Prior to its installation, the heavily traveled Northaven Trail on the west side of U.S. 75 and the Cottonwood Creek and White Rock Creek trails on the east side abruptly halted at the roadway. In order to access the trails on the opposite side of one of Texas’ busiest highways, cyclists and pedestrians had to detour through a dim underpass.
Mammoet teams worked with Ragle, Inc. and bridge designer HNTB to carefully plan the execution, considering multiple options to find the best fit. Installation with a crane would prove risky and complex, with no suitable area to set the crane without causing a significant impact on area traffic and road closures. Additionally, the bridge’s design would require a complex bracing system if supported at mid-span, so the use of a jacking system was also ruled out. Engineers decided on a method which utilized a gantry system with a jack and slide system on top. This would enable three directional movement to fine-tune adjustments during setting and account for misalignments.
The 61-meter (201 foot) bridge was assembled away from its installation location. On the Friday evening of the installation weekend, it was jacked up and loaded onto a pair of double 8-line SPMT trailers, then moved to the edge of the road. The length and width of the bridge required the use of turntables on top of the trailers for added maneuverability. On Saturday night, once the highway was fully closed to traffic, the bridge was transported to its installation position and the gantries were built around it. To ensure disruption was kept to an absolute minimum, at least one frontage road remained open, allowing traffic to move along U.S. 75 without a significant detour.
The bridge was then lifted off the trailers using the gantry/track combination. Steadily the bridge was raised above the road surface, skidded over, and set it on its piers at about 11:00 on Sunday morning.
Mammoet Engineer, Matthew Berlanga, states, “I am very proud to have contributed on a project that provides such a positive impact to the Dallas community. The success of this job was only made possible through all the hard work of everyone involved. Our top-notch crew, equipment and standard of working within Mammoet is what sets us apart and makes jobs like these seem easy.”
Kira Larson, HNTB’s Project Manager of Construction Phase Services adds, “the Northaven Trail Bridge is a highly complex structure with inherent erection challenges, and HNTB, TxDOT, Ragle and Mammoet needed to proactively communicate throughout construction to keep the project on schedule. When changes needed to be made at the construction site, the team would quickly collaborate to find solutions.” Larson continues, “Standing side by side with TxDOT out in the middle of U.S. 75 at 3-4 in the morning, watching a 201-foot, 800,000-pound bridge be literally driven over us all while still letting traffic through was something I will never forget.”
Shortly after, traffic was allowed to flow again as scheduled – causing minimal impact to travelers. The highly choreographed move was executed flawlessly over a total of 20 hours in one weekend.
