These days, building a bridge can be compared to constructing Legos on the weekend.
The accelerated bridge construction feature is perhaps among the most impressive and impactful of new innovations within the Department of Transportation.
The process can take place in a very short time frame using pieces that are put together – erector set style – in remote locations then lifted or slid into place. The technique cuts the number of hours or days a road needs to be closed. It can sometimes take place overnight.
Take for example the Mesquite, Nevada bridge for I-15. The entire structure was demolished and replaced in a weekend.
“This is just like a giant Lego set,” said Mendez, Federal Highway Administrator. “They build components of the bridge, sometimes the entire bridge, offsite.
“In Mesquite, Nevada, they demolished the old bridge and had already built the new bridge and slid it into place,” he said.
Arguably the most ambitious accelerated bridge construction demonstration to date was the “Fast 14″ project in Medford, Mass. The effort replaced fourteen bridges on I-93 in ten weekends between June and August, 2011. (see video above)
DOT estimates put the project on a four-year time frame using traditional construction methods. The accelerated method meant all the bridge work was completed in less than a year.
The bridge replacements, each done in 55 hours or less, were like massive ballets, according to Massachusetts officials who participated in them.
Each bridge replacement project started Friday night at 6 p.m. Traffic was funneled on the parallel bridge by 10 p.m. Demolition of the old bridge took most of Friday night and by Saturday at 6 a.m. crews started putting it back together. The first pre-fabricated piece “will start flyin’ in by 9 a.m.” said Ernie Monroe Jr., a MassDOT engineer. At the end of Saturday, the panels were in place and concrete began to be poured. The concrete, called “high early strength concrete” was specially designed to be quick curing and harden to traffic-bearing levels in four hours. Sundays were devoted to paving and reopening the highway to traffic.
While traffic backups were significant during the weekend, traffic lights on alternate routes were adjusted to handle the flow and the project beat its expected completion timetable by a few hours.
“The I-93 Fast Fourteen project has been called the most ambitious bridge replacement project in the country, ” said Massachusetts DOT administrator Frank DePaola, “and now it can be called one of the most successful.”