Bridge overhaul teaches engineers riveting lesson

“It turns out that they just don't make bridges the way they used to,” writes Martine Powers in the Boston Globe today. That fact has become apparent to contractors who are involved in the extensive reconstruction of the historic Longfellow Bridge, which traverses the Charles River to connect Boston and Cambridge.

Powers writes that one year into the project, “…contractors are getting an education on the construction practices of yore, poring over century-old bridge building manuals, reviving obsolete metalworking techniques, and scouring the region for building materials that have long disappeared from the market.”

One lost skill the workers are learning is the art of riveting—long in decline since the days of Rosie the Riveter. Powers quotes Mary Grieco, metals control engineer for the Massachusetts Department of Transportation, as saying, “People really haven’t been riveting for quite a while. It’s a learning curve for everybody. There are no specifications anymore that tell you how to rivet, so we make the best engineering judgment on how to do it.”

According to Mass DOT, “The Longfellow (originally, the Cambridge) Bridge is one of the most architecturally distinguished bridges in Massachusetts. Located on the site of the 1793 West Boston Bridge, this graceful steel and granite structure was completed in 1908, and renamed to honor Henry Wadsworth Longfellow in 1927. The bridge joins Cambridge Street in Boston with Main Street in Cambridge and carries the Massachusetts Bay Transportation Authority (MBTA) Red Line and two-way vehicular traffic across the Charles River. The bridge presently carries 28,000 motor vehicles, 90,000 transit users, and significant numbers of pedestrians and bicyclists each day.”

Powers in the Globe notes that the overhaul, scheduled to be completed in September 2016, will cost $255 million, including “…the expenses of hewing to historical accuracy. Contractors who signed on to the project were given advance notice that they would be expected to go to extraordinary lengths to uphold the structure’s antique character”—including mastering archaic building techniques.

“The art of riveting went out of fashion a half-century ago,” Powers adds. “The practice involves heating rivets, cylindrical metal shafts with round heads, up to 2,000 degrees, until they glow bright red, then quickly jamming them into a hole before they have a chance to cool. It’s slow, costly, and dangerous. That’s why construction largely switched to nuts and bolts that can more easily be screwed into place.”

She quotes Charles Sullivan, executive director of the Cambridge Historical Commission, one of the groups advising the Longfellow contractors on historical preservation, as saying, “The technology never totally went away. But you no longer see pictures of people standing on the frame of the Empire State Building throwing rivets through the air.”

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