I-85 Bridge Fire/Rebuild

Location:

Atlanta, GA
 

Owner/Engineer:

Georgia Department of Transportation (GDOT), Atlanta, GA
 

Contractor:

C.W. Matthews Contracting Co., Marietta, GA
 

Project Scope

Length:

• 4150-ft Viaduct
 

Structural Precast Elements:

• 61 prestressed, precast concrete bulb tees, 63 inches deep, ranging from 43 feet to 115 feet long
• 4 concrete intermediate bents with inverted-T caps
• 5,090 square yards of concrete bridge deck
 

Cost:

$16.7 million (including $1.6 million for demolition and $3.1 million in incentives paid)
 

Specifications & Details

 

Resources

 
 
 
 
 
 
I-85 Bridge Fire/Rebuild
I-85 Bridge Fire/Rebuild
I-85 Bridge Fire/Rebuild
I-85 Bridge Fire/Rebuild
I-85 Bridge Fire/Rebuild
I-85 Bridge Fire/Rebuild
I-85 Bridge Fire/Rebuild
I-85 Bridge Fire/Rebuild
I-85 Bridge Fire/Rebuild
I-85 Bridge Fire/Rebuild
 
 
 
 
 
 
 
 
 
 
 
 
 

PROJECT OVERVIEW

Georgia Department of Transportation officials had to act fast when an intense fire broke out under the I-85 viaduct near Piedmont Road and the heat collapsed part of the bridge. Fast action with close cooperation among departments and a prestressed concrete design allowed the bridge to reopen in less than six weeks.

The fire was caused by a homeless person lighting fire to stored materials under the viaduct which carries 243,000 vehicles per day, causing Governor Nathan Deal to declare a state of emergency. That action allowed FHWA to authorize $10 million in emergency funding and allowing GDOT to negotiate (vs. bid) the contract for repair and replacement, according to Bill DuVall, State Bridge Engineer in the Office of Bridges & Structures with GDOT. Contractor C.W. Matthews Contracting Co., which had responded quickly to an earlier bridge fire, was contacted and on-site that night assisting GDOT with lighting and traffic controls and eventually the reconstruction.

The heat of the fire caused a variety of problems. These included collapse of one span and significant damage to the intermediate bents on adjacent spans, plus loss of cover, buckling of column reinforcement, and significant cap damage. Extensive delamination and cracking of the bottom flanges of the prestressed beams also was found. “Ultimately, GDOT determined that three spans in each direction and four bents needed to be replaced,” DuVall says.

The project proceeded similar to a design-build project, with GDOT acting as designer working closely with CWM on issues related to the reconstruction. “We provided the contractor with intermediate details so they could immediately contact suppliers of reinforcement, beams, etc.,” DuVall says.

The contract was created for completion with a $1.5-million incentive if completed 20 days early, by May 25th (before Memorial Day) and $2 million if completed by May 21st. Some $200,000 was allocated for every day prior to that, up to $3.1 million.

PRECAST SOLUTION

The precaster that cast the bridge’s original beams, Standard Concrete Products, was contacted the night of the fire and began searching its plants throughout the southeast for the original AASHTO Type V PSC girder forms. Ultimately GDOT decided to redesign the required 61 beams using 63-inch bulb tees.

The damaged portion of the bridge featured complex layouts, including a slight curve with the typical bent laid out radially and a 50-degree skew where the viaduct crossed Piedmont Road. In the six spans needing replacement, one (over Piedmont) had skewed bents at each end, two spans were trapezoidal, and three had radial bents.

The southbound span over Piedmont Road had 12 lines of girders, while the other two southbound spans each had 11 girder lines. The northbound bridge had 9 lines of girders in each span. Six girder designs were created to detail and replace the 61 girders.

Restrictive Site
The beams were produced at two of SCP’s plants in in Atlanta and Savannah and beams were trucked with State Police escort, sometimes 3 loads per day, to the site. The contractor began work on the spans using the most conventional beams and then addressed the trapezoidal spans. In some places, cranes had to reach across 120 feet to set the beams. Crews also had to work around overhead transmission lines in some locations.

GDOT required the contractor to wet-cure the decks for a minimum of 3 days using curing blankets and soaker hoses. Uncoated reinforcement also was used to save time, as the new deck would provide sufficient durability compared to the 30-year-old deck on subsequent spans. The entire deck will be sealed soon to provide additional protection.

GDOT also utilized 24-hour accelerated concrete to construct the substructure, with fiber additives to minimize cracking. The mix design included Type III cement, but added 89 stone due to congestion of the reinforcement and to add workability.

Work moved so smoothly and efficiently that CWM generated the full $3.1 million in incentives. In addition to finishing so quickly, no injuries were reported during construction. “CWM did a great job with this project,” says DuVall. And, per GDOT, this may be the most inspected bridge in the state. The DOT logged more than 3,500 man hours of on-site inspections, with as many as eight inspectors on-site at a time. Inspections included examining the prefabricated prestressed concrete beams off-site and inspecting them again for size and spacing on-site. Inspectors also sampled and tested the concrete before it was poured.

 
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