Upstate Infrastructure

Rochester's Troup-Howell Bridge Gets Major Makeover

A primary transportation link for downtown Rochester undergoes a complete reconstruction - and a switch from a plate girder structure to a soaring suspension arch.

by Fred Fanning and Tom Stabile

The Troup-Howell Bridge over the Genesee River in downtown Rochester, N.Y., is getting a $37 million facelift and a dramatic, new three-rib arch. The project is part of the New York State Department of Transportation's $92 million, six-contract Western Gateway program to rehabilitate 3.5 mi. of Interstate 490 through Rochester's core.

The new 1,165-ft.-long crossing will be on roughly the same alignment as its plain 50-year-old plate-girder predecessor, which some motorists may not have noticed was a bridge as they zipped along I-490. Those traveling over the new bridge may never know that it has a unique structural frame to support its two roadway decks - using three ribs in its arch, instead of the more typical four ribs.

The project team is constructing the new bridge around and over the existing structure, which crosses the river linking the city's downtown to the historic Erie Canal, a 365-mi.-long waterway that stretches from Albany to Buffalo. The reconstructed bridge will partially open later this year when four lanes of traffic shift to the new deck. The project will wrap up next year after another four lanes open.

advertisement

Led by Edward Kraemer & Sons of Plain, Wis., the general contractor, the team leveraged the old bridge's deck to build the new structure.

First, it shifted traffic from both directions onto the old northern deck last year, allowing the bridge to remain in service during almost all of the reconstruction. That move also freed the old southern deck for staging to erect the three steel arch ribs over the span, said John Greene, project manager for Kraemer.

"We left the river span intact to help with the erection of the arches," he added. "That river span was kind of an island. We had to create access to get equipment on and off the bridge."

The team later demolished the old southern lanes. It will pour the new southern side deck later this year, and shift all traffic onto its four lanes. That, in turn, will allow it to demolish the old northern lanes and pour another new four-lane deck by next year.

The team erected the arch last summer, largely over three consecutive weekends and a fourth weekend, shutting down the highway on Friday evenings and reopening it to traffic Monday mornings. During these hectic weekends, workers placed cranes on the original road deck to accommodate lifts of the sections of arches and cross-braces - a method that avoided using cranes from a barge, which would have been farther from the work area and on a less steady surface.

The team erected the three ribs over the river one by one, finishing the third in late fall.

"We are hoping right now to get the hangers in place," Greene said of the next steps. "We are trying to be done by late December [2005]. We plan to come back in mid-March to pour the deck."

The 433-ft.-long main span that crosses the river will connect to cables suspended from each of the arch's three steel ribs. Each rib has 19 pairs of 3.1-in. diameter cable, which adds up to more than 5,000 ft. of cable for the project.

The cables will hang from each member in a fan-like configuration, with flatter angles toward the end of each rib. At the center, the cables will stretch vertically 65 ft. above the deck.

The steel arch ribs, manufactured by High Steel Structures of Lancaster, Pa., consist of hollow box beam-type structures, which will permit inspectors to access the interior components and will be able to house lighting equipment.

The team will install arch rib stiffeners at each point where cables attach to the main superstructure. The inside of the stiffeners will also be accessible for lighting and inspections.

The design of the dog-bone shaped stiffeners had both structural integrity and appearance in mind.

"We took care of all the aesthetic issues we could and made them structural," said Howard Ressel, project design engineer for the department of transportation's Region 4 unit, which is overseeing the assignment.

Aesthetics was a focus for the new bridge and for Erdman, Anthony and Associates, a Rochester-based engineering firm that is designing the entire Western Gateway project. It gathered local input from an aesthetics committee that the department of transportation formed with private citizens, Rochester officials, artists, and others hoping to shape the Flour City's skyline.

"There was a substantial amount of community involvement - more than usual," said Sam Anthony, a senior associate at Erdman Anthony who was the lead bridge designer. "I couldn't get over how productive it was. There were artists on the committee whose ideas I first thought might not work out, but we ended up incorporating quite a few of their suggestions."

Anthony said the most unique feature may be the three-ribbed arch - rare for a bridge with two roadway decks. The typical design calls for four ribs, two supporting either side of each deck.

The team chose a three-rib design largely because a four-rib system would have required more space than was available in the existing right-of-way. The new bridge's middle rib is thicker than the outer ribs, because it supports both decks, Anthony added. The bridge also differs from more common "tied" arches, which have a thick steel support member stretching across the entire span at the deck level, from one end of the arch to the other. Anthony said engineers often regard the tied arch as less aesthetically pleasing than a true arch, which has no such support brace but rather pushes its load directly into the foundations on either end.

The new bridge has a true arch that will deliver its 8 million lbs. of thrust into the foundations, largely because the team was able to build them into strong bedrock capable of handling the compressed load. To construct the new foundations on each side of the river, the team used about 8,000 cu. yds. of concrete.

The reconstruction effort also is demanding extensive traffic planning to manage the 100,000 vehicles that use the bridge daily, Ressel said.

"The bridge has five approach spans," he added. "We had an eight-lane bridge, and we reduced it to two lanes each way. We did a lot of things in the design to facilitate the construction."

Last year's damaging hurricane season also took its toll on the project because the casting maker for one of the cable sockets is in Mississippi. The plant has experienced manufacturing delays, which in turn have slowed the bridge project.

"Our intention is to complete the rest of the structure in late May and move traffic," Kraemer's Greene said. "We are going to run double shifts in summer. There is going to be a big push with a lot of local labor."

Useful Resources
www.trouphowellbridge.com
www.dot.state.ny.us/reg/r4/490gateway/490.html