NEW MADISION, INDIANA BRIDGE MENTIONED IN WALL STREET JOURNAL
April 6, 2013
Murray Johnson, a 55-year-old civil engineer from Vancouver, British Columbia, has designed, repaired, inspected or demolished more than 150 bridges. But he’s best known for sliding them.
When a deteriorating truss bridge—made of linear elements connected in triangles—must be replaced, Mr. Johnson figures out how to move it out of the way or slide a new one into its footprint. He engineers the plan that will send thousands of tons of steel gliding sideways over a river with the poise of a tightrope walker
Although truss-sliding isn’t new, Mr. Johnson has elevated what he calls “extreme bridge engineering” to an art form. It’s one that saves municipalities plagued by decaying infrastructure millions of dollars, while limiting bridge closures—and commuter headaches.
This summer, Mr. Johnson will meet his biggest challenge yet, launching the new 2,427-foot-long Milton-Madison Bridge over the Ohio River into a spot currently occupied by a 1929 bridge. It’s believed to be the longest bridge slide of its type in the world.
Other teams competing for the $103 million project proposed closing down the bridge for a year and running a ferry. Mr. Johnson saw a way to keep traffic flowing for all but 10 days of the three-year project, helping shave $28 million from its estimated cost. As the new bridge is constructed on temporary piers, cars whiz past it a scant 55 feet upstream on the old bridge. When work on the new bridge is finished, traffic will be briefly rerouted onto it, so the old one can be demolished.
In the grand finale this July, the new 15,260-ton steel bridge, pulled by powerful strand jacks, will slide slowly upstream on steel beams lubricated with high-grade silicon grease, before finally coming to rest in the footprint of the original bridge.
The logistical intricacies—and risks—awe seasoned bridge builders. Theodore Zoli, whose bridge engineering won him a MacArthur Foundation “genius” award in 2009, compares Mr. Johnson’s task to performing “open-heart surgery on the runner while he’s running a marathon.”
Mr. Johnson’s innovation was spawned by salmon. In 2009, his firm, Buckland & Taylor, won the bid to replace the Capilano River Bridge. There was a catch: Any construction in the river had to take place during two brief “fish windows”—a total of six weeks when the salmon were upstream.
Bridge Engineer Murray Johnson moves the old Capilano Bridge into a temporary roadway while a new bridge is built in British Columbia. Video courtesy of BC Ministry of Transportation and Infrastructure, 2010.
Bridge Engineer Murray Johnson completes the lift of the second bridge span over the Ohio River that connects Milton, Kentucky and Madison, Indiana. Video courtesy of Walsh Construction Company, 2012.
That wasn’t enough time to build a temporary detour. So Mr. Johnson’s team came up with a solution: move the old bridge upstream onto a temporary pier and abutments, and reroute traffic onto it while they built the new one.
The bridge’s aging trusses were jacked up so that their underbellies could be outfitted with sliding shoes—steel plates lined with Teflon-like pads—for a low-friction ride on greased steel tracks. A temporary pier in the middle of the river served as a runway.
Pairs of hydraulic jacks, pulling on three separate high-strength rods connected to bearings under the old bridge, slowly tugged it upriver, 6 inches at a time. Because the bridge had to be rotated slightly to fit in its new spot, Mr. Johnson calculated that each rod had to be pulled at a different speed.
Less than six hours later, the bridge swung neatly into place. It reopened to traffic the next morning.
“I always knew I was going to design or build things,” Mr. Johnson says, recalling hours spent banging nails into wood scraps as a little boy. When he was 12, his family moved to a remote island in British Columbia, which may explain why he “fell in love with big bridges.”
On site at Milton-Madison, Mr. Johnson’s office was a steel platform 100 feet above the river, equipped with a computer, a coffee maker and a porta-potty. In his hard hat and fall-arrest harness, he fit right in with the ironworkers, whose every move he choreographed long before they arrived on the work site.
Before he could slide the four-span bridge, Mr. Johnson had to figure out how to lift it—from the river itself. “Lifting is more exciting than sliding,” he says wryly. “It can’t fall down when you’re sliding it.”
One at a time, the bridge’s two center truss spans—the longer was 727 feet—were floated out to the middle of the river on barges, hooked up to bundles of steel cables and slowly raised 90 feet into the air by eight powerful strand-jacks on the lifting platform. Then came the real high-wire act.
While the truss span dangled in the air, a 100-ton steel girder, lifted by a floating crane, was inserted in a temporary pier, cut loose, and then maneuvered under the span’s bearings, to serve as a support and, ultimately, as a sliding track. “I figured out how to do this on a napkin,” Mr. Johnson says, doodling a picture of the giant girder cantilevered over the river like a diving board.
With each bridge, Mr. Johnson goes through a lot of paper, drafting thousands of pages of calculations, drawings and diagrams. Above, a concept sketch for sliding the 80-year-old Capilano River Bridge.
Next, Mr. Johnson has designs on New Jersey’s Bayonne Bridge, the fourth-longest steel-arch bridge in the world. Local officials want to elevate the roadbed of the 1931 bridge a full 64 feet, to accommodate the larger container ships that are expected after the widening of the Panama Canal in 2015. Mr. Johnson is working with a shortlisted contractor on a bid to pull off that feat while keeping traffic flowing. More than that, he won’t say.
If his work didn’t keep him up so late, he would probably wake up in the middle of the night worrying about it. He points out that the catastrophic 2007 collapse of a bridge in Minneapolis—which he wasn’t involved in—happened during construction work.
Mr. Johnson shows off a gray ring on his right pinkie: “It’s called the iron ring,” he says. In Canada, civil engineers wear the iron ring on their drawing hand as a symbol of their oath to protect life and limb. “We have to make sure everything we do is infallible,” he says.