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.
Source: Marketplace.org
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