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A Construction Marvel

Posted By Tina Grady Barbaccia On March 14, 2011 @ 7:30 pm In Better Bridges Research Papers,Contributed Stories,eRoadPro Newsletter | No Comments

More than 10,000 automobiles’ worth of steel bridge beams are going up on the new Sam Rayburn Tollway/Dallas North Tollway interchange.

Piece by piece and steel girder by girder, the five-level construction marvel known as the new Sam Rayburn Tollway/Dallas North Tollway (SRT/DNT) interchange is taking shape in Collin County.

In fact, during the next seven to eight months, construction crews will set all the steel beams that form the heart of the new interchange. The steel will help create eight direct-connecting bridges that will join the two major toll roads and effortlessly move traffic through what has been a highly congested area.

During this ongoing phase of construction, the steel beams are on center stage. Every weekend, crews use massive cranes to hoist two enormous steel beams at a time and then bolt and weld them into place.

Each beam section is about 300 feet long — meaning that if a beam section were placed on its end, it would be slightly taller than the new Cowboys Stadium or about as tall as a 20-story building. It would be barely shorter than the Statue of Liberty, from the base of the monument’s pedestal foundation to the tip of its torch.

When the SRT/DNT interchange is complete, crews will have set more than 18 million pounds of steel bridge beams — an amount equal to about 10,000 automobiles, more than the Eiffel Tower and more than the state of Texas bid out in 2010 for use in transportation projects.

Between now and when the last beam is placed, crews will continue to close SRT and DNT main lanes and frontage roads as necessary, primarily on Friday evenings through early Monday mornings. The closures are required to ensure the safety of motorists as well as NTTA contractors and staff as the steel beams are being set.

“We know these closures affect motorists and businesses, and we want to thank everyone for their patience while we complete the interchange,” said Elizabeth Mow, NTTA director of project delivery. “We promise that the pain will be worth the gain. We are building a significant, five-level interchange that will vastly improve regional mobility and further encourage the ongoing economic development in the area.”

The five-level SRT/DNT interchange by the numbers:

The interchange will be about 105 feet tall from the lowest roadway surface to its highest bridge.

o The SRT/DNT interchange will be about as tall as a seven-story building. By comparison, the High Five in Dallas is about as tall as a 12-story building.

o The SRT/DNT will feature more than 18 million pounds of steel beams.

This amount of steel:
o Is equal to the steel used to build about 10,000 automobiles.
o Weighs more than the steel in the Eiffel Tower.
o Is more than the state of Texas bid out in steel beams on transportation projects in 2010.

The steel beams are placed in sections that are about 300 feet long, which is as long as a football field. If stood on its end, the longest beam section would be:
o Slightly taller than the new Cowboys Stadium (which has a peak height of 292 feet)
o About as tall as a 20-story building.
o More than 50 feet taller than the tallest water tower in the City of Frisco.
o Barely shorter than the Statue of Liberty monument, from the pedestal foundation base to the tip of the torch (which is 305 feet, 6 inches tall).

A total of 30,000 linear feet of steel beams is being used in the interchange. This amount:
o If placed end to end, would reach the cruising altitude of many jetliners.
o Equals about 5.7 miles — a length that would wrap around the nearby IKEA building more than 15 times.

Crews are hoisting and setting two steel beams at a time, and the typical beam weighs between 500 pounds and 600 pounds per foot.
o The heaviest section weighs close to 200 tons, a weight comparable to lifting five typical backyard swimming pools full of water.
o On a typical weekend beam placement operation, crews have to line up and tighten into place nearly 2,500 bolts.
o Project-wide, nearly 150,000 bolts and miles of welds will be used to fabricate and secure all the steel beams in place.

This article was contributed by the North Texas Tollway Authority (NTTA)


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