The 1,485-ft-long steel arch bridge, with a 505-ft-long main span, forms a crucial crossroad: It carries eight lanes of Interstate 95 across the Harlem River, linking, with a swirling medley of eight ramps, the Cross Bronx Expressway with other key arteries, such as the George Washington Bridge and the Major Deegan Expressway, or Interstate 87. Two parallel steel arches on concrete foundations cross the river with a 135-ft clearance and concrete-and-steel-girder approach viaducts. The rehabilitation project is the largest in the history of the New York State Dept. of Transportation (NYSDOT), says Commissioner Joan McDonald. It involves replacing the deck, retrofitting the steel arch span and support beams, and repairing or replacing support piers and foundations—all while maintaining passage of 200,000 daily vehicles.
"It's like riding a bicycle while changing the tires," says Phillip Eng, assistant commissioner for NYSDOT. "How do you reconstruct it while keeping 200,000 vehicles a day flowing?"
The question was tough enough that when NYSDOT first solicited bids in 2007, it received no submittals. "We heard from the contracting industry that we needed to address how to reconstruct the ramps, maintain traffic and be able to work over the parks," Eng says. "We went back to the drawing board. We had our designers take another look and put together a plan of action upon which contractors could bid."
Five teams bid in January 2009. The winning team was a joint venture of the Chinese contractor CCA Civil Inc.—a Jersey City, N.J.-based subsidiary of the China State Construction Engineering Corp.—and Halmar International, Nanuet, N.Y. The contractors had recently begun to work together and were fresh off a successful design-build project to construct a new rail station near Yankee Stadium, not far from the Alexander Hamilton Bridge, or AHB.
"We dedicated a staff of 40 to this job," says Chris Larsen, Halmar principal. "It is the most complicated steel rehabilitation job I've ever seen."
The contract called for four temporary ramps, made up of eight bridge structures, to carry traffic while the original ramps were refurbished. CCA-Halmar decided it could revise the plan to reduce steel and speed up erection to ensure schedule adherence. "We undertook redesigning all the temporary supports and ramps—work worth an estimated $100 million," says Larsen. "We spent $5 million out of our own pockets and reduced the steel required by at least half."
The joint venture procured 4,500 tons of steel for the temporary structures in Shanghai. While this saved money and time because the fabricator provided a single source of supply, it presented additional challenges. "We had to figure out how to completely satisfy state specs," says Peter Wu, CCA executive vice president. "It was a learning curve on how to procure quality steel in China. We had to do our own quality assurance," adds Larsen. The team tested and certified 100 Chinese welders. Moreover, the fabricated components had to fit into 40-ft containers for shipping across the ocean.
The team also redesigned the temporary shoring towers. "We weren't confident that the [originally designed] towers would be adequate," says Larsen. "The original temporary structures incorporated jacking towers, much like a beefed-up scaffold tower," adds Jesse Jameson, CCA-Halmar project manager.
In order to minimize time and maximize space, "we came up with an idea to utilize the existing concrete columns as part of the shoring itself," says Larsen. "We tied these 30-in.-diameter pipe columns to the existing columns." The tubular towers, which vary in height from 15 ft to 90 ft, reduced the steel required and created more workspace underneath the bridge, which is squeezed between parks, the river and a commuter railroad.
Moreover, says Jameson, "there was a big concern about differential settlement of the [original] temporary towers. Each had four foundation points. If one leg settles differently than another, we have a problem." Now, each tower has just one point load, eliminating the risk of uneven settlement.