, and the upper strut each required a separate set of formwork and a completely separate set of platforms.
Each set of forms was preassembled in PERI’s Calumet Park yard, south of Chicago, and trucked to Louisville. Knowing they’d be working through the winter, the contractor also had PERI put insulation between the ribs of the forms. “That meant our guys didn’t have to mess around with the insulation,” St. John says. “I’m extremely happy we did that. It was a little extra money up front, but dealing with it onsite would have cost significantly more.”
The lower legs required four 15-foot mass concrete pours. Because that concrete required an extended cure time, the forms for each leg were designed to allow the contractor to use a leapfrog process.
Concrete for the tower has a minimum strength of 6,000 psi. It is batched by a local producer with plants on both sides of the river. With no preapproved mix designs for the project, the contractor was responsible for coming up with designs for both the mass concrete portion and a more rapid-strength-gain mix for the upper legs and struts.
“One of the more significant challenges of getting the concrete approved on these projects is that, like many other major projects now coming out, this job has a 100-year service life requirement,” St. John says. “That has a huge impact on your concrete mix design.”
A trestle built out from each shoreline provides access to the pylons. Almost all of the concrete for the lower legs was pumped, with the pump trucks located on the trestle ends that had been expanded and reinforced specifically for this purpose.