In one weekend, an outdated two-lane, four-span highway overpass was removed and replaced with a two-span bridge using a technique that was a first for the state of Georgia, and received recognition in a statewide engineering awards competition.
The State Route 299 bridge in Dade County, which crosses over Interstate 24, was designed by WSP USA and constructed using accelerated bridge construction (ABC). Georgia Department of Transportation (GDOT) selected ABC for this bridge to expedite project delivery without interrupting interstate traffic travelling below the construction site.
Since normal staged construction of the bridge would result in additional right-of-way expenses, a longer construction duration, and detours that could negatively impact small businesses, GDOT felt ABC was the most practical option.
“The ABC method successfully shortened construction time and minimized impact on the traveling public,” said Steven Jarrett, design project manager for WSP USA. “The technique allowed for the removal of the existing bridge and installation of the new bridge within an 81-hour period.
“Installing two new spans over live traffic marked this project as the first in the U.S. where two spans of a bridge have been replaced over a single weekend closure,” he added.
As lead designer, WSP was responsible for the bridge replacement structure, temporary support structures for the permanent superstructure, maintenance of traffic, utility coordination, geotechnical design, retaining walls, hydraulic design, erosion control and roadway design.
The success of the State Route 299 bridge project was recognized by the Georgia chapter of the American Council of Engineering Companies (ACEC), which recently honored the Route 299 overpass as the winner of its 2018 Engineering Excellence Award in the transportation category.
“I am proud and excited about the project winning the ACEC’s state award,” Jarrett said. “The attention received by winning this award has helped to spotlight our Atlanta office and strengthens our relationship with GDOT.”
In January 2016, WSP began design work to replace the functionally obsolete 240-foot-long bridge with a concrete bridge that included required roadway shoulders and barrier walls to meet current design standards. The plan called for the new bridge superstructure to be constructed north of the original overpass on temporary support structures. Using self-propelled modular transporters (SPMT) the bridge superstructure was moved into its permanent location. Construction was performed by Wright Brothers Construction Company Inc.
“Straddle bents installed under the existing bridge allowed most of the permanent substructure bridge elements to be constructed during the pre-ABC period with minor disruption to both the interstate and state route traffic,” Jarrett said. “Design techniques and the use of precast concrete pedestals incorporated in the design allowed the previously constructed bridge substructure elements to be raised to the required elevation during the ABC period.”
Once the existing structure was demolished, the two preassembled bridge spans—totaling 2.5 million pounds—were transported on SPMT into place on the current alignment over live traffic. This process began on May 12, 2017 and the new bridge was opened on May 14, 2017. The project was officially completed in October.
“It was imperative to maintain traffic on both the interstate and the state route during peak periods while ensuring safety for both the construction workers and the public,” Jarrett said. “The design-build team met these challenges by maximizing work zone areas during the pre-ABC period, minimizing the number of lane shifts necessary on I-24 within the construction limits, scheduling weekly meetings to discuss design and construction issues, addressing any safety concerns and implementing corrective measures as necessary.”
The success of the State Route 299 bridge opens the door for GDOT to consider ABC for future bridge projects.
“GDOT plans to use this project as a template for its ABC program,” Jarrett said. “The lessons learned during the construction of this bridge will enable GDOT to begin an ABC program to educate and illustrate how this technique can be similarly applied and used in other areas and projects throughout Georgia.”
The Federal Highway Administration also praised GDOT and the design-build team for completing the project within the specified parameters.
“It was truly an honor to be a part of a project that has been recognized by the Georgia engineering community,” Jarrett said. “GDOT’s first full ABC bridge replacement project is truly a great accomplishment—especially since it was designed and constructed within the specified time frame with no incidents or change orders. Coming together as a team and collaborating on design techniques and design alternatives truly made this an exciting project.”
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