Bridge Replaced Over A Weekend
By using a highly innovative, design-build construction technique called Accelerated Bridge Construction (ABC), the 45th South Bridge Replacement project spanning I-215 East in Salt Lake City was completed in early November by Ralph L. Wadsworth Construction Co. of Draper, Utah, with minimal disruption to normal traffic flows.
According to Rukhsana (Shana) Lindsey, director of research and bridge operations for the Utah Department of Transportation, the nearly $8-million project was a huge success and saved the traveling public an estimated $4 million, since I-215 was closed for only the weekend of Oct. 27–28 while the old bridge was demolished and removed, and the new one moved into place utilizing a Self-Propelled Modular Transport system (SPMT). A project of this size and scope, utilizing a traditional bid-build construction method, would have required significant traffic disruption and closures to I-215 East, at a huge cost to the public.
"Everything went according to plan," said Lindsey. "One of my goals is to do construction without impacting traffic. Construction is inevitable. If we can do it without closing roads for a long period of time by using innovative methods, I think we should. Congestion has a direct impact on the economy.
"We're documenting all the lessons we learned, or things we could have done better," added Lindsay on the 45th South Bridge project. "We hope to learn a lot from this process. This was one of the most ambitious projects UDOT has undertaken. By doing (ABC), it allows us to refine the process for future bridge projects."
ABC is a building concept where the contractor builds a new bridge structure off-site at a nearby location, away from the flow of regular traffic. Once the bridge is built, it is then moved into placed utilizing a complex SPMT system designed by the Dutch-based firm Mammoet. For this project, Mammoet set up two double-wide SPMTs with 64 total axles and a lifting capacity of 30 tons per axle, according to Bill Halsband, vice president of business development for Mammoet.
Halsband said his firm has done approximately 30 projects similar to this in North America using SPMTs, but none this difficult to figure out.
"This was by far the most challenging project for us because of all the grade differences we had to deal with," said Halsband. "The combination of location, weight and size of the bridge, the different grade elevations we had to deal with, made this a big challenge. The bridge is on a 14-degree slope, the highway on a 4-degree slope. Other (projects) we've done like this have been straight and flat — this one had many different tweaks with it. We had to work with the contractor and design team closely to come up with the right blocking system, along with the right jacking with hydraulics."
The entire process is designed to minimize traffic disruption and save the traveling public the associated costs to traffic delays, while providing better, safer working conditions for construction workers.
"It's definitely safer for my workers and for the traveling public — we don't have to work over live traffic," said Wayne Bowden, project manager for Wadsworth Construction. "Across the board, safety was by far superior than building any bridge over a highway."
Bowden said the project was very successful with very few hiccups, despite the complex nature of moving a 172-foot-long, 80-foot-wide structure weighing approximately 3 million pounds via the SPMT system across a highway with a 6-foot grade variation between southbound and northbound lanes.
"Building the superstructure off to the side was, relatively speaking, easy," said Bowden. "We didn't have to deal with traffic issues. We could form it, pour it, strip it, and paint it with no conflicts — that part was very efficient for us.
"The biggest challenge in my mind," he continued, "was getting the geometry accurate to where we could build a temporary structure to set the (bridge) superstructure on and make it fit with the different elevations on I-215 northbound and southbound. It was a big challenge having our designer, Michael Baker Jr., communicate with Mammoet and coordinate the design, and make the geometry and elevations match. Getting across the southbound lanes with a 6-foot grade variation and making sure it fit with the jacks and the system they had was a big challenge."
Crews from Wadsworth started working on the project at the end of May, with upwards of 60 workers on the job during peak construction activity.
"A typical project of this caliber is nine months," said Bowden. "From the moment we could get started, we let out an early action package so we could start working on temporary abutments and the superstructure. We did a couple of breakout packages to accelerate construction, which typically you can't do with a bid-build project. It was fast-track construction from the day we started. We had upwards of 60 guys just from our company working on one bridge. Typically a bridge project like this would maybe have 10 guys on it."
The success of this project means that UDOT officials will carefully be examining all future bridge replacement projects in the state to determine which ones will benefit from the ABC process.
Wadsworth is also the general contractor on the current $110-million I-80 reconstruction project from State Street to 1300 East in Salt Lake City. An estimated 14 of 17 bridges that need to be replaced along that stretch will be utilizing SPMTs, according to Bowden.
The first phase of the bridge replacement aspect for I-80 will require seven bridge structures built on a 6-acre site off the 1300 East westbound exit, and will be moved into place utilizing SPMTs. The next phase will include the construction of six bridge structures. The bridges will all be approximately 80 feet wide and ranging in length from 108 feet to 180 feet.
"When you drive down from (Parley's) canyon and into the Salt Lake Valley and see the (staging area) with seven bridges laid out on a 6-acre site, it's going to be impressive," said Bowden. "Most of these bridge structures will be challenging in a different way. The geometry is relatively flat. It will take roughly six months to build them all, so by early summer we will have seven for that initial phase done. Mammoet will then move all seven superstructures in at one shot — it's much more cost-effective doing it all at once."
"We can build (bridge structures) anywhere, not necessarily right off the side of the road," added Lindsey. "We can build it off-site and impact traffic just on the day we're moving it. It's safer for workers, and it is better quality because it's built in a controlled environment that can have longer cure times. In the future, we believe (ABC) bridge costs will come down and will pass traditional methods in cost savings."