“Big Lift” is High Tech Construction Choreography
By John Latta, Tina Grady Barbaccia and Mike Anderson
A bridge section the size of a football field has been lifted into place above the Mississippi River in New Orleans.
This demanding maneuver has been described as “the most visually exciting in the project’s seven-year course, and a rare technical feat,” according to the Huey P. Long Bridge Outreach Office and the Louisiana Department of Transportation and Development.
The work is part of the $1.2-billion Huey P. Long Bridge Widening Project. On June 19, this massive bridge segment was the first of three to be lifted in place using multiple barges and strand jacks. The four-span bridge, one of the three major Mississippi River crossings in the New Orleans metro area, began its truss widening in November 2009 with Span 1. When completed, the widened truss will allow the narrow bridge, which now carries 50,000 vehicles a day, to have three 11-foot lanes along with new inside and outside shoulders in each direction.
On the remaining three spans, the span-by-span construction method will be used. This involves pre-assembled span sections bigger than the size of a football field to be hoisted into position using strand jacks. The first “Big Lift” – as it is being referred to by the contractor – required a 48-hour road closure in addition to a period of restricted railroad and river traffic. Due to the size and weight of the span segments, such lifts are very rare, especially in bridge work, say the two agencies.
The contractor responsible for the Big Lift and Phase III is MTI – a joint venture of Massman Construction Co., Traylor Brothers, Inc. and IHI, Inc.
“To carry out this first Big Lift, MTI composed a methodical plan,” said the agencies in the days before the lift. “First, a four-barge assembly connected by three sectional barges was prepared. On the completed barges, two large stability frames were assembled to help support the bridge span section during the lift. At the same time, lifting towers, which will hold the strand jacks, were installed on each side of Pier II and Pier III. Currently, the construction of the pre-assembled span section on the barges is complete. On the day prior to the lift, the barges will be moved under the bridge following a well choreographed sequence. After the barges are positioned at their intended location, the span section along with the stability frames will be lifted approximately 135 feet using four 900-ton strand jacks. Once the span section is secured, the stability frames will be lowered to the barges and the span section will slide in 13 feet to its final position. The hoisted span segment measures 528 feet long and weighs 2,650 tons. A lift of this size and scope is extremely uncommon in bridge building.”
Tim Todd, project engineer for Louisiana TIMED Managers, says the contractor requested a stoppage of river, road and railroad traffic during critical parts of the lift. A major challenge was coordinating construction efforts to minimize the effect on the public and the traffic that traverses the river, he said.
According to Steve Underwood, Project Manager with MTI Underwood, two factors could have postponed the lift: high wind and a high river level.
The $453-million contract to widen the truss is expected to be completed in 2012. By then, an estimated 17,500 tons of structural steel and 750,000 new bolts will be used during this phase of the project. Construction on the original 75-year old structure began in 1932 and was completed in December 1935 at a cost of $13 million. The project also includes construction of new roadway approaches and is scheduled to be complete by 2013. v