High performance concrete mixes, new post-tensioning practice, alternative girder erection techniques, and the debut of an innovative cable cradle system for an architectural pylon combine for a spectacle unfolding along Interstate 280 in Toledo, Ohio. By mid-2006, that spectacle will yield a community landmark, local business catalyst, and vital Great Lakes freight corridor link.

Ohio's first large-scale installation of segmental precast girders, the $220 million Maumee River Crossing (MRC) is part of a $310 million package to widen I-280 from Navarre Ave. to the I-75 interchange across Toledo. The single largest job to date undertaken by the Ohio Department of Transportation (ODOT), it is being funded primarily by the Federal Highway Administration and the State Infrastructure Bank. The MRC will eliminate one of the Interstate Highway System's few remaining moving bridges — I-280's existing bascule lift span structure, presently known as the Craig Memorial Bridge.

The MRC is dubbed “Look Up, Toledo,” owing to an approximately 404-ft.-tall pylon likely to shape the city's skyline in a manner comparable to Toronto's CN Tower and Seattle's Space Needle. The pylon will support a cable-stayed main span, bringing Toledo a landmark crossing on par with other recent urban installations (S.R. 509 Bypass, Tacoma, Wash., 1997; Leonard P. Zakim Bunker Hill Bridge, Boston, 2003). Cast from high-strength concrete, the pylon will feature an endlessly changing array of colored lighting enclosed by glass — a signature product of a city known for companies like Libby Owens Ford and Owens-Illinois Inc. The latter company's headquarters building will remain the city's tallest structure — by a 60-ft. margin over the pylon.

PILE ON VALUE

Concrete technology touches nearly every aspect of the MRC, whose main span, approach and ramp area amounts to more than 1.2 million square feet. No component on the job, however, maximizes value engineering quite like the pylon. Mixes of 10,000 psi design strength enable the structure to be lean above the roadway and accommodate the unusual lighting effect. The leaner profile nevertheless will support 20 stainless steel tube cradles through which bundles of 0.6 in. diameter strand will be used to create cable stays supporting 612.5-ft. main spans. The 18-in. and 20-in. diameter stays will house from 82 to 156 epoxy-coated steel strands. (By comparison to the cable stays' cross section, a 60-ft. conventional prestressed concrete AASHTO I girder would typically carry approximately 20 of the same size strand.)

Bridge designer Figg Engineering Group offered the cradle scheme as the most economical means of streamlining the pylon profile, which in turn satisfied the Toledo community's aesthetic objectives. The cradle design hinged on the results of acceptance testing, requiring creation of a laboratory axial loading assembly to mimic what the bundled strand would encounter high above the Maumee River.

ODOT commissioned Skokie, Ill.-based CTL Inc. to measure strand friction, fatigue, leak and other factors that the stays and cradles would endure over a 100-year service life. After testing with 119-strand stay specimens validated projected performance, Figg Engineering finalized the design for the cradle and cable stays, incorporating a set of 40 reference strands (two in each stay) for programmed ODOT monitoring.

In addition to the aesthetic possibilities it opens up, the cradle system seizes upon a property for which conventional or high-strength concrete has no equal: performance under extreme compression. Such a condition is created as the cradles bear upon the pylon, which thereby carries the 42,000-ton weight of the main span unit. In addition, the pylon design includes the effect of ship impact loads of nearly 12,000 tons. Figg Engineering's cradle approach is an alternative to the more common method of using stay anchors, which apply tension across the pylon while transferring the vertical loads to the pylon without optimal gravity-load transfer.

LAND GEAR

After more than a year of MRC construction, the pylon remains an icon in project renderings, engineering drawings, the “Look Up, Toledo” campaign and community publications tracking the job's progress. The footing for the massive structure, though, is nearing completion and is accessed from a temporary bridge that runs parallel to and about 90 feet downstream from the Craig Memorial bridge. A frontage road links the temporary bridge to sites and areas where, under general contractor Fru-Con Construction Corp., the bulk of MRC activity is concentrated:

• A 16,000-sq.-ft. ODOT field office, with facilities for industry and community tours. In addition to special group appointments, project officials have maintained a regular tour regimen on the first and third Fridays of each month for groups of 14. Interest runs high: tours are all booked up two months in advance. The office is across the street from a parking lot and observation area that will provide prime viewing of south approach, main span and pylon construction.
• A 30-acre, 14-bed casting yard with two large, bridge crane-equipped enclosures for fabricating most ramp, approach and main span segments, plus specialty gore segments (ramp-to-approach conditions) and delta frames (anchoring cable stays below main span girders). The enclosures are primarily for the high-volume fabrication of segments by the match cast method, which uses finished segments and precision electronic surveying to adjust the next segment's dimensions prior to casting. Match casting enables production crews to maintain tight tolerances, even as slight changes are made in radii or other dimensions so that segments follow ramp or roadway alignment.
• Construction of five massive, south approach piers whose T-shaped configuration is dictated by right-of-way limitations, ramp geometries in the vicinity of a railroad bridge, and community-based aesthetic design requirements preempting the use of more land-intensive straddle bent structures. The use of precast segmental construction for ramps and approaches — and the attendant flexibility to erect girders in a top down, span by span sequence — helps crews conform to tight schedule restrictions for existing lanes. With I-280 the principal northwest Ohio and southern Michigan corridor, ODOT requires Fru-Con to keep four lanes open during peak times and at least one north and one south lane in nonpeak hours.
• A central mixed batch plant sitting adjacent to the casting yard within quick reach of most of the southern end of the project supplies all MRC material. Mindful of tighter quality control provisions driving both performance and color uniformity goals, local producer Integrated Resources Inc., the concrete division of The Stanley Group, retrofitted a mobile plant with a new 6-yd. twin shaft mixer — in lieu of an older, tilting drum model. MRC has a uniform slag cement/Type I portland cement spec with ratios of 50/50 on drilled shaft foundations and 25/75 on all remaining cast-in-place and precast members.

Drilled shaft and pier work, along with precast fabrication, has proceeded on schedule despite an usually cold — but dry — winter. Leading up to a scheduled October 2006 dedication, project officials are targeting the following milestones: main span commencement (December 2003); cable stay placement (beginning April 2004); pylon completion (May 2004); and, final precast production (August 2004).

MAUMEE RIVER CROSSING

AT A GLANCE

Location

Interstate 280, Toledo, Ohio

Construction

March 2002 — October 2006

Scope

• Twin, three-lane (58-ft.-wide) structures with 1,225-ft. main span and 29-span north (4,000-ft.) and 25-span south (3,350-ft.) approaches, four on-off ramps
• Segmental precast girders for ramps, approaches and main span, totaling 1.2 million sq. ft. of deck area with integral wear course
• Precast delta frames anchoring main span cable stays below roadway
• Cast-in-place, 404-ft. tall pylon (143 ft. below the deck, 261 ft. above) supporting 20 stay cables in fan/harp arrangement, bearing on a 104-ft.-diameter footing founded on seventeen 8-ft.-diameter drill shafts)
• 187 octagonal piers, typically 8- × 10-ft. for ramps and 8- × 12-ft. for approaches, most with 1-ft. walls; all bearing on 7- or 8-ft. diameter drilled monoshaft foundations

Project principals

• Ohio Department of Transportation, Owner
• Fru-Con Construction, Ballwin, Missouri, General Contractor
• HNTB/PB, Cleveland, Project Management Consultant
• Figg Engineering Group, Tallahassee, Florida, Design Engineer, ODOT On-Site Consultant (Segmental Concrete)
• DSI International, Bolingbrook, Ill., Post-Tensioning Supplier
• Integrated Resources Inc., the concrete division of The Stanley Group, Toledo, Concrete Supplier

Materials schedule

• 64,300 yd. of ready mixed concrete for cast-in-place foundations, piers and pylons
• 107,400 yd. for 3,057 precast segments and delta frames
• 1,550 miles of 0.6-inch strand for post tensioning and cable stays
• 17,000 tons of GranCem slag cement
• 3,000 tons of fly ash