Accelerated Bridge Construction Explained
It’s no secret that America’s bridges need work. According to a 2016 report from the American Society of Civil Engineers, almost 40 percent of the nation’s bridges have been around for 50 years or longer, and 9.1 percent of bridges are structurally deficient. To address the backlog of work that needs to be done and reduce the time it takes to plan and build bridges, many organizations such as the Accelerated Bridge Construction University Transportation Center at Florida International University (FIU) have promoted a new construction method called Accelerated Bridge Construction (ABC). This new method reduces traffic disruptions and risk for both drivers and construction workers, since it shortens the time it takes to install a bridge over a roadway.
However, in light of the recent collapse of a pedestrian bridge being installed at FIU in March using this method, some people have expressed concerns about ABC. The investigation into the collapse is still ongoing, so we don’t know whether design, engineering, construction, materials or a combination of factors were responsible for the tragedy. But this incident suggests contractors and municipalities ought to take some time to learn about ABC, especially if they’re considering a similar project. Here’s what you need to know.
What Is Accelerated Bridge Construction?
Accelerated Bridge Construction is a process that involves constructing large portions of bridges offsite, then installing them quickly, often within 48 to 72 hours. Doing so can reduce road closures, traffic delays and overall project costs, according to the Federal Highway Administration (FHWA). These bridges are also designed to have a long service life. (In the case of the pedestrian bridge at FIU, the bridge was supposed to last 100 years.)
The FHWA explains three ABC technologies used to construct these bridges:
- Prefabricated Bridge Elements and Systems: Bridge components built offsite or adjacent to a site and then installed in place. They often include the deck, beams and railings.
- Slide-In Bridge Construction: The process of installing those prefabricated elements or replacing an existing bridge with a new one.
- Geosynthetic Reinforced Soil-Integrated Bridge System: A method for constructing abutments and approach embankments that are less likely to create a bump at the end of a bridge, a common issue for bridges.
Once the main elements of the bridge are installed, crews can complete the project by adding pavement and other needed components.
While ABC does speed up the process of building and replacing bridges—especially the actual installation—it’s worth noting that it doesn’t mean the whole process is quick. The design and engineering phases of ABC can take significant lengths of time, since everything has to be perfect for the installation to go smoothly.
The Benefits and Risks of Prefabricated Bridges
Many bridges have been installed in the United States using ABC, resulting in many benefits:
- Faster installation time
- Fewer traffic disruptions and road closures
- Increased worker safety
- Lower construction costs
- Reduced environmental impact
- Improved bridge quality and longevity
Any construction method comes with risks, though, and ABC poses some unique risks compared to conventional bridge construction. For example, ABC relies on specialized equipment like self-propelled modular transporters (SPMTs) to move the prefabricated elements into place. This equipment must be properly used and managed at the jobsite, and all load cases for the bridge must be considered for the installation.
Because the installation process occurs so quickly, the execution of the project requires the right personnel and clear communication to reduce risk. Whenever any type of new construction method is used, having people with the right knowledge and experience is critical, so any contractor thinking of using new methods should do their homework.
Keep an Eye out for the Investigation Results
Some engineers have pointed out that the bridge at FIU used an unusual design, but it’s too early to say whether that played a role in the collapse. We can’t jump to conclusions and blame ABC for what happened. Any contractors or organizations thinking about ABC for future bridge work should be on the lookout for the results of this investigation. They may provide some insight into what risk factors require extra attention during this type of project.
It’s also worth noting that prefabricated materials in general are playing an increasingly large role in construction, even if those materials aren’t the size of an entire bridge deck. These new materials and structures change on-site processes, and these changes are something all contractors need to pay attention to.
All construction projects involve risk of some kind, regardless of whether they use new methods. To learn about how Viewpoint can help your business mitigate risk, get in touch. Our software solutions can help you track compliance issues, improve communication between teams and make collaboration easier.