Accelerated Bridge Construction (ABC) technologies are changing the ways State Departments of Transportation (DOTs) do business. Most notably, DOTs can replace bridges within 48 to 72 hours and reduce planning and bridge construction efforts by years. The accelerated project times significantly reduce traffic delays and road closures and could potentially reduce project costs. The innovative ABC planning and construction methods, designs and materials produce safer, more durable bridges with longer service lives than conventional bridges. The timely innovation comes when approximately 25 percent of our Nation’s aging bridges need repair or replacement and our highways are already congested without the added strain of road closures.
Three particular ABC technologies being promoted under EDC-2 are: Prefabricated Bridge Elements and Systems (PBES), Slide-In Bridge Construction, and Geosynthetic Reinforced Soil – Integrated Bridge System (GRS-IBS).
GRS-IBS is a construction method combining closely spaced geosynthetic reinforcement and granular soils into a new composite material. The method is used to construct abutments and approach embankments that are less likely to settle and create a bump at the end of the bridge. The GRS-IBS is easy to build and maintain and 25 to 60 percent more cost effective than conventional construction methods.
PBES are structural components of a bridge that are built offsite, or adjacent to the alignment – and includes features that reduce the onsite construction time and mobility impact time that occurs if conventional construction methods were used.
Slide-In Bridge Construction is a cost-effective technique for deploying PBES, or quickly replacing an existing bridge. A new bridge is built on temporary supports parallel to an existing bridge. Once construction is complete, the road is closed and the existing bridge structure is demolished or slid out of the way. The new bridge is slid into place, tied in to the approaches and paved within 48 to 72 hours.
When coupled with appropriate quality assurance, safety, project management and construction engineering practices, the following table lists the benefits of each ABC technology:
|Can Lower Construction Costs||•||•||•|
|Reduces Mobility Impacts||•||•||•|
|Shortens Onsite Construction Time||•||•||•|
|Reduces Environment Impact||•||•||•|
|Can Improve Quality||•||•||•|
|Eliminates "Bump at the Bridge"||•|
|Accommodates On-Site Modifications||•|
Construction along active highways can be dangerous for workers and motorists. ABC technologies help improve motorist and worker safety by shortening travel lane restrictions and road closure durations and by performing construction away from traffic. When traffic disruptions cannot be avoided, scheduling construction at nonpeak times, such as nights or weekends, can also help reduce work zone safety concerns.
The offsite production of PBES and shortened construction durations with slide-in construction can lessen the environmental footprint, or impact, on construction sites. ABC techniques may also be an effective solution, or alternative, for environmentally sensitive areas in which construction may be delayed or timed around environmental limitations, such as fish spawning seasons.
The construction of PBES in climate-controlled settings is another added benefit of ABC. Temperatures, humidity, rain and wind can affect quality and can delay conventional onsite construction. Often PBES can be constructed in prefabrication plants to avoid exposure to extreme weather conditions.
The market-ready ABC innovations have been deployed nationwide, and several States are developing policies for considering and using ABC in their project development process.