The 12 illuminated concrete arches that form the backbone of the new West 7th Street Bridge in Fort Worth, Texas, are an engineering and construction marvel. Using conventional construction techniques to reconstruct the nearly 100-year-old bridge would have meant closing it to traffic for 10 to 11 months – or more.
Instead, an extremely creative solution was proposed to replace the bridge as expeditiously as possible while minimizing the impact to businesses and the community: casting the arches offsite and then moving them into place.
Sundt began construction on the arches a full year before construction at the bridge began. The arches were cast lying flat on their sides, then post-tensioned and installed with stainless steel rods that run from the top of the arch to the tie. After they cured to a concrete strength of 6,000 psi, the arches were rotated into a vertical position with a gantry system and strand jacks, and shifted into the storage area where they were de-tensioned back into the final design requirement. In May 2013, the first arch was loaded onto two self-propelled modular transport trailers and slowly driven the four blocks from the casting yard and across the old bridge where twin Liebherr 1400 cranes lifted and set it into place on new foundations located alongside the original structure. The remaining arch setting occurred over the next 30 days, mostly at night to minimize traffic disruptions. Once all of the arches were placed, the team closed and demolished the old bridge and constructed the new one in its footprint.
West 7th Street Bridge re-opened to traffic just 120 days later – a full 30 days sooner than originally planned.
Texas Department of Transportation
West 7th Street Bridge