Video: Time-lapse shows bridge going up overnight
It’s not exactly the way Miami conventions look in chamber of commerce sales brochure, but the 600 or so highway administrators and engineers seemed to be having a great time at Miami’s Hyatt Regency Monday, playing patch-the-pothole with sample batches of asphalt (pretty much as messy as it sounds), watching videos of bridge construction (not nearly as boring as it sounds) and talking endlessly about Lego blocks (way less childish than it sounds).
So it went at Florida International University’s second annual National Accelerated Bridge Construction Conference, where highway-transportation industry officials gathered to talk about new techniques and technologies that can cut months and even years off the time it takes to build a bridge.
Those videos? Time-lapse photography of bridges going up literally overnight. The Lego blocks? An analogy for techniques in which pieces of bridges are built away from the construction site where they won’t disrupt traffic, then assembled in one speedy burst ranging from hours to days.
And the asphalt? Well, that was just asphalt, though a new type that sets much quicker and doesn’t require those giant heated cauldrons that can turn a summer Miami street that already feels like the seventh circle of hell into something closer to the surface of the sun.
All the chatter and demonstrations about accelerated bridge construction — or ABC, as it’s known to highway-engineering hipsters — made the convention-goers giddy. They think ABC, which began making inroads in the bridge-building industry about 10 or 15 years ago, is on the verge of a breakout.
“In a few years, maybe as few as five or so, we won’t even call it ‘accelerated,’” predicted Atorod Azizinamini, director of FIU’s Accelerated Bridge Construction University Transportation Center, which put together the conference. “It’ll just be the way we build bridges.”
The conference, which continues Tuesday, includes engineers, administrators and construction-company officials from 40 states. Many of them wondered why there weren’t more.
“This is hugely relevant to anybody who has anything to do with building or operating highways,” said Gus Pego, who runs the Florida Department of Transportation district that includes South Florida.
“It has a great impact on construction time, on drivers’ time, on the environment, and on safety — because work zones are the ones where accidents frequently happen.”
Florida was an early disciple of ABC, starting with the replacement of the Graves Avenue bridge on Interstate 4 in Orlando in 2006, which was accomplished with just two nights of closures. Construction of the massive interchange between State Roads 826 and 836 in west Miami-Dade bears some footprints of ABC, including the use of pre-poured concrete components.
In a few years, maybe as few as five or so, we won’t even call it ‘accelerated.’ It’ll just be the way we build bridges.
Atorod Azizinamini, director of FIU’s Accelerated Bridge Construction University Transportation Center
Some elements of ABC building have been around for decades. Railroads were using the technique known as sliding — when a new bridge is built right next to the old one, then pushed into place and hooked up — as far back as a century ago. And pre-casting some concrete components of bridges off-site has been a common practice for 40 years or more, devised by construction companies that found it cheaper.
But it’s only in the relatively recent past that the industry has begun to considered ABC as an all-encompassing system rather than a way to save a buck here and there.
Part of that is improvement in construction material used to bind the construction Lego blocks together, particularly important in seismic hot spots where state officials were leery of whether bridges would make it through major earthquakes.
But a bigger factor, many of the convention-goers said, was simple need: As the interstate highway system hit its 60th birthday in recent years, bridge repair and replacement has become a near-constant need.
“When they built the interstates, nobody had to worry about disrupting traffic, because there was none,” said Bala Sivakumar, a vice president of Kansas City-based HNTB, one of the country’s major bridge-engineering firms.
“These were almost all brand-new highways. Nobody was driving them because they hadn’t existed. But you close an interstate now, and thousands of drivers, sometimes hundreds of thousands, get displaced and delayed.”
Sivakumar’s company produced one of the videos being passed from computer to computer at the convention, a time-lapse view of a project on a freight-heavy section of Interstate 84, an hour north of New York City.
Using the sliding technique to replace side-by-side bridges, HNTB cut a projected two years of construction detours and delays into two nights. The video shows one of the 10-hour replacement operations in three fascinating minutes, with demolition vehicles attacking the old bridge like a horde of mechanical locusts, then nudging the new one over to take its place.
The sticker price on ABC projects is high — about 20 percent over the cost of conventional construction, according to one study. But Sivakumar says the video demonstrates why ABC is cheaper in the long run.
“About 80,000 vehicles use that bridge on an average day,” he said. “If the speed limit had been dropped from 70 mph to 40, the original plan, and it had gone on for two years, how much time do those drivers lose? Maybe an hour apiece, every day for two years?...
“That’s another reason ABC is catching on. Once the public sees it, it sells itself. And it’s going to be very difficult for the owners of these highways to go back to the old way of business as usual, because people won’t accept it.”