Photo: Courtesy Angelle Bergeron

Trusses to widen bridge deck are built on barges in left and right halves, floated under the bridge, lifted by strand jacks and installed in a swift weekend operation that minimizes disruption to rail, highway or Mississippi River traffic. The method is safer for the 75-year-old bridge and the workers than stick-building in place.

Steve Underwood, project manager with joint venture MTI, is orchestrating the span-by-span lift and assembly sequence for superstructure erection on the $1.2-billion widening of the Huey P. Long Bridge over the Mississippi River at New Orleans. He is using on a huge scale novel construction methods to minimize rail, shipping and highway disruptions.

Underwood has been instrumental in overseeing the coordination of many details and decisions that are contributing to this high-profile engineering success taking place on a piece of vital infrastructure over one of the world’s great commercial waterways.

MTI is a joint venture of Massman Construction Co., Kansas City, Mo., Traylor Bros. Inc., Evansville, Ind., and IHI Inc., New York City.

MTI’s $452.6-million part of the work is for superstructure widening to expand lane capacity on the 75-year-old steel-truss bridge. It is using a delicately balanced process of pre-assembling widening trusses for three spans and raising them from a barge platform in left and right halves. The center-section halves had to be drawn together once they were lifted high enough to clear the tops of previously widened piers.

The pre-assemble-and-lift scheme was deemed safer for both the old bridge and the contractor as well as less disruptive to navigation and highway and rail traffic than previous plans for stick-building in place.

“The state had one idea about how it should be built, but we came up with what we thought was a better, safer way of doing it,” says Paul Scharmer, Louisiana area manager with Massman Construction, the lead contractor. He says the scheme was the brainchild of several people. The design was worked out by John Brestin at HNTB, the venture’s engineering management firm. But Scharmer says Underwood has been the key to not only the successful execution of the lifts but also much else that Scharmer says is “fantastic” about the way the project is going together.

“If some were to ask me who had their thumbprints all over this project, my answer would be Steve Underwood,” Scharmer says.

The first span to be installed—a 528-ft-long, 2,650-ton segment—validated the process. The truss was assembled near the riverbank on a four-barge assembly platform, floated beneath the bridge, then raised 130 ft simultaneously in two halves, drawn 13 ft together and secured over a weekend in June.

Constructing the truss in two halves on the barges required the creation of a massive stability frame and a system of sliding tracks and counterweights to adjust ballast while the structure was being built. It also required the installation of an elaborate and novel monitoring system on both the bridge and the new components to guard against strain and deflection during both the construction and installation process.

Robert Kollmar, chief engineering officer of bridge owner New Orleans Public Belt Railroad, says he is “thrilled” because the method minimizes interference to rail traffic and produces less stress on the bridge. David Frank, bridge administration chief for the U.S. Coast Guard district, says the span-by-span lift is “a phenomenal improvement for navigation” over the obstructions caused by falsework for stick-built construction. The second lift went off beautifully on Nov. 13-14. The last is to happen in April.