Using three Link-Belt lattice boom crawler cranes, Britton Bridge Co. is in the midst of a $26-million project to widen the U.S. Route 27 – State Route 29 “Olgiati” bridge in Chattanooga, TN, spanning the Tennessee River.
Britton Bridge, a Mt. Juliet, TN-based division of Jones Brothers Co., is extending the bridge from four lanes, which includes two in each direction with no shoulders, to six lanes — three in each direction with full shoulders, with possible widening in the future. In an effort to restore a vital link in its infrastructure, the State of Tennessee has elected to rehabilitate the existing bridge across the Tennessee River near Chattanooga.
“We closely studied the alternatives and decided that this option would be economically feasible rather than adding a totally new structure. We were further able to create a significant taxpayer dollar cost savings by utilizing our own in-house design and engineering forces,” said Ken Flynn, assistant area regional manager, Tennessee Department of Transportation (TDOT).
The estimates to rehabilitate the existing structure were approximately $26 million, versus the $35 million estimated to design and construct another new bridge.
With this project, Britton Bridge faced two distinct construction challenges. First, add to and widen the existing 10 land-based piers to support the new bridge configuration.
This is the conventional part of the project. Phase two included extending the caps of the four massive water piers by adding twin steel cantilever beams and shoulder bracing to each pier without disturbing them or their foundations. Engineering tests had indicated that the existing water piers would support the built-up steel plate girders required to support the deck widening.
The eight cantilever beams (two for each water pier) are among the longest and heaviest single pieces of steel fabricated for the job. They are 142 ft. (43.3 m) long and weigh approximately 218,000 lbs. (98,883 kgs) each. These are shipped to the job by rail, where they are transferred to barges on the river and floated into position. Two large, barge-mounted Link-Belt crawler cranes, a 250-ton (225 t) capacity LS-278H and a 150-ton (135 t) capacity LS-518, lift the massive cantilever beams into position.
The 12-in. (30.5 cm) steel H-beam foundation support pile averaged between 30 and 60 ft. (9 and 18 m) long each. They are being driven to bearing, or refusal, depending upon location with a Link-Belt LS-138H crane and a Delmag 3032-pile hammer.
Soil engineering borings showed a mix bag of common riverbank to be driven through. Poured-in-place pile caps, pier foundations and land columns were added, and the varying height, 6- by 6-ft. (1.8 by 1.8 m) reinforced columns are then formed and poured. New pier caps are formed and poured and new structural steel was added for both the main bridge widening and for interchange improvements.
For the water work involving hanging the steel, each Link-Belt crane is mounted on a separate barge. The LS-278H is rigged with 160 ft. (49 m) of boom with a six-part line, load block and a whip line. The LS-518 has a 150-ft. (46 m) boom, a six-part load line and a whip line. Because of strict Coast Guard channel restrictions, Britton Bridge crews normally work shifts from 7 a.m. until midnight several days a week when hanging the transverse steel girders.
The steel erection, according to Jerry Britton, was facilitated by the use of several man lifts, also working from barges.
In the past, skilled ironworkers would ride the load up, bolt it together and walk across a 4-in. (10 cm) wide flange 200 ft. (61 m) in the air to bolt the other end of the beam in place. Then they would likely slide down the vertical flange to the ground only to start the procedure over again. It was all part of the job, but done at an unacceptably high industry-wide accident and injury rate.
Because of new safety standards, technology and a shortage of the old time ironworkers, today’s skilled craftsman rides a man basket to work, wearing a safety harness using an air impact wrench instead of the traditional spud wrench.
The 11.3 million lbs. (5.1 million kgs) of structural steel was manufactured, fabricated and painted by Carolina Steel Corp. of Montgomery, AL. It was shipped to the bridge job site by truck and rail. Some of the longest and heaviest transverse girders are offloaded directly from the existing bridge deck after temporarily closing down one lane of traffic. They are then lifted into position by the barge mounted Link-Belt LS-278H crane. No steel erection has ever begun until all steel is on hand for a full day’s work, according to Britton.
Because of the size and weight of some steel girders, they are fabricated in sections and assembled in place utilizing both barge-mounted Link-Belt cranes.
A case in point is the haunch girders. They are erected one piece at a time, each weighing approximately 102,000 lbs. (46,266 kgs) and being roughly 10 ft. (3 m) deep, and 137 ft. (42 m) long. When bolted together they would be too tall for over the road transport and too heavy to erect as a single unit. Utilizing both Link-Belt cranes, Britton Bridge LLC was able to easily achieve a balanced approach.
“We work very hard to achieve a safe, balanced lifting approach on every job that we do. That’s just one of the many reasons for our fleet of a dozen or more Link-Belt machines,” Britton said.
“I would like to have two additional 250-ton capacity LS-278H cranes here, but such is not the case, we only own one of them.
“However, we do a lot of our own engineering on a project and we knew that we could do all the work here with it and an older 150-ton capacity Link-Belt LS518,” explained Britton.
For more information, call 606/263-5200 or visit www.linkbelt .com.
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