EoW March 2012

Transatlantic Cable

Hudson, which chronicles the history of the Port Authority. He said that the bridge’s chief engineer, Othmar Ammann, at one point considered using eyebars instead of wire rope. The governor of New Jersey, Arthur Moore, pressured Mr Ammann to use wire rope because doing so would create jobs in the state. “It was a jobs issue,” Dr Doig said. Mr Ammann reserved a nal decision until he was able to complete an engineering analysis, whereupon he chose wire and placed the order with the Roebling Company. The New Jersey-based rm was run by the descendants of John A Roebling, who designed the Brooklyn Bridge. † Vast quantities of wire had gone into the George Washington by the time it opened, in 1931. Andrea Giorgi Bocker, the Port Authority’s resident engineer in charge of construction at the bridge, told the Times ’s Ms Haughney that the work of twisting 26,474 tightly coiled wires into four main cables occupied a full year. In our own era, replacing the suspension wire in stages will take eight years. In 2013 the PA will commence cleaning up the massive anchorages tying down the bridge’s foundation, replacing wires in the cables, and installing new dehumidi ers in the chambers where the anchors are held.Workers will clean the main cables by scraping o their zinc-paste wrapping and introducing dehumidi er. They then will focus on the less stable parts, replacing the suspender ropes that are spaced at 60-foot intervals along the 4,760ft bridge. † “This is a structural engineer’s dream,” Mrs Bocker, whose father managed the George Washington Bridge when she was growing up, told the Times . “Suspension ropes aren’t replaced every day. In the case of the George Washington Bridge, it’s happening for the rst time. So it’s a once-in-a-lifetime opportunity for an engineer to be a part of.” Port Authority o cials said they will pay for the repairs with revenue from tolls and fares.

The GeorgeWashington Bridge

The daunting task of cleaning the main cables and repairing the vertical suspender ropes on the world’s busiest vehicular bridge A thorough overhaul of the civil engineering marvel that spans the Hudson River just north of New York Harbour is long overdue. O cials of the Port Authority of New York and New Jersey say that comparable bridges normally have their wires replaced after 70 years or so. At 80, the George Washington is showing its age, and – after a $4.5 million, two-year study – the PA in December decided that action could not be postponed. The agency’s board authorised a rst instalment of $15.5 million on the estimated $1 billion-plus cost of a renovation that will create an estimated 3,600 jobs. Christine Haughney, who covers transportation for the New York Times , observed that the task of cleaning the four main cables of the bridge and replacing its 592 vertical suspender ropes is “daunting in its magnitude.” No more than three of the suspender ropes that stretch from the main cables to the roadway can be replaced at the same time. To attempt any more could destabilise the span. O cials of the PA emphasised that the 14-lane double-decker bridge is in no danger of collapsing from suspender deterioration. But waiting for a safety issue to develop would involve emergency repairs, and any driver who has experienced a tra c jam on “the George” will shrink from the prospect of a closed-o lane. (“At 80, George Washington Needs Bridge Equivalent of Hip Replacement,” 8 th December). The suspender ropes – which weigh 1,500 to 10,000 pounds each, depending on length – have never been replaced, but the procedure is expected to be similar to the “seismic retro tting” of the Golden Gate Bridge, in San Francisco. Ms Haughney wrote: “For that project, a rolling platform, known as a traveller, was placed atop the main cables, and then workers replaced the ropes, using temporary suspenders, jacking frames and jacks.” Details on the George Washington Bridge, provided by the Times include the following: † If placed end-to-end, the suspender ropes would be 32 miles long. The 283 wires in each suspender rope, if laid end-to-end, would be 9,100 miles long – more than one-third the circumference of the earth; † The wires were a worry-point for the bridge builders in the 1920s, according to Jameson W Doig, a research professor at Dartmouth College and the author of Empire on the

Image: www.bigstockphoto.com Photographer Zsolt Ercsel

The Detroit Auto Show

Amid a bonanza of emergent engineering trends, the US industry manifests a new and ‘decidedly globalist’ attitude An important change in emphasis at the North American International Auto Show, held 14 th -22 nd January in Detroit, was

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EuroWire – March 2012