Approximately two months of work are needed to finish the remaining portions of the project, including the bridge, fence and trail.
(Ragle Inc. photo)
Meticulous and detailed planning on the part of Ragle Inc. and the Texas Department of Transportation was amply rewarded when the new Northaven Trail Bridge — a pedestrian bridge spanning 201-ft. long with a 50-ft. tall arch — was transported by Self Propelled Modular Transporters (SPMTs) and placed by special hydraulic jacks and gantries.
Work on the project, which included building the new bridge, began in June 2021.
The 800,000-lb. bridge — spanning U.S. 75/North Central Expressway in Dallas, fabricated at a site nearby — is 20-ft. wide. The overall width of the structure is 18-ft. 4-in. and the width between the pedestrian and rail and the bridge is 14 ft.
"TxDOT Dallas crews and contractor Ragle Inc. made the seemingly impossible happen overnight one weekend when they moved the new Northaven Trail Bridge onto columns beside the mainlanes of North Central Expressway near Royal Lane," said Tony Hartzel, TxDOT's Northeast Texas communications director. "The end result is a gleaming addition to the North Dallas skyline that will forever grace the commutes for tens of thousands of motorists. The Northaven Trail Bridge also will directly serve a growing contingent of bicyclists, pedestrians and others who have longed for a new, safer connection from the Northaven Trail in North Dallas to the Cottonwood and White Rock Creek trails in Northeast Dallas."
Moving the Bridge
The bridge can carry a weight of 445,000 lbs., which is equal to the weight of 45 elephants or six fully loaded semi-trucks.
Cables and steel used for the bridge were manufactured by Houston area-based companies. SPS provided the cables and King Fabrication the structural steel. Mammoet provided the trailers and jacks.
As noted, moving the bridge was no piece of cake, and the planning had to be perfect and account for many potential hurdles.
The bridge was assembled between March and August, behind the Conn's Furniture Building, 2,000 ft. away from its permanent location.
"Structural steel and concrete were the main material components," said Sam Piland, Ragle's director of structures. "The majority of the bridge was prefabricated and then assembled on-site adjacent to the bridge's permanent location. The assembly site was large enough to store the majority of the materials."
Cranes, including Grove and Terex 80 ton to 130 ton all-terrain models, were used to assemble the bridge.
Once completed, the bridge was lifted by four 400-ton hydraulic jacks and then shored to four SPMTs.
It took one day to place the bridge on the transporters.
"Maintaining a level and controlled ascent as the bridge was lifted was a challenge," said Piland.
The next step was to move the bridge to the NB frontage road, which required both mainline directions of U.S. 75 to be closed in consecutive order and the erection of temporary barriers.
"We did this on Saturday night in approximately six hours," said Piland. "The challenges included multiple tight turns and grade changes between the assembly area and the highway."
With this movement complete, the bridge was transferred from the SPMTs to two large gantries, which moved the bridge and lowered it in place
"These highly specialized pieces of equipment were provided and assembled by Mammoet," said Piland. "The move took six hours with the gantries moving a few inches per-minute. Constant and continual communication between our teams on the ground ensured they moved in lockstep. It took approximately one hour to lower and set the bridge on the exact permanent location."
Additional Work
In regards to the remaining work, crews are installing the concrete span on either end of the arch and the remaining trail sections are being completed.
"Approximately two months of work are needed to finish the remaining portions of the project, including the bridge, fence and trail," said Piland.
Ragle's project team includes Superintendents Martin Sanchez and Juan Miramontes, Project Manager Tynor Larson and Project Engineer Alberto Zuniga.
"This project took a considerable amount of coordination and communication between the teams, along with TxDOT, HNTB and our suppliers," said Piland. "The effort and professionalism exhibited by our crews were top notch, the safety and quality they achieved is one of the proudest moments of the project."
The project's various phases required many Ragle and subcontractor employees on-site. Peak days had 20 people on hand. Among the subcontractors are Slaton Brothers for MSE retaining walls, Mammoet for movement of the arch, DFW Fence for pedestrian fencing, WG Engineers for electrical, Dallas Lite & Barricade for traffic control and EP Drilling for drilled shafts.
Equipment utilized for the move had to be in tip-top condition at all times.
"There were a lot of hydraulic components involved with the SPMT's, gantries and cranes for the movement and lifts," said Piland. "Mammoet had a couple issues with their equipment, but due to their highly experienced crews and foresight to bring extra components they were able to make on site repairs or replacements fairly quickly."
Ragle purchases and rents equipment from dealerships such as United Rentals, Sunbelt Rentals, Doggett John Deere and Mustang Cat in Houston, and Holt Cat, in Irving.
Project Background
"This was a unique project in many ways," said TxDOT Dallas County Area Engineer, Project Manager Nathan Petter. "It took a lot of ingenuity from TxDOT, Ragle and the designer, HNTB, to make this move effort a reality. The vision started with our regional partners at the North Central Texas Council of Governments [NCTCOG], as well as leaders at the city of Dallas and Dallas County. I'm proud to have played a role in making this a reality."
The project was jointly funded by the city of Dallas, Dallas County and the Regional Transportation Council at NCTCOG.
The innovative design broke new ground.
"Because the bridge was designed to be supported by cables from above, it did not require support columns in the middle of the highway," said Hartzel. "While that made construction and installation more challenging, the contractor came up with a plan to piece together the network tied arch bridge behind a nearby shopping center building and then move it into place. The bridge, which was designed with two curves, is said to be the first doubly-curved, network-tied arch bridge in the world."
While the bridge has been placed, the work continues. The final bridge and trail connections are expected to open by the end of fall 2023.
The bridge connects the existing Northaven Trail west of U.S. 75 with the White Rock Lake trail system to the east of U.S. 75.
"The project also will stand as a regional example of the positive benefits of appropriate location and design aesthetics for future bicycle and pedestrian trails and amenities," stated a project PDF page. "The structure is called a ‘network tied arch.' The bridge deck ties the ends of the arch ribs together, just like the string in a bow used for archery, and the crisscrossing hanger cables form a network pattern."
It also points out that "this structure has a doubly-curved deck, making it the only network-tied arch bridge in the world with a doubly-curved tie." CEG
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