Using multiple barges and a complicated strand jack system, the second of three massive bridge segments was lifted into place on November 20 at the $1.2 billion Huey P. Long Bridge Widening Project.
The bridge segment, larger than a football field, will provide the narrow bridge the capacity to add lanes allowing the narrow bridge the capacity to add lanes. Due to the sensitive nature of the event, the four-span bridge, which serves as one of the three major Mississippi River crossings in the New Orleans metro area, roadway and river traffic was restricted for 48 hours.
A traditional stick-built construction method is being used to widen one of the spans. On the remaining three spans, the contractor opted to use a progressive technique called the span-by-span construction method. It involves pre-assembled span sections to be hoisted into position using hydraulic jacks with steel cables, known as strand jacks. Due to the size and weight (almost 3 million pounds) of the span segments, the intended lifts are very rare, especially in bridge work. When completed, the widen truss will allow the narrow bridge to have three 11-foot lanes, along with new inside and outside shoulders in each direction.
"From a technical achievement perspective, the segment lift is an exciting milestone for this bridge project, because of its magnitude and because it represents another step toward completion of this much-needed project for the residents and businesses in Jefferson Parish and the New Orleans area, "said Sherri LeBas, P.E., Interim Secretary of the Louisiana Department of Transportation and Development.
The contractor responsible for the "Big Lifts" and the widening of the bridge is MTI - a joint venture of Massman Construction Co., Traylor Brothers, Inc. and IHI, Inc. To carry out the lifts MTI hired HNTB as consulting engineer. Together they composed the plan.
First, a multi-barge assembly was prepared. On the barges, two large stability frames and the bridge span were assembled. The strand jacks used to lift the span section were installed on the top chord of the widened structure. On the day of the lift, the barges were moved under the bridge following a well choreographed sequence. Then, the span section, along with the stability frames, were lifted approximately 135 feet using four 900-ton strand jacks. Once the span section was secured, the stability frames were lowered to the barges. Unlike the first big lift, the span section did not need to be moved laterally, and lifting towers were not required. The hoisted span segment measured 503 feet long and weighed 2,544 tons, which is 25 feet shorter and 100 tons lighter than the first lift. Lifts of this size and scope are extremely uncommon in bridge building, according to the LDOTD.
"Coordinating construction efforts to minimize the effect on the public and the river traffic has been a major hurdle but it has been manageable due to the cooperation between the Coast Guard, New Orleans Public Belt Railroad and DOTD" said Tim Todd, project engineer.
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. The entire Huey P. Long Bridge Widening project cost is estimated at $1.2 billion. Construction on the original 75-year old structure began in 1932 and was completed in December 1935 at a cost of $13 million. Today, it is considered one of the longest railroad bridges in the United States.
To watch a video of the big lift, visit http://bit.ly/HPLWebCams.