Pennsylvania installs prefab bridges

Marielle Segarra Jan 21, 2015

Pennsylvania installs prefab bridges

Marielle Segarra Jan 21, 2015

Building a bridge takes years. That’s a problem, because many states have crumbling infrastructures, and they’re looking for ways to shore it up with limited funds.

That’s why the Pennsylvania Department of Transportation is speeding things up. PennDOT is hiring a team of private contractors to quickly replace hundreds of state bridges.

“We expect that we’re going to deliver 558 bridges in 3½ years, instead of what would have taken us eight to 12 years under our traditional method,” says Barry Schoch, an advisor to Governor Tom Wolf and the state’s former Transportation Secretary. 

Prefab bridges

The key is mass production. First, the engineers will put together a couple dozen standard, cookie-cutter designs. They’ll mix and match pieces of those designs based on each bridge site.

Manufacturers will then make some of the concrete bridge parts, perhaps 50-foot bridge surfaces, for example. Everything can’t be made in a factory, but they’ll standardize whatever they can.

A construction crew usually has to wait weeks for each section of concrete on a bridge to harden and strengthen before they can move forward, says Andrew Swank, president of Swank Construction, who says his company will replace some bridges under the state’s new program. That means means construction on a small bridge can take months, he says.

Building a bridge with factory-made parts only takes a couple of weeks because the pieces are hardened ahead of time and arrive ready to assemble, Swank says.

It’s kind of like buying a bookshelf from IKEA. “The pieces will have slotted ends. This piece will fit into this piece and key into this piece,” he says.

The construction team uses a crane to lift the pieces, slides them into place and has “a bridge in very short order,” Swank says.

Engineers say factory-built bridge parts are actually stronger than poured concrete, because they’re made at the exact right temperature, away from rain, snow and weird weather.

Other states

Pennsylvania isn’t the first state to mass-produce its bridges. Missouri recently fixed and replaced more than 800 bridges in 3½ years.

Utah has also tried replacing some of its bridges with prefabricated parts, says Andy Herrmann, former president of the American Society of Civil Engineers. “Florida, New York, Washington and Virginia are also looking into it,” he says, “because they have so many deficient bridges they have to fix, and they’re trying to do it quickly.”

Pennsylvania is spending hundreds of millions of dollars on its program, which it says will still be 20 percent cheaper than traditional methods.

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