Wednesday, July 21, 2010

PA Turnpike Bridge Demolished, Now the Real Work Can Begin

The road was only closed for a couple hours, the controlled implosion only took a few seconds, but the benefits of the recycled steel from Pennsylvania Turnpike Allegheny River Bridge (ARB) will go on for many years.

Craig White, the project manager for ARB, estimates about 4000 to 5000 tons of steel will be recycled from the truss, floorbeams and other materials of the old bridge. A single ton of steel recycled conserves 2500 pounds of iron ore, 1400 pounds of coal, and 120 pounds of limestone.

It took about 200 lbs. of explosives, set at 150 precut points, to bring down the bridge. Approximately 300 individual explosive charges will be used to cut the truss into manageable sections for removal. The truss will drop around 50 feet while 680 feet of steel will fall onto land and about 533 feet will fall into the river.

An estimated 48 hours will be needed to clear the river of debris. Steel from the river navigational channel will be removed to create a channel for river traffic in 24 hours. The steel on the island and causeway in the back channel will be cleared in about two weeks after the blast.

The ARB was built in 1950, when the turnpike was merely 10 years old. It will be replaced by a new Allegheny River Bridge, which is scheduled for completion this November.

The new bridge, designed by Figg Bridge Engineers, was inspired by local landscape features and includes a variable-depth superstructure and stone pattern on twin-walled, rectangular piers. It’ll include some 3,000 tons of steel reinforcement as well.

The cost of the demolition, contracted to J.B. Fay Co., is about $3.2 million including the deck, girders, truss, piers, and salvage value for the steel that is recycled. The cost of the new twin 2,350 foot long bridges to replace ARB is estimated at slightly above $193 million.

Here is a video of the demolition:

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