Starting with research in the mid-1980s, accelerated bridge construction (ABC) has gathered attention as a possible way to improve on bridge construction. Only in recent years has it has gained traction as an actual and feasible building method. What is accelerated bridge construction and why use it? Here are the answers.
What is Accelerated Bridge Construction?
According to the Federal Highway Administration (FHWA), “ABC is bridge construction that uses innovative planning, design, materials, and construction methods in a safe and cost-effective manner to reduce the onsite construction time that occurs when building new bridges or replacing and rehabilitating existing bridges.”
ABC came about as an effort to make reducing the impact on the public’s mobility more of a priority. The goal is to reduce the time on-site and disrupting traffic, while not compromising on quality.
What Are the Benefits?
25 percent of the United States’ bridges need repair or replacement. Using current methods, construction on 150,000 bridges nationwide could be a huge hit to our lives and economy. In fact, the FHWA estimates that the direct and indirect cost, e.g., the loss in revenue for impacted businesses, of traditional bridge building are higher than the actual building costs.
Because ABC works to optimize the process – from planning to construction – it has a lot of benefits.
According to the FHWA, ABC improves:
- Site Constructability
- Total project delivery time
- Work-zone safety for the traveling public
And ABC reduces:
- Traffic Impacts
- Onsite construction time
- Weather-related time delays
Bridge construction can be a huge burden on the public and the flow of traffic. Traditional methods can take years. With ABC, on-site construction time can be reduced to 48 to 72 hours.
What Does This Look Like?
In the planning stage, ABC might look like early environmental clearance and permitting. Innovative, time-saving contracting methods, like A+B bidding, are also a big part of ABC planning strategies. Lastly, getting right of way acquisition and locating utilities before advertising the project are also part of ABC planning.
Geotechnical methods that speed up the time on-site, like mechanically-stabilized earth walls, lightweight backfill, and geo-synthetic reinforced soil (GRS) abutments, are all typically used. Other innovative methods like using self-propelled modular transporters to move components into place are also used during the construction. Sometimes ABC methods make use of traditional equipment in non-traditional ways, e.g., using a hydraulic jack to slide superstructure spans sideways and into place.
ABC also uses more efficient building materials. Materials like high performance steel, high performance concrete, ultra-high performance concrete, and fiber reinforced polymers. The cost might be higher, but the shortened time is a big enough benefit.
Prefabricated construction is a huge part of ABC. Prefabricated Bridge Elements and Systems are built offsite and transported and assembled on-site. The components could also be built on-site, but in a location that doesn’t impact traffic.
The FHWA uses two main metrics for measuring how effective ABC is: onsite construction time and mobility impact time. Onsite construction time measures the time from the very beginning to the end of construction. Mobility impact time measures how long the traffic flow is reduced. A reduction of these means the ABC methods are effective and should be used.