Napoleon complex

May 19, 2008

The challenge: Although the new Perry Street Bridge in Napoleon, Ohio, is not a complex structure in and of itself, the process of building it required addressing an array of complexities. The replacement bridge had to be built in just one year—in exactly the same location and with the same appearance as the old bridge—and without disturbing the river bottom during two months of the construction season.

The challenge: Although the new Perry Street Bridge in Napoleon, Ohio, is not a complex structure in and of itself, the process of building it required addressing an array of complexities. The replacement bridge had to be built in just one year—in exactly the same location and with the same appearance as the old bridge—and without disturbing the river bottom during two months of the construction season.

The solution: Apply a unique combination of precast, pretensioned and post-tensioned concrete solutions to replace the community’s critical Perry Street Bridge in only nine months, earning prestigious engineering and design awards along the way.

Timing was critical when the Ohio Department of Transportation (ODOT) decided to rehabilitate the Perry Street Bridge. A historically significant structure that opened in May 1930, the bridge unites the 9,300 residents in Napoleon, Ohio—a community that straddles the Maumee River in northwest Ohio.

Founded in 1834, Napoleon is home to the world’s largest Campbell Soup Co. plant, as well as several automotive industry manufacturers. The community’s economic vitality depends on efficient transportation for finished goods and for the residents who need access to the soup plant on the south side of the river and the thriving downtown commercial district on the north. Adding to the pressure on ODOT were planners who recognized the bridge needed an overhaul. Without another river crossing for several miles, emergency services rely on the Perry Street Bridge to maintain adequate response times in and around Napoleon.

Same as it was

ODOT started rehabilitating the existing structure in 2004, and with the assistance of engineering partner HNTB Cos. discovered that the concrete had deteriorated so much that repairs would cost as much as building it from scratch. And, because a patch job would last only 10 years, ODOT’s decision was clear—Napoleon needed a new bridge.

That decision, however, only exacerbated the complications. Because of existing infrastructure and the proximity of buildings around the Maumee River, ODOT would have to build the new bridge in exactly the same location as the existing bridge. In consultation with the community, ODOT determined that a typical two-year construction cycle for a new bridge was not viable for Napoleon, because the city would suffer economically from limited access to its businesses while ODOT would incur about $1 million a year in additional expenses from establishing temporary emergency medical services on the south side of the river. With the closest detour crossing adding almost 10 miles to every trip, ODOT responded with a commitment to minimize the project’s disruption to the city and region to one year.

In addition to the compressed demolition and construction schedule and the requirement of building exactly where the existing bridge stood, two other important design parameters emerged from ODOT’s public involvement regarding the new Perry Street Bridge.

First, because of the historical significance of the existing bridge and its connection to the historic downtown and Henry County Courthouse, residents wanted the new bridge to look like the old bridge. Despite engineering and construction advances since ODOT built the original bridge seven decades before, and even though a five-span bridge was both feasible and more efficient than the existing seven-span bridge, the community wanted the new Perry Street Bridge to have the same arched shape and the same number of spans as the structure it would replace. Residents also wanted to replicate the historic lighting and aesthetic railing prevalent in the downtown district, and to incorporate stamped and stained concrete to blend with the downtown’s brick pavers.

Second, environmental regulations protect spawning fish in the Maumee River and prohibit any construction that disturbs the river bottom from April 15 to June 15—two full months out of a construction cycle that was already squeezed to just nine months by extreme winter weather in northwest Ohio.

ODOT also determined that the replacement bridge should carry four lanes of traffic with full shoulders and sidewalks rather than the original bridge’s two lanes, which had caused quarter-mile backups during the city’s busiest travel times.

Combo’s intro

With these environmental, timing and design parameters set and with particular attention to the demands of completing the new structure in less than one year, ODOT chose HNTB, which was working on another bridge over the Maumee River, the I-280 bridge in Toledo, as the Perry Street Bridge designer.

Well aware of the challenges, Jim Barker, technical director for the Perry Street Bridge project at HNTB, said, “We knew that if we timed it just right, we could drop the old bridge early in 2005 and have the new bridge open by the time snow fell in November.”

Communication offered the best option for meeting ODOT’s ambitious timeline. HNTB began by hosting pre-bid workshops with contractors so they understood the project goals and the design plans for the new bridge and perceived the project risks. The value of this up-front communication proved out when the winning contractor, Fru-Con (now Bilfinger Berger Civil Inc.) submitted a bid for a 250-day closure—20 days shorter than originally planned—that also met the cost estimates.

Innovation also played an essential role in getting the Perry Street Bridge built. HNTB and Fru-Con’s final concept incorporated a unique combination of precast, pretensioned and post-tensioned construction schemes. While builders have applied each of these strategies individually, it is believed that no single project had ever before used this particular combination.

The Perry Street Bridge’s superstructure consists of 117 spliced, precast, bulb-T girder segments utilizing the top flange as the deck slab. Fru-Con longitudinally and transversely post-tensioned the segments in the field with steel strand. To achieve a simulation of the arch structure of the original bridge, the segments are haunched at the piers, another innovative application used for this project.

Fru-Con, which also was working with HNTB on the I-280 bridge, determined it could cast the Perry Street Bridge in 117 pieces (modules) at the Toledo construction site and then truck the 50-ft, 50-ton sections the 45 miles to Napoleon for on-site assembly. Coordinating with Toledo transportation authorities to move the modules before and after rush hours, Fru-Con used three trailers, each with their own configuration to support each specialized module, to haul the pieces one by one. These loads had to stay on state highways, and two of them required police escorts. The transportation team achieved its goals with an average delivery rate of three modules per day.

With the prohibition against construction that would disturb the river bottom between mid-April and mid-June, HNTB and Fru-Con knew they would face a two-month delay unless they completed the pier work by April. That likely would result in a failure to complete the bridge on time and meant incurring the $10,000 daily financial penalties written into the ODOT contract.

To overcome this challenge, HNTB developed a plan to drill shafts through the existing piers, founded with spread footings on shale, which limited the environmental impact of construction by not touching the bottom of the river except under the existing pier footings. The new shafts are 6 ft in diameter at the piers and 5 ft in diameter at the abutments, with four shafts in each pier. HNTB and Fru-Con avoided additional environmental impact by building a temporary rock causeway for large cranes to place the superstructure modules. Without the causeway, barges, which would have dragged along the river bottom in the shallow water during the dry summer construction season of 2005, would have been required to place the superstructure modules.

The multispan concrete barrel arch structure would have been unstable if removed in sections, so HNTB worked with Fru-Con to develop blasting techniques that would collapse each part of the bridge simultaneously and keep the project ahead of schedule. Demolition of the Perry Street Bridge took place March 6, 2005.

The rise of Napoleon

The new four-lane Perry Street Bridge—724 ft long and almost 73 ft wide—opened Oct. 29, 2005. HNTB and Fru-Con met ODOT’s timeline within the $19.9 million budget by applying the most advanced developments in precast, prestressed construction, including:

  • Using variable-depth, precast modules that simulated the original bridge’s concrete arches;
  • Utilizing cast-in-place splices at the quarter points of the spans and subsequent longitudinal post-tensioning to produce spans light enough for truck transportation from Toledo to the construction site;
  • Casting 8-ft sections of the slab on the precast elements and transversely post-tensioning them; and
  • Splicing longitudinal post-tensioning tendons to eliminate the need to stress and grout tendons in excess of 700 ft.

With an extraordinary degree of cooperation between HNTB, Fru-Con and ODOT in their adherence to the project’s parameters, the team used innovation and communication to deliver an efficiently designed and constructed bridge while limiting the effect on the region. That communication included two Internet-connected cameras that Barker could watch from his Toledo office to quickly resolve any challenges.

As a result of the public input process, the new Perry Street Bridge integrates both sides of the city and meets the historic preservation and aesthetic desires of Napoleon’s citizens, serving as a visual focal point for the historic community. Expected to last 100 years, it also meets ODOT’s demands for safe and efficient transportation for the bridge’s 16,000 daily users.

In addition to the satisfaction expressed by Napoleon’s citizens, the Perry Street Bridge has earned recognition from the American Council of Engineering Companies, which awarded the bridge’s HNTB design team with its 2007 Engineering Excellence Award for projects that demonstrate a high degree of achievement, value and ingenuity.

About The Author: Walters is a project manager with HNTB Corp., Cleveland, Ohio.

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